Substrate Integrated Waveguide Structure Research Articles

A design of compact wideband substrate integrated waveguide fractal koch surface slot antenna for Ka$$ Ka $$‐band applications

SummaryThis article analyses a substrate integrated waveguide (SIW) fractal koch surface (FKS) slot antenna performance for Ka‐band applications. This FKS slot shape is obtained by modifying the conventional rectangular slot with the first iteration of the FKS method. The resultant FKS slot behaves as a radiator in the provided space. A single‐ and two‐element FKS slotted SIW antenna characteristics are analysed on a 20 mil thick RT/Duroid 5880 substrate and compared with the conventional rectangular slot. The proposed antenna with dimensions mm3 achieves an impedance bandwidth from 27.4 to 32.1 GHz with a fractional bandwidth of 15.79% and achieves a gain of 8.3 dBi in broadside direction by improving space filling factor in SIW structure. The prototype of the SIW‐fed FKS slotted antenna array measurement results is satisfactory with the simulation results.

A compact, low‐loss, and wide passband ratio substrate integrated waveguide triplexer based on complementary split ring resonators for multiband applications

SummaryIn this paper, a design of a substrate‐integrated waveguide (SIW) triplexer with improved low‐loss performance, passband ratio, and compactness based on the complementary split ring resonator (CSRR) structure is presented. The proposed triplexer operates at three passbands of 6, 8, and 10 GHz that correspond to the passband ratios of 1.33 and 1.67. By appropriately designing square CSRRs on the surface of the SIW structure, the low‐loss and compact resonator filters below the cut‐off frequency of the SIW at each operation frequency can be realized. The wide passband ratio is obtainable by adjusting the dimensions of the T‐junction. The measured results show the minimum insertion losses of 1.5, 1.4, and 1.9 dB at 6, 8, and 10 GHz, respectively. In addition, the minimum measured return losses are −9.33, −11.3, and −12.4 dB at the corresponding three passbands. The measured isolation between output ports is better than −17 dB in the frequency range from 5 to 11 GHz. The measured results agree well with simulations which are conducted by the CST Microwave Studio simulator. The proposed triplexer is designed on a cost‐effective RO4003C substrate with a compact size of 35 25 mm2

Substrate integrated waveguide-based self-triplexing antenna-sensor

In this paper, a Substrate Integrated Waveguide (SIW) based self-triplexing antenna-sensor is introduced. The proposed structure can act as a sensor for concurrent detection of three chemical materials. Further, it can be used as a self-triplexing antenna for simultaneous operation at three different frequencies. To that end, initially, a half mode circular SIW cavity is designed. Then, it is divided into three parts. In each part, the position of maximum electric field is determined and subsequently, three holes are located in the positions for material insertion. Finally, considering the vacuum as the inserted material for each hole, each cavity is adjusted to operate at its operation frequency (4.8, 5.8, and 6.6 GHz). Altering the permittivity of the objects inserted in the holes, the resonant frequencies are changed and consequently the type of material is determined. The simulated and measured results validated the performance of proposed antenna-sensor as well. In all the frequency bands, the reflection coefficients as well as mutual coupling among ports are below −20 dB. It should also be expressed that such an SIW structure with the capability of sensing and propagation is provided for the first time.

A Multifunctionality Reconfigurable HMSIW Filter by Using EBG Structure and Diodes for C/X-Band Application

This letter presents a multifunctionality reconfigurable substrate-integrated waveguide (SIW) filter embedded in a microstrip line. The proposed filter used an electromagnetic bandgap structure (EBG) to compact the size and improve the electromagnetic features. The SIW filter consists of a three-cell EBG with metallic circular-shaped connected to the ground through cylindrical vias. Firstly, the base SIW structure offers a wide passband filtering response, and then, to obtain selective passband, wide band rejection, and controllable resonance frequencies, a three-cell EBG along with four diodes has been attached. The filter is designed and printed on a Rogers 4003 substrate with a thickness of 1 mm and is experimentally validated for functionalities operated at three modes with an average 3 dB bandwidth of 115 MHz in each frequency. In addition to that, two transmission zeros (TZ) have been produced in the upper band frequency. The filter’s response is also tunable by turning the diode off or on and changing the main parameters of EBG, the gab, and the position between cells. The study explores resonance frequency alterations in a three-state system of on/off. By eliminating or diminishing specific modes, and incorporating diodes, distinct resonance behaviors are observed. Moreover, shifting frequency resonance in a multiparameter system has been investigated. Increasing B1 induces a significant shift to lower values, while an increase in D1 leads to a decrease in the first and second resonance frequencies and an upward shift in the third. The designed filter has been fabricated and tested to compare and confirm simulated responses. Simulation and measurement results are in good agreement. The S-parameters of measured results gained a good response (>15 dB) within the passbands and stopbands and an insertion loss of 1.5 dB suitable for 5G and Wi-Fi systems.

