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Substrate Integrated Waveguide (SIW) involves the conductive via holes immersed in a dielectric substrate that connects two substrate plates. This article presents a new SIW technique to enhance the operational bandwidth of the Riblet Short-Slot coupler. To demonstrate the proposed SIW technique, two Riblet Short-Slot couplers are designed and investigated at two different high-frequency ranges, Ku-band and K-band. The bandwidth of the proposed couplers is improved by introducing multiple layers of SIW vias at the center of the couplers' side wall. Applying this approach minimizes the leakage loss between vias, indicating an improved overall operating bandwidth of 36.31% and 26.32% for Ku-band and K-band, respectively. All vias in both prototypes are realized using an alternative method, without using the Plated-Through-Hole Printed-Circuit-Board (PTH-PCB) machine. In addition, experimental results agree well with the simulated results. [ABSTRACT FROM AUTHOR]

This paper presents an expression to determine the complex wave impedance of a substrate-integrated waveguide for the dominant TE10 propagation mode, notably enhancing the accuracy in modeling the corresponding imaginary part. This was accomplished by systematically identifying the need to consider additional conductor losses caused by the interaction of the propagating fields with the conductor material. In fact, by using the proposed expression, the complex impedance can straightforwardly be determined by combining propagation constant data, and the resistance that represents the loss associated with longitudinal currents occurring at the top and bottom walls, which are influenced by the conductor surface roughness. This allows for completely describing the characteristics of the waveguide when assuming uniform propagation along its length. Furthermore, since the voltage–current, the power–current, and the power–voltage impedances can easily be obtained from the wave impedance, the proposal enables representing the matching characteristics of the waveguide for circuit design purposes. An agreement between simulated and experimental insertion loss is achieved for substrate-integrated waveguides of two different widths when reconstructing the corresponding S-parameters using the determined wave impedance. [ABSTRACT FROM AUTHOR]

Integrated sensing and communication (ISAC) is emerging as a main feature for 5G/6G communications. To enhance spectral and energy efficiencies in wireless environments, reconfigurable intelligent surfaces (RISs) will play a significant role in beyond-5G/6G communications. Multi-functional RISs, capable of not only reflecting or transmitting the beam in desired directions but also sensing the signal, wirelessly transferring power to nearby devices, harvesting energy, etc., will be highly beneficial for beyond-5G/6G applications. In this paper, we propose a nearly 2-bit unit cell of RISs integrated with sensing capabilities in the millimeter wave (mmWave) frequency band. To collect a very small fraction of the impinging signals through vias, we employed substrate integrated waveguide (SIW) technology at the bottom of the unit cell and a via. This enabled the sensing of incoming signals, requiring only a small amount of the impinging signal to be collected through SIW. Initially, we utilized Floquet ports and boundary conditions to obtain various parameters of the unit cells. Subsequently, we examined 1 × 3-unit cells, placing them on the waveguide model to obtain the required parameters of the unit cell. By using the waveguide and 1 × 3-unit cell arrays, the sensing amount was also determined. [ABSTRACT FROM AUTHOR]

A new compact design of bandpass filter using substrate integrated waveguide (SIW) is proposed and analyzed in this paper. It offers good in-band return loss, low insertion loss, wide passband, and high stopband attenuation. The filtering response is achieved by loading a couple of inverted tuning fork-shaped defected ground structures (DGS) on the bottom of the SIW cavity. DGS is utilized to enhance the upper stopband performance. To validate, the filter is fabricated using Rogers RT/Duroid 5880 with 0.508 mm thickness and tested. The filter has a center frequency of 15.44 GHz with 19% fractional bandwidth (FBW). The return loss is more than 20 dB and the insertion loss is about 1.2 dB. It finds its application in Ku band satellite communication. [ABSTRACT FROM AUTHOR]

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Abstract This letter presents a novel millimetre‐wave (mm‐wave) on‐chip substrate integrated waveguide (SIW) filtering crossover using 0.25 µm GaAs pHEMT technology. The design methodology of the proposed crossover is thoroughly illustrated. The proposed filtering crossover employs a dual‐mode cavity with TE102 and TE201 degenerate mode resonances at the intersection, leveraging the degenerate modes for in‐band resonance and inter‐channel isolation. Additionally, four TE101 mode resonant half‐mode SIW cavities are coupled around the dual‐mode cavity to achieve two third‐order bandpass response channels and reduce the overall size. A prototype is designed, analysed, and fabricated to validate the proposed approach, with measured results showing good agreement with simulations. The presented on‐chip SIW filtering crossover offers promising potential for mm‐wave applications, demonstrating the effectiveness of the design methodology and GaAs pHEMT technology integration.

