Substrate Integrated Waveguide Feeding Research Articles

Substrate‐integrated‐waveguide cavity‐backed circularly polarized antenna with enhanced bandwidth and gain

AbstractWe propose a method for increasing the bandwidth of a substrate‐integrated‐waveguide (SIW) cavity‐backed antenna with taper‐based microstrip SIW transition feeding. For radio transmission, a circular slot is etched on top of the SIW cavity. For optimal antenna design, the slot is etched slightly away from the cavity center to generate circularly polarized waves. Simulations show a wide axial ratio bandwidth of 7.860% between 11.02 GHz and 11.806 GHz. Experimental results confirm a similar wide axial ratio bandwidth of 4.9% between 10.8 GHz and 11.35 GHz. An SIW feed from an inductive window excites the radiating circular slot, resulting in a simulated wide impedance range of 1.548 GHz (10.338 GHz–11.886 GHz) and bandwidth of 13.93%. Experimental results show a wide impedance of 2.08 GHz (10.2 GHz–12.08 GHz) and bandwidth of 18.84%. The SIW cavity‐backed antenna creates a unidirectional pattern, leading to gains of 6.61 dBi and 7.594 dBi in simulations and experiments, respectively. The proposed antenna was fabricated on a Rogers RT/Duroid 5880 substrate, and the reflection coefficient, radiation patterns, and gains were tested and compared using a computer simulator. The developed broadband antenna seems suitable for X‐band applications.

High‐gain high‐selectivity TE20‐mode SIW‐fed metasurface filtenna array for 5G millimeter‐wave applications

AbstractA high‐gain high‐selectivity 4 × 4 metasurface (MS) filtenna array is presented in this paper for 5G millimeter‐wave (mmW) applications. The TE20‐mode substrate integrated waveguide (SIW) with two parallel coupling slots is applied as the differential feeding structure, which can produce a wide impedance bandwidth and good radiation performances, simultaneously. Additionally, the TE20‐mode SIW feeding line is well designed to operate as a λ/2 short‐circuited line at the upper edge frequency to gain a radiation null. Meanwhile, a folded U‐shaped slot is etched on each MS unit to generate a radiation null at the lower edge. As a result, a passband which covers our 5G mmW band (24.25–29.5 GHz) of interest can be realized. To validate the design, a 4 × 4 MS filtenna array was manufactured and measured. The simulated and measured results are in good agreement, demonstrating a −10 dB impedance bandwidth of 19.8%, a flat gain variation with a maximum value of 19.82 dBi, symmetrical radiation patterns, low cross‐polarization levels of –30 dB, and high out‐of‐band rejection levels of 25 dB.

Millimeter-Wave Monopulse Filtenna Array with Directive Dielectric Resonators

This paper presents a new millimeter-wave monopulse dielectric resonator (DR) filtering antenna (filtenna) array based on substrate-integrated waveguide (SIW) technology. The monopulse comparator realized by a square dual-mode (<i>TE</i><sub>102</sub> and <i>TE</i><sub>201</sub>) SIW feed cavity uses diagonal irises, of which couplings between the feed and next-stage cavities lead to almost identical filter responses for the sum and difference channels with compact size and a planar single-substrate structure. Both dielectric resonator antennas (DRAs) adopting <i>HEM</i><sub>133</sub> mode for enhanced directivity are implemented with two filters based on SIW. The DR acts as the last resonator and the radiator in the filtenna. The prototype is designed at the Ka-band with a center frequency of 27.65 GHz and an operation bandwidth of 700 MHz. The measurement shows a 15-dB fractional bandwidth of 2.36%, a gain of 10.84 dBi for the sum channel, and a null depth of -15.6 dB for the difference channel.

