Stub-loaded Multiple-mode Resonator Research Articles

Compact Low-Cost Reconfigurable Microwave Bandpass Filter Using Stub-Loaded Multiple Mode Resonator for WiMAX, 5G and WLAN Applications

This paper presents a compact, low-cost reconfigurable bandpass filter (BPF) for WiMax, 5G, and WLAN applications. The BPF consists of a half-wavelength resonator folded as C-shaped by a pair of symmetrical PIN diodes and a central quarter-wavelength resonator to form an E-shaped stub-loaded multiple-mode resonator (SL-MMR). The feed line is made of two subsections separated by a gap which acts as a fixed capacitance and allows the filter to have bandpass behavior. The proposed filter is modeled using the even and odd mode analysis to predict the locations of the resonant frequencies. The simulation results show that the filter covers the frequency range (3.38-3.95) GHz with a center frequency of 3.52 GHz at the ON state of a pair of PIN diodes. On the other hand, the BPF covers the frequency range (4.7-5.93) GHz with a center frequency of 5.2 GHz, at the OFF state of the diodes. The results also show a small insertion loss at the filter passband with two sharp transmission zeros at the stopband.

A Low-Cost Microwave Filter with Improved Passband and Stopband Characteristics Using Stub Loaded Multiple Mode Resonator for 5G Mid-Band Applications

This paper presents the design and implementation of a printed circuit microwave band-pass filter for 5G mid-band applications, using a Stub Loaded Multiple Mode Resonator (SL-MMR) technique. The objective of this article is to introduce a low-cost microstrip filter with improved passband and stopband characteristics, based on a mathematical analysis of stub loaded resonators. The filter cost is reduced by selecting the low-cost FR4 dielectric material as a substrate for the proposed filter. Based on the transmission line model of the filter, mathematical expressions are derived to predict the odd-mode and the even-mode resonant frequencies of the SL-MMR. The mathematical model also highlights the capability of controlling the position of the SL-MMR resonant frequencies, so that the 5G sub-band that extends along the range (3.7–4.2 GHz) can perfectly be covered with almost a flat passband. At the resonance frequency, a fractional bandwidth of 12.8% (500 MHz impedance bandwidth) has been obtained with a return loss of more than 18 dB and an insertion loss of less than 2.5 dB over the targeted bandwidth. Furthermore, a pair of parasitic elements is attached to the proposed filter to create an additional transmission zero in the lower stopband of the filter to enhance the suppression of the filter stopband. The measured and simulation results are well agreed, and both reveal the acceptable performance of the stopband and passband characteristics of the filter.

Compact UWB bandpass filter with dual-notch bands using asymmetric tri-section stepped impedance resonator

In this study, a novel high selective UWB band pass filter (BPF) with dual notch band is presented. UWB BPF is realized using stub-loaded multiple-mode resonator (MMR). The MMR is constructed by loading a quintuple mode open stub at the centre in an asymmetric tri-section stepped impedance resonator (ATSSIR). Five modes, including two odd modes and three even modes, placed within UWB band. Two transmission zeros generated by the fractal stub improve the passband selectivity greatly. Two half wavelength long fractal Hilbert resonators are embedded near I/O line to achieve notch bands at 5.1 and 5.9 GHz. Aperture-backed interdigital coupled-lines are implemented to improve the coupling. The proposed prototype is fabricated and tested. The measured insertion loss is observed to be within 1.5 dB over the passband. By virtue of two transmission zeros (TZs), on either side of the passband, at 5.1 and 5.9 GHz, respectively, the passband selectivity is achieved with measured roll-off factor at around 34 dB/octave. The out-of-band rejection of the filter is greater than 22 dB up to 18 GHz. The simulated results are in good agreement with the measured responses.

High-selectivity UWB bandpass filter with a notched band using stub-loaded multi-mode resonator

In this paper, a novel type of stub-loaded multiple-mode resonator (MMR) with electrical coupling is developed for exploration of a single band-notch UWB Bandpass Filter (BPF) with high selectivity. Based on even and odd mode theory, five resonant modes, including two odd modes, three even modes, and a notched band can be properly designed to form the UWB passband. The odd-mode resonant frequencies can be controlled by tuning the coupling strength between two open stubs with no impact on the even modes, which provides a high design freedom of the UWB filter. Moreover, a pair of transmission zeros (TZs) can be also generated at either side of the passbands for sharp skirts and a TZ is also created within the passband for interference signal rejection. The simulated and measured results show that a notched band is obtained at 8.0GHz, which can be controlled by arranging the parameters of the MMR, sharp attenuation slops at the lower and upper bands can be simultaneously realized, which validates the proposed design flow well.

