Patent Application
20180335512
mm-Wave Radar System Apparatus and Method of Operation for simultaneous medium distance and short distance sensing.
The present invention relates to a mm-Wave Radar Sensor apparatus concept and radar sensor operation method addressing capability to detected simultaneously medium distances larger than 10 m as well as short distances, below 20 cm.
There is a strong motivation to deploy the low cost, miniature small distance sensors particularly in the following applications:
Currently state of the art mm-wave radar systems being on the market are deploying FMCW radar concept, and they are operating in the frequency bands in 60 GHz Range (non-licensed band), 77-81 GHz automotive band, and 120 GHz band ISM band. In all cases integrated System on Chip supporting FMCW radar analog operation with or without PLL on the same die are proposed and used. These SoCs can be in many cases used for Doppler type of applications, where vibrations are detected.
Main application area for mm-wave radar sensor, currently on the market are:
These applications suffers in short distance detection, and due to the nature of the FMCW radar operations they cannot work for distances below 20 cm, as the obtained frequency which reflects the distance to the target is low.
In this invention we propose an apparatus for the future sensor module and it operations, being able to detect the distances in cm range level, by using other system concept than FMCW radar, based on specific CW mode operation.
The typical and essential application, addressed by this invention is effective calculation of the distance for parking sensor module, being able to replace ultrasound modules addresses distance sensing from 0 cm up to above 10 m, being fully integrated in the automotive enclosure, like in bumpers and fully invisible.
The following patents and patent applications published in last several years show the relevance of the topic and the state-of-the-art.
DE 102012201367, “The millimeter wave radar” introduces a millimeter-wave radar device with at least one millimeter wave circuit and at least one antenna, constructed as a module of a multi-layer multi-polymer board.
U.S. Pat. No. 7,782,251, “Mobile millimeter wave imaging radar system” introduces a short range complex millimeter wave imaging radar system, having scanned Tx and Rx antennae.
U.S. Pat. No. 4,929,958, “High precision radar detection system and method” describes the systems with four transducers to accurately determine the azimuth angle of a radar emitting object.
U.S. Pat. No. 8,779,969, “Radar device for detecting azimuth of target” by Denso, describes azimuth detection by analyzing echoes by spectrum performance, excited by frequency ramped signal, mixed by the excitation signal.
U.S. Pat. No. 5,657,027, “A Two dimensional interferometer array”, treats two dimensional problem approach using 4 receiving channels and specific digital processing.
U.S. Pat. No. 6,736,231, “Vehicular occupant motion detection system using radar” introduces ultrasonic radar approach for determining seat occupancy by detecting the vital signs information. Its “radar” based system has two physically separated receivers of reflected ultrasound signals, and two units for further processing.
This invention proposed apparatus 100 and method of operation for distance detection for various applications allowing detecting distances from 0 cm up to more than 10 meters.
The key system relevant components of the proposed apparatus 100 are:
The proposed system combines operation in FMCW and CW Mode. In the state of art non-military radar sensors for distance detection FMCW operation mode is used. This operation mode is especially used and widely deployed for the long range radar automotive system, covering the distances in the 300 m range. There is a strong attempt to used existing long range SoC RF functionalities for detecting distances below 20 cm. This is however hardly possible using FMCW operation mode.
In this innovation we are proposing, changing functional topology of the FMCW analog part with specific analog functionality, and introducing the new operation mode, where FMCW radar operation is switched off to the single frequency CW operations. The complete system observes the detected distances by FMCW operation and incoming power on at least one Rx input in RF SOC. After specific threshold distance L, is achieved, the complete Apparatus 100, is switching to the single frequency CW operation mode. That means the millimeter-wave radar with integrated front end on silicon 10, System on Chip, does not produce frequency ramps, it is starting to produce radiation on only one frequency. The threshold distance L is chosen after empirical evaluation of the sensor application scenario, which imposes the position of the sensor in the environment.