Vertically Polarized Broadband Gain Stable Yagi– Uda Antenna for Millimeter-Wave Applications

A millimeter-wave endfire Yagi–Uda antenna based on a monopole fed by a substrate-integrated waveguide (SIW) line is presented in this letter. The antenna consists of two substrates assembled perpendicularly in a 3-D configuration. The vertical plane supports the driven monopole antenna and a group of passive parasitic monopoles, all printed as conductor strips. The horizontal layer contains the SIW feeding line, where the top metallic face acts as a mirror for the monopoles. According to the beam direction and the achieved gain, a parametric study is conducted to determine the number of elements. Two versions are proposed, studied, and experimentally validated. The first version with one arm achieved a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$-$</tex-math></inline-formula> 10 dB impedance bandwidth of 23.5% (27.4–34.7 GHz) with a peak gain of 13.8 dBi. The second version with three arms of directors is proposed to achieve a stable gain of 15.1 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\pm$</tex-math></inline-formula> 0.5 dBi over 16% (27.1–32 GHz). The performance of the proposed antenna with relatively compact size makes it suitable for millimeter-wave systems.

Miniaturized Vivaldi Tapered Slot Antenna (VTSA) with Microstrip to SIW Feed Structure for X Band Application

Vivaldi tapered slot antenna (VTSA) families are low-cost, lightweight, and have a simple design structure with good electrical performance and consistent impedance over a wide frequency range. It can be fabricated on a fragile substrate to be used for various applications like an aircraft wing or in wearable networks. One biggest issue with this antenna is impedance matching. In this design, an antipodal Tapered slot antenna is used. The proposed antenna’s feed structure used a SIW (Substrate Integrated Waveguide) to microstrip transition. It allows us to design the characteristics of an antenna on a common substrate while maintaining a high-quality factor. The structure is simulated in CSTMWS (CST Microwave Studio) and the equivalent circuit of the transition part is also evaluated using ADS software tools. The operating frequency range of the structure is between 8 and 12 GHz (X band). This band has potential uses in radar, imaging, medical, space communication, and military applications. The whole structure is fabricated on the RO4003c substrate and measurements are taken with a VNA. The simulated and measured results are found to be very close to each other. The designed structure has a 40% percentage bandwidth and the overall dimension is 33 × 14 mm2.

Design of an Air-Filled Slot Antenna and Array for Millimeter-Wave Applications

This communication introduces a new structure of wideband slot antenna with high gain and stable radiation patterns for millimeter-wave (mmW) applications. It is the first attempt to apply an air-filled I-shape slot excited by a substrate-integrated-waveguide (SIW) feed. The slot can achieve lower <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$Q$ </tex-math></inline-formula> -factor contributing to a wider bandwidth. In addition, the feature of even electric field distributions across the operating bandwidth produces very stable gain performance for the proposed antenna. The proposed antenna is realized using a single-layered PCB substrate with plated-through-hole technology, which is cost effective and easy to fabricate. In addition, a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1\times8$ </tex-math></inline-formula> antenna array based on the proposed antenna element is developed with a planar 1–8 SIW feeding network. The measurement results show that the proposed array can achieve an impedance bandwidth of 36.6% from 58 to 84 GHz with a peak gain of 16 dBi. These performances ensure that the proposed antenna array is a promising candidate for mmW communications.

Developing Broadband Microstrip Patch Antennas Fed by SIW Feeding Network for Spatially Low Cross-Polarization Situation.

