Tone receiver for satellite position determination

The receiver has the function of processing the ranging signal, composed of tones in 40, 160, 800, 4000, and 20000 Hz, according to the NASA standard. This signal originates on the ground and is retransmitted back by the satellite. The processing consists of separating the tones, which jointly modulate the carrier, and comparing their phases with the phases of the corresponding original tones, transmitted from the ground. Tone separation is accomplished by second-order PLLs, which operate as narrowband filters. From each phase comparison results a signal with pulses modulated in width by the phase difference between the two waves in question. The five measured values are forwarded by the receiver to another apparatus, which computes the distance from these data.