Leaky-wave antenna on substrate-integrated waveguide with radiation pattern controlled by DC voltage

Abstract This paper presents the application of a substrate-integrated waveguide (SIW) for the design of a leaky-wave antenna (LWA). The antenna radiates through a wide slot in the top wall of the SIW structure in the forward direction. The effective width of the slot is varied by changing capacitances of two arrays of varactors connected between slot edges and inserted conducting strips. The radiation pattern of the antenna is by this way controlled by DC bias, which sets the capacitances of varactors. The maximum radiation direction in elevation can be varied within 35° by changing the DC bias from 2 to 12 V. This elevation angle is measured from the broad side direction perpendicular to the antenna substrate. The measured antenna characteristics are in accord with those predicted by simulation. The antenna can be simply fabricated by a planar circuit board technology.

Design and Performance Evaluation of Cavity-Backed SIW Antenna for Monopulse Applications

The design of a cavity-backed substrate integrated waveguide (SIW) dual-plane antenna for monopulse application is presented in this publication. The primary objective is to create a four-element circularly polarized cavity-backed slot antenna array that is compact and highly efficient. Two antenna subarrays are utilized to develop a complete analysis, design, and implementation of an antenna, and each antenna element can be used as an independent antenna for monopulse applications. The antenna element is made up of two square ring slot antenna components, a power divider, and a feed point. To produce sum and difference signals, the feed point of each antenna element can be connected to one of the input ports on a monopulse comparator. The antenna's performance at 10 GHz was assessed regarding radiation pattern, gain, return loss, bandwidth, axial ratio, and efficiency. A high-frequency structure simulator (HFSS) simulates a complete planar and compact SIW structure with a footprint of 61.6 mm x 58.1 mm. With a permittivity of 3.55 and a thickness of 1.524 mm, an antenna is manufactured using a photo-lithographic process on a single-layer Rogers RO4003 substrate. As per experimental findings, the antenna has a return loss of -40.17 dB, an RL bandwidth of 395 MHz, a gain of 13.11 dB, an axial ratio of 2.97 dB, and an efficiency of 89.85% at a frequency of 9.92 GHz. Experimental findings reveal exceptional performance parameters for the designed antenna, which can be used for monopulse applications at 10 GHz.

Dual Plane Monopulse Comparator Network System using Substrate Integrated Waveguide Hybrid Coupler

ABSTRACT This paper presents a new compact monopulse comparator network system (MCNS) using a modal substrate-integrated waveguide (SIW) hybrid coupler for the first time. The main objective of this research is to evaluate the performance of dual-plane MCNS based on return loss and coupling coefficients. A detailed analysis, design, and implementation of dual-plane MCNS is performed using the four modal SIW hybrid couplers. The sum and difference signals required by the monopulse antenna are generated with the proper orientation of couplers. The in-phase and out-phase characteristics of the couplers are generated using TE102 and TE201 orthogonal degenerate modes. A complete planar and compact SIW structure has a footprint of 58.2 mm × 58.2 mm. MCNS is fabricated on a single-layer Rogers RO4003 substrate with a permittivity of 3.55 and thickness of 0.787 mm using a photo-lithographic process. MCNS provides excellent return loss characteristics at all input and output ports. It measured the isolation better than 20 dB for all output ports in the desired frequency band. It achieved good coupling between all input and output ports. Simulation and measured results show that at 10 GHz, MCNS gives better performance parameters and can be used in monopulse antenna.

Advanced Modeling of SIW Structures by 2-D Finite Element Method

This article presents an advanced modeling of substrate-integrated waveguide (SIW) structures by the 2-D vector finite element method (FEM). All types of losses are considered, together with input/output coupling by the rectangular waveguide and coaxial cable. Multiple dielectric regions can be defined, allowing the modeling of partially air-filled SIW structures with excellent accuracy and efficiency.