A stacked multi-layer substrate integrated waveguide (SIW) microstrip patch antenna with broadband operating bandwidth and low cross-polarization radiation is provided. A complete study on the propagating element bandwidth and cross polarization level is presented to demonstrate the importance of the design. The proposed antenna includes three stacked printed circuit board (PCB) layers, including one layer for the radiating 2 × 2 rectangular patch elements and two SIW PCB layers for the feeding network. There are two common methods for excitation in cavity-backed patch antennas: probe feeding (PF) and aperture coupling (AC). PF can be used to increase the bandwidth of the antenna. Although this method increases the antenna’s bandwidth, it produces a strong cross-polarized field. The AC method can be used to suppress cross-polarized fields in microstrip patch antennas. As microstrip patch antennas are inherently narrowband, the AC method has little effect on their bandwidth. This paper proposes an antenna that is simultaneously fed by AC and PF. As a result of this innovation, the operating bandwidth of the antenna has increased, and cross-polarization has been reduced. Actually, the combination of probe feeding and aperture coupling schemes leads to achieving a broadband operating bandwidth. The arrangement of radiator elements and cavities implements a mirrored excitation technique while maintaining a low cross-polarization level. In both numerical and experimental solutions, a less than −30 dB cross-polarization level has been achieved for all of the main directions. A fractional impedance bandwidth of 29.8% (10.55–14.25 GHz) for < −10-dB is measured for the proposed array. Simulated and measured results illustrate good agreement. Having features like low cost, light weight, compactness, broadband, integration capabilities, and low cross-polarization level makes the designed antenna suitable for remote-sensing and satellite applications.

A 60 GHz Rhombic Patch Array Antenna With High Gain, Low Sidelobe Level, and Reduced Array Area

This work designs a 60 GHz rhombic patch array antenna with high gain, low sidelobe level (SLL), and reduced array area. This antenna consists of eight linear serial arrays with varying number of patches. A slot-coupled center-fed structure of substrate-integrated waveguide (SIW) is designed to simplify the complex feed network required for direct excitation of planar arrays and reduce insertion loss. The rhombic configuration utilizes the quantity ratio of patches for equivalent taper excitation to reduce SLL, rather than the use of tapered width as in traditional designs, which can achieve high gain and avoid cumbersome resizing of patches and connecting lines. An array factor analysis method is proposed to predict the SLL of the antenna. To form a planar array and further reduce the H-plane SLL, a -25-dB Dolph-Chebyshev SIW feed network is constructed. The measured gain of the rhombic array antenna is 18.2 dBi, and the E-plane and H-plane SLLs are less than -20 dB and -25 dB, respectively. This work also simulates a reference uniformly excited high-gain 8&#x00D7;10 array antenna. Compared to this reference antenna, the proposed rhombic array antenna has similar simulated gain but much lower SLL and 23% smaller array area.

Substrate-Integrated-Waveguide-Fed Wideband Filtering Antenna for Millimeter-Wave Applications

In this article, a wideband filtering antenna based on substrate integrated waveguide (SIW) structure for millimeter-wave (mm-wave) applications is proposed and studied. The proposed antenna is developed using multilayer printed circuit board (PCB) technology. It consists of an SIW feeding structure with a coupling slot, differential-fed <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$L$ </tex-math></inline-formula> -shaped probes as well as radiating patches. Such architecture provides wide impedance bandwidth along with good filtering characteristic in the lower stopband. Simultaneously, by introducing a pair of open slots on the individual radiating patch as well as two shorting loops on top of the coupling slot, good filtering response in the upper stopband is obtained. The suppression level in the lower stopband is then further improved by introducing a pair of shorted stubs in the coupling slot region. The proposed filtering antenna features no extra filtering circuits, but has wide bandwidth as well as low profile. To verify the proposed structure and design philosophy, antenna array prototypes have been designed, fabricated, and measured. It achieves a 29% bandwidth from 23.5 to 31.5 GHz. Good agreement is achieved between simulated and experimental results. The proposed antenna array is particularly suitable to be applied in 5G (the fifth generation) mm-wave backhaul communications.

Broadband and efficient patch array antenna fed by substrate integrated waveguide feed network for Ku‐band satellite applications

A new class of multi-layer microstrip patch antenna (MPA) array fed by substrate integrated waveguide (SIW) cavities is presented for Ku-band applications. An efficient compact multi-layer SIW feeding network is designed, which has lower losses than the conventional corporate feeding network based on microstrip lines or coplanar waveguides. A 4 × 4 array consists of four stacked layers, including three based on the SIW technology as a feeding network and one layer for the radiating antenna array. Each layer can easily be fabricated from a dielectric substrate and processed using the printed circuit board (PCB) technology. Afterward, all the PCB laminates are stacked together and tied by screws. The measured antenna operates from 11.2 to 13.6 GHz achieving 19.35% bandwidth. The measured peak gain at 12.5 GHz is 17.1 dBi, equivalent to 71.47% aperture efficiency. The fabricated array exhibits several advantages: broadband, low cost, compactness, high radiation efficiency, high aperture efficiency, and lightweight, which makes it a candidate for Ku-band satellite applications.

