Abstract: A secondary radar uses monopulse reception techniques to improve the estimate of the aircraft position and to improve the reliability of the reply decoding process. Digital signal processing techniques are utilized to replace the analog circuit used in the prior implementations. The secondary radar implements monopulse processing using a half angle phase method wherein the sum and difference signals are encoded in a complete phasor. The detection of the signal and extraction of the azimuth angle data is implemented using a digital receiver concept. The complex phasor is sampled at an intermediate frequency, down converted to baseband and detected. The azimuth angle is computed using arithmetic methods implemented by digital signal processing circuitry.

Abstract: A high power amplifier combiner for improving the linearity of an output of an amplifier. At least two prelinearizers are used to suppress all distortion products by using feedforward cancelling techniques. The effects of compression associated with the operation of the high power amplifier are reduced.

Abstract: A monitor signal injection system for a feedforward cancellation amplifier having at least one stage in which monitor signals having a constant relatively large amplitude are injected into, for example, a main amplifier. The monitor signals are used to measure the status of all individual components of the amplifier and are useful for fault detection and isolation. In addition, the monitor signals are cancelled in the output to a very low level and as a result, on-line monitoring can be performed without significant radiation of power from a load antenna.

Abstract: A gain compensating circuit for a feedforward cancellation amplifier which compensates inbalance (i.e., changes in gain of the power bank amplifier) due to changes in operating conditions or failures in various circuits in the amplifier. The gain compensating circuit compensates the gain variations and restores balance and fundamental cancellation to the circuit while retaining the highly linear characteristics of the amplifier.

Abstract: An active phase and amplitude modulator separates an input carrier into four phases. The phases are amplified and modulated separately. Summing circuits combine the phases into a single resultant output.

Abstract: An improved feedforward cancellation amplifier is disclosed, characterized by the arrangement of an adaptive cancellation modulator for each fundamental input signal at the input of a power bank amplifier. With such an arrangement, phase and amplitude modulation for adaptive cancellation of each fundamental signal is performed in the power amplification path of the feedforward canceller. Accordingly, the harmonics produced by the modulators for each fundamental signal are cancelled in the output of the power bank amplifier and the signal levels at the input to the power bank amplifier are less than those in the input sample path of the canceller.