Automatic impedance matching using resistive and reactive diodes

Claim 1

An automatic impedance matching device for isolating opposite ports of a four port hybrid, the four ports being designated the transmitter, antenna, receiver and load ports, comprising: first sampling means for providing a first sample of an input signal prior to the signals introduction into the transmitter port of the hybrid; first power splitting means, electrically coupled to said first sampling means for dividing said first sampled signal into first and second reference signals having equal magnitude and a 90° phase difference as a result of said second reference signal being shifted 90° in phase; a first coherent detector, electrically coupled to said first power splitting means, and utilizing said first reference signal as a reference; a second coherent detector, electrically coupled to said first power splitting means, and utilizing said second reference signal as a reference; second sampling means for sampling a mismatch signal at the receiver port of the four port hybrid; second power splitting means, having an input and two outputs, the input of which is coupled to said second sampling means and the outputs of which are coupled to said first and second coherent detectors, the function of said second power splitting means being to provide two output signals of equal magnitude having the same phase as the sampled mismatch signal from said second sampling means; and a variable impedance which terminates the load port of the four port hybrid having a variable reactance portion, the value of the reactance portion being a function of the output of the second coherent detector and the value of the resistance portion being a function of the output of the first coherent detector.