Single-layer Substrate Integrated Waveguide Research Articles

A single‐layer substrate‐integrated waveguide filtering antenna with three independently controllable radiation nulls

AbstractIn this paper, a single‐layer substrate‐integrated waveguide (SIW) filtering antenna with three independently controllable radiation nulls is presented. The antenna consists of a single‐layer SIW loaded with two radiation gaps, four metallization columns, and folded‐type slots etched on the chip. The back‐cavity double slots are responsible for extending the bandwidth and realizing the radiation function. Three radiation nulls are generated by analyzing the current distribution of the radiation chip, radiation gap, and folded slots. By adjusting the radiation gap distance, the length of the radiation gap, and the folded slot, three broadside radiation nulls are independently controlled without influence on each other. Therefore, flexible out‐of‐band suppression characteristic is obtained. For demonstration, a prototype is fabricated and tested. The measurements match the simulation results better. The filtering antenna operates at 3.70 GHz with a bandwidth of 5.68% (3.59–3.80 GHz), achieving an average realized gain of 5.10 dBi in a flat passband. The out‐of‐band rejection level exceeds 20 dB.

A simple SIW balanced directional coupler with high common‐mode suppression

AbstractIn this letter, a simple balanced directional coupler with high common‐mode (CM) suppression is designed by using a single‐layer substrate‐integrated waveguide (SIW). The SIW can be considered a naturally balanced structure. The CM noises are able to be intrinsically suppressed when differentially excited along the symmetric H‐plane of SIW. The coupling window with tapered transition is designed for broadening the bandwidth of 3‐dB coupling. The microstrip differential feeding structure with inductive vias and inductive matching section enables planar integration and better impedance matching. Finally, a SIW balanced directional coupler operating at 14–16 GHz is designed and fabricated. Measured results are in good agreement with simulated ones.

A broadband single-layer substrate integrated waveguide cavity-backed slot array antenna with improved gain

ABSTRACT A single-layer substrate-integrated waveguide (SIW) cavity-backed slot array antenna with broad impedance bandwidth and improved gain is presented in this paper. In the element design, a multi-branch slot and a pair of inclined slots are designed on the top layer of the SIW as radiating structure and the grounded coplanar waveguide feeding structure are used for impedance matching, which ensures that the triple special resonant modes with the odd TE120 mode, the half TE120 mode, and a hybrid mode can be excited successfully to obtain broad impedance bandwidth and high gain, because of its low order and adjacent working frequencies points. Following this, an array antenna consisting of four elements and a four-way microstrip feeding network using only single-layer substrate structure is simulated and fabricated. The measured impedance bandwidth of the four-element array antenna achieves up to 34.4% and the measure peak gain at desired frequency band is 14.4 dBi with an aperture efficiency of 71.1%. The measured results prove that the proposed design has advantages of simple structure, broadband, and high gain, which is expected to be applied in high-speed vehicular communication system.

A novel single layer SIW 6 × 6 beamforming network for 5G applications

A novel single layer 6 × 6 beamforming network (BFN) based on substrate integrated waveguide (SIW) is proposed for 5G applications. The proposed BFN is realized by 3 × 3 multi-aperture couplers (MACs), hybrid couplers, phase shifters, and crossovers. The BFN is designed for equal power division and ± 30°, ± 90°, ± 150° phase difference between output signals in the 28–32 GHz frequency band. By feeding a 6 × 2 SIW slot antenna array with proposed BFN, a six-beam antenna is implemented that generates six symmetrical beams in the ± 11°, ± 31°, and ± 52° directions. To confirm the simulation results, the proposed six-beam antenna is fabricated and measured. The simulation and measurement results show that the six-beam antenna has good radiation patterns, −10 dB impedance bandwidth from 28 GHz to 32 GHz, and a 3-dB wide-angle coverage of about 150°. The size of the antenna is 106 × 31.8 × 0.787 mm3, which is suitable for 5G applications.

