SYSTEMS AND METHODS FOR MACHINE CONDITION MONITORING POWERED BY EFFICIENT HARMONIC HARVESTER

Abstract

Systems and methods can include a transponder configured to communicate wirelessly with a receiver and sensor module (RSM), wirelessly communicate with a high-speed network, and radio-frequency (RF) powering of RSM. The high-speed network can include a wired network such as USB or Ethernet, or wireless network such as a Wi-Fi or cellular network. Additionally or alternatively, an antenna module can be configured to transmit radio-frequency (RF) power to a receiver configured to monitor a condition of a machine. A harmonic harvesting circuit design for harvesting unrectified AC power contained in the fundamental and harmonic at RF frequencies at the output of conventional rectifying circuits for storage and for powering of the entire RSM.

Description

TECHNICAL FIELD

This disclosure generally relates to systems and methods for machine condition monitoring and powering by a harmonic harvester.

BACKGROUND

Identifying accurately significant changes in machine performance indicative of an occurred failure, a likely to occur failure, or a future failure (e.g., fault) is an important component of predictive maintenance. In some examples, more than 80% of all complex mechanical equipment can fail accidentally and without any relation to their life-cycle period. Conventional techniques for condition monitoring involve positioning one or more sensors at or near a machine. Each sensor can be configured to monitor one or more condition parameters of the machine. Critical to accurate machine condition monitoring is the reliability of the sensors themselves. For example, without sufficient energy, sensors would experience down-time or even failures, and may go unattended for substantial period of times, in some instances, years, unless the machine has at least a regular power source as a backup.

SUMMARY

In an example, a transponder can be configured to wirelessly communicate with a receiver and sensor module (RSM), wirelessly communicate with a high-speed network, and radiofrequency (RF) power a RSM. The high-speed network can include a wired network such as USB or Ethernet, or wireless network such as a Wi-Fi or cellular network. The RSM may include a harvester module to efficiently convert harvested RF power to electrical energy for storage. In another example, the RSM may be solely powered by the stored power of the harvester module without requiring a regular power source such as a battery as a backup. In yet another example, the harvester module may harvest sufficient electrical energy to recharge the backup battery.

In another example, a transponder can include an antenna module that can be configured to transmit radio-frequency (RF) power to a receiver that can be configured to monitor a condition of a machine, and a control module that can be configured to dynamically adjust the RF power based on one of (i) a sensor signal generated by a sensor that can be configured to monitor for one or more events in proximity of the antenna module, and (ii) receiver data generated by the receiver, and a combination of (i) and (ii).

In an example, a system can include at least one sensor that can be configured to monitor one of a machine and/or local machine environment for a physical, electrical and/or chemical quantity. The at least one sensor can be configured to generate data quantifying at least one physical, electrical and/or chemical quantity. The system can further include an antenna module that can be configured to receive radio-frequency (RF) signals one of directed toward the antenna module, stray RF signals, RF signals generated by the machine, low frequency electromagnetic signals generated by the machine, and a combination thereof. The system can further include the harvesting module, e.g., including an antenna, that can be configured to harvest RF, or other frequency, energy from the received signals, and further configured to convert the received signals to electrical energy. The electrical energy can be provided to a storage element for storage and ultimately used to power entirely both the receiver and sensor module. In some examples, additional or alternative energy sources can be captured and/or converted, including but not limited to, heat, light, mechanical and/or other sources of energy.

One of the most important components in RF energy harvesting is a rectifier which converts RF signals into DC power. Low-barrier Schottky diodes are often used as switches in low-power, high-frequency rectifier circuitry due to their low turn-on voltage, small resistance, and small junction capacitance. However, typical conversion efficiency of ambient RF harvesters is less than 60% due to ohmic loss in diode resistance, forward voltage loss in the diode(s) and un-rectified energy in the harmonics produced by the diode's non-linear current and voltage (I-V) property and the latencies associated with charge migration within the diode that are part of the AC signal rectifying process. (Un-rectified signals/energy are AC signals/energy that are not converted into a DC signal/energy by the rectifying circuit. Other types of AC-to-DC converter circuits may also be used with the present embodiments.) Rectifying efficiency higher than 50% is very difficult to achieve at low RF input power level as in the case of most ambient RF signals and can only be achieved under very optimal conditions of impedance matching, minimum input power level, RF signal frequency, and load impedance.

In addition to being able to harvest the RF energy contained in the harmonics produced by the non-linear property of rectifying diodes, the novel circuitry as described herein can also improve the rectifying efficiency at the upper frequency limit of the rectifying diode where some portion of the input RF signal bypasses the diode through its junction capacitance. This produces un-rectified RF signals at the fundamental frequency at the output of conventional rectifiers. Such RF signals are shorted to the ground by the large DC hold capacitor, and thus, are wasted.

Disclosed herein is an example harmonic harvester circuit design that converts un-rectified signals at the output of conventional rectifier circuits. In an alternative embodiment, a harvester circuit as described herein connects between the output and input of a conventional rectifier circuit, thus forming a feedback loop circuitry. Additional embodiments of variations of harvester circuit topologies are comprised of different arrangements of rectifying diodes, filters, and impedance-matching circuits.

In addition to the novel features and advantages mentioned above, other benefits will be readily apparent from the following descriptions of the drawings and example embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an example industrial wireless sensor network system.

FIG. 2 illustrates an example enclosure of a receiver and sensor module (RSM).

FIG. 3 illustrates an example of a block diagram of a radio-frequency (RF) power harvesting circuit of a control, communications, and harvesting module (CCHM) of the RSM.

FIG. 4 illustrates an example block diagram of the CCHM of the RSM.

FIG. 5 illustrates an example block diagram of a customizable sensor puck module (SPM) of the RSM.

FIG. 6 illustrates an example of a mechanical model representation of a transponder.

FIG. 7 illustrates an example transponder control module.

FIG. 8 illustrates an example transponder antenna module.

FIG. 9 illustrates an example of installation of system hardware.

FIG. 10 illustrates an example of a flowchart representation of system-level operational functions and data transmission pathways.

FIG. 11 illustrates an example of a data flow diagram of a transponder.

FIG. 12 illustrates an example of a data flow diagram of a receiver and sensor module.

FIG. 13 is a flow diagram illustrating an example method for machine condition monitoring.

FIG. 14 illustrates an example of a harvester circuit using a standard Greinacher Voltage Doubler circuit with a single 2.45 GHz tone input.

FIG. 15 is the output power spectrum of standard Greinacher Voltage Doubler circuit shown in FIG. 14.

FIG. 16 is a Greinacher Voltage Doubler circuit with an example Harmonic Harvester circuit block added. The operating frequency is at 2.45 GHz.

FIG. 17 is the output power spectrum of the Harmonic Harvester circuit block shown in FIG. 16.

