Single-port weighting systems are shown for applying phase and/or amplitude weights to received signals. One system embodiment includes an array of antenna elements, a microwave power combiner, a plurality of microwave structures and a single microwave downconverter that is coupled to the power combiner and has a single output port for access to the received signals. Each of the microwave structures couple first and second signal paths between a respective one of the antenna elements and the power combiner, insert a phase shift in one of the first and second signal paths and insert first and second mixers respectively in the first and second signal paths wherein the mixers each have an input port for application of the weights.

Single-port weighting systems for GPS reception in multiple-interference environments

The invention relates to apparatus for reducing the masking effect in the doppler frequency domain of wind sheared clutter upon the radar returns of moving targets. The invention consists in forming two beams from the elements of a radar antenna array by means of adjustable complex weights which are then summed. One of the two beams is then delayed by a predetermined amount and added algebraically to the other beam to form a composite beam containing a narrow trough-like depression in beam angle/doppler frequency space. Means are then provided for adjusting the weights to bring coincidence between the depression and the clutter to cause attenuation of the clutter with a minimum reduction in the usable doppler frequency domain.

Apparatus for wind shear compensation in an MTI radar system

A displaced-phase-center antenna technique which compensates accurately forhe motion of an airborne radar system in both the boresight direction of the antenna and in the direction normal to the boresight. An antenna system comprising a broadside array of endfire arrays forms four receive beams which are displaced from each other in both the boresight direction and in the direction normal to the boresight. These four beams are used to produce signals which correspond to signals from two receive beams with phase centers having a separation equal in magnitude and direction to the aircraft's motion during the interpulse period. A signal scattered from a fixed object on a first transmitted pulse and received in one of the two receive beams will have the same phase characteristic as a signal scattered from the same fixed object on a subsequent pulse and received in the other receive beam. Upon proper delay of the first received signal, the returns from the fixed object may be cancelled.

Two-axis motion compensation for AMTI

A method and apparatus for removing the effects of radar platform movement and for otherwise processing doppler radar signals in a moving target indicator doppler radar in which targets in the main beam having reflective characteristics sufficient to override side lobe attenuation are tracked relative to the side lobes and the residual doppler frequency for such targets resulting from side lobe detection calculated. Based on this calculation, the appropriate ones of a bank of doppler filters are inhibited at the appropriate range bin to prevent a false target indication without inhibiting the display of moving targets in the main beam at the same range but having different doppler frequencies. A novel automatic gain control circuit which provides dynamic amplitude adjustment of the radar return signal to match the dynamic range of the radar processor on a range bin-by range bin basis is also provided as is a novel signal processing circuit for removing the effects of radar platform movement from the radar return signal. The use of a sensitivity time control is disclosed as is the method of vector rotation and quadrant resolution.

MTI System processor and method

In a continuous wave Doppler system in which a fixed transmitter transmits a continuous wave signal to be reflected by moving targets and by fixed structure, an aircraft receives the reflective signals at two spaced apart antennas. The signals reflected from moving targets are distinguished from ground clutter reflected from fixed structure by the phase difference between the Doppler signals receive by the two antennas. The signals reflected from moving targets are distinguished from the ground clutter in response to the phase difference between the Doppler signals received by the two antennas being not equal to a phase difference value determined to be the phase difference for clutter signals. The phase difference value for clutter signals is determined from a function expressing the phase difference value as a linear variation with the Doppler frequency of the signals.

Continuous wave doppler system with suppression of ground clutter

Platform motion of an airborne radar system of the moving target indicator type is compensated for by an adaptive displaced phase center antenna arrangement. The signals detected by the two receiving beams are combined to form sum and difference signals. Thereafter, the sum signals have subtracted therefrom delayed sum, difference and delay difference signals which are weighted by coefficients determined by cross-correlating these signals and the output signal obtained from the above subtraction. The system thus combines the DPCA and the side lobe cancellation concept to eliminate signals received from stationary targets. The receiving beams may be squinted to compensate for antenna rotation.

Applebaum S

Papers

Platform motion compensating for airborne radars