A Novel Tunable Combline Bandpass Filter Based on External Quality Factor and Internal Coupling Tunings

Authors

  • Lixue Zhou Microwave Engineering of Department Xi’an Electronic Engineering Research Institute, Xi’an 710100, P. R. China
  • Shijie Liu Microwave Engineering of Department Shanghai Aerospace Electronic Technology Institute, Nanjing 201109, P. R. China
  • Jun Duan Microwave Engineering of Department Xi’an Electronic Engineering Research Institute, Xi’an 710100, P. R. China
  • Min Xun Microwave Engineering of Department Xi’an Electronic Engineering Research Institute, Xi’an 710100, P. R. China

Keywords:

Absolute bandwidth, coupling coefficient, fractional bandwidth, quality factor, tunable filter, transmission zero

Abstract

A combline filter with quasi-elliptic performance with external quality factor and internal coupling tuning is presented in this paper. In this design, a wide center frequency tuning range with a constant 3-dB FBW (fractional bandwidth) and ABW (absolute bandwidth) is obtained. Also, it is demonstrated that the transmission zero located at the lower edge of passband can be adjusted with little effect on the passband characteristic. A prototype of the tunable filter with a tuning range of 1.27GHz to 2.25GHz is fabricated on a substrate with epsilon=10.2 and h=1.27mm. Through tuning internal coupling coefficient and external quality factor, one can make the filter operate over a wide center frequency tuning range, with a constant 3-dB FBW (fractional bandwidth) nearly kept at 54% or ABW (absolute bandwidth) nearly kept at 500 MHz.

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Published

2021-07-25

How to Cite

[1]
Lixue Zhou, Shijie Liu, Jun Duan, and Min Xun, “A Novel Tunable Combline Bandpass Filter Based on External Quality Factor and Internal Coupling Tunings”, ACES Journal, vol. 33, no. 06, pp. 690–696, Jul. 2021.

Issue

2018: Vol 33 Iss 6

Section

General Submission