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The possibilities for further development of mmWave fifth-generation wireless systems and their deployment in our lives are immense and will make human life simpler and faster. Fifth-generation wireless communication is opening up new possibilities for development in the near future. High data rates, low latency, and enormous bandwidth are the most essential factors. These factors are at the heart of making quality healthcare, smart education systems, and the fast and efficient distribution of energy. In account of the aforementioned benefits, 5G wireless systems are primarily made possible by high gain MIMO antenna with minimal coupling. The integration of traditional wave-guide components with planar circuits, on the other hand, is a difficult issue. SIW solves this problem by providing planar alternatives for waveguide-based devices like filters, antennas, and couplers. The SIW antenna has less interference, low radiation loss, excellent isolation, and outstanding shielding properties as compared with the conventional microstrip antenna. The proposed SISO SIW antenna has gain of 9.05 dBi with 87.54 % radiation efficiency. The −10 dB impedance bandwidth is 27.79–28.19 GHz. The SIW MIMO antenna has gain of 9.05 dBi with 81 % radiation efficiency. The antenna has an isolation 52 dB, and an ECC is 0.65 × 10−7 at 28 GHz. The proposed SIW MIMO antenna's MEG lies below −3 to −5 dB for Gaussian and isotropic medium. The CCL for the proposed MIMO antenna is 0.29–0.36 bits/s/Hz in the operating band. This article presents a high-gain and high-isolation substrate integrated waveguide (SIW) MIMO antenna using orthogonal diversity for increasing isolation between the radiating elements. The designed MIMO antenna is operating in the 28 GHz band (27.42–28.79 GHz), which comes under the n261 (FR2 5G-New Radio frequency band) band used for 5G wireless communication. [ABSTRACT FROM AUTHOR]

A wideband filtering antenna design has been proposed in this paper. The proposed filtering antenna design is cavity-backed substrate integrated waveguide (SIW) based on a single layer slot antenna. Two E-shaped slots are engraved onto the ground face of the design to improve filtering selectivity and operational bandwidth. For achieving wideband response, a modified half-TE110 mode and a decreased radiation null are all produced by the E-shaped slots in the right-half cavity. The design is simple and compact, with only one substrate layer and a larger working bandwidth than its counterparts. The filtering antenna has a 13.1 % fractional bandwidth and works at a frequency of 28 GHz. The proposed prototype has been structured, tested, and the simulation and measurement results were analyzed. [ABSTRACT FROM AUTHOR]

Summary In this paper, a high gain self‐triplexing antenna based on the substrate integrated waveguide (SIW) leaky wave technology is presented for tri‐frequency operation. Three identical T‐shaped slots are embedded on the upper layer of the proposed SIW antenna, which are energized by two tapered microstrip lines and a simple microstrip line; and the antenna resonates at three different frequencies (7.75 GHz, 9.1 GHz, and 10.15 GHz). The transverse part of the T‐slot achieves the first band (8.8 to 9.3 GHz), while the longitudinal part of the T‐slot achieves the second band (9.6 to 10.9 GHz), and when excited transversely, the T‐slot achieves the third band (7.5 to 8.2 GHz). The isolation level between the ports is more than 25 dB, which contributes to the phenomenon of self‐triplexing. The gain of the presented antenna is high when compared with other self‐triplexing antennas. [ABSTRACT FROM AUTHOR]

