US 3,947,834 A · Doppler perimeter intrusion alarm system using a leaky waveguide

Abstract

A flexible line distributed antenna, defining a perimeter of interest, radiates energy supplied from a transceiver. Motion around the flexible line causes the reflected energy which is intercepted by the flexible distributed antenna to be coupled back to the transceiver as a doppler frequency for processing in an alarm system. Reflected energy from the antenna to the transceiver is amplified and rectified into a DC voltage. This DC voltage is integrated to produce a time varying signal to a level detector that responds to a predetermined value of the integrated DC voltage. A response by the level detector provides an actuating signal to an alarm indicator through alarm logic. Ambient conditions around the extended flexible line distributed antenna are monitored by external sensors having outputs for controlling amplifier gain and triggering the alarm logic. For improved motion detection reliability, reflected energy from the antenna is coupled to a transceiver providing two output signals. These two output signals are processed separately for coupling to a voltage comparator driving an alarm indicator through alarm logic.

Claims28

Dependent claims

An antenna for use with a system for detecting motion through a perimeter, comprising in combination:

a center conductor extending to define a perimeter of interest and having one end arranged to be connected to the motion detecting system and energized by an excitation frequency;
and
an outer conductor coaxially spaced with respect to the center conductor,
said outer conductor including a plurality of groups of radiation slots to expose the center conductor and thereby enhance radiation along the outer conductor,
the groups spaced along the outer conductor at distances related to the excitation frequency of the motion detecting system.

2 more elements

A quadrature perimeter intrusion alarm system, comprising in combination:

a line antenna extending to define a perimeter of interest;
a transceiver for coupling energy to said antenna and receiving energy therefrom to generate first and second doppler frequency signals;
phase shift means responsive to one of said doppler frequency signals to shift the phase thereof relative to the second doppler frequency and having a phase shifted doppler frequency signal output;
means for summing the phase shifted doppler frequency signal with the second doppler frequency signal to provide an approach signal;
means for differentially combining the phase shifted doppler frequency signal and the second doppler frequency signal to provide a recede signal;
and
alarm means actuated by a difference between the approach signal and the recede signal greater than a predetermined magnitude.

4 more elements

Dependencies are inferred from the claim text.

Doppler perimeter intrusion alarm system using a leaky waveguide

Life of this patent

Doppler perimeter intrusion alarm system using a leaky waveguide

Life of this patent

Abstract

Claims28