Quarter-mode Substrate Integrated Waveguide Resonators Research Articles

Compact dual‐band bandpass filter with high selectivity based on spiral‐stub‐loaded dual‐mode QMSIW resonators

AbstractA novel miniaturized dual‐band quarter‐mode substrate integrated waveguide (QMSIW) bandpass filter with high selectivity is proposed in this letter. Two passbands are generated by the fundamental mode and the first higher order mode of the spiral‐stub‐loaded QMSIW resonator, respectively. Miniaturization is achieved by loading stubs and applying quarter‐mode cavities. High selectivity can be realized by introducing two transmission zeros (TZs) between the two passbands. One TZ is generated by adding coplanar waveguide coupling between the two resonators, the other TZ is synthesized by coupling between the modes of the resonator. The proposed dual‐band filter has the characteristics of miniaturization, high selectivity, and low loss, which is suitable for satellite communication related applications.

BCB-Based Thin-Film Ka-Band Quarter-Mode SIW Packaged Filters With Ultrawide Stopband and Independently Controlled TZs

In this article, quarter-mode substrate-integrated waveguide (QMSIW) filters featuring ultrawide stopband and flexibly allocated transmission zeros (TZs) are proposed. Eight higher modes with resonant frequencies up to 4.7 times of the fundamental mode are highly suppressed. It is realized by the combination of three approaches without extra circuit areas. First, a slot is cut in the first and last QMSIW resonators to make their resonant frequencies of higher modes different from those of other resonators. Second, avoid exciting the specific higher modes by setting the feed point in the area where the electric field strength of the higher modes is weak. Third, mismatch the higher modes when matching the passband. It is realized by using a stripline impedance transformer with its main body not exceeding the area of QMSIW resonators. Furthermore, except for the TZs derived by the classical cross-coupling matrix, two more independently controlled TZs are generated. The packaged filter is fabricated by using a benzocyclobutene (BCB)-based microelectromechanical systems (MEMS) process, which is suitable for millimeter-wave 3-D system-on-package (SOP) applications. The fabricated thin-film filter is measured with an insertion loss of 2.96 dB at 29.4 GHz and a fractional bandwidth (BW) of 17%. Higher mode suppressions up to 138.3 GHz are achieved.

Miniaturized Quarter-Mode SIW Filters Loaded by Dual-Mode Microstrip Resonator With High Selectivity and Flexible Response

A novel miniaturized multilayer quarter-mode substrate integrated waveguide (QMSIW) filter with high selectivity and wide stopband is proposed. First, an innovative multilayer dual-mode microstrip resonator is proposed to couple the QMSIW resonators located at the upper and lower substrate layers. The combination of the dual-mode resonator with the two QMSIW cavities leads to a fourth-order filtering response. Then, the coupling iris is opened at the position, where the magnetic field distribution in the QMSIW cavity achieves a peak value. Finally, sharp skirt is obtained by composing the modified box-like topology. In addition, different responses could be achieved by changing the position of the coupling iris, resulting in a wide stopband and flexible response. The size of the filter is also reduced through the multilayer QMSIW configuration and miniaturized multilayer dual-mode microstrip resonator.

Highly-Miniaturized Dual-Mode Bandpass Filter Based on Quarter-Mode Substrate Integrated Waveguide With Wide Stopband

This paper presents a novel design of a highly-miniaturized dual-mode bandpass filter (BPF) employing a quarter-mode substrate integrated waveguide (QMSIW). The QMSIW resonator is based on a square cavity with metallic vias along two sides, and open-ended edges at the remaining sides that contain orthogonal feed lines. An open slot is introduced along the two sides of the square cavity with metallic vias to form a magnetic wall. A single metallic via is assigned at the corner of the two open-edged sides to form an electrical wall, which produces different resonances. By loading a slot diagonally, the mode frequencies can be controlled independently, which allows us to realize a second-order BPF. The detailed design steps and a flowchart explaining the filter’s topology evolution are presented. The eigen-mode analysis, field distributions, coupling matrix, and full-wave simulation of the proposed QMSIW filter topology are used to determine the filter’s operating principle. To verify the proposed theory, a second-order BPF is realized, fabricated, and demonstrated experimentally. The BPF prototype exhibits excellent performance such as a small footprint of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.019\lambda ^{2}$ </tex-math></inline-formula> , a wide passband of 34.8-percent, low insertion loss of 0.43 dB, and a wide stopband of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$3.36f_{0}$ </tex-math></inline-formula> with a rejection level greater than 20 dB. Excellent consistency is found between the EM-simulated and measured responses of the device.