Substrate Integrated Waveguide Quasi-Elliptic Filter with Arbitrary Termination Impedances

This paper presents a quasi-elliptic filter (QEF) with arbitrary termination impedances (ATI). The proposed QEF is designed by adding cross-coupling between the first and last resonators of an ATI bandpass filter (BPF) with the Chebyshev response. The proposed QEFs with ATI can be designed in even-order resonators and the location of the pair transmission zeros (TZs) is controllable. To prove the validity of the proposed design, the fourth-order QEFs with ATI were implemented on a single-layer substrate-integrated waveguide (SIW) cavity at a center frequency (<i>f</i><sub>0</sub>) of 10 GHz with the pair TZs at 10 ± 1.4 GHz. These SIW QEFs with ATI improve frequency selectivity and effectively suppress the out-of-band signal with high power handling. The measured maximum insertion loss (|<i>S</i><sub>21</sub>|) and minimum return loss (|<i>S</i><sub>11</sub>|) of the SIW QEF with unequal real-to-real ATI are 0.93 dB and 17.4 dB, respectively, in the passband. Similarly, the maximum |<i>S</i><sub>21</sub>| and minimum |S<i>S</i><sub>11</sub>| of the SIW QEF with complex-to-real ATI are 1.2 dB and 18 dB, respectively.yer substrate-integrated waveguide (SIW) cavity at a center frequency (

Single-Layer Substrate-Integrated Waveguide Inline Filters With Flexible Transmission Zeros

This letter presents a novel class of single-layer substrate-integrated waveguide (SIW) inline filters with flexible transmission zeros (TZs). The basic structure is an oversized half-mode SIW (HMSIW) rectangular cavity (RC) perturbed by a pair of metallic via-holes or an open-ended slotline. Each perturbed HMSIW RC can provide one pole and two TZs. By changing the distance between the perturbation via-holes or the length of the perturbation slotline, one TZ can be moved either above or below the passband, while the other is always located above the passband. Based on these perturbed HMSIW RCs, two SIW three-pole inline filters are fabricated and measured to validate the design concept.

A planar balanced‐to‐balanced filtering power divider with in‐band common‐mode suppressions and self‐isolation

A compact balanced-to-balanced (BTB) filtering power divider (FPD) with in-band common-mode (CM) suppressions based in a single-layer substrate-integrated waveguide (SIW) is presented in this article. This FPD mainly consists of one full-mode and two half-mode SIW cavities where each cavity's differential-mode (DM) and CM are designed reasonably. The filtering DM signals to dual-ports power division is realized with a simple and compact configuration. Moreover, the CM signals can be naturally rejected without any additional isolation circuits. Ultimately, the BTB FPD with a center frequency of 10.5 GHz is designed, fabricated, and measured to verify the proposed design concept, which shows below −15 dB 6% DM filtering fractional bandwidth (FBW). The CM transmission is suppressed below −22 dB over 28.6% FBW. The proposed design exhibits the advantages of compact size, simple design, low loss, planarity, and multi-function fusion.

Wideband Butler Matrix Based on Dual-Layer HMSIW for Enhanced Miniaturization

This letter proposes a miniaturized wideband Butler matrix (BM) based on dual-layer half-mode substrate integrated waveguide (HMSIW) structure. By virtue of the excellent features of shorter guided wavelength, flatter in-band phase slope, and more compact size of HMSIW, simple and compact couplers and phase shifter are newly designed for BM. Finally, a BM prototype is designed, fabricated, and measured. Benefiting from the proposed structure, size miniaturization over 90% is achieved in comparison with the traditional single-layer substrate integrated waveguide (SIW) type.

Design of high roll‐off frequency selective surface based on single‐layer SIW cavity with fully canonical filtering responses

In this paper, a novel design of high roll-off frequency selective surface (FSS) is proposed based on a single-layer substrate integrated waveguide (SIW) cavity. Fully canonical filtering responses with three transmission poles (TPs) and three transmission zeros (TZs) are obtained by employing transversal signal-interference techniques (TSITs). The FSS unit cell can be regarded as a combined triple-mode cavity consisting of one cross-slot resonator and two SIW cavities. By using the filtering coupling matrix, the FSS can be well designed and analysed. Accordingly, to verify the design concept, a prototype is fabricated and experimented. Measured and simulated results are in good agreement, showing high performances in terms of high roll-off and low profile.