A dual-mode microwave sensor for retrieving permittivity of materials based on multiple complementary rectangular ring resonators

A dual-mode microwave sensor based on multiple complementary rectangular ring resonators (CRRRs) are proposed to characterize the permittivity of material under test (MUT) in this manuscript. The designed microwave sensor is based on substrate integrated waveguide (SIW) with multiple CRRRs etched on the top plane. With comparison to traditional microstrip line excited sensors, the proposed SIW sensor has a higher quality factor. The SIW structure has the feature of bandpass filter, and the geometrical parameters of SIW are optimized to achieve an ultra-wideband with the cavity resonant modes of TE101, TE102, TE103, and TE104. The four cavity resonant modes (TE101, TE102, TE103, and TE104) substitute the pass-band, and by utilizing the characteristic of quasi bandpass filtering of SIW, four pairs of identical CRRRs can produce two resonant modes in the passband, named by mode1 and mode2. The electrical field distribution of mode1 is mainly confined at two intermediate resonators, and mode2 has an intensive electrical field at resonators on both sides. As the resonant frequencies are altered with the variations of permittivity of MUTs, thus the mathematical expressions can be obtained. By using the mathematical expressions, the permittivity of MUTs can be predicted. Moreover, the error model is used to decline the error of measurement. The equivalent circuit model is established to illustrate the operating principle of the sensor. A good agreement between circuit model and simulation is acquired. In the measurement, the average sensitivities of proposed microwave sensor are about 6.33% and 6.17% for mode 1 and mode 2, respectively. Besides, the errors of retrieving permittivity are about 0.5% and 0.9% for mode 1 and mode 2, respectively.

A 7 × 8 Butler Matrix-Fed Multibeam Antenna Based on Substrate Integrated Waveguide Technology

In this letter, a novel 7 × 8 Butler matrix (BM) operating in the millimeter-wave band is presented. It is composed of a 3 × 4 BM, two 3 × 4-like BM, two phase shifters and two couplers, achieving equal amplitude output distribution and seven output phase differences (0°, ±45°, ±90°, ±135°). The proposed 7 × 8 BM can be realized by dual-layer substrate integrated waveguide structure easily, which is difficult for merging the two central ports of the traditional 8 × 8 BM. To verify the concept, a multibeam antenna fed by the proposed BM is designed and fabricated, achieving seven beams in the frequency range of 26.5–29.5 GHz. Compared with counterparts, the proposed antenna features compact size, broadside radiation, and relatively wide bandwidth.

Novel Compact Half-Mode SIW Bandpass Filters Based on Quad-Mode Resonator

Novel wideband half-mode substrate integrated waveguide (SIW) bandpass filters based on the quad-mode resonator are proposed in this brief. The proposed half-mode SIW bandpass filter A is composed of two half-mode SIW structures and two T-shaped slots on the top surface. The coupling matrix topology and equivalent circuit model are presented to analyze the performance. The wide band of filter A is designed on the basis of quad-mode resonator (TE101, TE102, TE103, and TE104). Besides, it can generate one transmission zero on the upper stopband due to the equivalent inductance (connecting metallic line between two half-mode SIWs) and the mutual capacitance coupling between two SIWs according to the equivalent circuit model. On the basis of filter A, two open-ended microstrip lines are added near the input and output ports (This filter is named by filter B), which will introduce two transmission zeros (TZs) in the lower stopband. The introduced TZs can improve the out-of-band rejection on the lower sideband. The resonant frequencies of the four modes are controlled by the T-shaped slots on the upper metal plate, which can reduce the overall size, significantly. The proposed two filters have compact size of 47.9mm <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mathbf {\times }\,\,14.9$ </tex-math></inline-formula> mm <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mathbf {\times }\,\,2$ </tex-math></inline-formula> mm. The prototypes have been fabricated and measured, and the measured results have a good agreement with the simulated ones.

Broadband filtering balun employing spoof surface plasmon polariton and substrate integrated waveguide

In this paper, two filtering baluns exploiting a combination of spoof surface plasmon polariton (SSPP) and substrate integrated waveguide (SIW) techniques are proposed. The characteristic of out-of-phase between two output ports can be achieved by employing the multilayered SIW structures. The sub-wavelength periodic slots in improved dumbbell-shapes are etched on the top and bottom surfaces of SIW transmission lines (TLs). The dispersion characteristics and transmission performance of the SSPP-SIW unit cells are meticulously investigated. The lower and upper cut-off frequency can be controlled independently by adjusting the physical sizes of the SIW and SSPP structures. For validation, two cases of filtering baluns are designed, fabricated and measured. The measured and simulated results have reached satisfactory agreements. The experimental results exhibit that the developed prototype can achieve a fractional bandwidth (FBW) of>66%. Furthermore, HMSIW is implemented to integrate with SSPP configuration to decrease the circuital area of SSPP-SIW filtering balun by 50%.

