A Low Phase Noise Feedback Oscillator Based on SIW Bandpass Response Power Divider

A low phase noise X-band oscillator based on the bandpass response power divider in single-layer substrate integrated waveguide (SIW) technology is presented in this letter. The power divider is embedded in the SIW filter; therefore, lower insertion loss and more compact area size can be realized than those using the independent design of both components. To achieve better phase noise performance, transmission zeros are introduced by cross coupling through the resonant cavities to increase peak group delay. In addition, by placing external feeding at the center of cavity edge, the second harmonic can be suppressed efficiently. The measured results verify the performance of the proposed bandpass response power divider and show that the phase noise of the oscillator can achieve -143.3 dBc/Hz at 1-MHz offset frequency.