Rotationally Symmetric Coupled-Lines Bandpass Filter With Two Transmission Zeros

Abstract

Abstract-A rotationally symmetric short-circuited stub-loaded structure is proposed to design a microstrip-line bandpass filter with two transmission zeros near the lower and upper cut-off frequency edges of operating millimeter-wave bands. Furthermore, interdigital coupled-lines and additional resonators are integrated into the proposed rotationally symmetric bandpass filter to improve the out-of-band rejection. As design examples, the in-band and out-of-band performances of two filter prototypes using single layer microstrip-lines are designed and experimentally examined. The measured results show that the filter without any interdigital coupledlines achieves a passband insertion loss of 0.97 dB at 40 GHz and out-ofband rejection of larger than 23 dB, while the filter with the interdigital coupled-lines realizes the suppressions in lower and upper-bands of, respectively, larger than 30 dB and 19 dB for the overall insertion loss of 2.1 dB at 40 GHz.

A Novel Compact Wideband Bandpass Filter Using Rotational Symmetric Loaded Structure

“…This is quite different from our previous work [10][11][12], and the coupling effect within the rotational symmetric structure is not concerned in our proposed structure. The rotational symmetric structure is seen as a novel open/short circuit with stubs loaded here and will be discussed in detail here.…”

“…The source-load coupling is an effective way to achieve a high selectivity and wide stopband as discussed in [9]. Recently, the rotational symmetric structure with coupling effect is proposed and discussed in [10][11][12]. The passband is obtained, and two TZs are also generated meanwhile.…”

Miniaturized Multilayer Dual-Mode Substrate Integrated Waveguide Filter With Multiple Transmission Zeros

“…Bandpass filters with high integration and sharp skirts are essential in the development of modern wireless and mobile communication systems [1][2][3][4][5][6]. Microwave dual-mode filters with microstrip or metal waveguide structure can provide valid solutions to satisfy these requirements owing to their high performance and easy design [7] Although the microstrip dual-mode filters are have been widely used and implemented, they have lower power-handing capability and lower resonator Q factor in higher frequencies [8,9].…”

Quasi-Elliptic Wideband Bandpass Filters Using Stubs Loaded Anti-Parallel Coupled-Line

“…Although it exhibited the quasi-elliptic frequency response, the BPF in [10] suffered from relatively large insertion loss. In [11], a good performance millimeterwave BPF with two TZs was designed by using LTCC technique. In [12], a good performance BPF with quasi-elliptic frequency response was designed by using open stub loaded anti-parallel coupled-line.…”

“…Coupled-line is an usual and classical structure to exploit lowpass filter [1], bandstop filter [2][3][4], bandpass filter (BPF) [5][6][7][8][9][10][11][12], reconfigurable BPF [13] and dual-band BPF [14][15][16][17]. Although the lowpass, bandstop, reconfigurable and dual-band filters with coupledline have good electrical performance, they often suffer from large circuit size due to the required quarter-wavelength or half-wavelength couple-line.…”