Substrate Integrated Gap Waveguide Research Articles

Integrated substrate gap waveguide millimetre‐wave filtering antenna with four controllable radiation nulls

AbstractThis study proposed a millimetre‐wave integrated substrate gap waveguide (ISGW) filtering antenna featuring four adjustable radiation nulls, with two located within each of its upper and lower stop bands. These nulls can be tuned by altering the dimensions of stepped‐impedance resonators, complementary U‐slots, and passive coplanar parasitic patches. Antennas offer the benefits of individually adjustable radiation nulls and the flexible modification of selectivity and gain curve roll‐off. Simulation results indicated that the antenna operated at a central frequency of 25.4 GHz, with a relative bandwidth of 14.3% (23.76–27.04 GHz), and attained an average gain of 7.6 dBi.

Wideband PCB-Based Planar Array Antenna With High Aperture Efficiency Based on Substrate Integrated Gap Waveguide

Wideband PCB-Based Planar Array Antenna With High Aperture Efficiency Based on Substrate Integrated Gap Waveguide

A Design Method and Application of Meta-Surface-Based Arbitrary Passband Filter for Terahertz Communication.

A meta-surface-based arbitrary bandwidth filter realization method for terahertz (THz) future communications is presented. The approach involves integrating a meta-surface-based bandstop filter into an ultra-wideband (UWB) bandpass filter and adjusting the operating frequency range of the meta-surface bandstop filter to realize the design of arbitrary bandwidth filters. It effectively addresses the complexity of designing traditional arbitrary bandwidth filters and the challenges in achieving impedance matching. To underscore its practicality, the paper employs silicon substrate integrated gap waveguide (SSIGW) and this method to craft a THz filter. To begin, design equations for electromagnetic band gap (EBG) structures were developed in accordance with the requirements of through-silicon via (TSV) and applied to the design of the SSIGW. Subsequently, this article employs equivalent transmission line models and equivalent circuits to conduct theoretical analyses for both the UWB passband and the meta-surface stopband portions. The proposed THz filter boasts a center frequency of 0.151 THz, a relative bandwidth of 6.9%, insertion loss below 0.68 dB, and stopbands exceeding 20 GHz in both upper and lower ranges. The in-band group delay is 0.119 ± 0.048 ns. Compared to reported THz filters, the SSIGW filter boasts advantages such as low loss and minimal delay, making it even more suitable for future wireless communication.

An mmWave dual-band integrated substrate gap waveguide single cavity filter with frequency selectivity

An mmWave dual-band integrated substrate gap waveguide single cavity filter with frequency selectivity

Millimeter-Wave Ferrite Circulator Integrated on Gap Waveguide Technology

In this work, a simplified analysis with a low dielectric-filled <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$Ka$</tex-math> </inline-formula> -band Y-junction circulator is designed and fabricated for the first time based on substrate-integrated gap waveguide (SIGW) technology. A new design equation is tailored based on a low dielectric filling considering the effect of fringing fields around the ferrite disk. The proposed circulator covers a wide frequency range with a good return loss and isolation at the center frequency. The proposed circulator can be incorporated with <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$Ka$</tex-math> </inline-formula> -band satellites and radars in the millimeter-wave range.

Bandstop filtering for integrated substrate gap waveguide high‐gain and wideband slot antenna for 5G

Slot antenna based on microstrip line and waveguide is a popular design for future 5G antennas. To improve performance of slot antenna, a high-gain wideband slot antenna based on integrated substrate gap waveguide (ISGW) is presented, in which a stepped impedance feeding line is adopted to broaden bandwidth, and ISGW is used to increase gain. First, the transmission characteristics and the effective relative permittivity of ISGW is discussed and calculated, with operation band from 25 to 45 GHz. The antenna has a passband of 24.9–38.1 GHz, that is, almost Ka band, and an average gain of ~9 dB. Further, bandstop filtering (BSF) characteristic is introduced in the above wideband antenna to achieve filtering antennas for 5G millimeter-wave (mm-wave) bands of 24.75–27.5 GHz for China, and 26.5–29.5, 27.5–28.5, and 37–40 GHz for n257, n258, and n260 of 5G new-radio (NR). The BSF is obtained by etching U-shaped CSRR on feeding patch of the antenna. First- and second-order BSF are achieved by etching first and second U-shaped CSRR on the antenna feeding patch, respectively, thus correspondingly one bandstop resonance at 34.6 GHz, and two bandstop resonances at both 32.5 and 34 GHz are obtained. It is found that the passband performance is unchanged, but the stopband radiation drops sharply at the boresight direction. The three antennas (wideband, and first- and second-order BSF antennas) proposed are all fabricated and verified.

