| 摘要 |
A reference source of digital pulses of a first frequency f1 is coupled to the input of a frequency synthesizer which is capable of providing a second frequency f2 output signal. The second frequency is related to the first frequency by a predetermined, rational fraction (e.g., as f2 = (M/N)f1). The synthesizer includes a phase control unit comprising an adder by way of which a first number N is added each sample period to a remainder, the sum output of the adder being operated upon modulo a second number M, e.g., by dividing by M and discarding a resultant quotient to obtain a remainder. The remainder, having a value between zero and M-1, is compared to a prefixed signal, illustratively the largest integer in M/2. If the remainder is less than the prefixed signal, a first logic state control signal is provided to a control system; else a second logic state signal is so provided. The alternation between the first and second logic states is such that M pulses of the second frequency occur for every N pulses of the first frequency. Thereby, the second frequency is synthesized responsive to the first.
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