Wideband Single-Layer Substrate Integrated Waveguide Filtering Antenna With U-Shaped Slots

A wideband single-layer substrate integrated waveguide (SIW) filtering slot antenna with compact structure is investigated, which is originated from a SIW resonant cavity operating at its TE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">110</sub> mode. A straight radiating slot is integrated on the top surface of the cavity. The resonator can be splitted into two half-mode resonators, generating a radiation null at higher edge of the passband. At same time, two U-shaped slots are etched on the bottom surface of the cavity. One of the U-shaped slots is used to introduce a radiation null at the left edge of the passband while the other U-shaped slot introduces the modified half-TE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">110</sub> mode in the right half cavity, broadening the bandwidth of the antenna. Finally, the third-order filtering antenna is obtained with 11.84% impedance bandwidth in only one SIW resonant cavity. To validate design, a prototype is fabricated and measured. Compared with other designs, the proposed antenna owns features of simple structure, wide bandwidth, and compact size, satisfying the increasing requirement for the miniaturization and integration of RF devices.

A wide stopband multilayer substrate integrated waveguide bandpass filter with suppression of higher-order mode coupling

AbstractThis paper presents a compact multilayer substrate integrated waveguide (SIW) bandpass filter with wide stopband. The square SIW cavity resonators in multilayer substrates are horizontally and vertically coupled with magnetic coupling. By properly designing the coupling structure, the couplings between the higher-order resonant modes can be suppressed. Compared with the conventional single-layer SIW filters, the proposed multilayer SIW filter also exhibits a compact size. To verify the design concept, a double-layered SIW filter is fabricated and measured. The measured results agree well with the simulations. The measured results show that the upper stopband of the filter is extended to 2.73 times of the center frequency 8.02 GHz.

A compact dual-fed highly isolated SIW based self-diplexing antenna

A compact high-isolation self-diplexing antenna is designed on a single-layered substrate integrated waveguide (SIW) cavity for dual-frequency communication in C-band. The antenna design procedure is straightforward. The antenna is backed by an SIW cavity for possible low back-lobe radiation and easy circuit integration. One rectangular and one triangular patch are created on the top-side of the SIW cavity to radiate at 4.18 GHz and 7.8 GHz respectively. Two planar inset-feed lines orthogonal to each other, are employed to excite the resonator. The inset depths of the feedlines are designed to obtain low interference and high isolation. The antenna achieves peak gain of 5.88 dBi and 6.62 dBi at lower and upper resonant frequencies respectively. The antenna supports independent frequency tuning-design and easy frequency-ratio control. The proposed design is fabricated on a RT/Duroid 5870 substrate and is characterized for validation.

The Design of Pixelated SIW Horn Antennas With Nearly Equal Beamwidths Using Binary Ink Stamp Optimization

In this paper, linearly and circularly polarized single-layer Substrate Integrated Waveguide (SIW) horn antennas with nearly equal half power beamwidths in principal planes for the 24 GHz ISM band are designed. The uniqueness of the solution lies in the application of a pixelated structure to the design of these SIW horn antennas. For the design, a novel heuristic algorithm called Binary Ink Stamp Optimization is proposed. At first, the ability of the proposed algorithm is proved over fifteen benchmark functions and compared with the results of six state-of-the-art optimization algorithms. Then, the novel algorithm is exploited for the design of the pixelated part of the antennas. The antennas are manufactured using low-cost 3D printing technology. The experimental results prove that the linearly polarized antenna has a reflection coefficient below −18 dB in the whole 24 GHz ISM band. At the center frequency of this band, the antenna gain is 14.2 dBi, and the level of side lobes is below −15 dB in E and H-planes. In addition, E and H-plane half power beamwidths are 26.5° and 25°, respectively. The circularly polarized antenna radiates a right-hand circularly polarized (RHCP) wave, the reflection coefficient, and axial ratio are below −12 dB and 3 dB in the whole 24 GHz ISM band, respectively. At the center frequency of this band, the antenna gain is 8.9 dBi and the level of side lobes is below −7.4 dB in both principal planes. Further, the half power beamwidths in principal planes are 30.6° and 33.4°, respectively.