Ka-Band Integrated Multilayer Pyramidal Horn Antenna Excited by Substrate-Integrated Gap Waveguide

This work proposed a solution of structures built from stacking several dielectric substrates with the conducting cladding, aiming for electrical contact between them [perfect electric conductor (PEC)–PEC]. At mm-wave frequencies, surface roughness or imperfect flat surfaces present possible gaps that cause severe unexpected leakage. Many engineers overlooked this problem. To prevent this leakage, we propose transforming one of the PEC–PEC surfaces into artificial magnetic conductors (AMCs), creating a PEC–AMC layer that suppresses any leakage even with no contact between the surfaces where the gap is less than a quarter wavelength. A wideband multilayer pyramidal horn antenna using substrate-integrated gap waveguide (SIGW) technology is proposed as an example that highlights the proposed solution. In each layer of the horn, the opening is surrounded by periodic cells to suppress leakage and surface waves. In addition, the upper surface surrounding the horn’s opening is surrounded by EBG mushroom cells to act as a soft surface that suppresses the surface waves and reduces the edge diffraction, and, in turn, improves the radiation characteristics of the horn. The horn achieved a gain of 11.5 dBi and 20.5% bandwidth (28.5–35 GHz). The simulated and measured results show excellent agreement with each other.

A Novel Circular Reconfigurable Metasurface-Based Compact UWB Hybrid Coupler for Ku-Band Applications

A novel circular reconfigurable metasurface (MS) based compact ultra-wideband (UWB) hybrid coupler is developed for Ku-band applications. The coupler is developed using the substrate-integrated gap waveguide (SIGW) technology. The coupler structure consists of two layers, the bottom layer represents the artificial magnetic surface of the periodic structures and the ridges in between that guide the wave in the required direction with minimum dispersion. It involves the coupling section with a centered etched slot and two additional vias to achieve the basic hybrid coupler properties. This layer is nominated as the ridge layer. The second layer is a circular shape of a dielectric gap loaded with the top ground. The top ground is left solid for a non-reconfigurable coupler. Concerning the reconfigurable coupler, this layer contains an artificial metasurface of Jerusalem cross elements where the copper is etched around. This layer is nominated as the gap layer. This MS surface is mechanically rotated to offset the magnitude and phase of the signal going to the through and coupled ports. The findings obtained from the simulations show that the reconfiguration can be accomplished by rotating the MS around the source coupler’s central axis. The rotation is tested between 0° to 180° in the counter-clockwise direction. The operating frequency range of the coupler is between 11.94 to 16.91 GHz, which covers approximately the whole Ku-band. The coupler delivers continuously adjustable amplitude between 2.6 and 4.8 dB while the phase differences within 77° to 105° over a fractional bandwidth (FBW) of 34.45%. It is manufactured using PCB technology and measured using network analyzer. A strong agreement is achieved between simulations and measurements. The proposed coupler can be used in traditional beam-forming and beam-steering networks by changing the rotation angle or the operating frequency. The developed coupler can replace the Butler and Bless matrices with their complication, heavy number of phase shifters, and crossover problems. The current work can be extended to operate in the mm-Wave band by changing the dimension and the material of the unit cell of the ridge layer of the coupler.

Characteristic impedance of integrated substrate gap waveguide

A theoretical method is presented by which characteristic impedance of integrated substrate gap waveguide (ISGW) is analyzed. The method is essentially based on a variational function for the transmission-line capacitance in Fourier-transformed domain with test/trial functions of charge density distribution, in which transverse transmission-line Green's function is used to facilitate the variational analysis. The presented method simplifies the determination of the potential distribution function which must satisfy the complex boundary conditions of the ISGW. Moreover, two types of ISGW, that is, two- and three-layer ISGW, working in K and E band are considered and analyzed by this method. Finally, the method is compared to the simulated using High Frequency Structure Simulator (HFSS) as well as measurements, and it is shown that the method leads to a very small inaccuracy compared to previously reported methods.

A new type of the air‐filled substrate integrated gap waveguide resonator

This article presents the design and analysis of an air-filled substrate integrated gap waveguide (ASIGW) resonator. The electromagnetic field of each resonant mode in the resonator is studied by theoretical modeling and EM simulation. Besides, the relationship between the dimensions and Qu is analyzed and the Qu of the resonator can be as high as 2080 at Ku band. Compared with conventional rectangular waveguide resonator and gap waveguide (GW) resonator, the proposed ASIGW resonator can be fabricated more easily. Compared with the substrate integrated waveguide resonator, the ASIGW resonator is more tolerant with dimensional errors and with less degenerate modes. As an example, a fifth-order band-pass filter based on the ASIGW resonators is presented to verify the previous conclusions.