FIG. 18 is the output power spectrum of standard Greinacher Voltage Doubler circuit of an alternative embodiment using a 5.8 GHz input.

FIG. 19 is the output power spectrum of one Harmonic Harvester circuit of FIG. 3 using a 5.8 GHz input.

FIG. 20 shows an example embodiment connecting multiple harmonic harvesters in a cascade fashion. The operating frequency in this embodiment is at 5.8 GHz.

FIG. 21 shows an example embodiment connecting a single or multiple harmonic harvesters in a loop-back configuration.

FIG. 22 shows an example circuit implementing the single harmonic harvester design based on the FIG. 16 design.

FIG. 23 shows the fabricated circuit board producing the measured conversion efficiency (dashed line) as a function of input power in comparison with the measured conversion efficiency (solid line) without the harmonic harvester.

FIG. 24 shows an example of an ADS circuit model implementation of a harmonic harvester circuit.

FIG. 25 shows an example circuit embodiment of FIG. 21.

DETAILED DESCRIPTION

In some examples, the long-term success of machinery performance (e.g., reliability, efficiency, etc.) can rely on condition monitoring. Condition monitoring is a process of monitoring a parameter of condition in machinery (e.g., vibration, temperature, shock, etc.) in order to identify a significant change which is indicative of a developing fault. Accurate machine condition monitoring can be an important component, to identifying, predicting and preventing machine failures. For example, the need to accurately predict excessive wear, functional abnormalities, imminent malfunctions (e.g., of pumps, bearings, turbines, etc.) can be important to the maintenance, and in some instances, timely replacement of machine components. Machine condition parameters need to be accurately measured (or collected) so that predictions can be made as to when maintenance should occur or when a machine should be replaced. The ability to correctly measure machine condition parameters and predict a system failure can reduce unexpected downtime, improve process control, and/or improve overall energy usage efficiency. For example, the progression of bearing failure has been correlated to increased vibration, increased temperature, and increased power consumption. The failure of a bearing can have serious consequences in many applications. Bearing failures may be caused by an ingress of dirt or foreign material, by excessive loading or by lubrication problems.

In some examples, to address energy requirements of a sensor itself, in some industrial environments, each sensor is connected via cabling to an energy source. Energy is continuously delivered via the cabling to provide power to the sensors. However, this need to collect long-term data can be balanced with the manufacturing environment's requirements to reduce cabling, avoid additional infrastructure installations, and minimize touch labor to the sensors or overall data system. The use of cabling and related infrastructure also creates a hazardous environment for workers and thus needs to be avoided. In other industrial environments, wireless sensors with replaceable batteries are used for machine condition monitoring. Although an effective alternative to avoiding the drawback associated with wired sensors, use of batteries requires periodic sensor maintenance such as battery replacement. As such, although the use of battery-powered wireless sensors addresses the drawbacks of wired sensors, these devices can create new problems by requiring periodic replacement of batteries.

FIG. 1 illustrates an example industrial wireless sensor network system 100. The wireless sensor network system 100 can include one or more transponders 102 connected with receiver and sensor modules (RSM) 104a-n. The transponder 102 can connect the RSMs 104a-n to a cloud 108 or other network, e.g., for processing, data storage, communications, etc., of data and/or other information received from the RSMs 104a-n. In some examples, the receiver(s) and sensor(s) of the RSM 104a-n can be incorporated in the same physical module, and in other examples the receiver and sensor can be implemented in separate modules and communicatively coupled together. The RSM 104a-n connect with machines 106a-n to monitor conditions of the machines 106a-n and/or the machines' 106a-n environments. In some examples, the RSM 104a-n can be configured to continually measure (or sample) chemical, electrical and/or physical quantities associated with the machine 106a-n and/or a local machine environment (e.g., air around the machine 106a-n). In some examples, the RSM 104a-n can be configured to generate data quantifying the physical, electrical and/or chemical quantities. As such, the data can include, but not limited to, temperature, vibration, an ultrasonic emission signature, pressure, voltage, current, a nature of the particulates in the vicinity, and chemical vapors such as those from volatile hydrocarbons. A sampling frequency of the RSM 104a-n can be fixed or dynamically adjusted to suit the specific application. Additionally, or alternatively, an enclosure of the RSM 104a-n can be fabricated and/or constructed to have customizable mounting features to accommodate any type of machine, and to facilitate a type of parameter being monitored.

In some examples, the RSM 104a-n can be physically attached to or in the proximity of a machine 106a-n to be monitored for a condition. In some examples, the RSM 104a-n can be configured to be attached to an industrial or commercial machine. The RSM 104a-n can be configured to simultaneously receive both RF power for conversion to useful electrical power and bi-directional RF data communication for reporting the condition of the machine 106a-n under observation. The RSM 104a-n can be configured to receive radio frequency (RF) power, either purposely broadcast or harvested from a surrounding environment, and convert the RF power into electrical energy. The electrical energy can be used by the RSM 104a-n for the purpose of monitoring the parameter(s) for which it is configured. Additionally or alternatively, in some examples other energy sources can be captured and/or converted to electrical energy, including but not limited to, heat, light, mechanical and/or other sources of energy.

The transponder 102 can communicate with the RSM 104a-n to send information from the RSM 104a-n to the cloud 108. The cloud 108 can include services such as Amazon Web Services (AWS), Microsoft's Azure, Google Cloud or similar service. The RSM 104a-n can be configured to communicate wirelessly with each transponder 102. The RSM 104a-n can be configured with an energy harvesting circuit. The energy harvesting system can be configured to capture wireless signals purposely transmitted by the transponder 102 at a corresponding RSM 104a-n, and in some examples, wireless signals in the industrial environment. In some examples, the transponder 102 can be configured to continuously or periodically (e.g., every given amount of time) generate wireless signals. In some examples, the energy harvesting circuit and control unit 300 can be configured to convert wireless signal energy to electrical energy, e.g., direct current (DC), based on the captured wireless signals. The electrical energy can be stored locally at an electrical energy storage element 316 on the RSM 104a-n. In some examples, the electrical energy can be used to provide power to one or more components of the RSM 104a-n, as described herein. In some examples, the energy harvesting circuit can be configured to receive the wireless signals generated by the transponder and continuously provide electrical energy for the RSM 104a-n. Accordingly, the systems and methods described herein include wireless charging of RSM 104a-n configured for monitoring a given machine condition associated with the machine 106a-n.

In some examples, a condition of the machine 106a-n can be monitored without the need for wires or replaceable batteries. In some examples, the system 100 can be configured to utilize an existing wireless network infrastructure in a machine environment by way of a single transponder 102 or a plurality of transponders installed in the proximity of one or more RSMs 104a-n. In some examples, the machine environment can include an industrial facility, a commercial facility, and the like.

