Abstract: A system of frequency-shifting of frequency modulated signals, continuously above or below a pre-established frequency, the shift being possibly also null. The system includes a source of frequency modulated signals, the frequency of which is to be shifted; a reference oscillator; a first phase locked loop to which is applied the signals from the signal source and the output of the reference oscillator, the arrangement being such that the first phase locked loop will be locked to a conversion frequency above or below the frequency of the signal source.

Abstract: A device for determining tracking errors in radar systems and the like through correlation between the radar echo signal and a signal related to the rotation of the antenna, using means for narrow band filtering and phase comparison, and amplifying means and means for AC-DC conversion and DC amplifying means in which the narrow band filtering means and phase comparison means carry out their functions through the alternate cyclical switching of the signal from one condenser to another synchronous with the movement of the antenna, and with a similar switching carrier out in other condensers in the stage formed by the AC-DC conversion means.

Abstract: A device for filtering and frequency discrimination includes a filtering section and frequency discriminator connected in tandem. The filtering section consists of a bandpass filter and two resonant components in series. The discriminator includes two resonant components with their inputs connected in parallel, followed by respective detectors connected to respective inputs of an output differential amplifier. Each of the resonant components is a respective sampled filter tuned to a given respective frequency. Each of the sampled filters is controlled by a respective control signal of corresponding frequency, all control signals being derived from signals supplied from a single high-stability oscillator. The oscillator is preferably a quartz crystal-controlled oscillator.