A PLL Frequency Synthesizer Using Feedback VCO with Miniaturized SIW Resonator at X-Band

In this paper, a Phase-Locked Loop (PLL) frequency synthesizer using feedback voltage-controlled oscillator (VCO) with miniaturized substrate integrated waveguide (SIW) resonator at X-band is proposed. The PLL synthesizer is based on a frequency synthesizer chip ADF4159 and an external feedback VCO. In this VCO configuration, the resonator works as a frequency stabilization element in the feedback loop and a reflective phase shifter is used to adjust loop phase. Due to the transmission zero near the upper passband of the resonator, a high group delay peak is produced, resulting in improved phase noise. Measured results show that, the phase noise of this proposed PLL is better than -122 dBc/Hz@1MHz and output power is -7.22 dBm at 9.77 GHz.