FIG. 2 illustrates an example enclosure 200 of the RSM 104a-n. In some examples, the RSM 104a-n can include a wireless module that be configured to mount to an exterior surface of the machine 106a-n being monitored by means of threads, clamps, crimps, magnets, adhesives and the like. The enclosure 200 can include joined sections 202, 204: e.g., a lower section 204, e.g., of a metallic material, to provide means to mount sensors(s) to the machine 106a-n firmly such that the measured properties, such as physical, electrical and/or chemical properties (e.g., vibration, temperature, audio signature, pressure, voltage, current, chemical vapors, etc.) can be measured by the sensors, and an upper section 202, e.g., made of plastic or other RF transparent material, to provide electromagnetic transparency for RF power and communication signals to transceiver (e.g., using a low-power protocol such an Bluetooth low-energy or similar). In an example, an interior of the enclosure 200 can include a control, communications, and harvesting module (CCHM) 206, a sensor puck module (SPM) 208 and provisions to mechanically secure each module to the enclosure 200.

The CCHM 202 can include an energy harvesting system. In some examples, the energy harvesting system can correspond to an energy harvesting system, as described in U.S. patent application Ser. No. 14/882,754, the contents of which are incorporated herein by reference. The energy harvesting system can be configured to capture either RF signals directed toward the RSM or otherwise stray, unused RF power, conceivably from the machine 106a-n under observation itself, or other ambient sources, to provide a power source for continually sampling and periodically transmitting measured data back to a transponder(s) and/or a centralized computing point (including but not limited to a cloud computing environment provided by AMAZON WEB SERVICES (AMS), or other cloud computing architecture) for analysis.

The CCHM 206 can further include a programmable microcontroller, a real-time clock, and low-power, bi-directional radio transceiver. Addition features include a rechargeable, non-serviceable energy storage device, a universal asynchronous receiver transmitter (UART) port for programming, non-volatile solid-state memory for data storage, and the ability to control power supplied to the SPM 208. In some examples, the SPM 208 is customizable. Once powered, the customizable sensor circuit card can be configured to communicate with the CCHM 206 by way of low-level serial and general purpose (analog voltage and digital control) lines. The customizable SPM 208 can be reconfigured during manufacturing to accommodate the specific sensors required for a given industrial application (e.g., for a particular machine condition). In an example, the sensor circuit card can include a three-axis accelerometer for monitoring machine vibration, a temperature sensor for monitoring machine case temperature, and an ultrasonic microphone for monitoring changes in the machine's acoustic signature.

In some examples, the enclosure 200 can be constructed to environmentally seal the RSM components, and provide a flexible, customizable mounting solution, and support low-power communications transceivers by maintaining radio transparency. The wireless nature of the RSM 104a-n, including a non-serviceable storage element, e.g. the electrical energy storage element 316 described below, can allow the enclosure 200 to be completely sealed, thus preventing liquid or particulate ingress through opening such as replaceable battery covers or signal transmission connectors. The lower section of the enclosure 200, where the SPM 208 can be located can be metallic to facilitate the transmission of measured characteristics to the internal sensors. For example, an internally potted metallic lower section 204 of the enclosure 200 can effectively transmit the machinery's vibration, temperature, and acoustic signatures to the internal sensor of the SPM 208. This lower section 204 of the enclosure 200 can take different forms depending on the type of data being collected and the desired mounting method. For example, the lower section 204 could take the form of a cable clamp to measure current, have a perforated opening to sample the atmosphere for chemical vapor, etc.

The RSM 104a-n can include a programmable microcontroller to implement various power, communications, and data sampling management strategies. These strategies can vary based on the specific application, but they are generally focused on maximizing sampling frequency and data transmission efficiency given the available incident RF power and communication channel availability. The ability to reconfigure the microcontroller allows the same type of RSM 104a-n to interface with a variety of types of SPMs 208, each being customized for a specific application. In some examples, the lower section 204 and/or the upper section 202 can include the CCHM 206, the SPM 208, and provisions to mount them therein. One or more RF power receiving antennas 210 can connect with the CCHM 206, e.g., by way of a circular RF connector 214 or other type of RF connector compatible with antenna 210. In other examples, the antenna 210 may be integrated with the CCHM 206, requiring no connector between the two elements.

In some examples, the antenna 210 can be detachable and replaceable with one having a form and type optimized for linear polarization and vertical orientation. Other antenna configurations optimized for linear polarization and horizontal or angled orientation can be used. In still other examples, antenna configurations optimized for circular polarization can be used. In some examples, the antenna of the RSM 104a-n can be replaceable or reconfigurable to allow for multiple placement orientations and optimization of the RF power source.

Referring to FIG. 3, in an example, an energy harvesting circuit and control unit 300 can include one or multiple receiving antennas 304 that can receive and provide received RF power to an RF impedance matching circuitry 306. The RF impedance matching circuitry 306 can improve delivery of power to a rectifier-charge pump 308. The rectifier-charge pump 308 can be configured to convert an alternating-current (AC) input signal into direct-current (DC) signal to supply a power management circuitry 312 with DC power. The rectifier-charge pump 308 can include a variety of configurations in order to improve the rectification efficiency depending on the application. An RF filter 310 can be configured to provide additional filtering to isolate the high-frequency RF AC from the DC power management circuitry 312.

For the sake of explanation, RF power, e.g., typically about 9 kHz to about 80 GHz, is discussed, but other electromagnetic field frequencies can be harvested and converted to energy. In some examples, one or more antennas and/or antenna modules of the system can be configured to harvest low frequency electromagnetic signals generated by the machine 106a-n, e.g., around 60 Hz, or other lower or higher frequencies than RF, can be harvested and converted using the systems and/or methods discussed herein. For low frequency EM signals, the signal can be dominated by the magnetic field part, and far less by the electric- or electro-field part). Instead of an antenna type energy coupling device, the energy coupling device can include a coil, with or without a ferrous core. A heat source can include a thermoelectric generator (TEG) and a light source can include a photoelectric generator (solar cell) to convert the source into electrical energy.

The power management circuitry 312 can perform several functions. In some examples, the incoming DC voltage can be stored by the power management circuitry 312 in a low-impedance, bulk capacitor 314. This capacitor 314 can allow the accumulation of enough converter RF power to perform subsequent power management and conversion functions. In some examples, the power management circuitry 312 can include a switching voltage converter, such as a “step-up” converter, to increase the voltage supplied to the non-serviceable energy storage component 316, such as an integrated electric double-layer capacitor that can provide extremely high capacitance in a small volume. The electrical energy storage element 316 can serve as the DC supply voltage for the RSM 104a-n. In some examples, the power management circuitry 312 can also include a rechargeable battery as the electrical energy storage element 316.