This letter presents a novel millimetre‐wave (mm‐wave) on‐chip substrate integrated waveguide (SIW) filtering crossover using 0.25 µm GaAs pHEMT technology. The design methodology of the proposed crossover is thoroughly illustrated. The proposed filtering crossover employs a dual‐mode cavity with TE102 and TE201 degenerate mode resonances at the intersection, leveraging the degenerate modes for in‐band resonance and inter‐channel isolation. Additionally, four TE101 mode resonant half‐mode SIW cavities are coupled around the dual‐mode cavity to achieve two third‐order bandpass response channels and reduce the overall size. A prototype is designed, analysed, and fabricated to validate the proposed approach, with measured results showing good agreement with simulations. The presented on‐chip SIW filtering crossover offers promising potential for mm‐wave applications, demonstrating the effectiveness of the design methodology and GaAs pHEMT technology integration. [ABSTRACT FROM AUTHOR]

Despite extensive research on integrating Substrate Integrated Waveguide (SIW) technologies with conventional transmission technologies such as Microstrip Transmission Line (MSTL), Co-planar Waveguide (CPW), Rectangular Waveguide (RWG), and Coaxial lines, a comprehensive evaluation and design framework has yet to be explored. This review addresses this critical gap by providing a detailed examination of recent advancements in interconnect technologies at millimeter-wave (mmWave) frequencies. The paper identifies unresolved challenges and introduces a Figure-of-Merit (FoM) for the first time designed to evaluate and decide the state-of-the-art in interconnect technologies. Furthermore, it proposes a novel design flow that aids interconnect designers by integrating reported advances into a well-defined process. As such, the study provides a basis for further developments, leveraging existing and SIW technologies to ease mmWave system development, along with a commercial perspective.

This paper introduces a streamlined design that includes a broadband directional coupler, a set of three-port union-T power dividers, and several microstrip transitions. These components leverage substrate-integrated waveguide (SIW) technology, operating across multiple frequency bands and offering equal power distribution in all output ports. The directional coupler, dividers, and transitions underwent a comprehensive design, simulation, and optimization process using CST Microwave Studio. A crucial aspect of the SIW design was the meticulous consideration of transitions necessary to achieve optimal matching between the SIW devices and the connected structure (such as microstrip or SMA connectors). This approach ensured a consistent focus on seamless integration. For validation purposes, the devices were manufactured physically using the RF-5880 substrate, which works with frequencies up to 40 GHz. The experimental results were then compared with simulations conducted in CST Microwave Studio, validating the prototypes. The findings confirmed that the design performs as intended, exhibiting expected behavior and showcasing a notable agreement between the simulation and experimental results. Furthermore, the designs were treated as standard rectangular waveguides, functioning within microwave and millimeter wave frequencies ranging from 8 to 40 GHz. The paper not only outlines these designs but also proposes practical dimensions for SIW technology, offering a tangible guide for the realization of these devices.

A slow-wave half-mode substrate integrated waveguide with a spoof surface plasmon polariton (SW-HMSIW-SSPP) transmission line structure is proposed, analyzed, and demonstrated. Results show longitudinal and lateral size reductions of more than 80% and 73%, respectively, as compared with an equivalent SIW at the same cutoff frequency while maintaining a low attenuation constant of 0.02 dB/mm. By altering the geometric parameters of the SW-HMSIW-SSPP the dispersion curve can be tailored. The dispersion and electromagnetic (EM) field distribution characteristics of the proposed SW-HMSIW-SSPP unit cell and overall structure are analyzed by HFSS simulations and an equivalent circuit, and pertinent performance parameters are compared to those of SW-HMSIW and HMSIW-SSPP structures. A proof-of-concept PCB SW-HMSIW-SSPP sample was fabricated, and measurement results showing a band-pass of 4.8-11.5 GHz are found consistent with simulation results. The SW-HMSIW-SSPP structure has applications in the design of miniaturized microwave circuits.

The design, manufacture and characterization of a slotted waveguide antenna using substrate-integrated waveguide (SIW) technology combined with a metasurface are described in this paper. The inclusion of the metasurface serves to augment the radiating aperture and narrows the E-plane cut of the antenna pattern, a characteristic that would otherwise be dictated by the slots. For demonstration, an 8-element slotted SIW (S-SIW) antenna array with a −20 dB sidelobe level Chebyshev distribution was designed and its performance was compared to that of a conventional slotted SIW array. Owing to the metasurface, the radiation pattern E-plane narrows and 3 dB gain improvement has been achieved, while keeping matching unaffected.

A novel approach is presented for synthesizing radiation patterns of substrate-integrated waveguide leaky wave antennas in two stages. In the first stage, the antenna is considered an equivalent rectangular waveguide with slots, and a comprehensive equivalent circuit model is constructed. Varying slot configurations are accommodated by the developed equivalent circuit model. Each slot section is represented as an admittance with the incorporation of Elliott’s slot theory. Computations of the relative aperture fields are performed using circuit theory, and the far-field pattern is estimated through array theory. In the second stage, the circuit model is utilized for genetic algorithm-based optimization, enabling customization of the radiation pattern to meet specific requirements. The methodology has a computational advantage over full-wave simulations, resulting in a significantly faster and more efficient design process. Numerical verification through simulation of various examples and experimental validation through antenna fabrication are presented, affirming agreement between calculated and measured results. Remarkable effectiveness in antenna engineering can be attained for future wireless communication systems by using the proposed technique.

