A C-band Low-noise Frequency Synthesizer Based on Digital Phase-locked Loop

To reduce phase noise of microwave-band frequency synthesizer based on phase-locked loop(PLL), the method that the output signal of VCO is mixed with a Lo signal and the IF signal is detected, is proposed. Then, the compatible loop filter is designed. Finally, the experimental results prove that the phase noise of improved frequency synthesizer is greatly lower than that of directly phase-locked synthesizer.