Ultracompact Quarter-Mode Substrate Integrated Waveguide Self-Diplexing Antenna

A highly compact substrate integrated waveguide (SIW) self-diplexing antenna, operating at wireless local area network bands (3.6 and 5.4 GHz), is proposed in this letter. The proposed antenna consists of two closely placed (0.022λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">g</sub> , where λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">g</sub> is the guided wavelength at 3.6 GHz) quarter-mode SIW resonators, exited by two coaxial probes. Two rectangular slots are added to the closed-ends of each resonator to generate additional capacitances. Therefore, both resonators operate below their fundamental frequencies, and hence, miniaturization is achieved. Moreover, a reliable circuit model is developed to validate the design process. The proposed antenna has ultracompact dimensions of 0.08λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">g</sub> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> with simulated gains of 4.9 and 5.34 dBi at 3.6 and 5.4 GHz, respectively. In addition, the simulated isolation levels are 32.5 and 36.6 dB at the lower and higher resonant bands, respectively. Furthermore, both resonant frequencies can be independently controlled by changing the length of the capacitive slots. Due to its compactness, independent resonance control and high isolation, the proposed antenna is suitable for compact and planar radio frequency components.

Empirical Quality Factor Prediction of Quarter-Mode Substrate Integrated Waveguide Resonators

Quarter-mode substrate integrated waveguide (QMSIW) is an effective technique to reduce the size of filters designed on SIW technology. An accurate prediction of the unloaded quality factor of QMSIW resonators helps to estimate the insertion loss of QMSIW filters. This article introduces new empirical equations to calculate the contribution of the finite conductor and radiation on the quality factors of QMSIW resonators. To show the accuracy of the equations, the calculated quality factor values are compared to values extracted from full-wave electromagnetic simulations for five different resonators at different frequencies and various substrate materials. For further comparison, these resonators were fabricated, and the quality factor values were extracted from measurements. The good agreement between simulations, measurements, and the predicted quality factors shows that accurate quality factor estimations can be made using the developed equations. Finally, a second-order filter is designed and fabricated to demonstrate the benefits of the proposed equations in microwave filter design.

SIW Cavity Backed Self-Diplexing Tunable Antenna

This communication presents a compact quarter-mode substrate integrated waveguide (QMSIW) cavity-backed self-diplexing tunable antenna. An open-ended slot is used to split the circular half-mode SIW (HMSIW) cavity resonator into two QMSIW cavity resonators. A varactor diode-loaded stub is added with each QMSIW resonator to achieve miniaturization and resonant frequency tuning. The miniaturization and tunability technique is demonstrated in a stand-alone QMSIW resonator and also in a QMSIW based self-diplexing antenna. The antenna is simulated, optimized, and subjected to practical testing inside a rectangular device. The device is treated as a quasi-receiver/transmitter, which consists of electronic circuitry and the proposed antenna. The resonant frequencies can be independently tuned by changing the values of the varactor diodes connected with each resonator. The simulated and measured results confirm that the proposed antenna can be tuned from 3.77 to 4.59 and from 4.96 to 6.1 GHz in the lower and higher frequency bands, respectively. The isolation between the two resonators in both bands is always better than 21 dB. The measured gains vary from 4.85 to 5.87 and 4.87 to 6.5 dBi in the lower and higher frequency bands, respectively. The proposed design shows stable and unidirectional radiation patterns in all tuning cases in both bands. The proposed self-diplexing tunable antenna is a competitive choice in compact and spectral-efficient radio frequency (RF) front ends where tuning is necessary for the efficient use of the frequency spectrum.

SIW Cavity-Backed Self-Quadruplexing Antenna for Compact RF Front Ends

A compact quarter-mode substrate integrated waveguide (QMSIW)-based self-quadruplexing antenna is proposed for compact radio frequency (RF) front ends. The QMSIW-based self-quadruplexing antenna has four unequal resonators resonating at the Industrial, Scientific, and Medical (ISM) band (2.45 GHz), fifth-generation (5G) band (3.5 GHz), wireless local area network (WLAN) band (4.9 GHz), and wireless fidelity band (5.4 GHz). All four resonators radiate through the open-ended wall of the QMSIW resonator and the arc-shaped slot inside the cavity. By properly optimizing the locations and dimensions of the resonators, higher isolation ( $>$ 29.9 dB) is gained. In fact, all four resonators operate on a common grounded substrate with negligible interference. A dummy rectangular device is used to keep the printed circuit board (PCB) and antenna in it to measure the S -parameters and radiation properties. The proposed antenna has a lower circuit size (0.23 $\lambda _{g}^{2}$ ), reasonable gain ( $>$ 3.85 dBi), high efficiency ( $>$ 82.7 %), and high isolation ( $>$ 29.9 dB). Based on the above-mentioned attributes, it is a good candidate for compact RF front ends.

