Substrate Integrated Waveguide Cavity-backed Slot Research Articles

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.

Multiple-input multiple-output dual-band dual-circularly polarised SIW cavity-backed slot antenna for satellite and 5G systems

ABSTRACT A dual-band 2 1 multiple-input-multiple-output (MIMO) antenna based on substrate integrated waveguide (SIW) cavity for both satellite (in K-band) and 5 G applications is proposed. Initially, the SIW cavity consisting of metallic vias on all four sides is implemented. For MIMO configuration, this cavity is divided into two smaller SIW cavities using a row of metallic vias and excited using the coaxial feed. By etching an asymmetric cross-slot (AXS) with tuned dimensions on top of the SIW cavity, a dualsense of circular polarisation (CP) in both frequency bands is obtained. The fabricated prototype of the proposed SIW antenna shows impedance bandwidth (IBW) of 15.36% (22.60–26.36 GHz; BandI) and 4.64% (29.04–30.42 GHz; BandII). The completely overlapping axial-ratio bandwidth (ARBW) with IBW of 15.16% (22.62–26.33 GHz) and 3.10% (29.20–30.12 GHz) with a peak gain of 12.47 and 7.71 dBi is obtained in BandI and Band II, respectively. The proposed antenna shows front-to-back ratio (FBR) of more than 20 dB in both resonating frequency bands. The measured results of the proposed MIMO antenna agree well with the simulation.

A triple-band dual-fed frequency-flexible SIW cavity-backed slot antenna

AbstractThis article presents a novel dual-fed triple-frequency bands antenna using quarter-mode (QM)/ Eight-mode (EM) substrate integrated waveguide (SIW) cavity resonators. A V-shaped slot is etched into the patch to divide the half-mode cavity into one QM and two EM cavities. One section of the EM cavity and QM cavity are excited with the help of individual micro-strip feedlines. This configuration yields two distinct frequency bands at 4.85 GHz due to TE110 mode of the EMSIW cavity and 5.87 GHz due to TE110 mode of the QMSIW cavity confirming the self-diplexing property. Later, when both the EM cavity sections are joined with the help of two metallic strips, an additional resonance appears at 7.34 GHz due to the excitation of TE120 mode. As compared to the conventional counterparts, the proposed structure is compact and simple. The footprint of the top patch is 0.6λ1 × 0.3λ1. To authenticate the proposed idea, the design is experimentally verified, and the measured results show a good covenant with the simulated results.

Development of a wideband hexagonal SIW cavity-backed slot antenna array

In this paper a novel wideband hexagonal cavity-backed slot antenna array using two sots including Resonant Narrow Slot (RNS) and Non-Resonant Wide Slots (NRWS) based on Substrate Integrated Waveguide (SIW) is proposed. First, a single element low profile wideband linearly polarized cavity-backed antenna using two slots is designed and analyzed. The antenna bandwidth is increased by NRWS, which makes both hybrid modes of TM110 and TM210 close to each other to be excited. Then, to improve antenna gain, an array of two elements cavity-backed slot including is designed and investigated. Moreover, in order to match the input impedance over the operating bandwidth, a special power divider using tapered line is introduced. The proposed single element and antenna array is made and successfully tested. The simulation and measurement results are in a good agreement for both single and antenna array. The measured gain and impedance bandwidth are 12 dBi and 14% respectively for the designed array.

Self-Quadruplexing Circularly Polarized SIW Cavity-Backed Slot Antennas

In this communication, three self-quadruplexing circularly polarized (CP) antennas are presented in substrate integrated waveguide (SIW) technology for quad-band wireless services. The proposed antennas radiate from four unequal length T-shape slots etched on a square SIW cavity. The antennas are excited by four microstrip lines. The T-shape slot placed at each corner of the cavity creates orthogonal electric fields having 90° phase difference, which leads to CP radiation. The first antenna provides left hand circular polarization (LHCP), while the second antenna provides right hand circular polarization (RHCP) in all the bands. The third antenna offers LHCP in two bands and RHCP in other two bands. The sense of polarization can be changed by simply changing the slot orientation. Furthermore, the bands can be tuned almost independently over a wide range of frequency. For all the antennas, the measured isolations among the ports are more than 26 dB, front-to-back ratio (FTBR) is more than 15 dB, and the measured gain is at least 5.2 dBi.

