Study of cylindrical multilayered ceramic resonators with rectangular air cavity for low-phase noise K/Ka-band oscillators

This paper first presents cylindrical low-temperature co-fired ceramic (LTCC) resonator configurations as a means of achieving high-Q values at millimetric frequencies in a reduced-size structure. The resonator contains a rectangular air cavity that only partially fills its volume. Simple analytical expressions are derived, which relate the via waveguide (VWG) heterogeneous structures to their conventional cylindrical resonator counterparts through the use of effective radius and dielectric constant (a_eff and ε_eff). A parametric analysis is then carried out showing the effects of the available design parameters on resonant frequency and Q. Excellent agreement between measured and analytical results is obtained. Finally, a low-cost miniaturized low phase-noise free-running oscillator is proposed by employing the novel high-Q VWG resonator in the same LTCC package that houses the monolithic oscillator active circuit. A 24-GHz low phase-noise oscillator is then carried out with an output power of 13.3 dBm and a phase noise of -106 dBc/Hz at 100-kHz offset, which is among the best results ever published for a free-running K/Ka-band oscillator.