A Dual Circularly Polarized SIW-Fed Phased Array Antenna With Wide-Angle Beam Scanning Range

We propose a dual circularly polarized (CP) substrate integrated waveguide (SIW) cavity-backed antenna with wide axial ratio (AR) beamwidth, which can generate the right-hand CP (RHCP) or left-hand CP (LHCP) radiation through exciting different ports. Dual CP radiations are accomplished by an SIW directional coupler (DC) in the bottom layer, which provides the desired amplitude and phase conditions for two orthogonal slots. By superposing phase centers of linearly polarized (LP) electric field elements, the proposed antenna achieves a good performance of 3 dB AR beamwidth of 165° in the desired azimuth cut plane. Furthermore, an eight-element dual CP linear phased array with a wide-angle beam scanning ability is comprised by this antenna prototype. Numerical and measured results show that the array antenna can scan its main lobe from – 59° to 58°. In general, the proposed antenna array fed by the SIW structure satisfies the requirement of a multipolarization wireless communication system for low profile, simple structure, and easy integration with planar circuits.

Integrated Microstrip Antenna Reflector Based on SIW for 5G Networks

High data rates, low latency, and low energy consumption are required for the fifth-generation (5G) mobile wireless network. One of the devices that garner interest to be developed is the antenna. Microstrip antennas are widely used in cellular communications because of their simple profile and easy fabrication. However, it has limitations in terms of performance. The millimeter-wave band has been selected to provide high-speed service in 5G wireless networks. Compared to other frequency bands, the propagation path in millimeter-wave is significantly decreased. The substrate integrated waveguide (SIW) technology aims to integrate all components on the same substrate, with low insertion loss and a low profile. Using a dielectric substrate on top and a metallic coating at the bottom with metalized holes, the SIW structure offers a compact form factor for integrating active circuits, passive components, and radiation elements within the same substrate. Therefore, this study aims to design and implement a reflector integrated microstrip antenna with a compact form and a working frequency of 26 GHz. The measurements showed the return loss value of -11 dB, voltage standing wave ratio (VSWR) of 1.9, and the antenna impedance of 63 Ω. The antenna that was designed and fabricated in this work is suitable for operation in the millimeter-wave range for 5G technology.

Microfluidic Microwave Sensor Loaded with Star-Slotted Patch for Edible Oil Quality Inspection.

In this paper, we present a new microfluidic microwave sensor loaded with a star-slotted patch for detecting the quality of edible oil. The relative dielectric permittivity and the quality of edible oil will change after being heated at a high temperature. Therefore, the quality of edible oil can be detected by measuring the relative dielectric permittivity of edible oil. The sensor is used to determine the edible oil with different dielectric permittivity by measuring the resonance frequency offset of the input reflection coefficient, which operates at 2.68 GHz. This sensor is designed based on a resonant approach to provide the best sensing accuracy and is implemented using a substrate integrated waveguide structure combined with a pentagonal slot antenna operating at 2.3~2.9 GHz. It can detect greasy liquids with the real part of the complex permittivity ranging from two to three.

Coplanar Meta-Surface-Based Substrate-Integrated Waveguide Antennas with Broadband and Low Reflections for K-Band Beam Scanning.

Four novel substrate-integrated waveguide (SIW) antennas are proposed, in order to obtain K-band beam scanning through the coplanar meta-surfaces of properly devised complementary split-ring resonators. More specifically, coplanar rhombus- and hexagon-shaped meta-surfaces replace the metallized via holes in the traditional SIW structure, achieving low reflection and wide bandwidth, respectively. Another trapezoid-shaped meta-surface is introduced, in order to realize good leaky-wave radiation performance with high-gain beam scanning in both rhombus- and hexagon-shaped SIW components. These designs are further extended to two different mixed types of two-row meta-surfaces, with the rhombus and hexagon structures combined in different orders to enhance the complex SIW transmission lines and antennas, which can simultaneously obtain good reflection and bandwidth with different priority, depending on the arrangement. We explain the performance differences with rhombus and hexagon meta-surfaces through the analysis of relevant equivalent circuit models and extracting the effective medium parameters, and we verify the bandwidths and radiations of four SIW antennas both numerically and experimentally. The maximum gains of the four antennas are 18.1 dBi, 17.0 dBi, 18.8 dBi and 17.1 dBi, where the corresponding relative bandwidths are 10.74%, 19.42%, 14.13% and 18.38%. The maximum simulated radiation efficiency and aperture efficiency of the proposed antennas are 91.20% and 61.12%, respectively. Our approach for generating flexible and selectable tuned electromagnetic fields from SIWs is applicable for the development of mm-Wave antennas or sensors on PCB-integrated platforms for highly directive scanning radiation.

