High quality factor microwave resonators using embedded structures in PCB

The market is always expecting miniaturization and cost reduction to provide continuous improvement for customer satisfaction. In the field of wireless communications, the digital components have been improved continually, but it is suffering from the low quality factor passive devices. Passive components such as inductors, capacitors, and resistors are constantly being redesigned to enable higher performance and smaller size. Inductors and resonators are among the chief components currently being studied to achieve higher quality factors and size improvements. It is essential to make high quality inductors and resonators with accurate values and cost effective methods for modern microwave applications.;Methods utilizing printed circuit boards (PCB) provide an effective solution for the fabrication of passive radio frequency components. A key technology in the PCB fabrication is the embedding of Thru-hole via. The new approach in this study is to use minimum feature size of standard PCB production to make embedded solenoids in a Duroid substrate with 2.2 relative permittivity. Each solenoid turn included two embedded copper vias of 125 mum radius and two surface conductors of 250 mum wide. Different pitch sizes, conductor lengths, solenoid heights, and number of turns were simulated and produced. The highest quality factor of 160.3 was received for a 500 mum pitch size and 1 mm conductor length in a substrate of 380 mum thicknesses.;This work shows the optimization of high Q resonators using the new solenoid inductor required a one turn solenoid. Furthermore, it introduces a series capacitance within the via to move the poles of characteristic function of the equivalent circuit toward higher frequencies. This provides significant enhancement in the quality factor which is realized using pole transfer. The result increased the resonance frequency to 12.25 GHz with a Q-factor of 306. Both the inductor and capacitive coupled resonator can be batch fabricated using conventional circuit board techniques. Analytical designs for the inductor and resonator were investigated using both a lumped circuit model and electromagnetic (EM) simulation. S-parameter measurements were in close agreement with simulations. The micro-solenoids and tuned resonator had a higher quality factor compared to the other counterparts.