Referring to FIG. 4, in an example, CCHM 206 components of the RSM 104a-n can include the energy harvesting and control unit 300 connected with a programmable microcontroller 402 and several peripherals 406-416 powered by the energy harvesting and control unit 300. The microcontroller 402 and the attached peripherals 406-416 can be selected to minimize power consumption while implementing a data sampling and communications strategy that can be customizable for each application. The RSM 104a-n can spend a majority of its time in “sleep” while the RF energy harvesting power supply accumulates usable energy. During “sleep” mode the microcontroller 402 can be in a low-power state, and be awoken by a real-time clock 408. A high-side DC switch 406 can be off in sleep mode leaving the microcontroller 402 and the real-time clock 408 powered. The real-time clock 408 can have the ability to “wake” the microcontroller 402 at either a certain pre-determined time or after a specific amount of time has passed since the last wake state. In “wake” mode the high-side DC switch can be activated, applying power to the Bluetooth low energy (BLE) transceiver 410, the non-volatile memory 412, the onboard sensors 414, and the SPM connector 416. The microcontroller 402 can transfer bi-directional data to the BLE transceiver for communication to the transponder 102. The non-volatile memory 412 can allow several data samples to be taken, without the need for communication using the BLE transceiver 410, until enough data is accumulated to allow for efficient data transmission back to the transponder 102. The onboard sensors can facilitate easy collection of measurements that can be common across multiple applications, such as temperature, vibration, etc. In an example, the SPM connector card 416 can supply power and communication/control lines to the SPM sensor array, which can be highly customizable based on application needs.

Referring to FIG. 5, in an example, the SPM 208 within the RSM 104a-n can include a customizable circuit card 500 that can include a variety of sensors in multiple configurations. The following description is just one example of the SPM 208. The RSM 104a-n can be configured to allow for any combination of sensors to be implemented in the SPM 208 and interfaced with existing CCHMs 206. For example, the SPM 208 can be configured with a circuit card that can have a power and communications connector 502 that can interface the SPM 208 with the CCHM 206. A thermometer 504 can be configured to monitor machinery temperature by means of thermal conduction with the exterior enclosure 200. An accelerometer 506 can be configured to monitor machinery vibration by means of mechanical conduction with the exterior enclosure 200. An ultrasonic microphone 508 can be configured to monitor machinery acoustic signature by means of an acoustically-transparent seal through the enclosure 200. A pressure sensor 510 can be configured to monitor pressure by means of a port on the exterior of the enclosure 200. A voltage sensor 512 can be configured to monitor external voltages by means of sealed electrical terminals exterior to the enclosure 200. A current sensor 514 can be configured to monitor AC or DC current by means of a measuring shunt or a magnetic field sensor built into the lower enclosure through which wire(s) can be routed. Particulate sensor 516 and chemical vapor concentration sensor 518 can measure particulate count, size, type, and chemical composition, respectively, of an environment by means of a sampling port. The SPM 208 can implement the appropriate physical interface or attachment to the RSM enclosure 200 to facilitate each physical attribute sensed. Additional or alternative sensors can be used, including but not limited to fluid level and/or fluid condition sensing, e.g., lubricating oil for the machine 106a-n.

FIG. 6 illustrates a mechanical model representation of the transponder 102. The transponder 102 can include an enclosure 600. The enclosure 600 can include a first section 602 and a second section 604. The first section 602 can be fabricated such that the first section is transparent to wireless signals (e.g., RF or other electromagnetic signals). In some examples, the first section 602 can include a transponder control module (TCM) 608 that can include a status indicator, e.g., a light emitting device. The light emitting device, in an example, can correspond to a multi-color light emitting diode. A given color can be used to provide a visual indication to a user. In some examples, the TCM 608 can include a proximity sensor to register the distance of a nearby object, e.g., a laser based, acoustic-based and/or IR based proximity sensor. The first section 602 and the second section 604 can be coupled to one another to seal one or more components of the transponder 102. In some examples, the one or more components can include a transponder antenna module (TAM) 606 and an antenna 610. The antenna 610 can be configured to transmit and receive wireless signals. In some examples, the antenna 610 can be configured to provide wireless signals for one or more sensors. The one or more sensors can correspond to the one or more RSM 104a-n. The antenna 610 can be configured to provide for bi-directional communication between the transponder 102 and the one or more sensors. Additionally or alternatively, the antenna 610 can deliver energy carrying signals to the RSM 104a-n.

FIG. 7 illustrates an example transponder control module 700. In some examples, the control module 700 can correspond to the TCM 608, as illustrated in FIG. 2. The control module 700 can include a controller 702. The controller 702 can be configured to evaluate sensor data generated by one or more sensors (e.g., the one or more RSM 104a-n). In some examples, the controller 702 can be configured to evaluate the sensor data and stored baseline sensor data in memory 704 of the control module. Additionally or alternatively, the sensor data can be evaluated remotely, e.g., on remote data processing devices and/or with cloud computing. The controller 702 can be configured to determine condition parameters for one or more machines (e.g., the one or more machines 106a, 106b, and 106n, as illustrated in FIG. 1) based on the evaluation.

The controller 702 can be configured to provide power and/or operational commands to an antenna module via an interface connection 706. In some examples, the antenna module can correspond to the TCM 608, as illustrated in FIG. 6. An antenna module can include a single antenna or multiple antennas, e.g., as needed to provide communication and/or harvesting. The controller 702 can be configured to via the interface connection 706 to set an RF signal frequency and power level, and RF amplifier gain. In some examples, variable gain amplifiers (VGA) can be used for the driver amplifier. The controller 702 can be configured to monitor a measured reflected RF power signal. The control module 700 can include a universal serial bus (USB) transceiver 708. The USB transceiver 708 can be used to interface with a software configuration tool. In some examples, the controller 702 can be programmed to provide the sensor data to the software configuration tool via the USB transceiver 708.

The control module 700 can include an in-circuit programming connection 710. In some examples, a device can be coupled to the in-circuit programming connection 710. The device can be configured to provide transponder configuration data. The controller 702 can be configured to change one or more operating parameters of the one or more components based on the configuration data. For example, the controller 702 can be configured to one of set the RF signal frequency and power level, and RF amplifier gain, and a combination thereof based on the configuration data. In some examples, the controller 702 can be configured based on the configuration data. For example, the controller 702 can be configured for a given antenna module. As such, the control module 700 can be configured to interface with a plurality of different of antenna modules, each of which can be unique for a given machine condition monitoring application. Components and functions are split between an antenna module and the control module 700 to permit the antenna module to be replaceable to implement a variety of antennas, RF sources, and RF amplifier configurations.