Investigation of SIW Cavity-Backed Slot and Patch Antennas With Conical Radiation Patterns

Substrate integrated waveguide (SIW) cavity-backed slot and patch antennas with conical radiation patterns are investigated. In a center-fed SIW circular cavity with the top wall removed, a series of cavity modes with conical radiation patterns can be excited, wherein the lowest two modes are the TM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">01</sub> and TM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">02</sub> modes. The cavity-backed slot antenna with either of the two modes can work independently, but the bandwidth is narrow. In order to improve the bandwidth, an SIW cavity-backed gap-coupled patch antenna is proposed. The antenna has a wide triple-resonance bandwidth, which includes the patch TM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">02</sub> mode, and the cavity TM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">01</sub> and TM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">02</sub> modes. The working principle and the mode characteristics are investigated. The antenna is designed, fabricated, and measured. Measurement results show that the antenna has a wide bandwidth of 64.6%. In the operation band, the antenna has a low reflection coefficient below -10 dB and provides a conical radiation pattern.

A novel substrate integrated waveguide cavity‐backed self‐diplexing antenna array with frequency beam scanning characteristic

This article presented a substrate integrated waveguide (SIW) cavity-backed self-diplexing antenna array with frequency beam scanning characteristic. The proposed array consists of 16 SIW cavity-backed slot antennas. The SIW cavity-backed slot antenna can be fed by two separate ports to resonate at two different frequencies and achieve high isolation better than 20 dB between two input ports. The proposed element is a typical self-diplexing antenna. These cavity-backed slot antennas are shunt-fed by a compact 1 to 16 SIW power divider and series-fed by a set of microstrip lines, respectively. As a result, this array achieves an unidirectional radiation pattern at 10.2 GHz with high gain of 15.10 dBi, and a frequency beam scanning characteristic from 7.0 to 9.0 GHz ranging from −50° to 46°.

SIW cavity‐backed self‐diplexing leaky‐wave antenna

A novel substrate integrated waveguide (SIW) cavity-backed self-diplexing leaky-wave antenna (LWA) is presented. The proposed design consists of 16 SIW cavity-backed slot elements. The SIW cavity-backed slot element can be fed by two separate ports to resonate at two different frequencies and offer good intrinsic isolation between two input ports. The proposed element is a typical self-diplexing antenna. By lining up these cavity-backed slot elements in a column, serial feeding the lower parts and the upper parts of these cavities separately, the SIW cavity-backed self-diplexing LWA can be achieved. The upper part of the proposed antenna works in 11-13.9 GHz with beam scanning from -5° to 39°. Meanwhile, the lower part works in 7.1-9.4 GHz with beam scanning from -43° to 56°. The isolation between two input ports is better than 20 dB. The measured results of the fabricated antenna prototype verify the simulation analysis.

Bandwidth improvement of substrate integrated waveguide cavity-backed slot antenna with dielectric resonators

In the paper, a low profile substrate integrated waveguide based circular-shaped cavity-backed antenna is delineated to work at WLAN U-NII mid band and a slender rectangular slot is then placed at its center on the ground plane for radiation. The parent antenna radiates at 5.33 GHz with a gain of 4.9 dBi; depicting a narrow impedance bandwidth of 50 MHz. The antenna is modified by placing dielectric resonators of different shapes over the slot to enhance the bandwidth. The new antennas thus produced have an impedance bandwidth of 750 MHz with cylindrical-shaped and rectangular-shaped dielectric resonators which reflect bandwidth enhancement of 700 MHz for both the cases and an impedance bandwidth of 710 MHz with hemispherical-shaped dielectric resonator reflecting bandwidth enhancement of 660 MHz. The gain of the modified antennas is of the order of 4.7 dBi which basically indicates not much degradation in gain as compared to the parent antenna. All the antennas are delineated using Arlon AD270 substrate material with the results obtained after simulation juxtaposed with the ones obtained through measurement.