For example in automotive related preferable application for the proposed invention for parking assistance, the aim is to replace the commonly used ultra sound systems by miniature and low cost radar sensors. Radar sensor are integrated in the bumper, or integrated in the lighting systems or in the automotive enclosure. Tx and Rx antennas of the radar system are having specific radiation diagrams. The specific threshold distance L can be set to the value lower than 50 cm, meaning that for distances below 50 cm, the distance is calculated by using primarily set of the polynomial coefficients in the polynomial equations having as unknown information the power of the signal being detected on the Rx input inside of the entity 10, where CW mode is active. The set of the polynomial coefficients are preset by the empirical evaluation of the sensor position and it's actual application. The numbers of the polynomial coefficients are chosen to be minimal by respecting calculation effort from one side and tolerances in mechanical enclosures, which are influencing accuracy just in case as the accuracy in RX power level acquisition. They typical application solution for parking sensor, aiming replacement of the ultrasound systems is proposed, by prosing 2N radiation elements antenna, where N can takes values from 1, 2, 4 or 8, being chosen to provide in elevation area narrow beam to minimize the reflections from driving surface, and in the same time to have wide angle range in azimuth, being explicitly wider as in elevation.
The digital part typically includes CAN and/or LIN interface allowing easy connection to the vehicle infrastructure. The means of short range wireless connection to the vehicle system 63 is optional and suited for the aftermarket usage. In aftermarket mode the proposed apparatus may have integrated audio and/or visual indicators.
Apparatus 100 is preferably integrated in the vehicle bumper being invisible, having line-of-sight towards the possible obstacles, in front of bumper. The basic generalized purpose of the proposed innovative approach is to provide the measurements of the distance from the sensor to the object. In proposed HW topology of the integrated mm-wave SOC, we are proposing introduction of the entity 70 addressing RF power coupling and RF power detecting, being realized by the plurality of the realization active and passive circuit topologies directly on the integrated RF IC SOC 10. The detail of the Entity 70, is shown in the
The state of art automotive FMCW radar sensor, which are realized in 77-81 GHz and which are addressing long range ADAS application, may work as close as 20-30 cm to the object. The minimum detection distance is related to the several constrains: FMCW principle, scattering performance of the objects which are highly complex where the distance to the object is close to the object dimensions, and system noise, due to small beat frequency. On the other hand parking sensor applications required the distance measurements below 30 cm typically up to 1-2 cm distance. So therefore we are proposing switching from FMCW mode operation to the single frequency CW operation mode, where the obstacles are close to sensor, as in typical parking application case.
Let us observe following parking sensor application case, being related to the preferable Apparatus embodiment presented in the
G1 [dBi] TX Antenna Gain inside bumper: 12
G2 [dBi]: RX Antenna Gain inside bumper 12
f [GHz]: 60
RAT [dB]: Losses 7 dB in bumper one way 7
P1 [dBm]: Power fed to Tx antenna after connection losses 8
We are noticing that the EIRP in above case is complying with ISM Band a worldwide regulation EIRP limits for 57-64 GHz operations.
And let us have a typical parking application case where another vehicle, or parking facility wall is close to bumper at 30 cm or less, as it is show in
Having this in mind we are introducing polynomial function, which relates detected power at receiver antenna (Prx) and distance to the target (R)
R=f(Prx)
This function maps as a close practical approximation the RX power to the detected distance in the following way:
R=A(PRx)̂(½)+B(PRx)̂(¼)+C
R— distance
Prx=power at the receiving antenna
A,B,C—calculated coefficients to get f
The polynomial coefficients are set after 3D electromagnetic simulations for specific bumper, material, specific vehicle, and specific antenna are conducted, for the set of the key, for practical application relevant, use cases.
After having sets of the parameters, two approaches are proposed:
These coefficients are that in the process of the empirical tuning for each specific vehicles fine-tuned, and provided for the each sensor look up table.
Taking into account proposed 60 GHz ISM band operation, or alternatively 77-79 GHz operation, and 4× antenna elements for 21 and 22, the approximate size of the device may be less than 2×2×0.5 cm, which would inherently allow practical use and integration capability in vehicles or in the industrial embodiment.
The entity 10 is preferably realized using SiGe BiCMOS technology that provides high performance. Alternatively CMOS technology may be used.