Compact, Wide Stopband, Shielded Hybrid Filter Based on Quarter-Mode Substrate Integrated Waveguide and Microstrip Line Resonators

A novel miniaturized bandpass filter (BPF) with high stopband rejection based on a hybrid structure is proposed with shielded quarter-mode substrate integrated waveguide (QMSIW) and microstrip technologies. The shielded QMSIW cavity provides a high-quality ( $Q$ ) factor with substantial size reduction. This filter exhibits flexible response with four poles and two controllable transmission zeros (TZs) by incorporating two quarter-wavelength microstrip resonators into two back-to-back QMSIW resonators. The working principles for higher order mode suppression and filter coupling topology are carefully illustrated by eigen-mode simulation, coupling matrix, and field distribution analysis, respectively. Compared with the reported works, the proposed four-order BPF demonstrates advantageous features in terms of a compact size of $0.62\,\,\lambda _{0}\times 0.62 \,\,\lambda _{0}$ , a low insertion loss of 1.2 dB, a wide passband (22.7%), and a high stopband rejection (better than 36 dB).

Compact SIW-Based Self-Quadruplexing Antenna for Wearable Transceivers

This letter proposes a low-profile substrate integrated waveguide (SIW) cavity backed self-quadruplexing antenna for wearable transceivers. The full-mode circular SIW cavity is split into four unequal quarter-mode SIW (QMSIW) cavities using the two slots on the upper layer of the cavity. The proposed antenna uses C-shaped and arc-shaped slots of different dimensions in each QMSIW resonator to operate at wireless local area network bands (3.5, 4.9, 5.4, and 5.8 GHz). The measured gains are 4.4, 5.07, 5.40, and 5.7 dBi at 3.5, 4.9, 5.4, and 5.8 GHz, respectively. The antenna is simulated and optimized inside a 48 $\times \text{76}\times$ 21 mm3 rectangular device by keeping the device on the chest of a realistic human model. The proposed antenna has unidirectional radiation patterns in all four operating bands with low backward radiations. Thus, it has low specific absorption rate at all four operating bands.

Design of a Novel Quarter-Mode Substrate-Integrated Waveguide Filter With Multiple Transmission Zeros and Higher Mode Suppressions

This paper presents a novel quarter-mode packaged bandpass filter with four transmission zeros (TZs) in substrate-integrated waveguide (SIW) technology. The filter has an insertion loss of 2.85 dB at 30 GHz and fractional bandwidth of 20%. The design methodology of the TZs was first demonstrated to increase the attenuations of the filter stopband. The quarter-mode SIW resonators were analyzed with high-mode suppression by properly setting their feed points. The packaged filter was consistent between the simulation and measurement results and offers the advantages of compact configuration and easy integration with other devices. Mode suppressions of up to 110 GHz were also provided. The proposed concept is attractive for designing miniaturized and high-performance-packaged filters for 3-D millimeter-wave transceiver systems.

Compact QMSIW bandpass filter using composite right/left‐handed transmission line in grounded coplanar waveguide

A novel compact quarter-mode substrate integrated waveguide (QMSIW) bandpass filter based on composite right/left-handed transmission line (CRLH TL) in grounded coplanar waveguide (GCPW) is proposed in this work. Two unit cells CRLH TL is implemented at the inductive window of two coupled QMSIW resonators, does not occupy any extra area and minimizes size of the proposed filter. The characteristics of the CRLH unit cell are analyzed in order to get one transmission zero (TZ) at the lower stop band and one pole at the center frequency of the filter. Therefore two unit cells CRLH TL gives two poles at the center frequency and one TZ at the lower stop band of the filter. In addition to this, the proposed structure of the filter gives two more TZs at upper stop band to obtain better selectivity and wide stop band performance. To validate the proposed method, a fourth-order bandpass filter (BPF) is designed and fabricated on a single layer Rogers RO3003 substrate. The measured results are 14% fractional bandwidth (FBW) with 8.4 GHz center frequency, a return loss (RL) better than −18 dB, and an insertion loss (IL) less than −1.55 dB. Three TZs are obtained at 7.42, 9.97, and 13.42 GHz with rejection levels of −31.51, −28.43, and −53.56 dB, respectively. The simulation result shows a good match with measured S-parameters.

