| 摘要 |
<p>A GPS-based frequency/time source of the present invention provides an accurate, traceable, low-cost reference. In particular, the GPS-based frequency/time source includes a GPS receiver (31), a variable frequency oscillator (35), and a microprocessor (33). The GPS receiver receives and produces as output signals GPS information, whereas the variable frequency oscillator has a frequency control input terminal and produces an output frequency signal, and is coupled to the GPS receiver. The microprocessor is coupled to receive the output signals produced by the GPS receiver and produces an error signal indicative of a difference in frequency between the GPS synchronized frequency and the output frequency signal of the variable frequency oscillator. Circuitry is responsive to the error signal to produce an electronic frequency control signal (37), which is applied to the frequency control input of the variable frequency oscillator so as to cause the difference in frequency to be reduced. In this manner, a low cost oscillator may be employed in such a way as to produce a very accurate output frequency signal.</p> |