This paper presents a linear-to-circular polarization converter (LCPC) used for multi-band functionality. The LCPC surface features symmetrically printed copper strips on a single-layer substrate and is surrounded by a square substrate integrated waveguide (SIW) cavity arranged periodically in two dimensions. The study successfully utilizes the LCPC surface to achieve a desirable axial ratio (AR) band width (BW) below 3 dB in multiple frequency ranges, specifically: 1) 4.51-4.80 GHz, 2) 6.51-6.80 GHz, 3) 9.01-9.20 GHz, 4) 10.90-12.40 GHz, and 5) 17.05-17.49 GHz. The LCPC induces a change in polarization as the wave propagates through it. In the first ( $f_{31}$ ) and fourth ( $f_{34}$ ) frequency bands, the initially linearly polarized (LP) wave transforms into a left-hand circularly polarized (LHCP) wave. Conversely, in the second ( $f_{32}$ ), third ( $f_{33}$ ), and fifth ( $f_{35}$ ) frequency bands, the wave converts into a right-hand circularly polarized (RHCP) wave. Measurement results indicate that the LCPC provides circularly polarized (CP) wave bandwidths of 12.72%, 4.8%, 2.4%, 11.39%, and 3.15% across frequency ranges of 3.9 - 4.43 GHz, 6.21- 6.52 GHz, 8.9-9.08 GHz, 10.51-11.78 GHz, and 16.85-17.39 GHz, respectively. This characteristic renders the LCPC suitable for utilization in the C (4-8 GHz), X (8-12 GHz), and Ku (12-18 GHz) frequency bands.

In this study, an eye bolt-shaped microstrip patch antenna (MPA) employing substrate integrated-waveguide (SIW) with and without slot is constructed and assessed. To evaluate the effectiveness of the constructed antenna, simulation, evaluation, and machine learning (ML) methodologies were combined. The design could achieve a gain of 5.5 dB, an optimal bandwidth of 8 GHz (28%), and a minimum return loss of − 38 dB using HFSS software simulations. This antenna's VSWR was 1.02, indicating strong impedance matching, and consequently, a significant efficiency of 87% was attained. In an attempt to forecast the suggested antenna’s return loss, four ML techniques are also used: random forest (RF) regression, extreme gradient boosting (XGB) regression, decision tree regression (DTR), and linear regression. Variance score, mean-absolute error (MAE), root-mean squared error (RMSE), and MSE are employed to assess the four ML model's performance. The XGB regression method outperforms than other three ML techniques in terms of prediction results among the four ML algorithms. Therefore, the proposed antenna is a perfect option for enabling machine-to-machine communications using 5G technology, due to its effectiveness. [ABSTRACT FROM AUTHOR]

A novel wideband high-selectivity substrate-integratedwaveguide (SIW) filtering antenna with controllable radiation nulls is proposed. This antenna is composed of a two-layered SIW resonator, two radiating slots on the top layer, and two coupling slots on the middle layer. A vertical SMA connector is located at the bottom and feeds two SIW cavities simultaneously. By adjusting the parameters of these slots, three radiation nulls will be achieved, and two radiation nulls can be easily controlled. For demonstration, one prototype of the filtering antenna is fabricated and measured. Measurement results show that the fractional bandwidth for |S11| < -10 dB is 8.9% (3.86-4.23 GHz), the gain is 6.08 dBi at center frequency 4.05 GHz, three radiation nulls are achieved at 3.7 GHz, 4.3 GHz, and 5.19 GHz, respectively. The out-of-band skirt selectivities of two sidebands are 150 and 332 dB/GHz, respectively. [ABSTRACT FROM AUTHOR]

In this letter, an substrate integrated waveguide ‐based self‐quadplexing antenna based on a modified Jerusalem cross‐shaped slot is presented. By introducing different lengths of the slots of Jerusalem cross, the antenna operates at four different closely spaced resonant frequencies 4.08, 4.37, 4.61, and 4.97 GHz. The proposed quadplexer antenna achieved a minimum port isolation of ≥ $\ge $20 dB between any two ports with an extremely low frequency ratio of 1.2. The quadplexer antenna has unidirectional radiation pattern and independent frequency tunability characteristics with a gain of 6.88, 6.51, 7.03, and 7.12 dBi, at corresponding resonant frequencies and a compact size of 0.14λ0 ${\lambda }_{0}$2, where λ $\lambda $0 is the free space wavelength at the lowest resonant frequency. The proposed antenna is suitable for C‐band multiplexing applications. [ABSTRACT FROM AUTHOR]