The control module 700 can include electrically erasable programmable read-only memory (EEPROM) 712. In some examples, the EEPROM 712 can be configured to store the configuration data. The controller 702 can be configured to retrieve the configuration data. The controller 702 can be reprogrammed for the given antenna module based on the configuration data. The control module 700 can include one or more wireless transceivers 714, 716. In some examples, the wireless transceiver 714 can be configured to communicate according to a given protocol and the wireless transceiver 716 can be configured to communicate according to another protocol, different than the given protocol. In some examples, the wireless transceiver 714 can include, but not limited to, a Wi-Fi serial transceiver, a cellular transceiver, and a combination thereof. The wireless transceiver 714 can be configured to communicate with a system. In some examples, the system can be on a cloud. The system can be configured as a centralized data storage and processing system according to the systems and methods described herein.

In some examples, the wireless transceiver 716 can include, but not limited to, a Bluetooth transceiver, a ZigBee transceiver, a Bluetooth low-energy (BLE) transceiver, and a combination thereof. The wireless transceiver 716 can be configured to communicate with the one or more sensors. The controller 702 can be configured to generate sensor configuration data. The wireless transceiver 716 can be configured to transmit the sensor configuration data to the one or more sensors. In some examples, the controller 702 can be configured to provide sensor identification data to the wireless transceiver. The wireless transceiver 716 can be configured to transmit the sensor configuration data to intended sensors based on the sensor identification data.

The controller 702 can be configured via the wireless transceiver 716 to one of periodically or continuously monitor nearby sensors for “awake” sensors. Upon discovering one or more awake sensors, the controller 702 can be configured to communicate with the sensors to receive sensor data. In some examples, the controller 702 can be configured to transmit the sensor configuration data. The memory 704, e.g., non-volatile flash memory, can be configured to facilitate storage of large amounts of data, pending transmission of the data to the centralized data storage and processing system or local data analysis by the transponder itself. The proximity sensor can be configured to monitor for objects, including personnel, within the vicinity and in the direction of the emitted RF power. This proximity sensor can be coupled with the measurement of reflected RF power from a TAM interface connection 706 to allow the transponder to function at higher power levels when unobstructed but operate within the established, regulated RF exposure levels when obstructed. In an example, TCM 608 can be configured to monitor the internal temperature of the transponder to maintain safe operational conditions should the environment temperature rise.

FIG. 8 illustrates an example TAM, e.g., the TAM 606 in FIG. 6. The TAM 606 can include one or more components such as a RF power transmitter on a separate circuit assembly controlled by the TCM 608. The TCM interface connector 706 can provide a standardized means of supplying power and data signals to the TAM 606. The RF source 810 can be configured to generate the synthesized RF signal across an adjustable spread spectrum to reduce interference with other data communication networks in the same frequency band and to minimize the peak power at any one particular frequency. A balun 812 can be configured to convert a differential signals, e.g., RF signals, into a single-ended signals for input into a power amplifier 814. The power amplifier 814 can increase power of the signal for transmission through the directional coupler 804 and eventual transmission by the power antenna 802. In some examples, multiple stages of amplifier and/or filters can be included as needed. The directional coupler 804 can provide means to sample the transmitted and reflected RF power at a known reduction such that the transmitted power detector 806 and reflected power detector 808 can accurately measure transmitted and reflected power, respectively. The TCM interface connection 706 can send/receive an RF source control, Serial Peripheral Interface (SPI) and/or General Purpose Input-Output (GPIO) signal to the RF source 810, and a DC supply and enable GPIO signal to the power amplifier 814.

Referring to FIG. 9, in an example, a machine condition monitoring system 910 can include a transponder 912, e.g. transponder 600, mounted overhead or affixed to support structure, in the vicinity of several RSMs 922, e.g., RSM's 104a-n, mounted directly or in the proximity of the machinery being monitored. The transponder can receive power from an existing power infrastructure 914 of the existing location, such as 120/240 VAC or 24 VDC, and can interface with the existing wide area network, such as wired or wireless Ethernet or Wi-Fi network. The transponder can implement a low-power, local area wireless network for bi-directional communication with a distributed array of RSMs 922. The transponder can simultaneously implement an emitted RF power source that can be broadcasted towards the RSM array for the purpose of reception and conversion into useful DC power. The emitted RF power and local-area wireless network can be broadcast symmetrically, over one or more axis, emanating from the front, RF functional side of the transponder. The transponder can implement an interchangeable mounting bracket and any necessary connectors (e.g., power, wired network, and USB for configuration programming) on the rear or side.

One or more types of RSM 922 can be placed or their corresponding type of machinery to be monitored. For example, it may be of interest to monitor the voltage, current, temperature, vibration, and ultrasonic acoustic signature of an electrical motor (a prime mover 924, as shown in FIG. 9). Another type of RSM 922 with a different sensor configuration can be used to monitor the temperature, via an IR sensor, cycle life, and particulate emissions of a mechanical clutch 926 or a mechanical brake 928, as shown in FIG. 9. A RSM 922 fitted with a multi-axis accelerometer can monitor the condition of a gear box 930, as shown in FIG. 9. Further RSM sensor customization would be possible to appropriately monitor a variety of mechanical loads 932, such as temperature of a stirred mixture, speed of rotation, multi-axis vibration, transparency (e.g., light absorption), etc.

Referring to FIG. 10, in an example, the machine condition monitor data flow can take the high-level form of a plurality of repeating loops. These loops can control the transponder data collection, generation, and analysis functions, the RSM 922 data sampling functions, and the RSM 922 data exchange frequency with the transponder. Within the transponder data management loop, the transponder first waits for a request for communication 1042 from one or multiple RSMs 922. In the case of two or more RSM 922 requesting communication simultaneously, the low-power local area network implemented by the transponder and the RSM 922 can provide means to assign a randomized time interval to each RSM 922 before they may re-issue a request. This serves to mitigate network traffic collisions and, over time, establish a sequential communication pattern among many RSMs 922. Once a request for communication has been received and acknowledged, the transponder can coordinate the reception of RSM sensor data 1044, and the combining of the data received from each RSM 922 into the overall transponder sensor data 1052, which can be stored within the transponder's internal flash memory 1056. The transponder can then generate updated configuration data 1054 to be sent to the RSM 922 as part of the next communication cycle 1046. This configuration data can be a function of the energy spent by the RSM 922 to acquire and transmit the sensor data, information that can be transmitted by the RSM 922 along with the sensor data itself. This can allow the transponder to configure each individual RSM 922 to acquire and transmit the most important type of data more frequently (based on the condition quality of the data itself) and for each RSM 922 to utilize the harvested energy with maximum efficiency.

