Incoherent demodulator and method of incoherently demodulating an IF signal

摘要

A demodulator includes a pair of analog mixers for incoherently demodulating modulated orthogonal signals with orthogonal local carriers to produce a pair of analog baseband signals, there being a phase rotation in the analog orthogonal baseband signals resulting from the incoherent demodulation. The analog baseband signals are converted to first and second digital signals. One of these is scaled by a gain controlled circuitry so that a difference between the average power values of the scaled first digital signal and the second digital signal is zero. The inter-channel rotating phase contained in the outputs of the gain controlled circuitry is removed by a phase shifter. The gain controlled circuitry may include a digital multiplier for multiplying the first digital signal with a control signal to produce a scaled first digital signal, averaging circuits for producing a first average value representing the average power of the scaled first digital signal and a second average value representing the average power of the second digital signal, and a control circuit for deriving a signal from the first and second average values and supplying the signal to the digital multiplier as the aforesaid control signal so that the difference between the first and second average values reduces to zero.