Design of a Voltage‐Controlled Oscillator Using Hybrid Diplexer With Large Frequency Ratio for Millimeter‐Wave Applications

A millimeter‐wave (MMW) voltage‐controlled oscillator (VCO) with parallel feedback architecture is proposed in this paper. A diplexer with large frequency ratio is exploited to act as a fundamental frequency stabilization and third‐harmonic frequency extraction component, simultaneously. It consists of an X‐band microstrip bandpass filter (BPF) and a Ka‐band substrate integrated waveguide (SIW) BPF. The characteristics of the proposed diplexer possess a decent performance of high isolation between the two output ports. To verify the proposed architecture, a Ka‐band VCO prototype is designed, fabricated, and measured. The observed outcomes indicate that the frequency tuning range is from 26.19 to 26.76 GHz, and the designed VCO achieves a superior phase noise (PN) of −128.7 dBc/Hz and the corresponding figure of merit (FOM) indicates −203.8 dB/Hz at 1‐MHz offset frequency.