An antenna design with a coplanar waveguide (CPW) fed wide band circular polarization (CP), inspired by compact metamaterials, is presented in this paper. Substrate Integrated waveguide (SIW), metamaterial with CPW feed, and monopole patch make up its construction. A three-GHz axial ratio bandwidth (ARBW) is obtained by adding a rectangular slot at the monopole stub to produce CP. Incorporating SIW and metamaterial into the antenna design improves gain, directivity, bandwidth, and efficiency. Metamaterial and SIW utilized in the design comprising monopole patch with a stub, slots at the edges and the stub improve the antenna properties efficiently. ISM band, WLAN, and WBAN applications are appropriate for the suggested antenna. The antenna has a 3.6 dBi gain and measures 20 × 20 × 0.8 mm3. A radiation efficiency of 98% and a fractional bandwidth of 63.9% are obtained by incorporating the advantages of CP in a broadband SIW antenna inspired by metamaterials (3.99–7.62 GHz). [ABSTRACT FROM AUTHOR]

Here, a single‐layered single‐fed slot antenna is realized with low cross‐polarization over the full operating bandwidth. This design consists of a circular‐shaped cavity resonator, employed by using substrate integrated waveguide (SIW) technique and a square‐ring slot on the upper metal cladding of the cavity. The antenna is fed using a probe feed which excites the design in dual mode, that is, slot mode and inset patch mode. Due to the proximity of these dual resonances, the antenna operates over a relatively wider bandwidth than previously suggested designs with the claim of low cross‐polarization. The proposed design helps to realize more than 35 dB of co‐to cross‐pol isolation in both E and H planes. Overall experimental results demonstrate a good radiation performance, it is confirming up to 15–20 dB improvement in cross‐polarization level with enhanced enhancement bandwidth which makes it appropriate for a modern wireless application. [ABSTRACT FROM AUTHOR]

In this letter, a compact circular cavity‐backed, circularly polarized substrate integrated waveguide (SIW) multiband antenna is proposed. In the outer circular cavity, an array of two periodic metal slots, tilted at an angle, resonate at 25.32, 26.44, and 28.83 GHz, and the inner circular cavity's periodic slots radiate at 28.01 GHz. Two concentric SIW cavities are structured in such a distinct manner that no loss due to leakage takes place thus, achieving a maximum isolation of −43.8 dB at 28.83 GHz. The miniaturized antenna has dimensions of 2.2λo × 2.2λo × 0.1λo where λo is the operating wavelength. It achieves a maximum gain of 9.1 dBi at 26.44 GHz, and VSWR < 2 is achieved at all frequency bands. The antenna is circularly polarized at 26.44 and 28.01 GHz as well. The design results are plotted in the Ansys high‐frequency structure simulator version EM19.2 tool. The proposed antenna is fabricated and tested using an Anritsu Vector Network Analyzer version v4.0 with an anechoic chamber setup. [ABSTRACT FROM AUTHOR]

This study presents an original parallel connected hybrid microstrip-substrate integrated waveguide (PCHM-SIW) bandstop filter. A low-pass filter implemented on a microstrip structure and a SIW-based high-pass filter are connected in parallel to each other. In this way, the aim is to obtain a bandstop filter in the novel hybrid design. The parallel connected hybrid microstrip-substrate integrated waveguide (PCHM-SIW) bandstop filter is synthesised, simulated, and produced. The effects of connecting filters in parallel are discussed. It is seen from the results of CST Studio Suite simulation that PCHM-SIW bandstop filter has a bandwidth of 2.85 GHz and a center frequency of 4.26 GHz. The frequency change rate of the center frequency between simulation and measurement is 7.02 % where it is just 3.76 % for the deviation in bandwidth. The results of the simulation and those of the measurement are close to each other. These results converge to ideal analytical results.

This paper presents an expression to determine the complex wave impedance of a substrate-integrated waveguide for the dominant TE10 propagation mode, notably enhancing the accuracy in modeling the corresponding imaginary part. This was accomplished by systematically identifying the need to consider additional conductor losses caused by the interaction of the propagating fields with the conductor material. In fact, by using the proposed expression, the complex impedance can straightforwardly be determined by combining propagation constant data, and the resistance that represents the loss associated with longitudinal currents occurring at the top and bottom walls, which are influenced by the conductor surface roughness. This allows for completely describing the characteristics of the waveguide when assuming uniform propagation along its length. Furthermore, since the voltage–current, the power–current, and the power–voltage impedances can easily be obtained from the wave impedance, the proposal enables representing the matching characteristics of the waveguide for circuit design purposes. An agreement between simulated and experimental insertion loss is achieved for substrate-integrated waveguides of two different widths when reconstructing the corresponding S-parameters using the determined wave impedance.

This study offers a 5G substrate integrated waveguide (SIW) antenna with vertical S zigzag shape slot. The suggested antenna's radiating patch depends on the shape of the slot. Two types of slots have been used, straight and zigzag S shape slot with vertical and horizontal direction, slots are etched on the patch to increase the antenna's overall bandwidth and gain. The suggested straight and zigzag SIW S slot antennas both resonate at 28 GHz, and the overall structure size is 7.10×14.93 mm. The presented design could achieve high gain, efficiency, and minimal losses, which are all important concerns. The presented antenna may produce a gain of 9.48 dB, a 95% efficiency, and a wider bandwidth of no less than 3.25 GHz at 28 GHz. [ABSTRACT FROM AUTHOR]