Wideband Sidelobe-Level Reduced $Ka$ -Band Metasurface Antenna Array Fed by Substrate-Integrated Gap Waveguide Using Characteristic Mode Analysis

substrate-integrated gap waveguide (SIGW)-fed metasurface antenna (metantenna) array with nonuniform excitation is proposed for wideband operation and sidelobe-level (SLL) reduction at millimeter-wave Ka -band. To achieve wideband and low profile, a $2 \times 2$ square patch-based metasurface is introduced based on characteristic mode analysis (CMA). The ridged microstrip-fed slot is employed to excite the metasurface, while the mushroom-like patches are positioned around feeding lines to operate as the SIGW for suppressing the undesired modes. Due to the compactness of the proposed SIGW, the amplitude of each element is controllable using unbalanced T-junctions. A nonuniformly excited $4 \times 4$ antenna array is designed and fabricated for validation. The measured results show an impedance bandwidth ( $\vert \text{S}_{11}\vert dB) of full Ka -band with a 3 dB gain bandwidth of 28–40 GHz (35.3%) and SLLs less than −12.1 and −15.6 dB in the E- and H-planes, respectively.

Millimeter-Wave Substrate Integrated Gap Waveguide Leaky-Wave Antenna for WiGig Applications

A new design of an H-polarized leaky-wave antenna (LWA) based on the substrate integrated gap waveguide (SIGW) technology is introduced. The antenna shows good scanning capability from the backward to a near broadside direction (from −36° to −15°) with a peak gain of 17.67 dBi within 1.3 dB variation over 57–64 GHz and a wide impedance bandwidth. A pair of LWAs is parallelly excited through a Y-power divider and terminated with the other end in series providing an additional 3 dB gain compared to the single LWA. Both designs show over 88% radiation efficiency and over 86% total efficiency. The fabricated prototypes of both antennas are made of multi-layered PCB technology. The measurement results show a good agreement with the simulations.

Millimeter-Wave Circularly Polarized Array Antenna Using Substrate-Integrated Gap Waveguide Sequentially Rotating Phase Feed

A substrate-integrated gap waveguide (SIGW) sequentially rotating phase (SRP)-fed 2 × 2 circularly polarized (CP) patch antenna array is presented for the wideband millimeter-wave application. The antenna element is composed of a truncated square patch, SIGW feedline with three layers of printed circuit board (PCB), and another layer of PCB with an air hole for supporting radiation patch. Each radiation patch is driven by an underneath coupling slot etched on SIGW. A wide axial-ratio (AR) bandwidth is achieved by deploying a 2 × 2 SIGW SRP feed network. Moreover, simple calculation expressions of the characteristic impedance and guide wavelength of SIGW are given for the design of SRP feed network. The fabricated prototype shows an impedance bandwidth of 25.6% covering 22.2–28.8 GHz, 3 dB AR bandwidth of 19% from 22.8 to 27.6 GHz, and peak gain of 11.53 dBic.

Transition from rectangular waveguide to empty substrate integrated gap waveguide

Empty substrate integrated waveguide (ESIW) is a hollow SIW with its inner dielectric removed to achieve a reduced insertion loss. One of the drawbacks is the top and bottom covers need to be soldered to the middle substrate. Gap waveguide (GW) technology solves the contact issue utilising contactless electromagnetic band-gap (EBG) structures. Therefore, empty substrate integrated GW (ESIGW) is a transmission line having both advantages of ESIW and GW. In this Letter, a wideband transition from rectangular waveguide (RW) to ESIGW is presented. RW is firstly matched to reduced-height RW using E -plane stepped waveguides. Then, a short substrate integrated GW (SIGW) section is introduced between the reduced-height RW and the ESIGW. This section not only serves as an impedance matching component, it also connects the two sides of the ESIGW and maintains the integrity of the substrate. To broaden the bandwidth of the transition, a triangular dielectric is added at the end of the ESIGW. A Ka-band back-to-back prototype of the transition is designed and fabricated. In addition, TRL calibration is used to measure the transmission performance of the ESIGW. The measured results show that the transition works well over the entire Ka-band.