A Triangular-shaped Quarter-mode Substrate Integrated Waveguide based Antenna for WBAN Applications

&lt;p class="Abstract"&gt;In this study, a compact quarter-mode substrate integrated waveguide (QMSIW) based dual-band antenna is proposed for wireless body area network applications. A QMSIW resonator is realised by splitting the full-mode substrate integrated waveguide cavity along the perfect magnetic conductor walls. The proposed antenna preserves the fundamental mode TE110 and the third order mode TE220 of the square SIW cavity. The proposed antenna is linearly polarised in the lower band at 2.45 GHz and circularly polarised in the higher frequency band at 5.8 GHz. The on-body performance of the antenna is validated on a piece of pork muscle tissue and it has been found to be stable with respect to surroundings. The proposed antenna covers the ISM bands 44 MHz (2.445 GHz - 2.489 GHz) and 225 MHz (5.730 GHz - 5.955 GHz) at 2.45 GHz and 5.8 GHz, respectively. The measured gain of the antenna on pork tissue is 1.87 dBi and 5.5 dBi at two bands. In addition, the specific absorption rate is obtained of 0.65 mW/g and 1.51 mW/g at two bands (wext = 2 mm), averaged over 1 g of muscle with 100mW input power. Moreover, the simulated and experimental results demonstrate a good agreement.&lt;/p&gt;

Compact Bandpass Filter With High Selectivity Using Quarter-Mode Substrate Integrated Waveguide and Coplanar Waveguide

This letter presents a bandpass filter (BPF) based on a hybrid structure of quarter-mode substrate integrated waveguide (QMSIW) and coplanar waveguide (CPW). By incorporating two CPW resonators into two QMSIW resonators, the proposed filter obtains a high selectivity as the coupling between two CPW resonators is electric coupling, which helps to generate two transmission zeros. It also achieves compact layout as the embedded CPW resonators do not occupy extra area. In order to verify the design, a BPF with a center frequency of 8.7 GHz is fabricated and measured. The measured results show good agreement with the simulation results.

Ultra-Miniature SIW Cavity Resonators and Filters

This paper presents ultra-miniature substrate integrated waveguide (SIW) cavity resonators, and filters by employing ramp-shaped slots as interdigital capacitors (IDCs) to force the structure to operate in the first negative-order resonance mode. Additionally, a metal patch in the middle metal layer along with disconnected vias is used to increase the equivalent series capacitance of the resonator and accordingly the miniaturization factor. By applying this method to half-mode SIW (HMSIW) and quarter-mode SIW (QMSIW) resonators, 90%, and 95% of miniaturization is achieved, respectively, compared to conventional full-mode SIW resonators. Afterwards, a two-pole bandpass filter is proposed based on the presented QMSIW resonator. Also, by using a combination of HMSIW and QMSIW ultra-miniature resonators, two trisection filters with a controllable transmission zero on either side of the passband are presented. To the best of authors' knowledge, this is the first disclosure of simultaneous use of HMSIW and QMSIW resonators to achieve asymmetric filter response with an ultra-compact size.

Compact Triple-Mode Filter Based on Quarter-Mode Substrate Integrated Waveguide

An isosceles right triangular waveguide with one electric wall and two magnetic walls is proposed to design a triple-mode filter implemented in a substrate integrated waveguide. The complete closed-form modal solutions are presented for both transverse electric and transverse magnetic modes in the isosceles right triangular waveguide. The resonant frequencies of a resonator made of a short isosceles right triangular waveguide can then be calculated. A structure called a quarter-mode substrate integrated waveguide (QMSIW) is introduced to realize the proposed triangular waveguide resonator in a compact and planar form. Simulated electric field distributions of modes excited in the QMSIW are in good agreement with theoretical predictions for the solid waveguide structure, demonstrating the feasibility of QMSIW resonators. Finally, a compact triple-mode filter is designed and fabricated based on the discussed QMSIW. The frequency responses and group delay of the filter are tested, and measured results agree very well with simulated ones. This demonstrates that the proposed QMSIW structure is an excellent candidate for compact triple-mode filters.

A COMPACT WIDEBAND BANDPASS FILTER USING NOVEL CSRR LOADED QMSIW RESONATOR WITH HIGH SELECTIVITY

A novel quarter-mode substrate integrated waveguide (QMSIW) resonator with back-to-back triangular complementary split-ring resonators (CSRRs) etched on the waveguide surface is proposed in this paper. The proposed CSRR structures allow the implementation of a forward-wave passband propagating with high selectivity below the characteristic cutofi frequency of the conventional QMSIW. Utilizing the property of ∞exible open structure on QMSIWs' two sides, a cascaded quadruplet (CQ) bandpass fllter (BPF) using the proposed QMSIW resonator and proximity coupling structure is presented. Compared with some other reported BPFs with SIW technique, the presented BPF using the novel QMSIW resonator has great improvements on size reduction and selectivity, simultaneously, with simple geometry. At the center frequency of 3.7GHz, the designed BPF fllter achieves a wideband with a fractional bandwidth up to 24.3% and a high selectivity with a shape factor of 1.23. The compact dimension of this fllter is as small as 0.36‚g £ 0:36‚g, where ‚g is the guide wavelength at the center frequency. The proposed fllter is simulated, fabricated and tested. The measured results are in good agreement with the simulation.