Abstract: A satellite signal identification system utilizes distinguishable unique coded identifiers impressed on a carrier sent from a transmitting ground station to be identified. The identifier is recieved and identified by the receiving station to specifically identify a particular underlying carrier signal for reception. The invention utilizes a data modem for transmitting to an earth relay satellite coded identification signals together with various data and error correcting information. An IF carrier signal may be combined with video and/or audio signals, such combined signals being relayed via satellite to the ground station. The MPU of a modem in the ground station finds its counterpart in the MPU of the downconverter that receives via a block downconverter the data, housekeeping and ID signals after the video has been removed. The downconverter first translates the satellite transponder frequency to an IF frequency and sequentially searches for a carrier and the PSK code.

Abstract: A dual conversion variable bandwidth telemetry receiver employs a phase locked loop which controls the second local oscillator to maintain lock on the carrier frequency; the phase locked loop employing a loop filter with a variable time constant integrator, the time constant of which can be varied as a function of receiver bandwidth and the integrator with its associated capacitor and resistor banks being employed in a sweep, i.e. search, oscillator circuit enabled when the carrier signal is lost. A coherent double-balanced mixer is employed to detect carrier lock and if lock is lost but the carrier is still detected, a rapid response anti-sideband circuit in the phase detector of the phase locked loop is employed to suppress the sidebands and greatly increase the probability of relocking on the carrier. A synchronous AM detector employs quadrature IF and reference signals at the same frequency to produce a dc signal when phase lock occurs; the signal falling rapidly upon loss of lock.

Abstract: A multiple bandwidth quadrature type FM demodulator employs a double-balanced mixer supplied with a frequency modulated IF signal directly and through one of a selectable plurality of bandpass circuits each having a different bandwidth, having a linear phase shift versus frequency characteristic and producing a 90.degree. phase shift at the IF frequency whereby to produce at the output of the mixer a signal level that varies as a linear function of frequency of the input signal, the demodulator including a bias control circuit for the mixer to establish a normalized output for all filters at full bandwidth modulation and further including circuits for establishing a signal balanced with respect to ground or other reference potential regardless of the filter employed.