Substrate Integrated Waveguide Research Articles

Wideband H-Plane T-Junction Power Divider With Compensation Elements Using Double Ridged Empty Substrate Integrated Waveguide

The empty substrate integrated waveguide (ESIW) presents the same advantages as the substrate integrated waveguide (SIW): low cost, low profile, and easy integration, but with lower insertion losses because the dielectric is removed. In order to increase the operational usable bandwidth, one or two ridge layers can be added to the ESIW, leading to the single ridge ESIW (RESIW) or the double ridge ESIW (DRESIW). A transition from microstrip to DRESIW has already been presented, but no other passive components have been implemented in this technology yet. This letter presents a broadband 3-dB DRESIW power divider based on an <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$H$ </tex-math></inline-formula> -plane T-junction with compensation elements, which can be easily manufactured using standard planar circuit manufacturing techniques. The manufactured prototype presents measured return losses greater than 12 dB from 6.9 to 20.4 GHz, representing a 99% fractional bandwidth (FBW), whereas the power division is rather symmetric since the maximum <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$S_{21}$ </tex-math></inline-formula> and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$S_{31}$ </tex-math></inline-formula> parameters are −3.98 and −3.78 dB, respectively.

A Dual-Polarized SIW Lens Antenna Array for Rx-/Tx-Integration at K/Ka-Band

The terminal antenna with dual-circular polarization reported here operates around 20 and 30 GHz, that is, in the down- and uplink frequency bands of current satellite communication systems. The passive array, this work focuses on, integrates the receive and the transmit (Rx/Tx) paths in a single aperture. This approach is shown to be advantageous compared to classical solutions with two separate antennas. The modules, the array consists of, are formed by a stack of eight linear subarrays that themselves are composed of an alternating series of four Tx-only and four combined Rx/Tx endfire antenna elements. The resulting brick architecture provides enough real estate for the future implementation of phased-array electronics. The array is implemented in substrate-integrated waveguide (SIW) technology. For improved matching, it is covered with a periodically shaped dielectric lens. A technique is proposed to mitigate cross-polarization in the pointing direction. A module is realized using standard technologies. The relevant array parameters are measured. The module patterns are synthesized from the individual element responses. They confirm the simulated results and, in particular, a bandwidth of more than 2.5 GHz for both Rx and Tx.

Design and Fabrication of PTFE Substrate-Integrated Waveguide Butler Matrix for Short Millimeter Waves

We attempt to design and fabricate of a 4×4 Butler matrix for short-millimeter-wave frequencies by using the microfabrication process for a polytetrafluoroethylene (PTFE) substrate-integrated waveguide (SIW) by the synchrotron radiation (SR) direct etching of PTFE and the addition of a metal film by sputter deposition. First, the dimensions of the PTFE SIW using rectangular through-holes for G-band (140-220 GHz) operation are determined, and a cruciform 90 ° hybrid coupler and an intersection circuit are connected by the PTFE SIW to design the Butler matrix. Then, a trial fabrication is performed. Finally, the validity of the design result and the fabrication process is verified by measuring the radiation pattern.

A Dual-Polarized Shared-Aperture Antenna With Conical Radiation Patterns and High Gain for 5G Millimeter-Wave Ceiling Communications

A dual-polarized (DP) antenna with a conical radiation pattern and high gain characteristics is proposed. It is mainly comprised of a horizontally polarized (HP) array, a vertically polarized (VP) element, a fence, and a feeding network. In the HP direction, a rotatable stacked substrate-integrated waveguide (SIW)-to-coaxial-to-SIW transition (SCST) is meticulously designed to yield omnidirectional radiation with low gain variations and low transmission loss. As for the VP direction, two orthogonal substrates that are arranged above the VP radiating element act as a holder to fix the director, resulting in gain enhancement. Here, the VP element is placed in the center of the HP array to share the aperture for size reduction. Moreover, the top-hat-shaped metal fence collaborates with the large-size ground plane to yield dual conical beams with high gain in DP directions. From the measured results, the HP direction has exhibited desirable bandwidth of 11.4% (24.8–27.8 GHz) with a peak gain of 11.6 dBi, and the VP direction has demonstrated wider bandwidth of 13.7% (24.5–28.1 GHz) with a corresponding gain up to 8.1 dBi. Notably, low gain variations of ±0.65 and ±0.8 dBi are also realized for the HP and VP directions, respectively. Therefore, a DP antenna with high-gain conical beams and low gain variations can be obtained for the fifth-generation (5G) millimeter-wave (MMW) ceiling communications.

