Substrate Integrated Waveguide Bandpass Filter Research Articles

Compact dual‐band balanced SIW bandpass filter with two adjustable closed‐passbands

A new compact multilayer dual-band-balanced bandpass filter (BPF) with two flexibly adjustable closed-passbands based on substrate-integrated waveguide (SIW) resonator is proposed in this letter. Both TE102-mode and TE201-mode of the resonator are utilised to achieve desired differential mode (DM) transmission and high common mode suppression. Two SIW cavities are properly coupled in the back-to-back form to realise a closed dual-passband-balanced response by virtue of singly one cruciform coupling aperture etched on the ground. Additionally, two pairs of perturbed slotlines are elaborately introduced on the top and bottom layers to perturb the resonant frequencies of TE102-mode and TE201-mode, realising both adjustable upper- and lower-DM passbands. For demonstration, a prototype dual-band-balanced SIW BPF operating at 12.7 and 15.5 GHz is designed, fabricated and tested. Measured and simulated results are in good agreement, verifying the feasibility of the design concept.

High CM suppression balanced SIW BPF and HMSIW directional coupler utilising perfect electric conductor/perfect magnetic conductor characteristic

In this study, high common-mode (CM) suppression balanced substrate-integrated waveguide (SIW) bandpass filter (BPF) and half-mode SIW (HMSIW) directional coupler are formed by two vertically stacked identical SIW or HMSIW single-ended ones and an aperture etched on the common ground between them. Under CM operation, the aperture is perfect magnetic conductor (PMC). When the height is less than λ g/4, the space between perfect electric conductor and PMC cannot transmit electromagnetic wave and a total reflection is got at the aperture edge. So, the aperture structure in SIW can effectively cut off CM noise over a wide frequency range. For the HMSIW, the spoof surface plasmon polariton structure is further loaded in the aperture near the open circuit plane to suppress the slot line mode (main TE mode). The CM suppression can be basically made independent of differential-mode response, which is very important to simplify the design and tuning processes. Finally, high CM suppression balanced SIW BPF and HMSIW directional coupler are designed and fabricated. Good agreements between the simulated and measured results demonstrate the validity of proposed configurations.

A novel dual-band bandpass SIW filter loaded with modified dual-CSRRs and Z-shaped slot

In this paper, a novel dual-band bandpass substrate integrated waveguide (SIW) filter has been presented by loading two modified dual complementary split ring resonators (CSRRs) and a Z-shaped slot on the top side of SIW. The modified dual-CSRR structure is obtained by folding its outer ring, adding T-shaped branch to its inner ring and placing the splits of the inner and outer rings of CSRR in the same direction. The modified structure allows the electromagnetic wave to propagate in the passband below the cutoff frequency of the waveguide. Compared with conventional CSRR of the same size, it has two passbands and work at a lower frequency. A dual-band bandpass filter is proposed by placing two proposed dual-CRSSs face-to-face on the top side of SIW. In order to improve the performance of the filter, the Z-shaped slot is introduced to enhance the electromagnetic coupling, thus increasing the transmission zero point, broadening the passband and enhancing the flatness in the band, and realizing the center frequency shift of the passband to the left. To validate the design and analysis, a dual-band bandpass SIW filter loaded with two modified dual-CSRRs and a Z-shaped slot is manufactured and measured. The first pass band of the filter has a center frequency of 1.94 GHz, a 3 dB band width of 0.28 GHz, the second pass band has a center frequency of 4.85 GHz and a 3 dB band width of 0.13 GHz, which is basically consistent with the simulation results.

Wide-Stopband SIW Filters Using Modified Multi-Spurious Modes Suppression Technique

A modified multi-spurious modes suppression technique is proposed to realize wide-stopband substrate-integrated waveguide (SIW) bandpass filters (BPFs), which is to set the external ports and internal coupling windows to the positions of weakest electric fields of specific spurious modes. To extend the stopband as wide as possible with the limited design degrees of freedom, different feeding and coupling positions are fully exploited to reject unwanted modes in specific cavities. By suppressing the out-of-band spurious peaks as much as possible and removing the first unsuppressed spurious resonance to the farthest position, the widest stopband can be achieved intrinsically. A second- and a third-order SIW BPFs are synthesized, designed, fabricated, and tested as demonstrations, realizing the stopbands of $2.51{f} _{0}$ and $3.85{f} _{0}$ with the rejection level better than 25 dB and 20 dB, respectively.

