A 3–16GHz wide band frequency synthesizer with high spectrum purity performance

In this paper, an approach of developing high spectrum purity 3-16GHz frequency synthesizer for radar simulation system is proposed. Using two single PLL (phase locked loop) switching structure to provide the local oscillators signal, with high-speed controlling of FPGA (Field Programming Gate Array), the wide band frequency synthesizer implemented in the paper has excellent performance on spectrum purity. The frequency step is 20MHz. The phase noise level is less than -83dBc/Hz@10kHz and the spurious level is below -60dBc. By adjusting the phase frequency detector (PFD) current in PLL to compensate the nonlinear property of voltage controlled oscillator (VCO), the loop instability and consequent degeneration of performance of synthesizer can be avoided.