In this paper, a self-multiplexing textile antenna aided by a substrate integrated waveguide (SIW) is designed for wearable applications. The proposed antenna operates at wireless body area network (WBAN) frequencies such as 5, 5.2, 5.5 and 5.8 GHz. Extended unequal half mode substrate integrated waveguide (HMSIW) cavities are utilised for self-multiplexing operations with the open-ended magnetic wall working as the radiator for the proposed textile antenna. All the four unequal HMSIW cavities share the same electric wall which is realised using brass eyelets. The textile antenna is fabricated and the antenna parameters are measured to elucidate the proposed antenna concept. The port isolation has achieved above 33 dB between any ports. The measured gains for the four frequencies are above 5.1 dBi with high efficiency. The proposed multiplexing antenna is designed in 90 × 65 * 0.57 mm3 dimensions and the proposed antenna has exhibited good performance which makes it suitable for integrating with wearable devices and obviating the extra multiplexer circuits. [ABSTRACT FROM AUTHOR]

In this letter, a compact circularly polarized (CP) microstrip patch filtenna designed by reusing dual‐mode substrate integrated waveguide (SIW) cavity is proposed. The dual‐mode SIW cavity, operating at its TE120 and TE210 modes, can be used not only as the first stage resonator of the filtering network but also feeds the four microstrip patches working at their TM10 and TM01 modes. A pair of asymmetric perturbed posts is inserted in the SIW cavity to perturb the electric field distributions of TE120 and TE210 modes so as to achieve one axial ratio (AR) minima. The other AR minima is realized by sequentially exciting the four orthogonal microstrip patches via the four rectangular slots that are etched on the top surface of the SIW cavity. In addition, four metal posts penetrated the SIW cavity is employed to improve the impedance matching. For verification, a CP filtenna prototype centered at 5.13 GHz is designed, manufactured, and tested. The measured results agree well with the simulated ones, demonstrating a fractional impedance bandwidth of 6.9% (4.95–5.3 GHz), a 3 dB AR bandwidth of 4.2% (5–5.21 GHz), and a maximum boresight realized gain of 8.4 dBic. [ABSTRACT FROM AUTHOR]

A novel E‐plane horn antenna fed with E‐plane Tee junction, conceptualized using the substrateintegrated waveguide (SIW) technology is introduced and investigated. Conventional SIW‐inspired horn designs are mostly limited to H‐plane sectoral horns, portraying confined radiation along the H‐plane while unconfined, fan‐beam‐shaped radiation along the principal E‐plane. Such radiation characteristics restrict its usage to designs requiring an electric field parallel to the structure and ultimately narrow confined radiation along the principal E‐plane of the embodiment. The proposed design provides a glue‐less solution to designing an E‐plane horn fed by an E‐plane Tee junction, both conceptualized by the SIW technology, having relative ease of fabrication on dual copper clad Printed Circuit Boards. Such a design operates from 17.15 to 18.8 GHz (~9.2% operating bandwidth) with a realized gain greater than 10.5 dBi, making it suitable for applications requiring light‐weighted high‐gain E‐plane sectoral horn antennas. [ABSTRACT FROM AUTHOR]

This letter describes a low‐profile three‐way fan‐shaped power divider integrable with aperture‐coupled antenna arrays. Each unit element is designed with a circular cavity‐based eighth‐mode substrate integrated waveguide. For better impedance matching, tapered feedlines are used at the output side. This structure is well suited for aperture‐coupled antenna arrays with a ground plane between the two substrates. The low‐profile power divider offers a 1 dB insertion loss (excluding the ideal power division of 4.8 dB). Magnitude and phase imbalance between output ports is ±0.2 $\pm 0.2$ dB and 0.8∘ $0.{8}^{\circ }$, respectively. The performance of the power divider is validated by using it as a feeding circuit for an aperture‐coupled array antenna with three circular patches. The antenna array resonates at 10.5 GHz and gives a gain of 4 dBi. [ABSTRACT FROM AUTHOR]

This paper presents a multi-layered composite right-left-handed (CRLH) slow-wave substrate integrated waveguide (SW-SIW) circularly polarized (CP) leaky-wave antenna (LWA) having wide impedance bandwidth (measured: 14.6–18.25 GHz). The CRLH unit cell consists of three radiating slots on top metallic layer, arranged in a crown-shaped fashion, to achieve wideband circular polarization.The bottom ground plane of the standard SIW is connected to the SW structure of the LWA that consists of internal metalized blind vias. Due to the SW effect, a 33% reduction in lateral dimension is achieved, compared to a conventional SIW having the same cut-off frequency. At the same time, the phase velocity is also reduced leading to a reduction in longitudinal dimensions. The dimensions of the antenna are relatively small, with a size of 3.2 × 0.4x.07 λ3. The operating mechanism of the LWA having symmetrical and continuous backward-to-forward scanning range from −64 ° to 64 ° (128 °) is explained by an equivalent circuit model. The measured CP bandwidth (14.6–18.43 GHz) of the LWA completely overlaps the 10-dB return loss bandwidth. The compact dimension, wide symmetric beam scanning, completely overlapped CP, and return loss bandwidths are the major advantages of the proposed antenna.The LWA exhibits stable gain with a peak value of 11.3 dBic (gain variation: from 9.7 to 11.3 dB). The radiation efficiency of the LWA is above 85% within the impedance bandwidth. [ABSTRACT FROM AUTHOR]