Within the RSM 922 data transmission loop, the RSM 922 can first check that ample energy has been harvested and accumulated in order to complete a successful transmission before a communication request can be initiated 1060. Energy can be continuously harvested by the RSM 922 so that the delay period 1058, when the low-power, local-area transceiver is powered down, can be used to accumulate stored energy. Once the transmit delay elapses and ample energy from harvesting is stored within the electrical energy storage element 316, the local-area transceiver can power on to send a request for communication with the transponder to transmit 1062 the acquired sensor data 1068 and receive updated configuration settings 1064. Both the compiled sensor data 1068 and the configuration data 1070 can be stored within the RSM internal flash memory 1072. After a complete transmission transaction, the local-area wireless transceiver can be shutdown 1066 and another transmit delay cycle begins 1058.

Within the RSM 922 data sample loop, the RSM 922 can first check that the sample delay 1074 has elapsed and ample energy from harvesting is stored within the RSM 922 before initiating a data sample 1076. Once started, the sensor sample acquisition 1078 can be performed according to the RSM configuration data 1070 received and stored in the RSM internal memory 1072 during the previous communication cycle with the transponder. Data from one or multiple sensors 1068 can be compiled in the RSM internal memory 1072 for transmit to the transponder at a later time. The RSM configuration data 1070 can include data that can define the data sample loop, such as sample delay time 1074 (for each individual sensor in the array) and data to be recorded about the sample acquisition 1080, such as the energy and time cost to perform the sample. Once the sample data is acquired, the sensor array can be configured to shutdown 1082 and the next sample delay 1074 begins.

Referring to FIG. 11, in an example, the transponder data flow may be diagramed in more detail. The transponder data flow process can begin with the RSM initiating communication 1100 and the transponder 102 receiving the incoming acquired sensor data 1102. The transponder 102 can record the sensor data within its internal data storage 1104 for further analysis 1106. The transponder can be capable of making multiple determinations based upon the received sensor data. The transponder 102 can be configured to make a preliminary assessment of the machine condition 1114 locally, without the need to transmit the data back to the cloud 108. In some examples, the cloud 108 can include a centralized data storage and processing (CDSP) server. For example, the transponder 102 can be capable of implementing low-level functions, such as basic analysis of acquired data, adjustment of the RSM data sampling strategy, and implementing emergency shutdown limits, the cloud 108 can implement the high-level data-analysis functions of the machinery condition monitoring system. The cloud 108 can coordinate communications and data sampling strategies between multiple transponders to facilitate the monitoring of large, cross-functional machinery setups. The cloud 108 can also provide complex data visualization and end-of-life prediction tools based on aggregated information from the complete installation site. Maintenance work orders can then be issued automatically, prioritized for the machinery nearest to failure and scheduled to minimize process downtime.

The functionality can allow the transponder 102 to adjust the sampling frequency 1112 as well as provide an alert to cloud 108 that this particular sensor data set can be flagged for further analysis. The transponder 102 can be configured to assess the amount of RSM 922 stored energy spent in acquiring the sampled data 1122 and the amount of energy spent transmitting the stored data back to the transponder. It should be noted that the RSM 922 can include the amount of harvested and stored electrical energy as part of the data transmitted back to the transponder 102. The transponder 102 can generate updated RSM configuration data 1110 based on both machine condition, specifically the possible need to sample that particular type of data to more closely monitor machines 106a-n that may be close to a service requirement, and the power requirement of transmitting that data back to the transponder 102, and thus the cloud 108 for analysis, more frequently.

Since the transponders analysis of the data can require more time than the relatively quick (for RSM energy conservation) sequence to transmit the acquired sensor data, the updated RSM 922 configuration data would be relayed back to the RSM 922 after the next RSM transmit delay 1108. The transponder 102 can be configured to make adjustments to itself based upon the analysis of the transmitted sensor data. In some examples, such as monitoring machines 106a-n that is close to failure, starting up, or shutting down, the transponder 102 can be configured to temporarily adjust 1118 the emitted RF power 1116 to facilitate more frequent data acquisition and communication with the RSMs 922. Additionally, the transponder 102 can be configured to identify a set of pre-programmed safety concerns 1130 in order to quickly alert an alert center server 1128, e.g., implemented by the cloud 108, by sending the compiled sensor array data 1126 out of the wide area network 1124 to any pertinent entities, such as a safety shutdown device, a maintenance group for prioritizing a work order, etc.

Referring to FIG. 12, in an example, an RSM data flow may be described in more detail. An RSM 922 can include a variety of sensors each with their own unique sampling strategy and frequency, since a given RSM 922 can take multiple forms, configured with different sensor puck modules (SPM) and customizable control, communications, and harvesting modules (CCHM). The RSM 922 can continually implement these data sampling strategies 1134, 1142 on their respective sensors 1132, 1140, accumulating the measurements in the RSM's 922 internal sensor data storage 1136. Simultaneously, RF power can be harvested 1138 from the environment, including reception of the RF power emitted by the transponder 102, to be converted to useful DC electrical power and stored with an electrical energy storage element 316, e.g., internal energy storage 1146. Once enough energy has been accumulated to complete a full transmit cycle 1154, the RSM 922 can be configured to compile the outgoing sensor data 1144 and initiate a communication cycle 1152 with the transponder 102. The incoming configuration data 1150, which can be generated by the transponder 102 based upon the analysis of the transmitted sensor data and data acquisition energy costs, can be received and stored within the RSM's 922 internal process data storage 1148. The dashed lines in FIG. 12 can indicate how the RSM 922 can be programmed to reconfigure both the sensor data sampling strategies and the data transmission criteria based upon reception of updated configuration data.

FIG. 13 is a flow diagram 1300 illustrating an example method for machine condition monitoring. A sensor can be configured to monitor one of a machine 106a-n and/or local machine environment for a physical, electrical and/or chemical quantity (1302). The at least one sensor can be configured to generate data quantifying the physical, electrical and/or chemical quantity. The system can further include an antenna module that can be configured to receive radio-frequency (RF) signals directed toward the antenna module, stray RF signals, RF signals generated by the machine 106a-n, low frequency electromagnetic signals generated by the machine 106a-n, and/or a combination thereof (1304). The system can further include a harvesting module that can be configured to harvest RF energy from the received RF signals, and further configured to generate electrical energy based on the harvested RF energy (1306). The harvested electrical energy can be provided to the electrical energy storage element 316 for storage (1308). The sensors can be powered with the stored energy (1310).

Described below are example embodiments of a harvesting circuit that are directed to improvements in RF to DC conversion efficiency, defined as a ratio of the final DC output power to the input RF power. All simulated results were obtained using a commercial Advanced Design System (ADS) Circuit Design Cookbook software.

FIG. 14 illustrates an example of a harvester circuit that may be used in the energy harvesting and control unit 300, using a standard Greinacher Voltage Doubler circuit with a single 2.45 GHz tone input. In practice, the harvester circuit (including the added harmonic harvester circuit block) may at least be implemented as the RF impedance matching circuitry 306, the rectifier charge pump 308, and the RF filter 310 of FIG. 3.

