United States of America as Represented by the Secretary of the Air Force

J Leon Poirier

Peter R Franchi

Nicholas V Karas

Walter Rotman

Ronald L Fante

Arthur D Yaghjian

Livio D Poles

Kotcherlakota V Rao

Robert V McGahan

Frederick S Holt

Philipp Blacksmith

A reflector antenna having an adaptive nulling assembly. The assembly comprises a disk shaped mounting plate having a shaft aligned with the rotational axis thereof and passing through the main reflector focusing surface. An absorber of electromagnetic energy is affixed to the disk and a microwave grating of metallic elements is positioned on the surface of the absorber. The amplitude of the nulling signal is controlled by rotating the assembly, and the phase of the nulling signal is controlled by the varying height of the grating above the reflector. Additional nulling elements can be used to null multiple interference sources.

Reflector antenna having sidelobe nulling assembly with metallic gratings

Target support structure for making bistatic radar cross section measurements. The support structure includes two parallel columns of circular cross section that may be coated with radar absorbing material. The rotational angle of the columns and the spacing therebetween are each adjustable to allow the bistatic reflections from each column to be phased to cancel each other at a selected bistatic angle and thereby minimize the background signal from the support structure.

Target support apparatus

Apparatus for measuring the near-field radiation of an antenna such that its far-field radiation characteristics can be determined. The invention utilizes the principle of the Foucault pendulum. It uses a bob attached to a long pendulum arm that is free to rotate. Rotation of the earth causes an apparent rotation of the swing plane of the pendulum with a period of T=24/sin (latitude). By attaching a field sensing probe to the pendulum bob and mounting the antenna under the Foucault pendulum, the entire antenna aperture can be scanned without moving the antenna. The motion of the probe covers part of an external sphere centered at the pivot point of the pendulum and having a radius equal to the length of the pendulum. Appropriate transformation of the measured near-field data gives the far-field radiation pattern.

Apparatus for scanning and measuring the near-field radiation of an

Uniform detection sensitivity along the periphery of an r.f. loop intruder detector system is realized by periodically electronically interchanging the input and termination ends of the system's leaky transmission line transmitting element. The intruder detector system comprises a length of leaky transmission line that encompasses the region to be protected, a receiving antenna within the protected region, an r.f. transmitter and a remotely located receiver and detector. R.F. energy is transmitted through the leaky transmission line and received by the receiving antenna and detector means to establish a normally quiescent field. Violation of the protected region by crossing the leaky transmission line disturbs the quiescent field condition and the intrusion event and the location is signaled by the detector. The effects of attenuation along the leaky transmission line are obviated by periodically switching the transmitter to alternate leaky transmission line ends. Switching of the transmitters is accomplished by solid state, mechanical, r.f. and other switching means.

Intruder detector system having improved uniformity of detection

The intrusion detection capability of a guided wave radar intrusion detection system is selectively disabled in certain areas, such as gates or portals to permit ingress and egress of personnel and vehicles without affecting overall system performance and without requiring an independent detection system. This is realized by means of an integral system portal enable-disable device. Guided wave radar intrusion detection systems employ two parallel leaky transmission lines, one transmitting and the other receiving radar signals. Violation of the area between the leaky transmission lines by an intruder results in a signal that indicates the occurrence and its location. Gate areas are remotely enabled or disabled by a switching circuit that switches a segment of non-radiating transmission line into or out of the transmitting leaky transmission line in each selected gate region.

Integral enable-disable means for guided wave radar intrusion detector

The detection, location and tracking of an intruder in an area to be protected is accomplished by dividing the area into a multiplicity of discrete regions, transmitting r.f. signals from transmitting transducers that comprise lengths of transmission lines deployed along the boundaries of the discrete regions, and receiving intrusion occurrence signals from receiving transducers located within each region. Violation of a boundary by an intruder results in an intrusion signal from the receiving transducers of as many as four possible adjacent regions thereby indicating an intrusion event. A coincidence logic circuit indicates which boundary has been violated. Intrusion occurrence signals are stored for suitable periods of time while past and current intrusion events are indicated on a display in order to locate and track intruders.

R F Area intruder detection and tracking system

An RF intruder system utilizes two concentric loops of wire spaced apart for a predetermined magnitude, either of which can transmit and/or receive electromagnetic energy. This area within the loops are to be protected against intrusion. Without intrusion, the received signal is steady. Upon intrusion, there are signal changes which are instantly noted by signal detection and processing.

RF loop intruder detection system

A radar intrusion detection system for isolated resources uses only one bistatic radar in combination with multiple passive reflectors to define the zone to be protected. Any intruder crossing a boundary of the zone within which is located the isolated resources interrupts the radar beam and thus may sound an alarm.

Growing community of inventors

Chelmsford, MA, United States of America

J Leon Poirier