Broadband Planar SIW Cavity-Backed Slot Antennas Aided by Unbalanced Shorting Vias

Two types of substrate integrated waveguide (SIW) cavity-backed slot (CBS) antennas are proposed for bandwidth enhancement. First, a quad-resonance SIW CBS antenna is proposed using a cross-shaped slot and loading unbalanced shorting vias. Additional half- $\textrm {TE}_{120}$ mode is successfully excited along with three other independent modes including half- $\textrm {TE}_{110}$ and odd and even $\textrm {TE}_{210}$ modes. Next, a penta-resonance SIW CBS antenna with a cross-shaped slot is proposed, in which two pairs of shorting vias are loaded. Two additional hybrid modes of half- $\textrm {TE}_{210}$ and half- $\textrm {TE}_{120}$ modes are introduced along with three other independent modes including half- $\textrm {TE}_{110}$ and odd and even $\textrm {TE}_{310}$ modes. Furthermore, the working mechanism of these two types of SIW CBS antennas is explained. Finally, prototypes of these two antennas are fabricated and measured at X -band. Their measured fractional bandwidths are $\text{20.0}\%$ and $\text{20.8}\%$ , respectively. Simulation and measurement results agree very well, which confirms the validity of the proposed designs.

Gain-enhanced SIW cavity-backed slot antenna by using TE410 mode resonance

A gain-enhanced low profile substrate integrated waveguide (SIW) cavity-backed slot antenna is presented in this paper. By etching three parallel transverse slots on the center and both edges of the rectangular SIW cavity as the radiating elements, higher resonance mode of TE410 can be excited to achieve gain enhancement. Radiating mechanism and parameter effects of the three radiating slots have been investigated. Using the proposed multi-slot structures, an antenna is designed, fabricated and characterized, respectively. The fabricated antenna demonstrated a gain of 9.2 dBi, a front-to-back ratio of 17 dB, and a maximum cross-polarized radiation level of −19.7 dB at 10 GHz. Furthermore, the proposed antenna constructed using a single-layer printed circuit board (PCB) yields a better radiation performance and configuration advantage over that of the conventional planar antenna by taking advantage of the TE410 cavity resonance.

A Self-Triplexing SIW Cavity-Backed Slot Antenna

In this letter, a new design of self-triplexing slot antenna using substrate integrated waveguide (SIW) technique is demonstrated for multiband communication systems. The proposed antenna operates at triple frequency bands (around 6.53, 7.65, and 9.09 GHz) simultaneously utilizing a slot inserted on the top of the SIW cavity and is excited by three separate microstrip lines. By properly optimizing the antenna parameters, an isolation of better than 19 dB is realized between any two input ports, which helps to achieve self-triplexing property. The proposed triplexing antenna preserves simplicity, compactness, and a planar configuration that makes it suitable for highly integrated handheld devices. To demonstrate the significance of the proposed work, the antenna is prototyped, and experimental results show a close agreement with simulations. Moreover, the proposed antenna exhibits the measured gain of 3.1, 4.7, and 3.9 dBi at resonant frequencies with stable radiation patterns.

