Abstract: The invention pertains to a homodyne receiver, in particular for angle-modulated carrier signals in which the converted signal (ZF) has a d.c. voltage portion, and a process for correcting the converted receiving signal. Essentially three classes of errors occur with homodyne receivers: d.c. offset, amplitude difference and phase errors between the in-phase (I) and quadrature (Q) branches. Standard adjustments of the local oscillator with phase-locked loop (PLL) do not work in the case of weak signals. To use cost-effective, rapid analog/digital converters, particularly the d.c. offset has to be separated out. In so far as this has been done previously and the I and Q signal were corrected also, these corrections could be accomplished only with expensive components in the RF class. To avoid this the invention provides an arithmetic unit that is designed for converting into a circle the ellipse set by the distorted I and Q signals.

Abstract: The invention pertains to a homodyne receiver and a process for direct conversion of angle-modulated carrier signals, especially those that have a d.c.-voltage component in the converted signal (IF). With many types of-modulation the (short-time) d.c. component of the conversion signal contains information about the modulating signal. Additional d.c. offsets are usually separated out by using a bandpass for the IF signal. In the process, however, the information-containing d.c. components of the converted signal are lost; as a result the demodulated signal is disturbed and in particular the distortion factor is raised. To avoid this the invention provides that the local oscillator for generating inphase and quadrature signals has a frequency offset from the carrier frequency of the receiver signal so that the frequency differential between carrier and frequency and oscillator frequency is in the transmission band of the bandpass used to suppress undesirable mixes, carrier reminders and d.c. offsets.

Abstract: Method and apparatus for correcting signal-pairs from vectors that represent inphase signals (I) and quadrature signals (Q). The values for correction of the amplitude error .alpha. and phase error .delta. are determined by calculating the most probable correction values of offsets from a center point of the signal-pairs using signal probes from the stream of the inphase and quadrature signals. The amplitude error .alpha. and phase error .delta. are calculated corrected as a function of the signal probes only after a preceding correction of the center point.