Improved grounded coplanar waveguide‐to‐multilayer substrate integrated waveguide transition for efficient feeding of an antipodal Vivaldi antenna for imaging applications

AbstractThis paper presents a novel transition junction between a grounded coplanar waveguide (GCPW) and a multilayer substrate integrated waveguide (SIW) that is intended as a feed for an SIW antipodal Vivaldi antenna. Compared to other similar transitions, this transition has better matching and lower insertion loss. More specifically, the junction between GCPW and multilayer SIW is designed to improve matching between the two‐layer feed line and the multilayer SIW, thereby reducing unwanted radiation from the transition and improving the radiation pattern of the SIW antipodal Vivaldi antenna. These improvements are illustrated through simulation and measurement of a 34.5–37.5 GHz antipodal Vivaldi antenna that is fed by a SIW feed connected to a GCPW via the improved junction.

Efficient Transition Hybrid Two-Layer Feed Network: Polarization Diversity in a Satellite Transceiver Array Antenna

In this article, an efficient solution for the development of a new class of two-layer microstrip patch antenna (MPA) with orthogonal polarization ports, based on substrate-integrated waveguide (SIW) through an aperture coupling technique, is presented. Applying the SIW feeding network and aperture coupling to feed the MPA reduces the losses resulting from the feeding circuit and gives a more compact and efficient system. The proposed 4 × 4 array consists of two stacked layers, including an SIW layer as a feeding network and one layer as an antenna layer. The main design feature is the dual orthogonal port to generate different linear polarizations (LPs) (horizontal, vertical, 45°, and 135°). Each layer can be easily fabricated by a single layered printed circuit board (PCB) technology, and then PCB laminates are fixed together using screws. The measured -10-dB impedance bandwidth spans from 9.25 to 10.2 GHz (9.76%). The maximum measured gain at 9.9 GHz is 18.2 dB. The peak radiation efficiency is 84%. The proposed dual orthogonal port antenna exhibits low cost, ease of design, lightweight, high efficiency, and compactness, which makes it a suitable candidate for the polarization diversity in a transceiver for Earth-station applications.

Wideband and High-Gain D-Band Antennas for Next-Generation Short-Distance Wireless Communication Chips

This article presents two kinds of low-cost antennas for D-band short-distance wireless communication applications. Both the antennas are excited by a substrate integrated waveguide (SIW) feed line based on the printed circuit board (PCB) process. The first type is a stainless-steel-based horn antenna, fabricated by electric-discharging machining (EDM) process and selective laser melting (SLM) 3-D printing, respectively, for reducing cost. To integrate the horn antennas with the SIW feed line, a wideband transition structure from SIW to the rectangular waveguide is designed by suppressing higher order eigenmodes. The experimental data show that the integrated horn antenna can achieve 18.9% (129.5-156.5 GHz) -10 dB impedance bandwidth and a peak gain of 15.46 dBi. The second type of antenna is a single-layer rectangular patch antenna fed by SIW. By locally widening the SIW feed line to generate an equivalent shunt capacitance instead of using complex resonators, a wide impedance bandwidth can be realized. The measured -10 dB impedance bandwidth and the peak gain of the patch antenna are 20.8% (125.3-154.4 GHz) and 7.26 dBi, respectively. The two proposed antennas can provide comparable performance for different application requirements under the premise of a low fabrication cost.