High Gain, Broadband and Dual-Polarized Substrate Integrated Waveguide Cavity-Backed Slot Antenna Array for 60 GHz Band

In this paper, a compact substrate-integrated waveguide (SIW) cavity-backed slot antenna array with high gain, broadband, and dual-polarization performances is proposed for 60-GHz applications. An enhanced 17.1% impedance bandwidth was achieved by cutting semi-circle edges on the conventional slot radiator. A simplified SIW feed network is aperture-coupled vertically and constructed on a double-layered structure to implement the dual-polarization operation. By adopting innovative techniques on both radiating element and double-layered SIW feed networks, a high-gain, broadband, and dual-polarized $8\times8$ antenna array was designed on three-layered printed circuit board that allows for mass production. This configuration also resolves the trade-off between the bandwidth and gain of the existing 60-GHz dual-polarized antenna array. Its feasibility is proved by obtaining a measured gain in the range of 19.7–22.3 dB and an enhanced impedance bandwidth of 17.1% over 55.7–66.1 GHz for both horizontal and vertical polarizations. With advantages of high-gain, broadband, and dual-polarization performances in a low-cost low-profile structure, the proposed antenna array is a promising candidate for millimeter-wave wireless systems.

Wideband Triple- and Quad-Resonance Substrate Integrated Waveguide Cavity-Backed Slot Antennas With Shorting Vias

A triple-resonance and a quad-resonance substrate integrated waveguide (SIW) cavity-backed slot antennas using shorting vias are presented in this paper. The antennas have wide bandwidths and low profiles. The working mechanism of the triple-resonance antenna is explained with its electric field distributions and equivalent circuit models. By loading the SIW cavity with shorting vias, the lowest mode (half-TE110 mode) is shifted upward and coupled with two higher modes (even and odd TE210 modes). As a result, a wide bandwidth with triple resonances is achieved for the antenna. Based on the similar principle, a quad-resonance antenna having an even wider bandwidth is also developed. Prototypes of the two antennas are fabricated and measured. With a low profile of 0.03λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> (wavelength in free space), the triple-resonance design has a bandwidth of 15.2% and a peak gain of 4.80 dBi, and the quad-resonance design has a bandwidth of 17.5% and a peak gain of 7.27 dBi.

SIW antennas as hybrid energy harvesting and power management platforms for the internet of things

A novel antenna-harvester co-design paradigm is presented for wireless nodes operating in an Internet of Things context. The strategy leads to compact and highly-integrated units, which are able to set up a reliable and energy-efficient wireless communication link, and to simultaneously harvest energy from up to three different sources, including thermal body energy, solar, and artificial light. The core of the unit consists of a substrate-integrated-waveguide (SIW) antenna. Its surface serves as a platform for the flexible energy-harvesting hardware, which also comprises the power management system. To demonstrate the approach, two different SIW cavity-backed slot antennas and a novel compact dual linearly polarized SIW antenna are presented. These topologies facilitate the integration of additional hardware without degrading performance. In the meantime, they enable comfortable integration into garments or unobtrusive embedding into floors or walls. Measurements on prototypes validate the integration procedure by verifying that the integrated hardware has a negligible influence on the performance of all discussed SIW antennas. Finally, measurements in four well-chosen indoor scenarios demonstrate that a hybrid energy-harvesting approach is necessary to obtain a more continuous flow and a higher amount of scavenged energy, leading to a higher system autonomy and/or reduced battery size.

Design of Self-Diplexing Substrate Integrated Waveguide Cavity-Backed Slot Antenna

In this letter, a novel design technique to realize planar self-diplexing slot antenna using substrate integrated waveguide (SIW) technology is presented. The proposed antenna uses a bowtie-shaped slot backed by SIW cavity, which is excited by two separate feedlines to resonate at two different frequencies in X -band (8–12 GHz). By properly optimizing the antenna dimensions, a high isolation of better than 25 dB between two input ports is achieved, which helps to introduce self-diplexing phenomenon in the proposed design. The behavior of the individual cavity modes at two resonant frequencies is explained using half-mode theory. The proposed antenna resonates at 9 and 11.2 GHz with unidirectional radiation pattern and a high gain of 4.3 and 4.2 dBi, respectively.