Post-Loaded Substrate-Integrated Waveguide Bandpass Filter With Wide Upper Stopband and Reduced Electric Field Intensity

In this letter, we present analytic approaches to obtain a wide upper stopband and to reduce the magnitude of the electric field intensity in designing a bandpass filter using the fundamental mode of post-loaded substrate-integrated waveguide (SIW) resonators. As the filter is made with two commercially available substrates, there are two dielectric and three ground layers. This letter particularly shows that the ground layer in the middle has an impact on the upper stopband and the electric field intensity and proposes a methodology to control them. For demonstrating our new approach, we have designed a third-order filter centered at 5 GHz with the bandwidth of 330 MHz.

Miniaturized SIW Bandpass Filter Based on TSV Technology for THz Applications

A miniaturized substrate integrated waveguide bandpass filter with an area of 0.682 × 0.210 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> is proposed based on through-silicon via (TSV) technology for terahertz (THz) applications. The design method of the THz cavity filter based on rectangular TSV is introduced and the filtering characteristics are investigated by the finite element method and the mode matching method. The rectangular TSV is substituted by cylindrical structures and the THz cavity filter is fabricated and measured in order to investigate the possibility of integration with typical three-dimensional integrated circuit manufacturing processes. The cavity filter utilizing cylindrical TSV exhibits a bandwidth of 0.051 THz centered at 0.331 THz, an insertion loss of 1.5 dB, and a reflection of higher than 15 dB in the passband.

Editorial

Chris Toumazou & Ian White 2019 has been a year of exciting development for Electronics Letters. The subjects of our published papers continued to diversify, reflecting the expansion of its editorial board – the board now has in excess of 240 members, with 21 new members joining in 2019. 40 countries are represented, and we are certainly hoping to expand further, given that over sixty countries are numbered amongst the 4000 submissions to the journal. The submissions span the entire scope of electrical and electronic engineering, from implantable antibacterial electronics to distinguishing LEDs based on spectral features; or from optical self-injection to machine learning in a variety of forms. A solution for the ubiquitous problem of DOA estimation for co-prime arrays won the 2019 IET Premium Award: ‘Improved DOA estimation algorithm for co-prime linear arrays using root-MUSIC algorithm’, by Dong Zhang, Yongshun Zhang, Guimei Zhang, Cunqian Feng and Jun Tang, [Electronics Letters, 2017, 53, (18), pp. 1277–1279]. This paper proposes an improved algorithm, which provides a solution to the matching error problem. The algorithm also makes full use of signal space and noise space to improve the estimation accuracy with low complexity. The judges were impressed by the mathematical derivation of the proposed algorithm and the completeness of its description. The submission has proved popular and has been cited many times, reflecting the necessity of the solution and the effectiveness of the method. We have had some fantastic contributions from members of our editorial board. One such contribution comes from board member Alexander Wong along with Mohammad Javad Shafiee, Brendan Chwyl and Francis Li in their submission “GenSynth: a generative synthesis approach to learning generative machines for generate efficient neural networks”. [Electronics Letters, 2019, 55, (18), pp. 986–989]. Wong et al gave an insight into their work on GenSynth, which can automatically generate highly efficient deep neural networks. This generative synthesis is a powerful approach for accelerating and improving the building of deep neural networks for on-device edge scenarios. We look forwards to hearing more about future work involving GenSynth and how it can be applied to image and signal processing tasks. Electronics Letters’ wide scope means we publish a wide variety of interesting research. An example of such a submission was published towards the end of 2019: ‘Implantable cathodic voltage controlled electrical stimulator’ by K. Weeks, C. Clark, M. Tobias, E. McDermott, T.Duquin, M. Ehrensberger and A. H. Titus, [Electronics Letters, 2019, 55, (23), pp. 1215–1217]. This fascinating work presents an implantable device for use with orthopaedic devices. The iCVCES (cathodic voltage controlled electrical stimulation) device could be used in the future to reduce the rate of periprosthetic joint infection, the complications of which are currently projected to cost the US economy over $55 billion by 2030. One of the biggest benefits of the device is that it can be implanted without requiring wiring to the external environment, meaning it can remain in a patient for an extended period of time. In addition, it can wirelessly monitor the patient and transfer data via Bluetooth to a computer. Antennas and Propagation is one our most popular categories year-round. This year has seen a great number of interesting papers on novel antenna and component design, for example: ‘Balanced triple-mode substrate integrated waveguide bandpass filter’, by Qing Liu, Dalong Lv, Dongfang Zhou and Dewei Zhang. [Electronics Letters, 2019, 55, (15), pp. 843–845]. The proposed substrate integrated waveguide bandpass filter boasts a high common-mode suppression, a compact size and a controllable bandwidth. The device could see use in in a number of radiofrequency and microwave applications, especially in the emerging 5G market. It's always fantastic to see so many innovative designs in this field. These highlights, as well as the hundreds of papers published each year by Electronics Letters, represent the great journey ahead for the journal and for the subject as a whole. Finally, we would like to thank the editorial and production teams at the IET, the editorial board, and of course the many thousands of peer-reviewers who make the journal possible. That the reviewers and our board members take the time out of their busy schedules and roles to support the community is hugely appreciated, and is one of the reasons that the community, not just Electronics Letters, is flourishing.