Ultra-wideband bandpass filters with triple and quad frequency notched bands

Two novel ultra-wideband (UWB) bandpass filters (BPFs) with multiple notched bands are presented. A stub-loaded multiple-mode resonator is used to realize an ultra-wide bandwidth, and two L-shape folded shunt open-circuited stubs are placed on the feed lines to control the quantity and frequency of notched bands within the desired bandwidth. This improves the selectivity and rejection of the filters as well. Then the stepped impedance structure connected with the feed lines on both sides is introduced to enhance the return loss performance. Finally, the prototypes of the UWB BPFs with triple and quad notched bands are implemented and measured. A good agreement between the predicted and measured results is obtained.

Compact dual-band bandpass filter with controllable bandwidths using stub-loaded multiple-mode resonator

A compact microstrip-line dual-band bandpass filter using a stub-loaded multiple-mode resonator is presented. This multiple-mode resonator is formed by loading three stubs (one short-circuited and two open-circuited stubs) in shunt to a simple uniform impedance resonator in the centre and two symmetrical locations, respectively. By properly adjusting the lengths of the three stubs, the first two resonant modes of this multiple-mode resonator can be allocated within the first passband, whereas the third and fourth resonant modes can be allocated within the second passband of the dual-band filter. This results in the formulation of a novel dual-band filter with compact-size and high isolation between passbands by incorporating this multiple-mode resonator with source-load coupling. Two coupling paths are used to control the bandwidth of each passband independently. To illustrate the concept, two dual-band filters of different frequency ratios are designed, fabricated and measured. Simulated and measured results are found to be in good agreement with each other, showing that a rejection level of 15 dB up to more than four times the first passband frequency can be obtained.

Novel UWB Bandpass Filter Using Stub-Loaded Multiple-Mode Resonator

Novel compact ultra-wideband (UWB) bandpass filter (BPF) using stub-loaded multiple-mode resonator (MMR) is presented in this letter. The MMR is constructed by loading three open stubs in a uniform-impedance resonator, i.e., one stepped-impedance stub at the center and two uniform-impedance stubs at the symmetrical side locations. Five modes, including two odd modes and three even modes, could be designed within UWB band, and two transmission zeros generated by the stepped-impedance stub improve the passband selectivity greatly. The letter shows modal resonant frequencies against the step-impedance-stub-loaded parameters, which can control the even modes flexibly, while the odd modes remain the same. A compact planar UWB BPF is simulated, fabricated and measured. The simulated and measured results are in good agreement and show good in-band filtering performance and sharp selectivity.

COMPACT QUINTUPLE-MODE UWB BANDPASS FILTER WITH GOOD OUT-OF-BAND REJECTION

In this paper, a novel compact quintuple-mode UWB bandpass fllter (BPF) with sharp rejection skirt and wide upper- stopband performances is realized using stub-loaded multiple-mode resonator (MMR). The proposed resonator is formed by attaching two pairs of circular impedance-stepped open stubs in shunt and a pair of short-circuited stubs to high impedance microstrip line. By simply adjusting the radius of circular impedance-stepped open stubs and the lengths of short-circuited stubs, the flrst flve resonant modes of the resonator can be roughly allocated within the 3.1{10.6GHz UWB band meanwhile the high resonant modes in the upper-stopband can be suppressed. The short stubs in pairs can generate two transmission zeros near the lower and upper cut-ofi frequencies, leading to sharper rejection skirt outside the desired passband. Finally, a quintuple- mode UWB BPF is designed and fabricated, and the measured results demonstrate the feasibility of the design process.

Reply to Comment on “Compact UWB Bandpass Filter Using Stub-Loaded Multiple-Mode Resonator”

In the comment of Chiou and Kuo regarding the above paper, they investigate where the fourth resonance of the proposed stub-loaded multiple mode resonator (MMR) and the transmission zero at the upper pass-band edge come from. The following is the authors reply to their comment.

Compact UWB Bandpass Filter Using Stub-Loaded Multiple-Mode Resonator

A compact microstrip-line ultra-wideband (UWB) bandpass filter (BPF) using the proposed stub-loaded multiple-mode resonator (MMR) is presented. This MMR is formed by loading three open-ended stubs in shunt to a simple stepped-impedance resonator in center and two symmetrical locations, respectively. By properly adjusting the lengths of these stubs, the first four resonant modes of this MMR can be evenly allocated within the 3.1-to-10.6 GHz UWB band while the fifth resonant frequency is raised above 15.0GHz. It results in the formulation of a novel UWB BPF with compact-size and widened upper-stopband by incorporating this MMR with two interdigital parallel-coupled feed lines. Simulated and measured results are found in good agreement with each other, showing improved UWB bandpass behaviors with the insertion loss lower than 0.8dB, return loss higher than 14.3dB, and maximum group delay variation less than 0.64ns in the realized UWB passband