Differential doppler detection for rf intruder alarm systems
阅读：221发布：2023-05-04
专利汇可以提供Differential doppler detection for rf intruder alarm systems专利检索，专利查询，专利分析的服务。并且An intruder detection system in which an RF transmitter is connected through a length of transmission line to a transmit/receive antenna, both transmitter and antenna are matched to the line. Diode detectors are connected in opposite directions to the line at points spaced a quarter wave length apart. The diodes connect through low-pass filters to the balanced inputs of an AC coupled amplifier which extracts the doppler sine wave from the oppositely traveling transmitted and received waves on the line. The doppler sine wave is squared and the pulses are integrated to trigger an alarm. A band pass filter is so positioned in the line to reduce false alarms by defining a specific radio frequency bandwidth and also allows the detectors to be used to time the transmitter oscillator.，下面是Differential doppler detection for rf intruder alarm systems专利的具体信息内容。
1. A method for detecting an intruder moving within a given area under surveillance with a system which includes an alarm indicator, a transmitter, an antenna, and a feed line connecting said transmitter with said antenna; said method comprising the steps of: transmitting electromagnetic energy along said line from said transmitter to said antenna; radiating said transmitted energy from said antenna and into said area; receiving at said antenna said radiated energy as reflected by objects within said area, and propagating said received energy along said line toward said transmitter; sampling doppler frequency components of the resultant of the oppositely traveling transmitted and received energy on said line at points spaced apart by one-quarter of the wave length of said electromagnetic energy to extract doppler signal information from the energy reflected from said moving intruder; differentially combining the energy sampled by said elements to produce said doppler signal; and actuating said alarm indicator in response to said doppler signal.
2. In an intrusion alarm system operative to produce an alarm in response to the presence, within a given area, of a moving intruder; said system having an alarm indicator, a transmitter for generating electromagnetic energy of a given radio frequency, an antenna for radiating said energy throughout said area and for receiving said radiated energy as reflected by objects within said area, a feed line connecting the output of said transmitter with said antenna, and means for extracting a doppler signal from the energy reflected from said moving intruder, said doppler signal extracting means comprising: means for sampling doppler frequency components of the resultant of oppositely traveling transmitted and received energy on said line; said sampling means including a pair of elements coupled to said line at points spaced apart by one-quarter of the wave length of said electromagnetic energy; means for differentially combining the energy sampled by said elements to produce said doppler signal; and means for actuating said alarm indicator in response to said doppler signal.
3. In an intrusion alarm system operative to produce an alarm in response to the presence, within a given area, of a moving intruder; said system having an alarm indicator, a transmitter for generating electromagnetic energy of a given radio frequency, an antenna for radiating said energy throughout said area and for receiving said radiated energy as reflected by objects within said area, a feed line connecting the output of said transmitter with said antenna, and means for extracting a doppler signal from the energy reflected from said moving intruder, said doppler signal extracting means comprising: a pair of detectors coupled to said line at points spaced apart by one-quarter of the wave length of said electromagnetic energy for sampling doppler frequency fluctuations in the envelope of the resultant of oppositely traveling transmitted and received energy on said line; a differential amplifier circuit having an output and a pair of inputs, one connected to each of said detectors, so as to produce a signal corresponding to said envelope fluctuations at said output; and signal processing means including a doppler band pass filter connected to the output of said amplifier, and means connected between the output of said filter and said alarm indicator for actuating said alarm indicator in response to a predetermined minimum signal from said amplifier.
4. In an intrusion alarm system operative to produce an alarm in response to the presence, within a given area, of a moving intruder; said system having an alarm indicator, means for producing a doppler signal in response to the motion of said intruder within said area, and means for actuating said alarm indicator in response to a predetermined minimum doppler signal, said doppler signal producing means comprising: a transmitter for generating electromagnetic energy of a given radio frequency, an antenna for radiating said energy throughout said area and for receiving said radiated energy as reflected by objects within said area, a feed line connecting the output of said transmitter with said antenna; said antenna being matched to the characteristic impedance of said feed line to present a matched load to signals from said transmitter, and said transmitter being matched to said impedance to present a matched load to signals from said antenna; a pair of detectors coupled to said line at points spaced apart by one-quarter of the wavelength of said electromagnetic energy; a pair of low pass filters, one connected to each of said detectors; and a differential amplifier having a pair of inputs, one AC coupled to the outputs of each of said filters, and having an output connected to said alarm indicator actuating means.
5. An intrusion alarm system according to claim 4 further comprising: a resistive pad connected between said feed line and said transmitter.
6. An intrusion alarm system according to claim 4 wherein said detectors comprise a pair of reverse connected diodes.
7. An intrusion alarm system according to claim 4 wherein the characteristic impedance of said line is 50 ohms.
8. An intrusion alarm system according to claim 4 wherein said given frequency is in the order of 915 megahertz.
9. An intrusion alarm system according to claim 4 further comprising: a band pass filter tuned to said given frequency and connected in said line at a point one-eighth of the wave length of said energy from said antenna most diode and between said antenna and the detector nearest said antenna.
10. In a transmitting system including a transmitter tunable about a given frequency, an antenna, and a transmission line connecting said transmitter with said antenna, said antenna and transmitter being matched to the characteristic impedance of said line; a transmitter tuning indicator circuit comprising: a pair of envelope detectors coupled to said line at points spaced apart by one-quarter of the wavelength of a wave on said line at said given frequency; a narrow band pass filter tuned to said given frequency and connected to said line between the antenna and the detector nearest said antenna, said filter being spaced from said antenna-most detector one-eighth of the wavelength of the signal at said given frequency; and means for differentially comparing the signals from said detector and for generating a tuning indication signal in response to the difference between said detector signals.
11. A detector circuit for producing, at the output of said detector, a small difference frequency signal from oppositely traveling waves on a transmission line, said line being terminated at each end in a load matched to the characteristic impedance of the line; said detector comprising: a pair of detector elements coupled to said line at points spaced apart by one-quarter of the wavelength of one of the waves traveling on said line; a pair of low pass filters, one connected to each of said detectors; and a differential amplifier having a pair of inputs, one AC coupled to the outputs of each of said filters; said amplifier having an output connected to the output of said detector circuit.
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