Compact and Wide Stopband Substrate Integrated Waveguide Bandpass Filter Using Mixed Quarter- and One-Eighth Modes Cavities

This letter presents the design of mixed quarter- and one-eighth modes substrate integrated waveguide (SIW) bandpass filter (BPF). The transmission zeros (TZs) of the proposed SIW BPF can provide wide stopband response and high selectivity characteristics by using different mode SIW cavities. For validation, two- and three-stage SIW BPFs with Chebyshev response were designed at a center frequency ( $f_{0}$ ) of 8 GHz. The measured results are consistent with the simulations. For two-stage BPF, the insertion loss smaller than 0.9 dB is measured within the passband of 0.65 GHz (7.75–8.4 GHz). The return loss higher than 19.7 dB is measured within the same passband. The spurious is produced at around 18 GHz ( $ ). The stopbands are attenuated more than 17.31 dB from the dc to 5.68 GHz ( $0.71f_{0}$ ) and from 9.28 GHz ( $1.16f_{0}$ ) to 16.67 GHz ( $2.08f_{0}$ ). The TZs are produced at 10 GHz and around 18 GHz due to a small cross-coupling between source/load and the interaction of the higher resonant modes of cavities, respectively. For three-stage BPF, the $\vert S_{21}\vert $ and $\vert S_{11}\vert $ smaller than −1.3 dB and −18 dB are measured within the passband of 7.57–8.45 GHz fractional bandwidth (FBW = 11%), respectively. The TZs are produced at 1.102, 1.9, and $2.39f_{0}$ and provide higher selectivity and attenuation compared to two-stage BPF.

Compact reconfigurable triple‐mode triple‐band substrate integrated waveguide bandpass filter

In this study, a reconfigurable triple-band triple-mode substrate integrated waveguide filter is designed and fabricated in the C-band spectrum. A novel and simplified design procedure based on analytical equations is proposed. The filter design also benefits from a reconfigurable structure, using metallic via holes as perturbation, allowing wide-band selectivity of the C-band spectrum (from 4.4 to 6.9 GHz). Moreover, the filter benefits from a magnetic coupling solution between the resonators, which only couples the first three modes and rejects the next resonating modes. Therefore, a large bandgap in the spectrum is achieved. The proposed structure is fabricated and measured, and a high similarity between the simulation and fabrication is observed. The measured results show that the first band can be tuned in the frequency range of 4.4 to 7, the second band can be tuned in the range 5.8 to 7.7 GHz, and the third band from 5.8 to 7.7 GHz. The insertion loss 1.5 to 2.5 dB, 2 to 3 dB, and 2.5 to 3.5 dB for the first, second, and third bands, respectively.

New negative coupling structure and its application on substrate integrated waveguide bandpass filters

To design cross-coupled substrate integrated waveguide (SIW) bandpass filters (BPFs) with high performance, a new negative coupling structure is proposed, which is constructed by two coupled lines with shorted ends. The negative coupling structure is analyzed in detail. The stracture which can realize both relatively weak and strong negative coupling strength. The optimization method based on characteristic polynomials and reference zeros and poles of scattering parameters is realized for the filter design. To verify the proposed negative coupling structure, two fourth-order cross-coupled SIW BPFs with the center frequency of 10 GHz based on the optimized coupling matrixes are designed. The first one has a normalized bandwidth of 3% with a negative coupling in one cross-coupling path to illustrate the realization of weak negative coupling strength, and the second one has a normalized bandwidth of 8% with a negative coupling in one main coupling path to illustrate the realization of strong negative coupling strength. Finally, the two BPFs are fabricated and measured. Simulation and measurement results are in good agreement, which demonstrates the feasibility of the proposed negative coupling structure and its application on cross-coupled SIW filters with high performance. The influence of weak disperse cross coupling on locations of transmission zeros is also discussed.

