Precision measurement of submillimeter wave frequency

A submillimeter wave frequency measurement set-up is developed. This system employs an all solid-state 4MM frequency source obtained by the injection phase locking of a 1.25CM Gunn oscillator and a varactor tripler. The accuracy of frequency measurement of this system is better than 5E-8. By means of this set-up the frequency of HCN laser (337/spl mu/m) can be measured. The experimental results are given.