AD (analog to digital) conversion functionality 30 converts the analog conditioned signal or two quadrature signals, I and Q, of the entity 10, and feeds digital representation of signal or signals to the Digital processing functionality 40 for further processing. Entity 30 is realized by plurality of the realization options, with sampling frequency typically under 1 MHz and typically at least 8 bit resolution. Entity 30 may be integrated on the same chip as Entity 10. Entity 30 may be integrated on the same chip as Entity 40. Entities 40, 10, and 30 may be all integrated on a single chip. Entity 60 is providing interface to vehicle infrastructure by using typical vehicle wired interfaces like CAN interface 61, and/or LIN interface 62, optional custom digital interface 64, and optional short range wireless interface 63. Standard interface, preferably CAN, is obligatory for all applications where the apparatus is integrated in vehicle during manufacturing. For aftermarket applications the short range wireless interface, preferable Bluetooth, may be integrated in entity 60. Supporting circuitry 50 optionally includes additional memory, manual switching, power supply regulation circuitry, mechanical support, and any additional functionality required for easy integration, during manufacturing or later in aftermarket. The mechanical support structure for integration of all functionality is preferably provided using advanced polymer technologies. Optionally, in case of the aftermarket operation, entity 50 may also include battery, loudspeaker or warning light sources, allowing autonomous operation.
Digital processing functionality 40 may be realized by the plurality of technologies, such as: advanced CPUs, FPGAs, advanced μC, DSP, or ASIC, or their combinations, where the digital processing may be performed by “soft” approach or by hard-wired approach or by their combination. Preferably functionalities 60 and 40 are integrated on a simple ASIC, having CPU on one digital SOC. Digital processing functionality 40 includes functionalities 41.
In
The Tx and Rx antenna systems are preferably realized as the planar printed dipoles with ellipsoid-like antenna shapes, with the two parts printed on opposite sides of the dielectric layer, which also provides mechanical support. Prints on the opposite side of the dielectric area are depicted using dashed lines. Preferred antenna elements are fed by symmetrical strip lines. On the bottom of the Apparatus 100 the metalized reflector is introduced allowing radiation perpendicular to the printed antenna area. Symmetrical strip line may be advantageously connected to differential mm-wave inputs and outputs of the entity 10 by using metalized micro-vias produced by advanced polymer technology.
As preferred embodiment realization solution proposed Apparatus 100 is realized using polymer technology, without PCB structures.
The proposed apparatus 100, and its sub-system entity 10, can have optional functionality for direction of arrival detection also using CW operation mode. In that case for example, before reaching L switch value, azimuth angle toward the obstacle may be detected. This information in conjunction by approaching the switch value L, for switching from FMCW mode to CW mode, can be used to use the changed sets of the coefficients: A B, C, deepening of the detected angle of arrival. In praxis that means, if the vehicle which is parking toward the obstacle being in the azimuth specific angle, which is not perpendicular to the sensor, come close to the obstacle, toward the switch value L, that means that the obstacle is thin, and portion of the detecting receiving power for small distances is smaller as the obstacle is approaching sensor in perpendicular mode. So the corrected set of values, as some art of the automatic system calibration is than used, being depended on the obstacle angle in azimuth.
If the Apparatus 100 has besides FMCW distance sensing functionality also direction of the arrival functionality, this may be advantageously used with simple CW detection approach proposed in this invention. Namely, if with FMCW mode at distances larger than L switch value, Apparatus 100 is detecting the distance and azimuth angle towards the obstacle, this information can be advantageously used for adjustment of the coefficients in the CW mode operation. In practical implementation, that means, if vehicle is moving towards the obstacle, and if immediately before L switch value is achieved, angle of arrival, meaning direction in azimuth towards obstacle, is detected being different as being perpendicular to the sensor, that means the obstacle is thin, and the level of the detected Rx power in the CW mode operation will be smaller, compared to the perpendicular case. In that case changed set of the coefficients: A, B, and C will be applied for distance calculation, for values being smaller than L switch value. Set of the coefficients: A, B, and C are advantageously provided in the look up table for the ranges of the angle toward the obstacle. Those ranges and set of coefficients A, B, and C, are empirically set for the specific vehicle.
