Patent Application
20080088432
These and other features, aspects, and advantages of the present invention will become better understood with regard to the following description, appended claims, and accompanying drawings wherein:
A method for implementing an embodiment of the present invention, as shown in
In the case where noise is detected, the frequency of the noise is determined in step 105. This noise frequency is directly representative of fluorescent light flicker frequency (RF). The flicker frequency (RF) is compared in step 107 to a transmit rate (RT) stored in a memory means. The transmit rate (RT) is a rate, or frequency, at which an interrogator pulse is emitted by a transceiver means. The transceiver means may be a Microwave transceiver or other such detection device that may be affected by fluorescent light. If the flicker frequency (RF) is equal to the stored transmit rate (RT), the process advances to step 113, where the transceiver means is directed to transmit an interrogator pulse at the stored transmit rate (RT).
However, in the event that the flicker frequency (RF) does not equal the stored transmit rate (RT), the transmit rate (RT) is synchronized to the flicker frequency (RF) in step 109 and the new transmit rate (RT) is stored in a memory means in step 111. Subsequently, the process continues to step 113, where the transceiver means is directed to transmit an interrogator pulse at the newly synchronized transmit rate (RT).
Referring back to step 103, in the case where no noise is detected above the predefined threshold, the process advances from step 103 to step 115, where a default transmit rate (RT) is set and stored in the memory means. Subsequently, in step 113 the transceiver means is directed to transmit an interrogator pulse at the default transmit rate (RT), which may be a rate of 50 HZ, 60 Hz, or any other appropriate frequency. The interrogator pulse interrogates, or scans, the monitored area for indications of an intrusion.
This process may be configured to continuously monitor the ambient noise conditions of the environment in which the detector is situated. In this way, when changes occur, such as a fluorescent light being turned on or off, the transceiver can be properly adjusted to compensate for the noise.
Referring to
A synchronization means 208, receives the filtered signal from the filtering means 206. The synchronization means 208 determines the frequency of the filtered signal, thus determining the flicker rate of the fluorescent light, and adjusts the transmission timing of the transceiver 210 to match the flicker rate.
The transceiver means 210 transmits an interrogator signal at a microwave frequency in sync with the flicker of the fluorescent light. There are several microwave frequencies including approximately 24 GHz, 10.2 GHZ, and 2.4 GHZ that may be utilized as an interrogator signal. In this way, the return signal reflected by the gas of the fluorescent light will not register as an intrusion, because the intrusion detector 200 would not detect any relative motion.
In addition, the intrusion detector 200 is powered by DC or AC voltage transmitted over wiring 214 running between the intrusion detector 200 and a security system controller (not shown), or DC voltage produced from an internally housed battery or other power generation device, such as a solar cell. A data line 212 is provided as well, connecting the intrusion detector 200 with the security system controller. While the data line 212 may be provided as wiring, alternatively the data line 212 may be a wireless transmission unit.
In an embodiment of the present invention, as shown in
The high gain amplifier 308 amplifies the AC signal and relays the amplified signal to the bandpass filter 310. The bandpass filter 310 is adapted to filter either the 100 Hz or 120 Hz second harmonics from the amplified signal. However, a preferred bandpass filter would have a center frequency of 110 Hz, thus allowing the bandpass filter to filter both 100 Hz and 120 Hz second harmonics adequately. Other center frequencies may be used, as well, depending on the specific situation.
The filtered second harmonics are passed to a squaring amplifier 312, which receives the sinusoidal waveform of the second harmonics and outputs a corresponding square-wave signal. The output square-wave signal is provided to a micro-controller 314 as a control signal input used to provide the synchronization timing for a motion detection system. This apparatus would essentially provide a 5′ antenna at a minimum—longer in most cases—having a 1K minimum impedance to ground. However, switching noise and test signals originating from the security system control panel must be regulated to reduce interference.
Alternatively, in
Since AC power lines emit electromagnetic noise into the surrounding environment at a frequency equal to the AC line frequency, detecting this electromagnetic line noise would allow a determination of the line frequency of the power being provided to fluorescent light fixtures. The AC line frequency, which in the U.S. is set to 60 Hz, is directly linked to the flicker rate of the fluorescent light.
Further, the flicker rate can be detected directly using a light emitting diode (LED) or photo diode, as shown in
As shown in
As in the previous embodiments of the detector means, the bandpass filter 506 filters the amplified noise signal and the second harmonics of the noise signal are output to the squaring amplifier 508. The squaring amplifier 508 receives the sinusoidal waveform of the second harmonics and outputs a corresponding square-wave signal. The output square-wave signal is provided to a micro-controller 510 as a control signal input used to provide the synchronization timing for a motion detection system.
Furthermore,
The advantage of using the noise off the Microwave channel is that if not enough noise is present to be detected, then there would not be enough noise to cause a problem for the intrusion detector. If this method were used, a soft synchronizing scheme would preferably be used, allowing the sample rate to be changed slowly. This is to prevent normal walking activities causing false triggering, because certain walking speeds will generate legitimate signals around 100 and 120 Hz.
Any of the above-described detector system may be incorporated into the assembly described in