Microwave Dual-Crack Sensor with a High Q-Factor Using the TE20 Resonance of a Complementary Split-Ring Resonator on a Substrate-Integrated Waveguide.

Microwave sensors have attracted interest as non-destructive metal crack detection (MCD) devices due to their low cost, simple fabrication, potential miniaturization, noncontact nature, and capability for remote detection. However, the development of multi-crack sensors of a suitable size and quality factor (Q-factor) remains a challenge. In the present study, we propose a multi-MCD sensor that combines a higher-mode substrate-integrated waveguide (SIW) and complementary split-ring resonators (CSRRs). In order to increase the Q-factor, the device is miniaturized; the MCD is facilitated; and two independent CSRRs are loaded onto the SIW, where the electromagnetic field is concentrated. The concentrated electromagnetic field of the SIW improves the Q-factor of the CSRRs, and each CSRR creates its own resonance and produces a miniaturizing effect by activating the sensor below the cut-off frequency of the SIW. The proposed multi-MCD sensor is numerically and experimentally demonstrated for cracks with different widths and depths. The fabricated sensor with a TE20-mode SIW and CSRRs is able to efficiently detect two sub-millimeter metal cracks simultaneously with a high Q-factor of 281.

An End‐Fed Programmable Metasurface Based on Substrate Integrated Waveguide for Novel Phased Array

A programmable metasurface antenna based on electrically tunable elements operating in 5G millimeter‐wave band, which has the features of low cost, easy manufacturing, low profile, easy integration with planar circuits, is proposed herein. The prototype consists of a 128‐element metasurface array, an 8‐channel beamforming chip as equal amplitude power divider networks, and a control network. Elements mounted with varactors to realize different states are controlled by DC bias signal from the back of a printed circuit board (PCB). By assigning different voltage values, array coding can be dynamically changed, thereby realizing beam steering. Both element dimensions and its location along substrate integrated waveguide (SIW) are optimized to better antenna performance. Experiment results show that the proposed metasurface can achieve not only the scanning range of ±70° for unidirectional beam in azimuth and ±40° in elevation but also ±50° for dual beam in azimuth. The whole prototype is fabricated based on PCB technologies, and good agreements among simulated and measured results are obtained. The proposed electrically tunable metasurface array is a good alternative to the traditional expensive phased array and has a great potential application prospect in radar and communication systems.

A Deca-Band, Shared-Aperture, Dual-Mode Composite Antenna for Microwave and Millimeter-Wave 5G Applications

This paper presents a single-layer, deca-band, shared-aperture MIMO antenna that utilizes composite-mode technology for microwave (Mw) and millimeter-wave (MMw) 5G applications. The antenna structure comprises a dual-slot substrate-integrated waveguide (SIW), an Inverted-L conventional metallic strip structure, and finite coplanar patches. The MMw radiator (slotted-SIW) is fed using a simple tapered 50 Ω microstrip feed line (Port 1), covering four MMw 5G bands. A dual-frequency single slot (Slot 1) is linked to resonant modes at 33 GHz and 38 GHz, while radiations at 28 GHz and 40 GHz are due to Slot 2 and finite coplanar patches, respectively. Port 2 feeds an asymmetrical T-shaped conventional metallic monopole strip, exciting six resonant modes at (1.6-6.0 GHz) and one MMw resonant mode at 28 GHz. Moreover, this paper extends the use of the mode-composite method to propose a tri-port MIMO antenna with a step impedance stop band resonator built on the SIW antenna. The paper obtains MIMO performance parameters, including S-parameters, envelope correlation coefficient, total efficiency above 73%, and radiation patterns, from both simulated and measured results. The achieved results demonstrate that the proposed antenna represents a favorable solution for current 5G applications. Finally, a general framework for the design of dual-mode composite antennas is presented to pave the way for interested antennas’ researchers.

