Abstract: For measuring the group delay of amplitude modulated transmitters a variable measurement frequency is modulated by a fixed frequency so as to obtain the sum and difference frequencies which are sent to the input of the transmitter under test; the two waves corresponding to the same side-band are obtained at the transmitter output, are frequency shifted, filtered and detected to give their beat, filtered again to obtain only the beat at a frequency twice the modulation frequency; and said beat is compared with a signal of the frequency but coherent with the modulating signal, the comparison providing a direct voltage component which is a linear function of the group delay of the side-band corresponding to the measurement frequency. The invention also concerns the apparatus for realizing the method, comprising also the known units allowing to measure the amplitude of each side band.

Abstract: A matching coupler in an antenna system to power transfer in matching characteristic impedance of an antenna and a transmission line using a ganged variable capacitance with a resonate coil and another variable capacitance in series with a transmission line and an antenna.

Abstract: Prior art circuits used in space diversity systems for combining the two received signals employ either continuously variable phase shifters, which have return-to-zero problems, or 90 degree phase steppers which combine the signals to within .+-.45 degrees. Both of these limitations are avoided by the use of the combination of a continuously variable phase shifter (14) and a 90 degree phase stepper (13). Control means (19, 20) are provided for actuating the stepper when the phase shift introduced by the variable phase shifter reaches a prescribed limit.