High factor frequency multiplication in a high-performance 2.4 GHz VCXO

Modern communications protocols require low phase jitter of L-band reference signals in voltage controlled oscillators. Low cost and small size of the oscillators are essential as well. High factor frequency multiplication is a technique to make voltage control crystal oscillators that meet all the requirements. However, there are two difficulties. First, the technique applied to transfer signals from 150-200 MHz to L-band, leads to 20-25 dB phase noise degradation. Second, it also gives rise to sub-harmonic in the spectrum of output signal. Gate type circuit oscillators have phase noise power spectral density low enough to compensate the degradation. It is shown that sub-harmonic suppression can be achieved by choosing a special operating mode of the BJT frequency multiplication stage.