Integrated passive device fabricated and chip‐on‐board packaged filter employing mixed electric–magnetic coupling scheme

Abstract

Compact and high-performance radio-frequency devices require several optimisation processes in the design, fabrication, and packaging, as well as a thorough reliability verification. The authors propose a compact planar dual-band bandpass filter comprising mixed electric-magnetic coupling open-loop resonators. To increase the coupling performance and minimise the structure size, the resonators were topologically optimised into both external stepped-impedance resonators and internal half-wavelength spiral resonators. Besides the electric length of the resonators, the centre frequencies and transmission zeros were tuned to the desired values by controlling the coupling coefficients and quality factors. Moreover, in their design, the in-band flatness and bandwidth can also be adjusted. To validate their approach, they fabricated a filter on a gallium arsenide substrate using the advanced-integrated passive device process. Then, the filter was packaged by attaching it to a printed circuit board using a chip-on-board technique. The measurement results were consistent with those obtained from a simulation. A series of tests verified that the utilised fabrication and packaging techniques notably enhance the device reliability and its long-term stability even in harsh environments.