Design of Substrate Integrated Gap Waveguide and Their Transitions to Microstrip Line, for Millimeter-Wave Applications

This paper offers an approximate, but very convenient and accurate, manner to find the desired strip width for substrate integrated gap waveguide (SIGW) with a given characteristic impedance and the conductor and dielectric attenuation constants, without any complicated manual calculations or time-consuming full-wave simulation and optimization iterations. Moreover, the investigation of the transition between SIGW and microstrip lines will prove that an additional transition structure, such as a conventional microstrip taper, is not required any more at millimeter-wave frequencies for the desired transmission performance. This is a useful feature in circuit design and compactness. Both of the above works will be of great help to realize future feeding networks for SIGW antenna arrays or other types of cost-effective SIGW passive components at high frequencies. Two SIGW prototypes, working at Ka and V bands, are fabricated and offer experimental verifications, which present good agreement with the simulation results.

A Low-Profile Substrate-Integrated-Gap-Waveguide- Fed Magnetoelectric Dipole

In this letter, a magnetoelectric (ME) dipole antenna with characteristics of low profile, easy integration, wide band, and high gain is proposed. The ME dipole is composed of rectangular patches and metallic via holes, and is embedded in a square aperture etched on substrate-integrated gap waveguide (SIGW). In particular, the ME dipole is fed by a coplanar strip line, which is designed in SIGW to realize a low profile of 0.19 λg ( λg is the guide wavelength at center frequency). The measurements show that the 10 dB impedance bandwidth of the antenna is 29%, ranging from 22.4 to 30 GHz, with a mean gain of 8.04 dBi. Furthermore, the antenna emits a stable radiation pattern, validated by the far-field measurements.

Broadband 60 GHz Antennas Fed by Substrate Integrated Gap Waveguides

The first antenna based on substrate integrated gap waveguide (SIGW) is presented. Using two contacted metal strips to build the required conducting ridge, the SIGW addresses the defects inherent in the printed gap waveguide at millimeterwave frequencies. Moreover, a bandwidth enhancement method is proposed and demonstrated by tuning the cavity that excites the slot antenna. The achieved bandwidth can be more than 21 GHz centered at 60 GHz (35%). Different tuning configurations are carefully investigated, and a design guideline is provided, in which different substrates for the gap and via layers of the SIGW are considered. Two fabricated antennas using low-cost PCB verify the simulation results and design guidelines. The first one is a single-slot antenna, and the second is a four-slot linear array. The measured S <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sub> , realized gain, and radiation patterns of the fabricated antennas have good agreement with the simulated counterparts.

A Substrate Integrated Gap Waveguide Based Wideband 3-dB Coupler for 5G Applications

A wideband 3-dB coupler using substrate integrated gap waveguide (SIGW) is proposed based on the principle of the branch-line coupler structure. The SIGW coupler design is comprehensively studied. It is found that SIGW conducting ridge vias play a significant role and have a strong impact on the cavity resonance, passband, and impedance matching. A prototype of the proposed SIGW coupler is fabricated and tested, and the measured agrees well with the simulated. The coupler, better than the reported, has a passband of ~5 GHz from 23.59 to 29 GHz with the isolation above 20 dB, covering the 24.25–27.5-GHz and 27.5–28.5-GHz frequency bands of 5G.

Millimeter-Wave Substrate Integrated Dual Level Gap Waveguide Horn Antenna

Substrate integrated H-plane horn antenna design is introduced based on elevated substrate integrated gap waveguide (E-SIGW) configuration. The E-SIGW topology allows designing the horn from two substrates of different thicknesses. A thin substrate for the feed line to eliminate the radiation losses and a thicker one for the radiating aperture. The proposed configuration allows the H-plane horn aperture to be three times thicker than the feed line substrate, which is not possible with the conventional substrate integrated waveguide technology. The transition between the horn layers enhances the matching bandwidth without any aperture modification. The outer surface of the horn around its aperture is loaded with soft surfaces realized by transverse strips. As a result, more symmetric fan beam radiation patterns with suppressed back lobes are achieved.

Study of Bend Discontinuities in Substrate Integrated Gap Waveguide

This letter presents a study of bend discontinuities in the substrate integrated gap waveguide (SIGW), and proposes a simple solution to minimize the discontinuity effects. Both curved and chamfered right-angle bends are studied. It is found that with a proper ratio of the chamfered length and the bend via diameter, the possible cavity resonances can be suppressed and the desired performance is achieved. The curved bend, however, allows the bend via to have a larger diameter, which could be required due to the fabrication issue. This letter will be of great help to realize future feeding networks for SIGW antenna arrays or other types of cost-effective SIGW passive components, where many discontinuities are naturally present. The proposed discontinuity solution is validated experimentally by a fabricated SIGW prototype of two 90° bends.