Apparatus for acquiring and collecting radio signals coming from a plurality of stations

摘要

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. The resulting digitized level indications are statistically analyzed and the result of this statistical analysis is used for adjusting the level of the gain control input of the receiver. According to an embodiment, only those detected levels which correspond substantially to input signals carrying messages retained for demodulation are used for determining an average level indication over a time period such as that for a full revolution of the satellite. The thus determined average level is compared with a reference value to adjust the receiver gain, thus eliminating gain variations due, for example, to aging of the components.