Compact wideband bandpass filter with equiripple response in both magnitude and delay

Abstract

Aiming at the reduction of the in‐band delay variation, a wideband bandpass filter with equiripple response in both magnitude and group delay is presented and studied. The filter is composed of one section of end‐connected coupled line and two short‐circuited shunt transmission line stubs, all of them are uniform and equal in electrical length. Design formulas are given to calculate the characteristic impedances of the lines to meet the filtering specifications. By changing the coupling strength of the coupled line section, the group delay can be controlled to be equiripple in band, while the remaining equiripple response in magnitude unchanged. For verification, a filter sample is fabricated and measured. In experiment, it exhibits a delay variation of 0.11 ns and minimal insertion loss of 0.2 dB within its passband (|S11| < −14 dB) from 0.48 to 1.46 GHz, which validates the theoretical predictions.

Equiripple design of low‐pass filter using stub‐loaded Z‐shaped coupled‐line section

“…The TFs in Table 1 are similar to those in [8,9]. Therefore, a similar design approach can be employed to demonstrate the filtering performance.…”

“…Coupled lines can be widely found in microwave-distributed circuits [1], such as filter [2][3][4][5][6][7][8][9], coupler [10][11][12], phase shifter [13,14] and impedance transformer [15][16][17], due to its controllable coupling strength and ease of planar implementation [1]. In practical circuits, coupled lines appear generally as 'sections', which can be categorized by the number of ports, connecting topology, and ending condition [18].…”

Response Diversity of Stub-Loaded Ring Bandpass Filter Based on Commensurate Line Element: Single- and Dual-Band Applications

“…Therefore, this urgent demand leads to many new design The associate editor coordinating the review of this manuscript and approving it for publication was Roberto Gomez-Garcia. theories for wideband BPF [4], such as the multiple mode resonance (MMR) [5]- [9], stub-loaded topology [8]- [13], and the signal interference technology [14]- [17].…”

“…When all the stubs and line segments are equal in electrical length, namely commensurate, this topology enables the facilitation in mathematical modeling and analysis, but, suffers from relatively large size due to its cascading structure [11]- [13]. Besides, the circuit area can be reduced by folding the connecting line into a coupled line section, with an improved equiripple delay response [14]. The signal interference is another new concept in filter design [15]- [18].…”

“…In most of the reported wideband BPF designs, the group delay characteristic is ignored or fixed, because the design methodologies are derived entirely from magnitude response. In our recent works, two new wideband BPFs are given to show the co-existence of equiripple responses in both delay and magnitude, one of which is utilized by coupled lines section [14] while the other one is achieved by commensurate line ring [18]. The common part of the two BPFs in structure is a pair of short-ended stubs.…”