Frequency acquisition technique for injection-locked clock generator using asynchronous-sampling frequency detection

An injection-locked clock generator with a frequency acquisition scheme, which eliminates a conflict between the injection and the frequency acquisition loop is described. In the proposed frequency detector (FD), the oscillator clock is sampled by the reference clock, which, respectively, becomes asynchronous sampling and synchronous sampling before and after injection locking. By taking advantage of this aspect, the proposed FD does not generate any active output once the oscillator is injection-locked, and therefore the conflict is completely resolved. Moreover, it is not turned off but just produces no output, hence it can immediately react to a sudden loss of injection-locking. The FD is implemented with a low hardware overhead of only six flip-flops and a few logic gates. The validity of the feasibility of the proposed scheme is verified by a circuit simulation.