Manipulation of Arbitrary Polarizations and Phases Based on Metasurfaces

AbstractPolarization and phase are two essential properties of electromagnetic (EM) waves. A transmissive metasurface is proposed that can simultaneously manipulate the polarization and phase of the EM waves. The design has a powerful capability of rotating the polarization to any desired azimuth direction for a linearly polarized (LP) wave and achieving the cross‐polarization conversion for a circularly polarized (CP) wave. Meanwhile, the transmission phase of the cross‐polarization can be dynamically controlled for the CP wave. The proposed metasurface is composed of two types of substrate‐integrated waveguides (SIW) in a cross arrangement, which has an insertion loss of less than 0.3 dB from 9.7 to 10.3 GHz. Some samples are fabricated and measurements are performed, which are in satisfactory agreement with the theoretical and simulated results, indicating the feasibility of the proposed method. It is believed that the proposed design has many potential applications in the fields of imaging, communication, and radar systems.

Measurement of Complex Permittivity for Rapid Detection of Liquid Concentration Using a Reusable Octagon-Shaped Resonator Sensor

Substrate-integrated waveguides (SIWs) are widely used in microwave systems owing to their low cost and ease of integration. In this study, an SIW-based resonator that reacts to the complex permittivity variation of solutions with dimensions of 79.2 mm × 59.8 mm is introduced. This octagon-shaped sensor can be installed on a preliminary monitoring system to test water quality by observing the parameter variations caused by external factors. The resonant structure was used to test different concentrations of ethanol-water and acetone-water mixtures for verification. The resonant frequency and quality factor (Q-factor) were found to vary with the relative complex permittivity of the liquid in the S-band, and the electric field distribution varied when liquid droplets were placed in the center of the substrate. The designed sensor operates at 2.45 GHz in the air, and the observed minimum resonant frequency shift with liquid was 15 MHz. The measurement error was approximately 3.1%, and the results reveal a relationship between the resonant frequency and temperature as well. Considering the observed sources of error, the measured relative permittivity is consistent with the actual values. The proposed sensor is economically convenient and suitable for various test environments.

Design and analysis of microstrip transceiver array antennas with the function to suppress beam deflection for 77 GHz automotive radar

A microstrip transceiver array antenna with high beam pointing accuracy is designed for automotive radar. Considering the influence of the lossy conductor on the excitation current, the beam deflection problem formed by the passive microstrip series-feed linear array is analyzed and solved. Compared with the traditional microstrip series-feed linear array, the microstrip series feeder array designed in this paper has good beam pointing accuracy. A power divider based on substrate-integrated waveguide (SIW) and microstrip line (MSL) with Chebyshev amplitude distribution(applied to the transmit array antenna) and binomial amplitude distribution(applied to the receive array antenna), respectively, is designed as the feeding network of the linear array. The fabrication and measurement of the prototype transceiver array antenna are completed to verify its beam directivity. The simulation and measurement results show that the E-plane main beam of the transceiver array antenna radiation pattern has good pointing accuracy, which makes the detection accuracy of the automotive radar significantly improved.

Phase Shifting Enhancement of a Substrate-Integrated Waveguide Phase Shifter Based on Liquid Crystal

A novel technique to enhance the phase shifting range of a liquid crystal (LC)-based, substrate-integrated waveguide (SIW) phase shifter by inserting inductive posts (IPs) is presented for the first time. The IPs inserted in the LC-based SIW phase shifter produce a phase advance based on the relative permittivity of the LC, resulting in an additional differential phase shift. At 28 GHz, the proposed structure with IPs achieves a ratio of maximum differential phase shift (∆ϕmax) to maximum insertion loss (ILmax) (FoM1) = 52.82 °/dB and ratio of maximum differential phase shift to length (FoM2) = 2.62 °/mm. Compared with conventional LC-based SIW phase shifters that lack an IP and use the same amount of LC, the FoM1 increased by 16% and the FoM2 increased by 55%. In addition, compared to the typical structure that uses additional LCs instead of IPs, the FoM1 decreased by 7%, and FoM2 increased by 21%. Therefore, inserting IPs into the LC-based SIW phase shifter can reduce the dimensions of the phase shifter and the amount of LCs required to achieve the desired differential phase shift. We believe this work can contribute to the design of compact and efficient SIW phase shifters for future telecommunication systems.

