| 摘要 |
A receiver accurately measures the Doppler shift of a radio signal from a transmitter having a known frequency and moving with respect to the receiver by using the signal from another transmitter of known frequency as a reference. The signals from the two transmitters are received by a single antenna, separated, and processed in separate channels. In a typical application using Global Positioning System satellite signals, each signal is discretely extracted by auto-correlation with its own pseudorandum noise signal, filtered, amplified, and applied to second mixers in phase locked loops in the respective channels. The two resulting second IF signals are applied to an output mixer whereupon the resulting difference output signal represents the difference in frequency between the two Doppler signals. |