Compact UWB Half-Mode SIW Bandpass Filter With Fully Reconfigurable Single and Dual Notched Bands

Compact ultra-wideband (UWB) bandpass filters based on the half-mode substrate integrated waveguide (SIW) with fully reconfigurable single and dual notched bands are proposed in this article. The lower stopband of the UWB bandpass filter is formed by the intrinsic cutoff frequency of the half-mode SIW, and transmission zeros in the upper stopband are created by utilizing three U-shaped slot resonators. Coupling microstrip resonators loaded by varactor diodes are placed along the open side of the half-mode SIW and microstrip feeding line to construct the in-band notches. By controlling the bias voltages and the size of resonators, fully reconfigurable single and dual notched bands can be obtained. Moreover, the frequency and bandwidth of each notched band can be controlled independently. To demonstrate the proposed technique, five and seven distributed coupling microstrip resonators are first applied to obtain the fully reconfigurable single notched band with the suppression level of 30 and 36 dB, respectively. Then, reconfigurable dual notched bands are demonstrated by changing the bias voltages using the same prototype with seven resonators. At last, nine resonant cells with two sets of different sizes are shown to design reconfigurable dual notched bands with frequency tuning range covering almost the full UWB passband.

A Low-Profile Vertically Polarized Magneto-Electric Monopole Antenna With a 60% Bandwidth for Millimeter-Wave Applications

A millimeter-wave (mmW) low-profile wideband magneto-electric (ME) monopole antenna with the vertically polarized endfire radiation is presented by combining a pair of the top-loaded electric monopoles with a thin open-ended substrate integrated waveguide (SIW) with the extended lower broad wall. The antenna has a profile of 0.19 wavelength at the center frequency of the operating band, a wide bandwidth of 60.7% (from 23.5 to 44 GHz) covering all the fifth-generation (5G) mmW bands in the Ka-band, a stable gain of around 7 dBi, and a tilted radiation pattern. Then a 1 × 8 ME-monopole array is designed to investigate the beam scanning properties and the effects of the metallic ground and the polycarbonate radome, which should be considered in practical applications. As a sample, a 1 × 8 array fed by an SIW feed network, assembled on a metallic ground plane, and covered by a polycarbonate radome is finally designed, fabricated, and measured. The prototype achieves promising radiation features with a gain up to 15.3 dBi. Owing to the compact low-profile structure with good performance, the proposed design would be valuable to the mmW applications.

A Compact Wideband Circularly Polarized Magneto-Electric Dipole Antenna Array for 5G Millimeter-Wave Application

A compact wideband circularly polarized (CP) magneto-electric (ME) dipole antenna array is proposed. In order to achieve compact size and wideband characteristics, a novel substrate integrated waveguide (SIW) to coaxial transition (SCT) was designed to connect the lightning-shaped ME-dipole antenna element and an SIW feeding network. Particularly, an SCT-based power divider network together with the sequential-rotation (SR) technique was employed to improve the axial ratio (AR) bandwidth of the $4\times 4$ antenna array. The antenna array prototype was fabricated to verify the design. Measured results show that an impedance bandwidth of 27.7% (23.3–30.8 GHz) and 3 dB gain bandwidth of 25.3% (23.5–30.3 GHz) were achieved. Moreover, a 3 dB AR bandwidth of 27.8% (23.2–30.8 GHz) with a peak gain of 20.2 dBic was also recorded. Therefore, it is a good candidate for the fifth-generation (5G) millimeter-wave (mm-wave) communications.