A low‐profile planar end‐fire broadband antenna with wide beamwidth

AbstractA low‐profile planar end‐fire broadband antenna with wide beamwidth is presented. The proposed antenna consists of a grounded coplanar waveguide (GCPW), an antipodal dipole, and a pair of directors. A transition from the GCPW to the substrate integrated waveguide (SIW) with tapered coupling slots is designed to achieve a wide impedance bandwidth. Wide beamwidths of the proposed antenna are realised through the antipodal dipole with bilaterally symmetrical sector arms. A pair of directors are symmetrically located on both sides of the sector arms to further widen the beamwidth. An antenna prototype operating at Ka band with a size of 2.18 λ0 × 0.77 λ0 × 0.06 λ0 (λ0 is the wavelength of the centre frequency) is fabricated based on the conventional printed circuit board process. The measurement results show that the reflection coefficient is lower than −12.5 dB in the frequency range of 32.2–37.0 GHz. At 35.5 GHz, the peak gain is 3.8 dBi, and the half‐power beamwidths (HPBWs) in E‐plane and H‐plane are 116° and 215°, respectively.

A monopulse array antenna based on SIW with circular polarization for using in tracking systems

In this paper, a monopulse slot array antenna with substrate integrated waveguide (SIW) has been designed and fabricated for application in tracking systems. This antenna has circular polarization and has a very simple design. For increasing the efficiency of the antenna and maintaining its one-layer structure, this design utilizes two modes (TE120, TE210) to excite the slots rather than the complex feed network commonly used in monopulse antennas. The feeding ports are well-isolated due to the orthogonality of the two modes. The feeding cavity is operated in these two modes to obtain the difference and sum patterns. The proposed antenna at the center frequency of 10 GHz has an impedance bandwidth of 200 MHz, and the reflection coefficient in this bandwidth is less than −10 dB. The zero depth of the difference pattern is less than −24 dBi, while the obtained gain of the sum pattern is 13.6 dBi. The polarization axial ratio is less than 3 dB in the range of 9.98–10.02 GHz. Also, the antenna aperture efficiency is 50 % at the desired frequency.

A Singly-Fed Dual-Band Aperture-Sharing SIW Cavity-Backed Slot Antenna With Large Frequency Ratio

A singly-fed dual-band aperture-sharing slot antenna with a large frequency ratio is investigated, based on the substrate integrated waveguide (SIW) technology. The dual-band antenna consists of a rectangular slotted SIW cavity operating at 40 GHz millimeter-wave (MMW) band and a ring slotted SIW cavity operating at 5.2 GHz microwave (MW) band. Due to the self-shielding effect of the SIW cavity, the two radiating elements can be tightly nested with each other, leading to a compact structure with a high ratio of radiating aperture utilization. The MW and MMW SIW radiating elements are fed via a common microstrip line through two separate slots, and they are excited in the hybrid TMh (120, 210) mode and TMh (230, 320) mode respectively. In order to avoid the signal crosstalk, a transverse stub of half-wavelength (in terms of MMW frequency) is added onto the microstrip feed line to prevent the MMW signal from getting into the MW element, while the MMW element can naturally reject the MW signal for its high-pass characteristics. Consequently, good radiation performance is obtained at both the MW and MMW bands, and moreover, the two bands can be independently adjusted.

Substrate Integrated Waveguide Radial Sixteen-Way Power Divider

A substrate integrated waveguide (SIW) radial sixteen-way power divider is presented. This power divider adopts two layer substrates, one of which is used to design the radial power divider cavity of the SIW, and the other layer is used to design the star-shaped microstrip isolation network. To improve the isolation performance, radial slots are cut in the metal layer of the SIW, and isolation resistors are added. The step impedance probes ensure good matching of input and output ports. For verification, a SIW radial sixteen-way power divider is manufactured and measured. The measured result shows that the 15-dB input bandwidth and output bandwidth of the SIW sixteen-way power divider reaches 12.6% and 20.2% respectively, the insert loss (IL) is lower than 2 dB, and the isolation between the output ports is better than 15 dB.