This article introduces a novel microstrip slot antenna array (SAA) configuration for radar applications. The proposed antenna is specifically designed for operation in the K-band, spanning from 23 to 24.3 GHz. The antenna structure comprises two substrates: the feed network and ground plane are on the bottom substrate, and the radiating slots are on the top layer of the first substrate. The incorporation of a unique grid feed configuration, featuring 50 Ohm center excitation for the first time, improves the feed mechanism of the microstrip SAA. This innovation contributes to achieving a compact size and high gain. To enhance the side lobe level, the design incorporates a substrate-integrated waveguide-backed cavity, which significantly reduces surface waves. The SAA consists of 25 radiating elements with a gain of 14 dBi. In the elevation and azimuth planes, the half-power beamwidths are measured at 12.1° and 69.1°, respectively. The proposed antenna array's measured impedance bandwidth ranges from 23.15 to 24.75 GHz, guaranteeing a reflection coefficient (S11) of less than − 10 dB. The suggested antenna's applicability for automotive multi-input multi-output radar has been validated. [ABSTRACT FROM AUTHOR]

Abstract This article introduces a novel microstrip slot antenna array (SAA) configuration for radar applications. The proposed antenna is specifically designed for operation in the K-band, spanning from 23 to 24.3 GHz. The antenna structure comprises two substrates: the feed network and ground plane are on the bottom substrate, and the radiating slots are on the top layer of the first substrate. The incorporation of a unique grid feed configuration, featuring 50 Ohm center excitation for the first time, improves the feed mechanism of the microstrip SAA. This innovation contributes to achieving a compact size and high gain. To enhance the side lobe level, the design incorporates a substrate-integrated waveguide-backed cavity, which significantly reduces surface waves. The SAA consists of 25 radiating elements with a gain of 14 dBi. In the elevation and azimuth planes, the half-power beamwidths are measured at 12.1° and 69.1°, respectively. The proposed antenna array’s measured impedance bandwidth ranges from 23.15 to 24.75 GHz, guaranteeing a reflection coefficient (S11) of less than − 10 dB. The suggested antenna's applicability for automotive multi-input multi-output radar has been validated.

Aimed at the interconnection between coaxial transmission line and substrate‐integrated waveguide (SIW), a wideband coaxial‐to‐SIW transition was proposed and applied in a 1‐to‐4 radial power divider. First of all, a fan‐shaped region was designed on the end of a SIW transmission line. Then, a coaxial transmission line was inserted into this region. To improve the impedance matching at the coaxial port, a feeding ring was designed on the back of the transition where the coaxial line was inserted. Next, the transition was applied in a 1‐to‐4 radial power divider to realize an equal power division. Finally, to validate the correctness of the designs, prototypes were fabricated and measured. For the coaxial‐to‐SIW transition, measured reflection coefficient |S11| was less than −15 dB from 7.84 to 12.18 GHz. Transmission coefficient |S21| was between −0.52 and −0.24 dB. For the 1‐to‐4 radial divider, measured |S11| was less than −15 dB from 7.91 to 12.4 GHz, and the transmission coefficient was around −6.9 dB. Measurement and simulation agreed well with each other. Therefore, the proposed design can be used in coaxial‐to‐SIW interconnection scenarios. [ABSTRACT FROM AUTHOR]

This work proposes and investigates a wide‐angle band‐pass frequency selective surface (FSS) with two sharp sidebands. The presented FSS element is made up of three metallic layers and two substrate layers in between, which are surrounded by a substrate‐integrated waveguide (SIW) cavity. The top metallic layer is identical to the bottom layer, composed of a square patch etched with a hexagonal groove, while the middle layer is a similar patch but with rectangular notch edges. This structure achieves a second‐order band‐pass response with highly frequency selectivity on either side of the passband. At the same time, this FSS demonstrates excellent stability for both transverse electric and transverse magnetic polarizations with incident angles between 0° and 60°. The electric current and field distributions are demonstrated for deep analysis. Furthermore, an equivalent circuit model is developed to further understand the operating mechanisms. To verify the validity of the design, we construct a prototype of the SIW‐based FSS (SIW‐FSS) and measured it. There is a fair degree of agreement between the measured and simulated results. Finally, we loaded it onto the horn antenna and tested its application in filtering antennas. [ABSTRACT FROM AUTHOR]

