Research on mm-wave frequency synthesizer with low phase noise and full-phase-coherence

A mm-wave frequency synthesizer with small step and full-phase-coherence was developed. For LO (local oscillator) section, DDS(direct digital frequency synthesis) frequency, reference divider and PLL(phase locked loop) divider are triple tuned, so that spurious components from DDS are suppressed and the frequency resolution is enhanced; For transmitter (TR) section, twice frequency-mixing is used, so the presetting of tuning voltage is avoided, the circuits are simplifed, and the phase coherence between TR and LO signals is ensured. The developed synthesizer with channel step below 1 MHz achieves low spurious level of -60dBc, phase noise of -90dBc/Hz@ 10kHz -97dBc/Hz@ 100kHz and switching time of 15us. The output frequency is within Ka band.