A low phase-noise oscillator with a planar capacitively loaded microstrip resonator

A low phase noise oscillator incorporated with a capacitively-loaded microstrip resonator was analyzed and designed in the 2 GHz range for wireless communication applications. The planar capacitively-loaded microstrip resonator provides two very close resonances such that its Q value can be dramatically enhanced compared with a single quarter-wavelength microstrip resonator. The measured results shows that the phase noise is effectively reduced to -110 dBc/Hz at 1 kHz off carrier by the capacitively-loaded microstrip resonator.