Uniplanar Beam-Forming Network Employing Eight-Port Hybrid Couplers and Crossovers for 2-D Multibeam Array Antennas

A multibeam beam-forming network (BFN) for generating 2-D multibeam array antenna (MAA) is proposed using single-layer substrate integrated waveguide (SIW) technology. Firstly, a new topology for building $16\times 16$ BFNs is proposed, which successfully transforms the traditional topology from a 3-D configuration to a 2-D (or uniplanar) one. Two major challenges are tackled during this transformation, namely, the planarization of basic components and the reduction of excessive intersections between multiple paths. To this end, a novel design of eight-port hybrid couplers, as critical components of this BFN, is developed to transform a 3-D to a 2-D structure. Furthermore, a new design of eight-port crossover, which can address four path intersections simultaneously, is proposed to reduce the total number of path intersections from 16 to only 4. The proposed topology for $16\,\times \,16$ BFNs allows all the basic components, including eight-port hybrid couplers, eight-port crossovers, and phase shifters, to be placed within a single-layer configuration. Fed by the proposed uniplanar $16\times 16$ BFN, a 2-D MAA with 16 ( $4\,\times \,4$ ) beams, which is capable of switching the beams in both elevation and azimuth directions, is realized. Compared with the previous 2-D Butler matrix (BM) designs using multilayer technology, it is for the first time that a uniplanar design of $16\times16$ BFN is proposed and realized, which significantly simplifies the design and fabrication complexity.

Compact dual mode X-band SIW bandpass filter with wide spurious suppression using split square ring slot resonator

PurposeThis paper aims to design a dual mode X-band substrate integrated waveguide (SIW) bandpass filter in the conventional SIW structure. A pair of back-to-back square and split ring resonator is introduced in the single-layer SIW bandpass filter. The various coupling configurations of SIW bandpass filter using split square ring slot resonator is designed to obtain dual resonant mode in the passband. It is shown that the measured results agree with the simulated results to meet compact size, lower the transmission coefficient, better reflection coefficient, sharp sideband rejection and minimal group delay.Design/methodology/approachA spurious suppression of wideband response is suppressed using an open stub in the transmission line. The width and length of the stub are tuned to suppress the wideband spurs in the stopband. The measured 3 dB bandwidth is from 8.76 to 14.24 GHz with a fractional bandwidth of 48.04% at a center frequency of 11.63 GHz, 12.59 GHz. The structure is analyzed using the equivalent circuit model, and the simulated analysis is based on an advanced design system software.FindingsThis paper discusses the characteristics of resonator below the waveguide cut-off frequency with their working principles and applications. Considering the difficulties in combining the resonators with a metallic waveguide, a new guided wave structure – the SIW is designed, which is synthesized on a planar substrate with linear periodic arrays of metallized via based on the printed circuit board.Originality/valueThis study has investigated the wave propagation problem of the SIW loaded by square ring slot-loaded resonator. The electric dipole nature of the resonator has been used to achieve a forward passband in a waveguide environment. The proposed filters have numerous advantages such as high-quality factor, low insertion loss, easy to integrate with the other planar circuits and, most importantly, compact size.

High-Gain SIW Filtering Antenna With Low H-Plane Cross Polarization and Controllable Radiation Nulls

In this communication, a high-gain substrate-integrated waveguide (SIW) filtering patch antenna with low H-plane cross-polarization (cross-pol) and controllable radiation nulls is proposed. The antenna is composed of a radiation patch integrated with three pairs of shorting pins and a single layer SIW cavity with two transverse slots. The shorting pins loaded on the patch can improve the gain and reduce the H-plane cross-pol of the antenna. The long slot on the middle layer can not only split the TE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">110</sub> -mode resonator into two half-mode resonators but also generate magnetic coupling between half-mode resonators and the patch. Another short slot achieves mixed electric and magnetic coupling between the left half-mode resonator and the patch that introducing controllable radiation nulls to improve the selectivity. By adjusting the parameters of the short slot, the positions of two radiation nulls can be easily controlled. Finally, one prototype filtering antenna is fabricated and measured for demonstration. Experimental results show that the proposed SIW filtering antenna achieves a high gain of 9 dBi with only one radiator and has the merit of high-frequency selectivity as well as low H-plane cross-pol of lower than -43 dB.

