Rana found that we had a frequency counter SR620 which might be helpful for lock acquisition of the green phase lock.
It has a response of 100MHz/V up to 350MHz which is wide range and good for our purpose. And it has a noise level of 200Hz/rtHz @ 10Hz which is 1000 times worse than that Matt made (see the entry).
The attached figure is the noise curve measured while I injected a signal of several 100kHz. In fact I made sure that the noise level doesn't depends on the frequency of an input signal.
The black curve represents the noise of the circuit Matt has made, the red curve represents that of SR620.