Maintaining acceptable radiation performance over the entire operation bandwidth is a significant challenge in development of a miniaturised reconfigurable antenna. To address this issue, a new Substrate Integrated Waveguide (SIW) based reconfigurable antenna using slow wave structure is presented in this study. The proposed SIW antenna is based on a layered construction with metallic blind vias connecting to ground plane of SIW. The multi-layer structure of SIW with blind vias helps to separate magnetic and electric fields in the SIW cavity. Thus, a slow wave effect is also utilised and it leads to 36% reduction in the antenna size as compared to conventional SIW cavity. To attain the polarisation and frequency reconfiguration, a cross slot is introduced in the top metallic layer of the SIW cavity and four PIN diodes are connected into the cross-slot arms. Experimental results exhibit frequency reconfigurability in different operating regions with resonant frequencies 4.35, 5, 5.8, 6.4, and 9.6 GHz. The polarisation reconfigurability of the proposed antenna is achieved at 5 GHz with LP/RHCP/LHCP. The proposed antenna exhibits 3-dB axial ratio bandwidth of 4.8 to 5.2 GHz with peak gain of 4.2 dBi. [ABSTRACT FROM AUTHOR]

This paper provides an idea for designing a high-gain narrow-band substrate integrated waveguide (SIW) antenna. The high gain is achieved due to the epsilon-near-zero (ENZ) technique, and narrow-band performance is achieved due to impedance matching provided by a pair of symmetric shorting pins. In this paper, SIW is used near its cut-off frequency to realize the ENZ characteristics. Further, two symmetric open stubs are incorporated to reject the out out-of-band frequency signal. To attain narrow-band performance, pair of symmetric shorting pins are employed in place of the conventional way, i.e., tapered line transition to couple the energy from microstrip to SIW. To validate the proposed concept, a high-gain narrow-band SIW antenna has been designed for a frequency band on a 0.79 mm thick RT- DUROID 5880 substrate. Within the 7.77–8.07 GHz band, the proposed antenna radiates with gain and radiation efficiency of 6.51 dBi and 96%, respectively. The measured and simulated results are found to be consistent. The overall size of the proposed antenna is 28 X 22 mm2. [ABSTRACT FROM AUTHOR]

A dual-wide-band triple resonance half mode substrate integrated waveguide (HMSIW) cavity-backed antenna with an extra shorting via is presented in this paper. Three modes of the HMSIW cavity are utilized to generate the dual-wide-band resonances. The HMSIW cavity along with three rectangular slots is fed coaxially which helps in achieving triple resonance and size miniaturization. An additional shorting via is loaded at the position of electric null between the 2nd and 3rd modes to bring the modes closer and couple them. The antenna exhibits one narrow band and one wide-band response. The dual-wide-band antenna is fabricated and tested on a low-profile substrate of 0.05 λg. A relative bandwidth of 1.03% (10.58–10.69 GHz) and 6.12% (12.47–13.25 GHz) is attained by the two bands. A stable broadside and unidirectional radiation pattern is achieved with a peak gain of 4.5 dBi, 5.81 dBi, and 6.18 dBi at 10.6 GHz, 12.68 GHz, and 13.2 GHz, respectively. Thus, the proposed dual-wide-band antenna can be effectively utilized for satellite applications. [ABSTRACT FROM AUTHOR]

In this paper, a compact differential bandpass filter with wide‐stopband is presented. The proposed differential filter is designed using two circular substrate‐integrated waveguide (SIW) cavities coupled through a pair of symmetric coupling slots. The filter operates in TM110 mode of the circular SIW cavity. The degenerate TM110 mode is shifted to higher frequency by the introduction of two pairs of perturbation vias. The center frequency of the differential passband can be tuned by changing different design parameters such as location of perturbation vias and length of the slotlines. As a proof of the proposed concept, a second‐order differential bandpass filter is designed, fabricated, and measured. The measured results are in good agreement with the electromagnetic‐simulated ones. [ABSTRACT FROM AUTHOR]