A single layer SIW H-plane Horn Antenna with nearly equal E- and H-plane beamwidths

ABSTRACT In this paper, a novel Single-layer Substrate Integrated Waveguide (SIW) H-plane horn antenna with equal beamwidths in the principal planes is proposed. To equalize radiation patterns in E- and H-plane, descending tapered-length triangular grated transitions are used at the aperture of the horn. Then, an elliptical dielectric slab with ascending tapered-diameter air holes is utilized to improve the gain and bandwidth of the antenna. Its radiation patterns in E- and H-plane are nearly equal and the H-plane planar horn antenna works as a 3D pyramidal horn. The antenna has small dimensions of 76.62 mm × 22.9 mm × 3.175 mm (5.62λ0 × 1.68λ0 × 0.23λ0). It covers the frequency range of 17 GHz-26 GHz with S11 < −10 dB, i.e., 41% bandwidth. The gain of the antenna is 12.6 dBi ± 2.5 dBi over the operational bandwidth. The proposed horn antenna is a suitable feed for small symmetric reflectors with negligible blockage and respectable efficiency. To validate the simulation results, the antenna is fabricated and tested. There is a good agreement between the simulation and measurement results.

Single-Layer Dual-Band Balanced Substrate- Integrated Waveguide Filtering Power Divider for 5G Millimeter-Wave Applications

A single-layer substrate-integrated waveguide (SIW) filtering power divider (FPD) with fully differential operation at 28 and 39 GHz is proposed in this letter. This FPD consists of three SIW cavities where the differential and common modes of each cavity were properly designed to form three-pole dual passbands, facilitate deployment of isolation resistors, and introduce transmission zeros while attaining high in-band common-mode rejection. To improve the output return loss and isolation in dual bands, a novel and simple approach to find the proper location of isolation resistors is presented. At operating frequencies, the measured differential-mode input or output return loss, minimum insertion loss, isolation, and common-mode suppression are >14.1 dB, 14.9 dB, and >30.3 dB, respectively. The amplitude and phase imbalances between outputs are < 0.48 dB and <4.2°, respectively.

Compact-Balanced BPF and Filtering Crossover With Intrinsic Common-Mode Suppression Using Single-Layered SIW Cavity

In this letter, compact-balanced bandpass filter (BPF) and filtering crossover are proposed with intrinsic common-mode (CM) suppression by using a single-layered substrate-integrated waveguide (SIW) cavity. The SIW cavity with low profile is TEn0m mode resonator, which has only one nonzero electric field component. Hence, it is also a natural frequency selection device of the differential signal. Meanwhile, the CM signal cannot excite the cavity due to the characteristics of perfect electric conductor (PEC) and perfect magnetic conductor (PMC). For the design of the balanced SIW BPF, the differential-mode (DM) equivalent half circuit is a single-ended SIW filter with height halved. Furthermore, the microstrip differential transition structure is designed to excite the SIW cavity and has little conversion between DM and CM. On this basis, a compact SIW-balanced filtering crossover is proposed using the degenerate modes TE102 and TE201. Finally, compact third-order SIW-balanced BPF and filtering crossover are designed and fabricated, and the measured results show good agreement with the simulated ones.

Development of Low-Profile Filtering Antennas With Dual-Mode Cavities

Two filtering antennas implemented on the dual-mode cavities are proposed, investigated and experimentally verified in this paper. They are developed based on the single-layer substrate integrated waveguide (SIW) technology. The rectangular SIW dual-mode cavities (using TE102, TE201 and TE301 modes) are effectively stimulated with a simple capacitive feeding near the diagonal line of the cavity. Surface current distribution is firstly analyzed for the optimal positions of slot radiators. Two rectangular slots are etched on the top surface of the SIW cavity, which are used to interfere the original current flow of one particular mode and generate radiation. These orthogonal dual-modes are used to obtain a filtering response. Their resonance frequencies are close to each other leading to field rotation and interaction with a radiation null generated outside the passband. The radiation and filtering function are achieved simultaneously by the dual-mode cavity, therefore only one cavity is required, resulting in a compact and simple antenna configuration. Good agreement has been observed between the simulation and measurement. They offer a variety of nice features, such as interesting working mechanism, low-profile, high radiation gain and good passband selectivity, which are also suitable for high-frequency antenna application.