Multi‐layered dual‐mode substrate integrated waveguide bandpass filter with input and output ports located on same substrate layer

This study reports a multi-layered dual-mode substrate integrated waveguide (SIW) bandpass filter (BPF), in which the input and output ports are located on the same substrate layer (i.e. the upper one). The dual-mode SIW cavity in the lower substrate layer is coupled to the upper dual-mode SIW cavity by two crossed slots, which can independently control the inter-couplings. The proposed filter can be modelled by a dual-extended doublet coupling scheme with considering bypass couplings between source and load. Based on the proposed structure, single- and dual-band filtering responses with four controllable finite-transmission zeros (FTZs) are realised and analysed. For the demonstration, a single-band filter and a dual-band filter were fabricated and measured. The measured results agree well with simulated ones.

Triple‐mode bandpass filter

triple‐mode bandpass filter

Balanced triple‐mode substrate integrated waveguide bandpass filter

This Letter proposes a novel balanced triple-mode substrate integrated waveguide (SIW) bandpass filter for the first time. The new triple-mode resonator is realised by a square-shaped SIW cavity with a capacitive loading patch. The resonance of higher-order mode TE 301 can be controlled and shifted to that of modes TE 102 and TE 201 . High-performance common mode suppression, controllable bandwidth, compact size and quasi-elliptic differential mode response can be achieved. For demonstration, a balanced triple-mode SIW filter is designed, fabricated and measured.

A Millimeter-Wave Gain-Filtering Transmitarray Antenna Design Using a Hybrid Lens

This letter proposes a millimeter-wave gain-filtering transmitarray (TA) antenna using a hybrid lens. The hybrid lens is incorporated by a substrate integrated waveguide (SIW) cavity bandpass filter and a dielectric lens. The dielectric lens serving as a phase shifter is seamlessly coated on the SIW bandpass filter to achieve a codesigned architecture. The proposed hybrid lens unit cell (UC) is required not only to fulfill the desired phase shifts but also maintain a stable bandpass response, simultaneously. Therefore, the specific shape of the dielectric-lens UC must be optimized to minimize its impacts on the bandpass response of the original SIW bandpass filter as much as possible to ensure the filtering performance of the proposed hybrid-lens UC. After some optimizations, the dielectric-lens UC based on the air-perforated dielectric square post (APDSP) is determined finally. The simulated results show that the bandpass responses of the hybrid-lens UC are still maintained when the profile of the APDSP-based dielectric-lens UC is varied to satisfy a full phase-cycle (2π). The proposed hybrid-lens UCs are arranged reasonably to construct a TA antenna to fulfill the high gain and gain-filtering performance. The simulated and measured results are consistent, revealing the proposed TA antenna has a gain of 25.5 dBi at 35 GHz and a bandpass gain-filtering response over 30-40 GHz.

Two- and Four-Pole Multilayer SIW Filter with High Selectivity and Higher-Order Mode Suppression

Abstract This letter presents an approach to design two-pole source-load coupling and four-pole cross-coupling substrate integrated waveguide (SIW) bandpass filters based on multilayer process. Utilizing the field distribution, the vertical magnetic and electric coupling of fundamental mode is designed by suppressing the first spurious mode. Then, source-load and cross-coupling schemes are realized with controllable features in two-pole and four-pole filters, respectively. The harmonic passband produced by TE102 mode can be suppressed by proper coupling technique enabling the connection with TE102 mode in two- and four-pole filter designs, respectively. Three transmission zeros, which are derived from source-load coupling, are introduced around the passband of two-pole filter to improve its selectivity. In the four-pole filter design, a six-order cross-coupling scheme including source and load produces four transmission zeros around the passband, leading to a sharp selectivity. In addition, another transmission zero is generated at the adjacent location of the passband to improve the out-of-band rejection. Compared with conventional horizontally coupled filters made of single layer, the proposed filters show a compact size. To demonstrate the proposed design method, a two-pole and a four-pole double-layered SIW bandpass filters are fabricated and measured. Measured results show that the proposed filters exhibit high selectivity and good out-of-band rejection, as well as a good agreement between simulated and measured results.