Referring to FIG. 14, an example embodiment of a standard Greinacher Voltage Doubler circuit commonly used to convert RF signals into DC power is shown. A single 2.45 GHz tone RF source at −10 dBm power level may enter the circuit from the left. It is followed by an impedance matching circuit IMN comprised of a single-stub tuner for minimizing power reflection back into the source. The capacitor CI is for blocking the DC signal from going to the RF source while allowing the RF signal from the source to pass through. Next are two rectifying diodes DI and D2 that may be, for example, the SMS7630 low-barrier Schottky diodes.

The rectified output DC signal level may be smoothed by a charge holding capacitor C2. The output may be connected to a 1K (Kilo ohm) resistor at the right hand side. Ideally, all RF energy should be converted into DC power and has a high conversion efficiency of almost 100%, except for some ohmic loss to the diode resistance. All diodes operating under low bias voltage conditions, as in the case of ambient RF energy harvesting, have non-linear I-V (current-voltage) properties. This produces harmonic signals whose frequencies are multiples of the fundamental frequency. In addition, the finite junction capacitance across the diode's P-N junction allows a small portion of the input RF signal to leak to the output.

The amount of leakage may increase with frequency. Therefore, the output of a practical rectifying circuit, or “rectifier,” may contain more than just DC. This may be demonstrated by FIG. 15, which shows a power spectrum observed at the output of the rectifier (e.g., diode D2) as shown in FIG. 14. It shows significant power present at the fundamental and harmonic frequencies based on the amount of DC power generated from the −10 dBm RF source, where a conversion efficiency is approximately 24.8%.

FIG. 16 is a Greinacher Voltage Doubler circuit with a Harmonic Harvester circuit block 10 added. The operating frequency is at 2.45 GHz. FIG. 16 shows a harmonic harvester circuit block 10 added to the output of the conventional rectifier 12 (D2) shown in FIG. 14. The harmonic harvester circuit block 10 in this example embodiment may include a DC blocking capacitor 14 (C2), followed by an impedance match network circuit 16 (IMN2), a rectifying diode 18 (D3), and a RF blocking inductor 20 (LI) for preventing fundamental and harmonic signals from getting shorted to the ground through C3.

In FIG. 16, the un-rectified RF energy present at the fundamental and harmonic frequencies at the output of D2, may be stopped by the RF blocking inductor L1 and redirected to the harmonic harvester circuit 10 that is comprised of the DC blocking capacitor C2, an impedance matching circuit IMN2 (which is preferably different from IMNI), and rectifying diode D3 (which in one embodiment may be the same as DI and D2, but it does not have to be the same).

The computed output power spectrum of FIG. 16 observed at Vout is shown in FIG. 17, which shows that the power levels at fundamental and harmonic frequency have been significantly reduced by the harmonic harvester circuit block 10. Some of this energy has been converted into DC by the harmonic harvester circuit block 10. This results in a conversion efficiency increase from 24.8% to 40%.

In an alternative embodiment, additional components may be added to provide a more sophisticated frequency control. For example, instead of the single capacitor C2, a simple high-pass filter may be used; instead of a single inductor L, a simple low-pass filter may be used. These electrical circuit elements may also be replaced with more complicated L/C circuitry to achieve a more sophisticated filtering.

In an alternative embodiment to FIG. 14, the frequency of the input signal may be increased from 2.45 GHz to 5.8 GHz to demonstrate reduced conversion efficiency due to more RF energy leaking through the junction capacitance of the rectifying diodes DI and D2. Comparing the output DC power level in the FIG. 18 output power spectrum to that obtained in FIG. 16 at GHz shows significant DC power reduction. The conversion efficiency in this case is 16%.

In an alternative embodiment to FIG. 16, the frequency of the input signal is increased from 2.45 GHz to 5.8 GHz. The output power spectrum in FIG. 19 shows that the DC power is increased compared to that in FIG. 18. The resultant conversion efficiency at 5.8 GHz fundamental frequency increases from 16% to 22%.

FIG. 20 shows an example embodiment of the present invention of connecting multiple harmonic harvesters 22 in a cascade (in-series connection) fashion for harvesting more power into DC—especially in high-leakage situations as the output of each harmonic harvester circuit 22 could still have non-DC component. It is important to keep the number of the harmonic harvesters to a minimal since additional diodes in each harmonic harvester circuit also add more ohmic loss, thus lowering conversion efficiency.

FIG. 21 shows an example embodiment of the harmonic harvester circuit 24 of connecting a single or multiple harmonic harvesters in a loop-back 24 configuration. This loop-back 24 configuration is equivalent to the multiple harmonic harvester 22 embodiment in FIG. 20, except without using multiple harmonic harvester 22 circuits, thus saving size and cost compared to the series configuration shown in FIG. 20. The dotted line around the harmonic harvester portion of the circuit in FIG. 21 may be a general representation that the harvester circuits (e.g., harvester circuits of FIGS. 16, 20) may be used as a feedback loop in FIG. 21 (for example, use of the harvester circuits of FIGS. 16 and 20 as a feedback loop that requires taking the loop back to the input of the rectifier D2). FIG. 24 illustrates one example embodiment of the feedback loop circuit of FIG. 21.

FIG. 22 shows an example circuit implementing the single harmonic harvester design (based on the FIG. 16 design). FIG. 23 shows a fabricated circuit board and the measured conversion efficiency (dashed line) as a function of input power in comparison with the measured conversion efficiency (solid line) without the harmonic harvester. In this case, the harmonic harvester of FIG. 22 (based on the FIG. 16 design) may increase the conversion efficiency by 5% to 18% for input power above −5 dBm.

FIG. 23 shows a fabricated circuit board of the measured conversion efficiency (dashed line) as a function of input power in comparison with the measured conversion efficiency (solid line) without the harmonic harvester. FIG. 24 is an example of an ADS circuit model layout with an implementation of a harmonic harvester circuit. The impedance matching network IMN portion 26 of the circuit may be realized as a section of transmission line TL69 and tee junction T9, and a shorted stub TL68. During the design optimization, the ADS will search automatically for the best lengths of TL69 and TL68 that produce maximum DC output.

FIG. 25 shows an example of the harmonic harvester circuit 24 used in a feedback embodiment of FIG. 21.

It should be noted that the disclosed harmonic harvester circuitry in FIGS. 14-25 may be implemented to harvest energy from the RF signals to power a transponder 102 in FIG. 1.

