Microwave intrusion or movement detectors

• US 4,195,289 A
• Filed: 01/31/1978
• Issued: 03/25/1980
• Est. Priority Date: 12/03/1975
• Status: Expired due to Term

• Current Assignee: Vision Systems Ltd. (Danaher Corporation)
• Original Assignee: IEI Proprietary Limited
• Inventors: Cole, Martin T.
• Primary Examiner(s): Caldwell, Sr., John W.
• Assistant Examiner(s): Nowicki, Joseph E.
• Application Number:
  US05/873,922
• Time in Patent Office: 784 Days
• Field of Search: 340/554, 343/5 PD, 343/7.7, 343/702, 343/772, 343/773, 343/774, 343/778, 343/781 R, 343/786
• US Class Current: 340/554
• CPC Class Codes: G01S 13/56 for presence detection presence detection using near field arrangements G01V3/00, e.g. G01V3/08, G01V3/12; burglar, theft or intruder alarms with electrical actuation G08B13/22 - G08B13/26

Abstract

A microwave movement detector which is capable of discriminating between progressive or unidirectional movement such as that by an unauthorized intruder and reciprocating movement such as by a curtain. The detector includes a pair of receiver/mixer diodes into which a transmitted signal is mixed with a surveying signal causing a phase difference so that the resultant signals have a different phase relationship amplifying the resultant signals feeding the signal into an integrating circuit in similar counter so that an alarm is sounded when the counter reaches a high or low threshold level.

Claims

1. A microwave movement detector, comprising:

a transmitter for generating and radiating a microwave signal;

a microwave receiver for detecting reflected surveying signals from said transmitter;

a microwave transmission means for coupling a reference signal from said transmitter to said microwave receiver;

said microwave receiver comprises;

a waveguide;

a plurality of receiving/mixing means producing outputs which are a function of said reference signal and said reflected surveying signal, each of said receiving/mixing means positioned within said waveguide for creating a unique phase delay between said reference signal and said reflected surveying signal;

phase comparison means responsive to each of said receiving/mixing devices for creating first and second level signals as a function of the relative phase delay between the outputs of said receiving/mixing means;

a counter means for counting in a first direction in response to signals of said first level from said phase comparing means and in a second direction in response to signals of said second level from said phase comparing means; and

means to produce an alarm when said counter exceeds a predetermined upper or lower count.

2. An apparatus as defined in claim 1 wherein said microwave transmission means is coupled to said waveguide at a position which will cause said reference signals to be received by all of said receiving/mixing means in common phase relationship.

3. An apparatus as defined in claim 1, further comprising:

first and second amplifier means for increasing the amplitude of the outputs of said receiving/mixing means and coupling said amplitude increased signals to said phase comparator.

4. An apparatus as defined in claim 1 wherein said receiving/mixing means are diode detectors.

5. An apparatus as defined in claim 1 wherein said waveguide is a hollow member having conductive inner surfaces having a cross section dimension which is a function of the wavelength of the frequency of said transmitter.

6. An apparatus as defined in claim 1 wherein said waveguide is rectangular in cross section.