A compact and wideband array antenna with efficient hybrid feed network

This study presents a high-efficient, compact, and broadband microstrip patch antennas (MPAs) based on substrate-integrated waveguide (SIW) for X-band applications. The proposed array consists of three stacked layers from top to bottom, including one layer as the antenna layer and two SIW layers as a feeding network. The performance was focused on improving the impedance bandwidth and radiation efficiency by mitigating the loss from the feed network while also maintaining the compact design. To this end, the SIW feeding network was designed to feed the MPA to save the physical aperture size which resulted in a more compact and efficient radiating structure. The overall size of the proposed array is compact and extra surface area around the radiation aperture has not been occupied. The measured −10 dB impedance bandwidth span is from 8.9 to 10.9 GHz (20.2%). The maximum measured gain at 10.6 GHz is 10.6 dBi. The results show that the simulated radiation efficiency and the measured aperture efficiency are more than 75% and 50%, respectively. The fabricated array exhibits great advantages such as wide operating bandwidth, lightweight, low-cost, high aperture efficiency, high radiation efficiency, and compactness which make it a good candidate for X-band applications.

Substrate integrated waveguide based cavity‐backed self‐triplexing slot antenna for X‐Ku band applications

A planar substrate integrated waveguide (SIW) based cavity-backed self-triplexing slot antenna is proposed for X-Ku band applications. The antenna comprises of the SIW cavity, radiating slots, and feeding networks. The radiating slots; that are etched on the upper metallic plane of the SIW, are backed up by the three radiated quarter cavities (QCs). The radiating slots in the respective QCs are of different lengths, excited by three separated orthogonal feed lines to resonate at three different frequencies as 11.01, 12.15, and 13.1 GHz. By fine-tuning the antenna parameters, an intrinsic input port isolation of better than 26 dB is realized which helps in achieving the self-triplexing property. The behaviors of individual cavity modes at three resonant frequencies are explained with the help of Z-parameter. The proposed antenna layout is easy to integrate with the planar circuit. The proposed antenna is fabricated and measured results display a close concern with the simulated results. Moreover, a unidirectional radiation pattern and gain of 5.1, 5.54, and 6.12 dBi at resonant frequencies are realized.

A Wideband Circularly Polarized Microstrip Patch Antenna With Embedded Shielding Package Based on Quarter-Mode Substrate Integrated Waveguide Feed

In this paper, the feasibility of using the half-mode/quarter-mode of a substrate integrated waveguide (HMSIW/QMSIW) cavity to feed microstrip patch antennas (MPAs) is explored; based on this, a circularly polarized (CP) MPA fed by the sequential rotation QMSIW cavities is proposed. For more compact and higher integration, the active circuits are packaged inside the microstrip patch antenna. Correspondingly, the QMSIW cavities have also been chamfered, and slots are designed on the upper surface to reduce the influence of the chamfer operation. The SIW cavities introduced an additional resonant mode, which can essentially enhance the bandwidth of the MPAs. The fabricated prototype shows a bandwidth of about 9% (1.42GHz - 1.55GHz) with an average CP gain of 7 dBic. In addition, the adoption of HMSIW/QMSIW cavity excitation allows the microstrip patch antenna to retain a seamless ground plane as well, which facilitates further integration with other components of the communication system by printed circuit board lamination technology.

Nose-Cone Conformal Substrate-Integrated Waveguide Slot Array Antenna for X-Band Radar Applications

This paper presents the design of nose-cone conformal substrate-integrated waveguide (SIW) slot array antenna for modern radar applications. Firstly, the wave propagation characteristics have been investigated in doubly curved SIW, and it has been observed that they are non-uniform along the longitudinal direction of nose-cone conformal SIW. To ensure the constant wave propagation along the length of conformal SIW, the conventional design of SIW is reformulated for nose-cone conformal SIW and circuit model modification has been demonstrated. Secondly, the procedure for designing a SIW-based array on curved surfaces has been developed. In the proposed design, rectangular waveguide (RWG) to SIW feeding structure has been used to avoid spurious radiations. Finally, 1 × 6 element-based nose-cone conformal slotted array has been designed and compared with planar and cylindrical conformal arrays. It has been observed from the results that the nose-cone conformal slot array offers low sidelobe levels (SLLs) and high gain. For the validation of the proposed design, the conformal slotted array has been fabricated and measured, which exhibited a reasonable agreement between the measured and the simulated data.