This study presents an original parallel connected hybrid microstrip-substrate integrated waveguide (PCHMSIW) bandstop filter. A low-pass filter implemented on a microstrip structure and a SIW-based high-pass filter are connected in parallel to each other. In this way, the aim is to obtain a bandstop filter in the novel hybrid design. The parallel connected hybrid microstrip-substrate integrated waveguide (PCHM-SIW) bandstop filter is synthesised, simulated, and produced. The effects of connecting filters in parallel are discussed. It is seen from the results of CST Studio Suite simulation that PCHM-SIW bandstop filter has a bandwidth of 2.85 GHz and a center frequency of 4.26 GHz. The frequency change rate of the center frequency between simulation and measurement is 7.02 % where it is just 3.76 % for the deviation in bandwidth. The results of the simulation and those of the measurement are close to each other. These results converge to ideal analytical results. [ABSTRACT FROM AUTHOR]

This paper presents some microwave circuits, designed for characterization of materials’ permittivity. These include single and multiple-resonant types, transmission line approaches, radiation structures and planar circuits. They have either theoretical analysis, simulations, behavior analysis, or fabrication results. A simple half-wavelength coaxial system is used for measuring velocity factor or dielectric constant of the cable. This method presents very accurate results. A planar multi-dielectric antenna structure is proposed whose layers comprise the dielectric under test. The near field as well as the radiation performances are influenced by the permittivity, which is the basis for determining this parameter. Also, a planar resonant cavity is designed and optimized to give enhanced coupling performance and gets higher quality factors. It has a small size and its sensitivity is improved employing a chamfer. The values of dielectric constants are extracted from scattering parameters. In another method, a three-section microstrip line is used whose time domain response is employed to retrieve the dielectric constant. This method can be generalized to other planar lines. At last, a simple method for measuring complex conductivity of lossy planar conductors is studied and it is employed for characterization of a graphene oxide layer.

Low cost, miniaturization, and high gain are the most essential prerequisites for multiband antennas (MBA). Therefore, a tactical effort is made in this paper to realize a small-size MBA (X, Ku, K-band) with considerable gain. The E-shaped patch embedded in a substrate integrated waveguide (SIW) cavity contributes to the primary radiation. The E-shaped patch with defective ground structure (DGS) helps to achieve multiband operation. Two additional metallic vias are placed near the tapered position to improve the impedance matching as compared to conventional tapered microstrip transition. The equivalent circuit model (ECM) is developed to examine the resonant frequencies. The circuit elements are identified and tabulated with equivalent changes in the geometric parameters. The parametric variation using ECM and the full-EM model are presented. The SIW structure provides the advantage of improved gain and small cross-polarization levels. The proposed antenna size is 0.68 × 0.95 × 0.05 λ03. The performance parameters of the fabricated prototype are tested and found to exhibit the same behavior as depicted by simulated results. The measured peak gain at 10.29, 11.87, 14.15 and 19.36 GHz are 5, 6.5, 5.2, 5.92 dBi, respectively. The proposed structure finds applications in stringent radar applications and satellite communications in emergency circumstances (e.g. electronic news gathering (ENG) and satellite news gathering (SNG), television outside broadcast and electronic field production). This antenna also reveals the significant advantages of being lightweight and gain efficiency. [ABSTRACT FROM AUTHOR]

A broadband high‐efficiency high‐gain empty substrate integrated waveguide cavity‐backed filtenna with dual beams is proposed. The antenna is vertically stacked by three cavities. Two rectangular slots are etched above the uppermost cavity to realize the radiation function. Since the interior of the cavity is covered with metal, the characteristics of the antenna are independent of the used dielectric substrate. The fractional bandwidth of the proposed filtenna is 21.1%, and the efficiency can reach more than 90% in the operational band. The antenna has good frequency selection properties, and the ratio of the −10 dB impedance bandwidth to the −3 dB impedance bandwidth is 0.88. Good gain flatness is obtained, the maximum gain of the filtenna within the operational band is 8 dBi. The proposed dual‐beam filtenna can realize broadband and filtering simultaneously, with low cost and high efficiency. It can be used in wireless communication systems. [ABSTRACT FROM AUTHOR]

This paper presents some microwave circuits, designed for characterization of materials’ permittivity. These include single and multiple-resonant types, transmission line approaches, radiation structures and planar circuits. They have either theoretical analysis, simulations, behavior analysis, or fabrication results. A simple half-wavelength coaxial system is used for measuring velocity factor or dielectric constant of the cable. This method presents very accurate results. A planar multi-dielectric antenna structure is proposed whose layers comprise the dielectric under test. The near field as well as the radiation performances are influenced by the permittivity, which is the basis for determining this parameter. Also, a planar resonant cavity is designed and optimized to give enhanced coupling performance and gets higher quality factors. It has a small size and its sensitivity is improved employing a chamfer. The values of dielectric constants are extracted from scattering parameters. In another method, a three-section microstrip line is used whose time domain response is employed to retrieve the dielectric constant. This method can be generalized to other planar lines. At last, a simple method for measuring complex conductivity of lossy planar conductors is studied and it is employed for characterization of a graphene oxide layer. [ABSTRACT FROM AUTHOR]

