Fabrication of high quality factor RF-resonator using embedded inductor and via capacitor

These High quality factor resonators are key components in RF-circuits. Fabrication of on-chip LC tank circuits is costly and suffers from low Q-factor. Design, simulation, and fabrication of a novel off-chip resonator with high quality factor are reported. Minimum feature size of standard PCB fabrication has been used to make imbedded solenoids in Duroid substrate with 2.2 relative permittivity. A solenoid turn included two imbedded copper via of 125 µm and two surface conductors to shape a rectangular coil. The pitch size was 250 µm for a substrate 3.02 mm thick. A series capacitance was introduced in the via to move the poles toward higher frequencies. It divides the inductance, resistance, and stray capacitance. The result would increase the resonance frequency into 12.25 GHz. It also raised the Q-factor into 306. In addition to the very high Q-factor, the resonator benefits from facilitated design and ease of fabrication. Analytical design has been investigated by a lumped circuit model. The result of S-parameter measurements was in close agreement with the designed circuit. The tuned resonator had a higher quality factor compared to all silicon based counterparts.