D.c. offset compensation in a radio receiver

A zero-IF radio receiver eliminates DC offset without distortion or loss of the low-frequency and DC components of the received or desired signal by initially differentiating the received signal to filter out the DC offset. The signal is amplified to a suitable level and then integrated to recapture the original DC and low frequency signal components. The integration essentially restores the filtered components to the original value in the amplified signal using an arbitrary constant of integration of bounded magnitude to generate a restored signal. Using various techniques that exploit predetermined signal patterns or inherent signal properties of the desired signal, the DC offset can be reasonably estimated. The DC offset estimate is then subtracted out of the restored signal leaving the amplified, received signal substantially free from distortion. An advantageous method for differentiating and digitizing the received signal uses the technique of companded delta modulation.