What have been described above are examples. It is, of course, not possible to describe every conceivable combination of elements, components, or methods, but one of ordinary skill in the art will recognize that many further combinations and permutations are possible. Accordingly, the disclosure is intended to embrace all such alterations, modifications, and variations that fall within the scope of this application, including the appended claims. Additionally, where the disclosure or claims recite “a,” “an,” “a first,” or “another” element, or the equivalent thereof, it should be interpreted to include one or more than one such element, neither requiring nor excluding two or more such elements. As used herein, the term “includes” means includes but not limited to, and the term “including” means including but not limited to. The term “based on” means based at least in part on.

Claims

1. A system, comprising: at least one sensor configured to monitor one of a machine and/or local machine environment for at least one of a physical, electrical and chemical quantity, the at least one sensor being configured to generate data by sampling and quantifying the at least one physical, electrical and chemical quantity;an antenna module configured to receive at least one of radiofrequency (RF) signals directed toward the antenna module, stray RF signals, RF signals generated by the machine, and low frequency electromagnetic signals; anda harvesting module configured to harvest energy from the received signals, and further configured to convert the harvested energy to electrical energy based on the harvested energy, wherein the electrical energy is provided to an electrical energy storage element for storage and use by the at least one sensor, wherein the received signals are alternating-current (AC) signals, and the harvesting module comprising a circuit comprising:a direct-current (DC) blocking circuit configured to pass the AC signals and block DC signals generated by an AC-to-DC converter circuit from the received signals;an impedance matching circuit connected to the DC blocking circuit and configured to receive the AC signals;a rectifying circuit connected to the impedance matching circuit and configured to convert the AC signals; andan AC blocking circuit configured to pass the DC signals, wherein the AC blocking circuit is connected to the AC-to-DC converter circuit and the DC blocking circuit.

2. The system of claim 1, further comprising a controller configured to maximize one or a combination of: sensor data gathering frequency, data transmission efficiency based on an amount of electrical energy stored in the storage element.

3. The system of claim 1, further comprising a controller, the controller configured to receive data quantifying the at least one physical, electrical and chemical quantity, the antenna module being configured to transmit and receive RF signals including the quantified data to and from a transponder.

4. The system of claim 3, where the antenna module transmits the RF signals to the transponder according to one of a Bluetooth, Bluetooth low energy (BLE), and a combination thereof.

5. The system of claim 2, further comprising a real-time clock configured to control a plurality of operating states of the controller, the plurality of operating states comprising a sleep state and a processing state, wherein in the sleep state the controller is configured to draw less power than in the processing state.

6. The system of claim 5, wherein the controller is in the sleep state during a time period that the harvesting module is harvesting the RF energy.

7. The system of claim 6, wherein the controller is configured to operate in the processing state in response to an awake signal generated by the real-time clock, wherein the real-time clock generates the awake signal based on one of at a pre-determined time and an amount of time that has elapsed since a previous operating state.

8. The system of claim 7, wherein the real-time clock is further configured to control one or more operating states of one of the at least one sensor.

9. The system of claim 8, wherein in a first state the at least one sensor is configured to monitor one of the machine and/or the local machine environment for the at least one physical, electrical and chemical quantity.

10. The system of claim 1, wherein the at least one physical, electrical and chemical quantity comprises one of a temperature, a vibration, an ultrasonic acoustic signature, a pressure, a voltage, a current, a nature of particulates in the local machine environment, chemical vapors, and a combination thereof.

11. The system of claim 1, wherein a sampling frequency of the at least one sensor of the at least one physical, electrical and chemical quantity is selected from one of fixed and dynamically adjusted based on a type of the at least one physical, electrical and chemical quantity.

12. The system of claim 1, further comprising an enclosure to house the at least one sensor, the antenna module, and the harvesting module.

13. The system of claim 1, wherein the at least one sensor comprises two or more of: a thermometer, an accelerometer, a gyroscope, a microphone, a pressure sensor, a voltage sensor, a current sensor, magnetic field sensor, a chemical vapor concentration sensor, a chemical composition sensor, a particulate sensor, a fluid level sensor, a fluid condition sensor.

14. The system of claim 1, wherein the electrical energy storage element comprises one or a combination of: a capacitor, a capacitor bank and a rechargeable battery.

15. The system of claim 1, wherein the harvesting module further comprises a thermoelectric generator and a solar cell to convert a heat source and a light source to electrical energy.

16. The system of claim 1, wherein the RF signals are within a spectrum of 9 kHz to 80 GHz, and the low frequency electromagnetic signals are in a mains power alternating-current (AC) range.

17. The system of claim 1, wherein the antenna module comprises a plurality of antenna elements optimized for linear polarization, circular polarization, horizontal. vertical or angled orientation, narrow, wide or omnidirectional directivity.

18. The system of claim 3, wherein the antenna module of the sensor is configured to receive RF power transmitted from the transponder, and the RF power transmitted to the antenna module of the sensor is dynamically adjusted in response to the quantified data generated by the sensor.

19. The system of claim 3, wherein the transponder is configured to transmit control data to the sensor to control one or more functions of a controller in the sensor.

20. The system of claim 19, wherein the control data comprises one of data frequency measuring information, transmission timing for the sensor to the transponder, condition monitoring parameters, and a combination thereof.

21. The system of claim 1, wherein the sensor is configured to adjust a data transmission frequency to the transponder in order to maximize data sampled by the sensor based on the control data.

22. The system of claim 1, wherein the circuit being a first harmonic harvester circuit, wherein at least a second harmonic harvester circuit of identical arrangement to the first harmonic harvester circuit but with element values configured to rectify harmonics of the AC signals, is cascaded in series after the first harmonic harvester circuit to improve AC to DC rectifying efficiency.

23. The system of claim 1, wherein the circuit a two-port feedback circuit connected in parallel to an AC-to-DC converter circuit, such that a first port of the two-port feedback circuit is connected to an input port of the first AC-to-DC converter circuit and the second port of the two-port feedback circuit is connected to an output port of the AC-to-DC converter circuit.

24. The system of claim 1, wherein the two-port feedback circuit comprises: a direct-current (DC) blocking circuit having a first end and a second end, the first end of the DC blocking circuit is connected to the first port of the two-port feedback circuit, and the DC blocking circuit configured to pass alternating-current (AC) signals and block DC signals;an impedance matching circuit having a first end and a second end, the first end of the impedance matching circuit connected to the second end of the DC blocking circuit to receive the AC signals;a rectifying circuit having a first end and a second end, the first end of the rectifying circuit connected to the second end of the impedance matching circuit to rectify the AC signals to output DC signals at the second end of the rectifying circuit, wherein the second end of the rectifying circuit is connected to a second port of the two-port feedback circuit; andan AC blocking circuit having a first end and a second end, the first end of the AC blocking circuit is connected to the first end of the DC blocking circuit and the second end of the AC blocking circuit is connected to the second end of the rectifying circuit.