X-band low-phase noise oscillator employing substrate integrated waveguide dual-mode filter

A novel low-phase noise oscillator employing a substrate integrated waveguide (SIW) dual-mode bandpass filter as a frequency stabilisation element within its feedback loop is proposed. The SIW dual-mode filter is implemented based on the use of the two degenerate modes (TE₁₀₂ and TE₂₀₁) and has a larger group delay peak than the conventional SIW cavity resonator. By taking advantage of the large group delay peak, the phase noise of the oscillator has significant improvement. An X-band oscillator with a GaAs HEMT packaged transistor has been designed and measured. At an oscillation frequency of 9.04 GHz, the measured phase noise is -111.9 dBc/Hz at 100 kHz offset. The output power is 6.1 dBm and the figure of merit is -198 dBc/Hz.