Anti-burglar mini-radar

Claim 2

In an anti-intrusion Doppler effect mini-radar comprising means for generating and transmitting a pure microwave signal, means for detecting and demodulating microwave energy and coupled to receive the microwave energy transmitted by the mini-radar and to receive the microwave energy reflected towards the mini-radar, means for amplifying the Doppler frequency shift signals at the output of said detecting and demodulating means resulting from the demodulation of microwaves reflected from objects in motion, an alarm control circuit connected to receive the amplified Doppler frequency shift signals; the improvement comprising a servo-control circuit responsive to the level of signals applied to said alarm control circuit for controlling the gain of said amplifying means and a timing circuit responsive to a sudden increase in signal level in said amplifying means for blocking said servo-control circuit and inhibiting the operation of said alarm control circuit for a determined time period following said sudden increase in signal level.

Claim 3

The anti-intrusion Doppler effect mini-radar of claim 1, wherein said amplifier means comprises an automatic gain controlled preamplifier connected to receive the output of said detecting and demodulating means and having a gain control terminal connected to receive the output of said servo-control circuit, and an adjustable high gain low frequency amplifier connected to receive the output of said preamplifier, and means connecting the output of said low frequency amplifier to the input of said alarm control circuit.

Claim 4

The anti-intrusion Doppler effect mini-radar of claim 2, in which said servo-control circuit has a high time constant.

Claim 5

The anti-intrusion Doppler effect mini-radar of claim 2, wherein said timing circuit has an input connected to the output of said adjustable high gain low frequency amplifier, a first output connected to block said servo-control circuit, and a second output connected to inhibit operation of said alarm control circuit.

Claim 6

The anti-intrusion Doppler effect mini-radar of claim 2, wherein said means connecting the output of said low frequency amplifier to said alarm control circuit comprises a rejection filter tuned to a frequency of any A.C. electric energy source in the vicinity of said mini-radar.

Claim 7

A doppler effect radar system comprising, means for generating and transmitting microwave energy, means for demodulating microwave energy and coupled to receive transmitted microwave energy and microwave energy reflected back to the radar system, means coupled to the output of the demodulating means for amplifying Doppler frequency shift signals appearing at said output in response to the demodulation of microwave energy reflected from objects in motion, an alarm control circuit having input means coupled to the output of the amplifying means so as to receive the amplified Doppler frequency shift signals, a servo-control circuit having a given time constant, said servo-control circuit including an input coupled to the output of said amplifying means and an output coupled to a gain control input of said amplifying means for automatically controlling the gain thereof as a function of the signal level at the output of the amplifying means, and a timing circuit responsive to a given change in the signal level in said amplifying means for deriving first and second and second control signals for respectively blocking the operation of said servo-control circuit and inhibiting the operation of said alarm control circuit for a predetermined time period following said change in signal level.

Claim 8

A doppler effect radar system comprising, means for generating and transmitting microwave energy, means for demodulating microwave energy and coupled to receive transmitted microwave energy and microwave energy reflected back to the radar system, means coupled to the output of the demodulating means for amplifying Doppler frequency shift signals appearing at said output in response to the demodulation of microwave energy reflected from objects in motion, an alarm control circuit having input means coupled to the output of the amplifying means so as to receive the amplified Doppler frequency shift signals, a servo-control circuit having a given time constant, said servo-control circuit including an input coupled to the output of said amplifying means and an output coupled to a gain control input of said amplifying means for automatically controlling the gain thereof as a function of the signal level at the output of the amplifying means, and a timing circuit responsive to a given change in the signal level in said amplifying means for deriving first and second and second control signals for respectively blocking the operation of said servo-control circuit and inhibiting the operation of said alarm control circuit for a predetermined time period following said change in signal level.

Claim 9

A radar system as claimed in claim 6 wherein the time constant of said servo-control circuit is relatively long in relation to the time period of the Doppler frequency shift signals.

Claim 10

A radar system as claimed in claim 6 further comprising a rejection filter tuned to a frequency approximately twice the frequency of the AC supply voltage at the site of the radar system and coupled between the output of the amplifying means and the input means of the alarm control circuit.

Claim 11

A radar system as claimed in claim 6 wherein said radar system is subject to undesired transient signals capable of producing false actuation of the alarm-control circuit, and said timing circuit is responsive to a transient signal and includes means for deriving said first and second control signals with a time period that is longer than the expected time period of said transient signal.