Abstract
In this letter, a compact dual-mode bandpass filter (BPF) with an ultra-wide stopband that employs two folded open-loop resonators (FOLRs) and stub-loaded resonators (SLRs) is proposed. The dual-mode resonators are optimized by loading two SLRs onto the folded open-loop resonators, and this process is analyzed using the dual-mode theory. To miniaturize the device size and increase chip performance, the proposed BPF is fabricated by a III–V compound semiconductor-fabrication process using a high-performance GaAs substrate based on the integration passivation device (IPD) fabrication process. A compact dual-mode BPF with low insertion loss and high return loss is designed and fabricated. Two extra transmission zeros (TZs) located in the high-frequency range increase the wide stopband, and the two TZs near the passband result in a higher selectivity. A resonant frequency centered at 7.45 GHz with an insertion loss of −1.21 dB and a measured return loss of higher than −23.53 dB and 3 dB fractional bandwidths of 5.8% are achieved. The stopband can be suppressed up to 20 GHz owing to the two tunable TZs resulting in higher selectivity and wideband rejection. The size of the filter was drastically optimized using a simplified architecture of two FOLRs and SLRs.
Highlights
The rapid development in current wireless-communication systems has resulted in remarkable challenges and demands for high performance, low-cost, and high-yield microwave devices, such as filters, couplers, power dividers, and balanced-to-unbalanced
A 200-nm-thick Si3 N4 passivation layer was deposited by plasma-enhanced chemical vapor deposition (PECVD)
A folded open-loop resonators (FOLRs) with stub-loaded resonators (SLRs) has been researched for a dual mode bandpass filter (BPF) based on even and Return odd-mode operations
Summary
The rapid development in current wireless-communication systems has resulted in remarkable challenges and demands for high performance, low-cost, and high-yield microwave devices, such as filters, couplers, power dividers, and balanced-to-unbalanced (balun). Dual-band filters have become key components in dual-band microwave devices. Dual-mode bandpass filters (BPFs) have become attractive components in modern communication systems [1,2,3,4,5,6]. Compared with PCBs, the LTCC and silicon-based semiconductor-fabrication techniques offer more advantages in terms of high integration and miniaturization. All these approaches suffer defects, such as high substrate loss, low accuracy, and difficult integration with systems
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