A miniaturized mm‐wave leaky wave antenna based on CRLH slow‐wave SIW for symmetric wide angle beam scanning

In this article, a novel miniaturized wide beam scanning range multi-layered mm-wave leaky-wave antenna (LWA) based on slow-wave (SW) substrate-integrated waveguide (SIW) is presented. The SW effect is introduced by loading conventional SIW with internal metalized blind vias connected to the bottom ground plane. The SW effect in the SIW structure causes the separation of the electric and magnetic field components in the structure which leads to the reduction in lateral dimensions of the proposed topology by 35% as compared to the conventional SIW. The proposed LWA exhibits a miniaturized volume of 6.6 × 0.41 × .07 λ3. The radiation in the proposed design is realized by introducing U-shaped slots in the unit cell of the SW-SIW structure. Experimental results show that the proposed SW-SIW LWA achieves almost symmetric and continuous beam scanning from −48° to 52° including the broadside direction within the impedance bandwidth of 23.7–28.1 GHz. The proposed antenna achieves a peak gain of 14.52 dBi and the half-power beamwidth of LWA is as low as 10°. The proposed antenna also exhibits radiation efficiency of above 90% within the bandwidth. The proposed design can be a potential candidate for mm-wave frequency beam scanning applications.

Efficient approach for modeling substrate integrated waveguides

In this letter, a highly accurate surrogate model of substrate integrated waveguide (SIW) is proposed. This model allows designers to design SIW structures more efficiently compared to existing complex and CPU-intensive fine approaches. Based on the multivariate linear regression technique, an accurate equation linking the physical parameters of the proposed surrogate but simple model to the fine but complex model was obtained. The accuracy and efficiency of the proposed modeling procedure were demonstrated through a practical design example.

A digital SIW-slot antenna array with FPGA implementation of beamforming

The future satellite platform and 5G communication systems place high demands on antennas, in which the antenna should offer low-cost, lightweight, electronically steerable features. In this paper, the design of a digital slot antenna element based on substrate integrated waveguide (SIW) is proposed. SIW guides the microwave inside the substrate confined with planar metallic covers and through-hole synthetized side-walls in conventional applications, and can also radiate the microwave towards free space in antenna applications through opening slots in its metallic covers. The slot antenna element is realized by implementing PIN diodes across the gaps on both sides of the pad in the center of the slot antenna, to provide the switching freedom of the slot antenna element between radiating and non-radiating states. Besides, radial decoupling stubs are introduced into the bias line so as to reduce the leakage of the energy in the SIW structure. Applying a series of on/off states to the diodes produces various radiation patterns, thus wide range scanning is possible supposing that enough array elements are equipped. Finally, a digital SIW-slot array composed of 8 by 4 elements with tunable field programmable gate array circuits are fabricated and measured. The measured results validate the reconfigurable characteristics for the radiation pattern of the proposed digital SIW-slot antenna array without heavy engineering of phase shifter in conventional antenna arrays. The antenna is consisted by 4 by 8 elements and its dimension, simulated gain and radiation efficiency are 145 mm times 127 mm times 1.524 mm, 15 dBi and 53.5%, respectively. Our designed SIW antenna has the advantage of both size and weight. Furthermore, its digitalized control of beamforming allows a programming-friendly interface for smart antenna development.

Bandpass filters based on integrated aperture‐ and gap‐coupled discontinuities

An electromagnetic coupling mechanism is discussed for distributed-element aperture- and gap-coupled discontinuities based on rigorous lumped-element equivalent circuit analysis. The two discontinuities are analysed in terms of their transmission poles and transmission zeros for the selectivity enhancement of microwave and or millimetre-wave components. The integration of these two discontinuities is put forward for bandpass filter design. A frequency-dependent lumped-element equivalent circuit is employed to study the behaviour of the two distributed-element discontinuities in the transverse direction. Bandpass filters are characterised based on the dual aperture- and gap-coupled discontinuities integrated within substrate integrated waveguide structures. It is shown that multiple transmission zeros close to transmission poles are realised due to the magnetic and electric field cancelation in the gap-coupled discontinuity, while the aperture-coupled discontinuity contributes to a resonator with a higher quality factor. The integration of both aperture- and gap-coupled discontinuities shows the priority of this kind of microwave resonator in terms of selectivity, size, and upper stopband in comparison with the conventional aperture-coupled one.