Abstract: An adaptive interference canceller for use in a dual polarized radar system for receiving cross-polar and like-polar signals and generating an output signal corresponding to the received cross-polar signal with a like-polar interfering component cancelled therefrom. A modified adaptive filter is provided with a self-adjusting impulse response conforming to a least means square adjustment cancelling the influence of the like-polar signal, which is generally much stronger on the cross-point signal. The resulting output has a high target-to-clutter ratio and therefor a high probability of detection.

Abstract: A radar arrangement which is particularly useful for the terrain following radar of an aircraft avoids disturbances from rain echoes by utilizing an antenna arrangement with a transmitting/receving directional antenna which is circularly polarized. A supplementary receiving antenna of orthogonally-circularly polarized type is used in conjunction with the directional antenna. From a comparison of the signal level distinctions is made between a target and a rain echo. The rain echo can thus be suppressed to give a truer target signal.

Abstract: A radar apparatus transmits right circular polarized signals and selects the right circular polarized components of the corresponding returns. It also transmits left circular polarized signals and selects the left circular polarized components of the corresponding returns. The selected left and right circular polarized compoments are processed by, for example, averaging them, producing a weighted average of them, or selecting the component of larger value.

Abstract: The radar is designed to identify and then eliminate rain clutter signals. For this, the radar works in circular polarization with alternately identical and opposite polarization directions at transmission and reception, from one recurrence to the next one. The signals are identified by a comparator which compares the sigma video signals relating to the same distance quanta for two successive recurrences, the identifying criterion being a major difference in the level of the signals compared, for rain clutter signals, and little difference for useful echo signals. A switch controlled by the comparator eliminates the parasite signals.

Abstract: A radar transceiver is disclosed which operates with circularly polarized waveforms. A single circularly polarized antenna is used to transmit and receive circularly polarized waveforms. A 3-dB directional coupler splits the signal to be transmitted into two signals 90.degree. out-of-phase for transmission by the antenna and also combines the horizontal and vertical components of any return signal.

Abstract: A controllable dual input/output port power divider coupled with a controllable phase shifter feed a dual ported dual polarized microstrip antenna structure. By controlling the power divider and phase shifter, arbitrary orthogonal polarization (e.g., linear, circular or elliptical) radiated r.f. fields are obtained. Virtually the entire structure comprising the dual port power divider, phase shifter and microstrip radiator may be formed of shaped photo-chemically etched microstrip conductors disposed a very short distance (e.g., less than one-tenth wavelength) above a conductive reference surface.

Abstract: A reduced size and weight beam forming network for a circularly polarized N element array antenna system is achieved by interconnecting quadrature couplers without intermediate phase shifters and adding twisted waveguide phase shifters at the coupler outputs to equalize the phase at the array elements.

Abstract: A leaky-feeder or other form of guided radiocommunication system serving a linear route or track is equipped at intervals with static marker devices which successively modify a radio signal passing those points between a fixed base station and a personal or mobile station travelling the route. By reference to the resulting overall modification to the signal as received at the mobile or fixed station the position of the mobile station may be determined or delimited.