Tunable bandpass filters with constant absolute bandwidth cascaded trisection topology

Abstract

A novel cascade trisection (CT) coupling structure, based on half-wavelength resonators, is proposed for designing constant absolute bandwidth (CABW) tunable bandpass filters. The tunable resonators have both electric and magnetic dominant coupling regions with predefined coupling coefficients. The third-order and fifth-order tunable bandpass filters (BPFs), which can realize CABW and a high side cross-coupling transmission zero (Tz), are designed based on the proposed CT structure. Measurement results show that the central frequency tuning of the third-order filter is from 1.47 to 1.83 GHz with −3dB bandwidth of 108.75 ± 2.05 MHz, and the high side 3 to 25 dB attenuation slope is 327.32–623.57 dB/GHz. The tuning range of the fifth-order filter is from 1.45 to 1.92 GHz with −3dB bandwidth of 101.9 ± 1.3 MHz, and high side 3 to 30 dB attenuation slope is 442.75–843.59 dB/GHz.

KEYWORDS:

• Cascaded trisection
• constant absolute bandwidth
• tunable filter
• cross-coupling

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was supported by the National Natural Science Foundation of China (NSFC) [61771408], [61831017], [61934008], [62090012]; Fundamental Research Funds for the Central Universities [2682014RC24]; Key Laboratory Funding [6142001190101].

Notes on contributors

JingJing Yang

Jingjing Yang received the BE degree from Hefei Normal University, Hefei, China in 2019. She is currently studying for Master Degree in Southwest University, focusing on microwave technology and wireless power transmission technology. Her research interests include reconfigurable RF filter design and active rectifier design.

Qianyin Xiang

Qianyin Xiang received the BE degree in communication engineering, and PhD degree in the communication and information systems from Southwest Jiaotong University, Chengdu, China. He is currently with the School of Information Science and Technology, Southwest Jiaotong University. He was awarded as the Young Scientist “Sishi Star” of SWJTU. His research focuses on reconfigurable/tunable RF circuits and systems, and MMIC design for communications and wireless power transfer systems.

Xiaoguo Huang

Xiaoguo Huang received the B.Eng. degree in Microelectronics and PhD degree in communication and information system from Southwest Jiaotong University, Chengdu, China, in 2008 and 2015, respectively. He is currently working in Science and Technology on Communication Information Security Control Laboratory, Jiaxing, China. His research interests include Analog/RF/microwave device, circuits and systems.

Dinghong Jia

Dinghong Jia received the B.Eng. degree in microelectronics and PhD degree in communication and information system from Southwest Jiaotong University, Chengdu, China, in 2011 and 2016, respectively. He is currently with the Ceyear Technologies Co., Ltd, Qingdao, China. His research interests include passive circuit design, tunable filters, and THz devices and systems.

Quanyuan Feng

Quanyuan Feng received the MS degree in Microelectronics and Solid Electronics from the University of Electronic Science and Technology of China, Chengdu, China, in 1991, and the PhD degree in Traffic Information Engineering and Control from Southwest Jiaotong University, Chengdu, China, in 2000. He is the Head of Institute of Microelectronics, Southwest Jiaotong University. He has been honored as the “Excellent Expert” and the “Leader of Science and Technology” of Sichuan Province because of his outstanding contributions. His research interests include RF and microwave circuits, antennas, EM compatibility, and environmental electromagnetics.