Gain-Enhanced SIW Cavity-Backed Slot Antenna with Arbitrary Levels of Inclined Polarization

This letter describes a gain enhancement method for a dual-polarized substrate integrated waveguide cavity-backed slot antenna by using a high-order cavity resonance to generate arbitrary levels of inclined linear polarization (LP). To do so, the metal posts are embedded in a main cavity to excite the ${\rm TM}_{220}$ mode of the cavity and control the amount of coupling to generate adjustable inclined linear polarization. To validate the simulated results, an antenna is designed, manufactured, and tested. The proposed antenna exhibits high front-to-back ratio (F/B) of more than 20 dB in the broadside direction and a relative gain of 6.9 dBi at the resonant frequency. The antenna can also provide an adjustable inclined LP with an aspect ratio of $E{x_{\max}}/E{y_{\max}}$ ranging from 0.23 to 4. The proposed method can also be utilized to achieve even higher gain by exciting higher order mode cavity resonances, such as ${\rm TM}_{440}$ and ${\rm TM}_{660}$ . The proposed antenna exhibits the advantages of simple feed network and more compactness compared with the SIW cavity-backed slot antenna/array that has the same gain with inclined polarization.

Broadband Substrate Integrated Waveguide Cavity-Backed Bow-Tie Slot Antenna

A novel design technique for broadband substrate integrated waveguide cavity-backed slot antenna is demonstrated in this letter. Instead of using a conventional narrow rectangular slot, a bow-tie-shaped slot is implemented to get broader bandwidth performance. The modification of the slot shape helps to induce strong loading effect in the cavity and generates two closely spaced hybrid modes that help to get a broadband response. The slot antenna incorporates thin cavity backing (height <;0.03λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> ) in a single substrate and thus retains low-profile planar configuration while showing unidirectional radiation characteristics with moderate gain. A fabricated prototype is also presented that shows a bandwidth of 1.03 GHz (9.4%), a gain of 3.7 dBi over the bandwidth, 15 dB front-to-back ratio, and cross-polarization level below -18 dB.

Wideband LTCC 60-GHz Antenna Array With a Dual-Resonant Slot and Patch Structure

This paper presents a wideband 60-GHz antenna array with a dual-resonant slot-patch structure. A multilayered low-temperature co-fired ceramic substrate was used for antenna fabrication. A half-wavelength resonant slot was designed with a backed substrate-integrated waveguide (SIW) cavity to enhance the front radiation. The inverted microstrip center-fed structure was designed for easy signal excitation and superior impedance matching. A parasitic patch was also applied to enhance for bandwidth and gain enhancement. The effects of the SIW cavity-backed slot antenna with and without parasitic patches were empirically examined. The simulated results show that adding parasitic patches increased the resonance of the poles and improved antenna gain by 1.85 dB and bandwidth by 9%. A 2 × 2 dual-resonant slot-patch antenna array was designed to further enhance the gain and bandwidth. The equipment setup for on-chip measurements of gain and radiation patterns was established. The measured S11 showed a wide bandwidth of 23%. The measured gain for the four-element antenna array was 9 dBi with slight fluctuations over the 57-64-GHz frequency range.

A Reconfigurable SIW Cavity-Backed Slot Antenna With One Octave Tuning Range

A reconfigurable Substrate Integrated Waveguide Cavity-Backed Slot (SIW-CBS) antenna is presented with one octave tuning range and six different tuning states using a new tuning method. The method is based on loading the SIW cavity with shortening posts and manipulating the field distribution within the cavity. This tuning method shifts up the operating frequency of the antenna. Based on the number of the posts and their location, this frequency shift can be controlled. Benefiting from a two-layer structure and therefore being totally isolated from the biasing circuit, the CBS antenna can be easily tuned by switching the posts using p-i-n diodes. Using this technique a frequency tuning ratio <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$(f_{TR}=f_{up}/f_{low})$</tex> </formula> as high as an octave (1.1–2.2 GHz) is achieved. The impedance and radiation characteristics of the CBS antenna are presented and discussed. The antenna shows similar radiation patterns with low cross-polarization levels and high front to back ratio for all six states. To the authors' knowledge this is the first presentation of a SIW-CBS tunable antenna with one octave tuning and also the technique used for antenna tuning.