Design of High-Q Tunable SIW Resonator and Its Application to Low Phase Noise VCO

Abstract

In this letter, a low-cost continuously tunable substrate integrated waveguide (SIW) resonator and a low phase noise SIW voltage-controlled oscillator (VCO) are presented. A simple new structure for coupling varactor to the SIW cavity is proposed, which realizes a simple circuit layout for the tuning resonator. Equivalent circuit model is given for the varactor coupled resonator. Relation between the coupling coefficient <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$k$</tex></formula> and the relative tuning bandwidth is analyzed. Prototypes of tunable SIW resonator and a low phase noise SIW VCO have been designed and fabricated. Measured results show that the proposed resonator possesses unloaded Q factor of 286–299 for a tuning range of 492 MHz, and the phase noise of the SIW VCO is <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">${- 93}\mathchar"707B -95.6~{\rm dBc}/{\rm Hz}$</tex></formula> at 100 kHz offset for the whole oscillating frequency range of 455 MHz at X-Band.