Abstract This paper presents an effective and novel design procedure employing a novelty named as Perturbation Factor to predict the resonance frequency of resonant cavities in SIW technology perturbed by a shape perturbation. The design procedure can be applied in tunable cavities and bandpass filters with shunt reactance of symmetrical inductive window, and regarding the application technologies, rectangular waveguide resonators and resonant cavities in SIW can be employed due to the equivalence of operation between both technologies. Its straightforward application allows a frequency variation of up to 20% using only one metal post which allows the reduction of the fabrication cost and the preservation of the frequency response across the considered bandwidth. To validate the design procedure, two resonant cavities were fabricated, a rectangular resonant cavity designed to operate at 5.0 GHz and 6.0 GHz and a square resonant cavity designed to operate at 6.0 GHz and 7.2 GHz, and frequency variations of 17.74% and 21.81% were obtained for the rectangular and square cavities, respectively. Still regarding the reached results, was verified a mean error of 1.75% for the predicted resonance frequency, which validates the design procedure. The experimental results are in good agreement with the full-wave computational results and electromagnetic theory.

Efficient wide-band transitions play a critical role in integrating substrate-integrated waveguide (SIW) and air-filled substrate-integrated waveguide (AFSIW) systems with conventional rectangular waveguide (RWG) systems in millimeter wave communication. However, existing techniques lack a systematic design approach, overlook mode purity, encounter performance issues, involve tedious optimizations, and feature complex structures. This paper presents a first-of-its-kind design technique that addresses these limitations, enabling seamless transitions from RWG to both SIW and AFSIW. For the first time, a clear and systematic design flow is introduced, covering both transition scenarios. The proposed technique eliminates the need for separate design procedures, simplifying the process, reducing complexity, and offering a cost-effective solution with state-of-the-art performance. The key innovation lies in the analytical expression for the shortest transition length, derived for both SIW and AFSIW cases, facilitating the design process and optimizing transition performance. The effectiveness of the design flow is extensively validated through four design examples, evaluating mode purity, reflection coefficient, and insertion loss. The results demonstrate excellent performances, confirming the accuracy of the approach. Furthermore, a fabricated prototype achieves remarkable results with an insertion loss of 0.35 dB and a relative bandwidth of 40%, exhibiting state-of-the-art performances when compared to reported works in the literature. In summary, the novel design technique enables seamless wide-band transitions from RWG to both SIW and AFSIW, offering a unified approach with state-of-the-art performance.

This paper introduces a proof of concept design for the first phased array antenna design enabled by liquid metal (LM) technology. The proposed LM phased array antenna system is based on substrate integrated waveguides (SIW) to excite an $1\times 4$ printed dipole antenna array. To effectively control the phase distribution on SIW power dividers, the liquid metals performed as a shorting pin along the body of the SIW are implemented. The proposed LM integrated SIW structure enables a large-phase tuning ratio of 360°. This new LM based phase shifters perform stable, low loss and wideband performance for the phased antenna array. In addition, a reconfigurability of the phase controls on the proposed phased antenna array can be realized when the LMs are filled in and out on the designated vias on the SIWs. To validate the proposed antenna array, simulation and measurement are carried out in this work. A prototype of the proposed LM phased array antenna operates at 10 GHz is measured, which confirms the array can have a 12% impedance bandwidth and the maximum gain of 8.3dBi with the scanning range of ±38° along the end-fire direction. This proposed technology is reliable and cost-effective for wideband phased array applications

A single-layer corporate-fed substrate integrated waveguide slot array antenna is newly proposed and verified. It is characterized by low profile, easy fabrication, low cost, low sidelobes, wideband operation, and high efficiency. A V-band $16\times 16$ -element array with uniform excitation is designed for demonstration. The radiating elements and feeding waveguides are arranged within a single-layer substrate, whose dielectric constant and loss tangent are appropriately selected. By adopting the full-corporate feed, the $16\times 16$ radiating slots are excited by the $16\times 16$ output ports of the feeding circuit, which is composed of cascaded H-plane T-junctions. For further bandwidth improvement, a metal grid plate is introduced on the top of the radiating slots. The test antenna is fabricated by the conventional PCB process. The measured bandwidth for $\vert S_{11}\vert < -10$ dB is 16.2%, fully covering the 57–67 GHz frequency range. Meanwhile, the measured antenna gain higher than 30 dBi associated with the antenna efficiency higher than 45% is achieved over the $58-65$ GHz frequency range.