A Compact Wideband SIW Bandpass Filter with Wide Stopband and High Selectivity

A novel method to design a wideband substrate integrated waveguide (SIW) bandpass filter (BPF) with compact size, wide stopband and high selectivity is presented. In this method some unique electromagnetic band-gap (EBG) cells are periodically etched on the top layer of SIW to realize a wide passband propagating below the equivalent waveguide cutoff frequency. By changing the configuration of EBG cells, undesired harmonics in upper stopband can be suppressed and a wideband BPF with wide stopband can be obtained. By symmetrically loading two complementary split ring resonators (CSRRs) on the tapered gradient lines of the input/output ports, a transmission zero near the passband can be introduced, and it makes the frequency selectivity of upper sideband improve significantly. As a verification, a wideband SIW BPF with a 3.02 GHz absolute bandwidth (ABW) and a 64.7% fractional bandwidth (FBW) centered at 4.67 GHz is designed, simulated, manufactured, and measured. The results of the experiment and simulation are in good agreement.

Wideband Substrate Integrated Waveguide Bandpass Filter Based on 3-D ICs

This paper proposes a substrate integrated waveguide bandpass filter (SIW BPF), exploiting the through-dielectric via (TDV)-based 3-D integrated circuit (3-D IC) technology. The SIW BPF is designed on the dielectric cavity that is etched on the traditional low-resistivity silicon (LRSi) in a 3-D IC system, acting as the insulating material between through-silicon via plugs and LRSi. This construction can reduce prominent eddy current losses in LRSi and coupling losses among TDV plugs for the millimeter-wave application. Benzocyclobutene and glass are chosen as the dielectric cavity due to the low dielectric constant and loss tangent. The detailed design procedure beginning from the normalized Chebyshev low-pass filter to the final optimized SIW BPF is presented. The filter having a 12.5% fractional bandwidth is centered at 159.67 GHz. The return losses and insertion loss across the passband are about −10 and −1.5 dB, respectively. Numerical analysis of the advanced design system and full-wave simulation results of Ansoft’s HFSS show a good agreement.

Design and optimization of a planar folded substrate integrated waveguide bandpass filter exploiting aggressive space mapping

Substrate integrated waveguide (SIW) is a new structure for microwave transmission. In this paper, a planar folded sixth-order SIW filter is designed with aggressive space mapping (ASM) algorithm. Its center frequency is 22 GHz, 3 dB bandwidth 1 GHz, and in-band return loss 22 dB. The filter satisfies design specifications after four iterations, and is fabricated using micro-electro-mechanical systems (MEMS) technology with a chip size of 7.5 mm × 8.5 mm × 0.4 mm. Measurement results show that the center frequency of the filter measures at 22.2 GHz, 3 dB bandwidth at 1 GHz, insertion loss at 3.57 dB, return loss at 22 dB and out-of-band rejection at 40 dB.

SIW bandpass filters in modified box‐section scheme with bypass/constant/frequency‐dependent coupling in diagonal cross‐coupling path

Here, three fourth-order bandpass filters (BPFs) in modified box-section schemes using substrate integrated waveguide (SIW) are proposed and researched. The proposed filters are based on a conventional box-section structure with considering bypass/constant/frequency-dependent coupling (FDC) in the diagonal cross-coupling path to construct new filtering responses. Based on the different type of the cross-coupling path, the frequency response of each proposed structure is analysed and presented, which indicates that the proposed filters have flexible response in terms of finite transmission zeros (FTZs). The proposed filters can realise generalised Chebyshev responses with one/two/three FTZs at arbitrary positions. Moreover, one FTZ may be produced by using bypass coupling and direct inductive coupling window to improve lower stopband performance, which is verified by a coupling matrix. For the demonstration, three quasi-elliptic response filters were designed, fabricated, and measured. Good agreement is achieved between simulated and measured results.

Substrate Integrated Waveguide Bandpass Filters in Box-Like Topology With Bypass and Direct Couplings in Diagonal Cross-Coupling Path

Substrate integrated waveguide (SIW) bandpass filters in box-like topology based on combining single- and dual-mode cavities are presented. Two coupled TE101-mode-based cavities are coupled to one square-shaped dual-mode (modes TE102 and TE201) cavity to realize the box-like coupling scheme in which bypass and direct couplings can provide the diagonal cross-coupling path. Based on the characteristics of dual-mode SIW and multiple energy flow paths, the superior design flexibility in terms of TZ positioning has been realized and demonstrated. Finally, two asymmetrical response SIW filters with two lower TZs, a quasi-elliptic SIW filter with three TZs and a filter with linear-phase response are simulated, fabricated, and measured to demonstrate and verify the proposed structure.