Abstract: Apparatus for acquiring and processing incoming radio signals received from a plurality of stations, the frequencies of which are contained in a predetermined frequency band.The received signals are mixed with a local oscillator frequency which is repeatedly scanning the input frequency band at a fast rate produced from a frequency synthesizer whose control input is modified step by step to cycle through a corresponding predetermined set of programming values. The sweep rate of the programming value of the frequency synthesizer is so high that the stabilization time for the frequency at its output is significant with respect to the dwell time of the control signal of each programming value.The varying frequency signals at the output of the mixer are applied to the inputs of band pass filtering channels, to derive the frequency range of the incoming signals for frequency selective circuitry arranged to demodulate the received signals.

Abstract: An apparatus for acquiring and collecting messages aboard a satellite which are transmitted via respective radio-signals over different frequencies from a plurality of beacons comprises a receiver having an adjustable gain control input. An automatic gain control loop is provided for maintaining the gain of the receiver at a constant value. While the input frequencies of each input signals and time of arrival thereof are not exactly known, it is known that all these input frequencies are contained within a predetermined input frequency band which is periodically scanned by a frequency analyzer. This analyzer operates by scanning the center frequency of a band pass filter over the input frequency band and detecting the level of signals at the output of this filter for a plurality of successive frequencies within this input frequency band. The detected levels are digitized.

Abstract: An apparatus for receiving messages transmitted from a plurality of radio signal sources operating at different frequencies within a predetermined frequency band. Means are provided to frequency scan the receive signals, deriving information for determining the frequency range in which said signals lie. A demodulating phase locked loop is connected to receive the radio frequency signals, and an initial operating frequency for the phase locked loop is provided by the frequency range information determined from the means for frequency scanning. A resetting circuit is included to maintain the phase locked loop oscillator frequency at a value independent of the frequency of the radio signals.

Abstract: In a satellite which asynchronously receives radio frequency signals from a lurality of beacons scattered at the surface of the earth, each signal received has a pure carrier wave portion followed by a phase modulated message carrying portion. The frequencies of the signals are not known within a predetermined frequency band. The satellite has a plurality of essentially identical processing units which each receive on their input all the signals present at any given instant in the input frequency band. Each processing unit has a phase locked loop which may be progressively tuned to the frequency of one of these input signals in response to a frequency estimate of this signal to which the operating frequency of the phase locked loop is preset. This frequency estimate is updated until the phase lock occurs on this input signal, ready for demodulation of the message part to begin. The estimate frequencies are derived from an input band frequency spectrum analyzer.