Compact CEBG Filter for High-Frequency Applications With Low Insertion Loss

Abstract

A compact configurable electromagnetic bandgap (CEBG) filter and a low-loss low-temperature cofired ceramics (LTCCs)-based electromagnetic bandgap (EBG) filter have been proposed. To the best of the authors’ knowledge, this is the minimum size configurable bandpass filter (BPF) ever reported using EBG material. The proposed circuits successfully integrate an integrated passive device (IPD) technique-based high- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$Q$ </tex-math></inline-formula> capacitors and LTCC-based built-in capacitors with EBG substrates. The frequencies of the filters can be easily adjusted by controlling the capacitors. For proof-of-concept demonstration purposes, CEBG filters and LTCC-based EBG filters were designed and experimentally validated from the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$C$ </tex-math></inline-formula> -band to the Ku-band. The measurement results demonstrated the filters’ compact size, wide stopband, and reduced insertion loss (IL) as working frequency increases. Four LTCC EBG filters are implemented and fabricated with the highest working frequency of 17 GHz, a minimum IL of 1.91 dB, and a 3-dB fractional bandwidth (FBW) of 3%. The CEBG filter demonstrated a compact size of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1.6\times1.35$ </tex-math></inline-formula> mm, a configurable frequency from 6.88 to 13.5 GHz with an almost constant FBW. Insertion losses of the EBG filters reduce as their working frequencies increase which shows an excellent high-frequency application capability of the filters.