Low-Loss Self-Packaged Ka-Band LTCC Filter Using Artificial Multimode SIW Resonator

In this brief, a low-loss self-packaged Ka-band LTCC filter is proposed based on an artificial multi-mode substrate integrated waveguide (SIW) resonator. Two ridges and two metal strips are tightly integrated in one SIW cavity to form the artificial quad-mode resonator. Due to the shielding of the SIW cavity, the resonator realizes a high Q factor, which contributes to an extremely low loss of the Ka-band filter. A fast design method for the bandpass filter based on an artificial multi-mode resonator is introduced. A simple approach to accurately extract all external Q factors for multiple resonant modes at the same time is also discussed. A pair of transmission zeros are generated to improve the filter skirt selectivity. For verification, a filter operating at 28 GHz is fabricated on the LTCC process. The measured result shows a low insertion loss of 0.8 dB, which is attracted in millimeter-wave applications.

Circularly Polarized Corporate-Feed Beam-Scanning Array With Low Profile

A low-cost low-profile circularly polarized (CP) corporate-feed beam-scanning array is presented. As the main part of the feed network, we found that the sidewall reflection of the parallel plate waveguide (PPW) is the major reason for the deterioration of the beam-scanning performance at large angles. Therefore, a hybrid feed network composed of PPW and substrate integrated waveguide (SIW) is proposed. Mechanical beam-scanning is realized by a planar parabolic reflector-based line source generator (LSG). To expand the beam-scanning range, an SIW delay line-based phase compensation structure is introduced after theoretically analyzing the phase deviation generated by the LSG. The CP radiation is realized by improved CP antenna elements with a wide 3 dB axial ratio (AR) beamwidth. These CP antenna elements are fed by a corporate-fed network to avoid the frequency-dependent squint beam. A K-band prototype of an <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$8\times14$ </tex-math></inline-formula> array is fabricated and measured to verify the design. According to the measured results, the beam-scanning range of 0°–51° in elevation with the peak gain of 22.3 dBi is realized. The gain variation and ARs in this scanning range are less than 2.9 and 2.5 dB, respectively.

Substrate-Integrated Waveguide Band-Pass Filter and Diplexer With Controllable Transmission Zeros and Wide-Stopband

In this brief, a substrate integrated waveguide (SIW) bandpass filter (BPF) with wide out-of-band rejection is researched and fabricated with the center frequency of 45.8 GHz and 3-dB FBW of 2.18%. Due to the exploitation of electronic excitation, higher order modes mismatch and orthogonal transmission, the simulated and measured out-of-band rejection is better than 20 dB with frequencies up to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$7.6f_{0}$ </tex-math></inline-formula> and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$2.4f_{0}$ </tex-math></inline-formula> , respectively. Diplexer with stopband suppression better than 30 dB up to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1.87f_{0}$ </tex-math></inline-formula> is proposed based on the theory of the proposed filter. Dual-mode resonator operating with TE301 mode (43.8 GHz) and TE103 mode (45.8 GHz) has been designed to provide the transition of two filter channels. High isolation better than 27 dB over the whole band can be achieved. Transmission zeros (TZs) are generated by spurious resonances under electrical excitation, resulting in high selectively of the passbands. Good agreements between simulations and measurements can be observed.

Compact Microstrip Patch Filtenna Array Based on Reusable High-Order SIW Cavity

In this letter, a compact microstrip patch (MP) filtenna array designed by reusing high-order substrate integrated waveguide (SIW) cavity is investigated. The SIW cavity operating at TE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">201</sub> mode not only acts as the first-stage resonator of the filter, but also serves for the four-way dividing realized by the mode power allocation. In addition, by appropriately controlling the coupling coefficient of the output window of the SIW cavity, the radiating 2 × 2 MP array can become the second-stage resonator of the filter. Finally, benefiting from the reuse of the employed high-order SIW cavity, the proposed filtenna array exhibits good performance such as low loss, high efficiency and compact structure. For demonstration, a filtenna array prototype centered at 13.6 GHz is fabricated and tested, showing 13 dBi peak gain and 90% peak efficiency. Good agreement is obtained between simulated and measured results.

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.