In this paper, a bandpass filter is designed and fabricated for C-band satellite communication applications. The substrate integrated waveguide and defected ground structures are used in the design process. CST Microwave Studio software is used to analyze and design the proposed filter. It is built over DiClad 880 laminate having a thickness of 0.508 mm, and formed by etching three cascaded DGS cells on the SIW's top plane. There is a good agreement between the simulated and measured results. The filter is centered at 6.175 GHz with 500 MHz bandwidth (8.1% fractional bandwidth) in line with applicable US Federal Communications Committee Rules. The simulated insertion loss at the center frequency is around 0.80 dB and the return loss in the passband is better than 30 dB. The measured minimum insertion loss is 1.4 dB, and the measured return loss in the passband is better than 14.5 dB. The obtained results are presented, discussed, and compared with other studies. It can be said that the features of the proposed filter such as size, order, return loss, insertion loss, upper band rejection, etc. are better than those of many other filters given in the literature. [ABSTRACT FROM AUTHOR]

A microwave atmospheric pressure plasma jet (MW‐APPJ) generator based on a substrate‐integrated waveguide (SIW) resonator is proposed. A thin, straight plasma needle with a length of 9 cm could be obtained. Higher than 90% of microwave feeding efficiency is obtained under a wide range of gas flow rates without a microwave matching network. As the gas flow increased from 1 to 14 L/min, a transition from laminar to turbulent mode is observed in the plasma jet's morphology. Furthermore, a preliminary surface treatment was tested for the device. The polyimide film became super hydrophilic after a 5‐min treatment with the developed SIW‐based plasma generator. Generally, the SIW‐based MW‐APPJ is low‐cost, electrodeless, and low‐profile along the plasma jet length direction. [ABSTRACT FROM AUTHOR]

Substrate integrated waveguide (SIW) technology represents a good solution for the design of couplers. Coupler structures proposed in most relevant reports cannot achieve excellent performance in the case of weak coupling. This work proposes a new weak coupling coupler architecture, similar to the branch line coupler. The metal via arrays is used to reshape the electric field distribution of the SIW structure, making the overall structure achieve weak coupling characteristics. The even-odd mode decomposition method analyzes this structure's equivalent transmission line model. For this purpose, a systematic design procedure is deployed to achieve several coupling values over a wide frequency bandwidth. A novel half-mode substrate integrated waveguide (HMSIW) coupler with a 29 dB coupling is designed and fabricated for verification based on the proposed method. Good agreements between the calculated and simulated results are observed. The proposed coupler has the advantage of high directivity within the broadband and can be used for SIW-based circuits and power detection in the Ku-band. [ABSTRACT FROM AUTHOR]

In this paper, a novel low-profile circular polarization (CP) substrate integrated array antenna is proposed which is designed as a multilayer printed circuit board (PCB) structure, consisting of a lower feeding part-substrate integrated waveguide (SIW) and an upper radiating element - sixteen hollow square patches (HSP) evenly distributed in a square array and divided into four groups. The circular polarization (CP) characteristic is realized by chamfering each HSP in the left and right corners, and the greatest common bandwidth of the return loss and the axial ratio (AR) is obtained by adjusting the top chamfer size of each HSP. Simulation results show that the overall usable CP bandwidth is 41.2 GHz-42.1 GHz, the gain in the operating frequency band and the radiation efficiency (RE) are up to 16.1dBic and 91%, respectively, and the low-profile of antenna is less than 0.1λ0. [ABSTRACT FROM AUTHOR]

In this paper, a wideband planar substrate integrated waveguide (SIW) horn antenna based on surface wave excitation through loading metamaterials is designed. Strong coupling effect is realized between the employed bilayer metamaterial unit with the top layer as a π‐shaped‐slotted patch while the bottom layer as the complementary cross‐shaped‐slotted patch. The equivalent permittivity of the extended substrate in front of the planar horn aperture can be effectively reduced to unity and impedance mismatching for conventional planar SIW horn antenna can be reduced in a wide bandwidth. Results indicate that the working frequency of the antenna is 12.3–15.8 GHz with the relative impedance bandwidth of 24.6%. [ABSTRACT FROM AUTHOR]

Millimeter-wave (mmWave) antennas are indispensable components in the fifth-generation (5G) wireless communication systems. With the inherent advantages of integration capability, substrate integrated waveguide (SIW) antenna is an excellent choice for applications in the mmWave frequency bands. However, reflection losses occur at dielectric-filled thin apertures of SIW antennas. These reflections can be overcome by impedance matching between the aperture and the free space. In this study, we introduce an mmWave SIW horn antenna having impedance matching transitions (IMTs) across the horn's aperture width. The designed antenna, operating in the 24-28 GHz band, is simulated with a full-wave analysis tool. The simulation results of the modified SIW horn have been confirmed by the experimental results and shown to be satisfactory. The IMTs result in an enhancement of the front-to-back ratio (FTBR). The modified SIW horn antenna with a novel printed transition achieves sidelobe levels (SLLs) of better than -9 dB at 27 GHz, with an enhanced FTBR above 15 dB. In the 24-28 GHz band, the antenna has a reflection coefficient variation of better than -10 dB. [ABSTRACT FROM AUTHOR]