A novel multiple-tunable millimeter-wave frequency synthesizer

In this paper, a novel multiple-tunable frequency synthesizer structure to achieve both high frequency resolution and fast switching speed without degradation of spurious performance is proposed. According to this structure, a high performance millimeter-wave frequency synthesizer with low spurious, low phase noise, and fast switching speed, is developed. This synthesizer driven by the direct digital synthesizer (DDS) AD9956 can adjust the output of DDS and frequency division ratios of two variable frequency dividers (VFDs) to make the spurious components outside the loop bandwidth of phase-locked loop (PLL). Moreover, the ADF4252 based microwave PLL can further suppress the phase noise. Experimental results from the implemented synthesizer show that remarkable performance improvements have been achieved.