Minimized reflectionless bandpass filter with four notches and low insertion loss

ABSTRACT

A size-minimized low-insertion-loss reflectionless bandpass filter with four notches is presented in this paper. The insertion loss of two quasi-elliptic-type filters is studied and optimized by a new approach based on cascade resonators branches. Parameters extraction procedure for the desired position of notches is illustrated. The inband performance, bandwidth and notch width are studied. This novel approach brings lower insertion loss. It can be extended to reflectionless bandpass filters with arbitrary number of notches. The size of filter is also minimized. This filter is designed, simulated, fabricated and measured. It is centered at 3.481 GHz with a 3-dB bandwidth of 276 MHz. The minimum measured in-band insertion loss, including the loss of SMA interface, is 1.239 dB. Four notches are located at 2.827, 3.238, 3.825 and 4.306 GHz, respectively. S₁₁ of this filter is less than −10 dB during 2–5 GHz.

KEYWORDS:

• Bandpass filter
• microstrip filter
• notches
• reflectionless filter

Additional information

Funding

This work is supported by the National Natural Science Foundation of China (NSFC) under grant [61771408, 61531016, and 61401375], the Fundamental Research Funds for the Central Universities under Grant [2682014RC24], the Sichuan Provincial Science and Technology Important Projects under grant [2018GZ0139, 2017GZ0110], and the Graduate Academic Literacy Improvement Program of SWJTU under grant [2018KCJS32].

Notes on contributors

Mingye Fu

Mingye Fu received the B.E. degree from Southwest Jiaotong University, Chengdu, China in 2017. He is now studying for Master Degree in Southwest Jiaotong University, focusing on microwave technology. His research interests include reconfigurable/tunable RF circuits, MMIC design for broadband/high speed communications.

Qianyin Xiang

Qianyin Xiang received the Ph. D. degree in the Communication and Information Systems from Southwest Jiaotong University, Chengdu, China, in 2013. He is currently with the Institute of Microelectronics, Southwest Jiaotong University. He has been the leader and researcher in many national research projects supported by the National Natural Science Foundation of China, and Chinese national 863 plan. In recent 5 years, he has published more than 30 research Journal papers on microwave circuits. He is also an active peer reviewer for IEEE Transactions on Microwave Theory and Techniques, IEEE Microwave and Wireless Components Letters, and so on. In 2015, he was awarded as the Young Scientist "Sishi Star" of SWJTU. His current research focuses on reconfigurable/tunable RF circuits, and MMIC design for broadband/high speed communications.

Quanyuan Feng

Quanyuan Feng received the M.S. degree in Microelectronics and Solid Electronics from the University of Electronic Science and Technology of China, Chengdu, China, in 1991, and the Ph.D. 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.