Summary In 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 ×$$ \times $$ 25 mm2 [ABSTRACT FROM AUTHOR]

This paper presents a novel wideband circularly polarized antenna that is fed by substrate‐integrated waveguide. Based on the design of placing a pair of chamfered semicircular patches above a slot, a π ${\rm{\pi }}$‐shaped radiator is introduced between the semicircular patches. Multiple resonance points are generated by the combination of the entire radiating structure and a dumbbell‐shaped slot, resulting in improved impedance bandwidth and axial ratio (AR) bandwidth. The proposed element exhibits a wide impedance bandwidth of 50.5% (24.5–41.1 GHz) and an AR bandwidth of 44.2% (25.1–39.3 GHz) with a 44.2% overlapped bandwidth. Then, a 4 × 4 antenna array adopting the sequential rotation technique is constructed. The measured results demonstrate that a 40.6% overlapped bandwidth and a peak gain of 19.1 dBic are achieved. The proposed antenna array shows excellent performance, making it a good candidate for applications in millimeter‐wave wireless communication systems. [ABSTRACT FROM AUTHOR]

A novel‐shaped dual‐polarized low‐profile multiple‐input multiple‐output (MIMO) antenna with high isolation is proposed for 5G/WLAN application. An 8‐element MIMO antenna design comprises two unique planar radiators (chamfer, circular). Each radiator has dual feed and dual polarization characteristics. The prototype is fabricated with an FR‐4 dielectric substrate. A decoupling structure maintains desirable isolation for self‐isolated elements (≤ $\le $−12 dB) using substrate integrated waveguide stubs between inter‐ports and high isolation among the adjacent radiating elements (≤ $\le $−15 dB). The simulation was performed by using CST microwave studio. The simulated results of the proposed MIMO antenna are compared with the measurement results. Furthermore, ECC and DG are investigated. [ABSTRACT FROM AUTHOR]

A terahertz band (0.1–10 THz) has the characteristics of rich spectrum resources, high transmission speed, strong penetration, and clear directionality. However, the terahertz signal will suffer serious attenuation and absorption during transmission. Therefore, a terahertz antenna with high gain, high efficiency, and wide bandwidth is an indispensable key component of terahertz wireless systems and has become a research hotspot in the field of antennas. In this paper, a high-gain broadband antenna is presented for terahertz applications. The antenna is a three-layer structure, fed by a grounded coplanar waveguide (GCPW), using polytetrafluoroethylene (PTFE) material as the dielectric substrate, and the metal through-hole of the dielectric substrate forms a substrate-integrated waveguide (SIW) structure. The metal fence structure is introduced to reduce the coupling effect between the radiation patches and increase the radiation bandwidth and gain. The center frequency is 0.6366 THz, the operating bandwidth is 0.61–0.68 THz, the minimum value of the voltage standing wave ratio (VSWR) is 1.00158, and the peak gain is 13.14 dBi. In addition, the performance of the designed antenna with a different isolation structure, the length of the connection line, the height of the substrate, the radius of the through-hole, and the thickness of the patch is also studied. [ABSTRACT FROM AUTHOR]

Design and realization of a broadband H-plane Substrate Integrated Waveguide (SIW) power divider with equal and unequal output powers is presented. The configuration of the proposed structure is based on the three equal width SIW lines. In proposed SIW power divider septum has been realized with a row of metalized vias. The inclusive input bandwidth in the proposed structures is achieved due to the proper septum design. The output powers are controlled with the septum offset. The parametric analysis shows that the magnitude of outputs could be adjusted with septum offset and the width of SIW could control the cutoff frequency. Power flow from input port toward output port confirm the proposed design concept. Two SIW H-plane power dividers with the same and different outputs have been designed and produced. There are good agreements between simulation and measurement results for both structures. The input impedance bandwidth for equal and unequal prototypes is 3.4 GHz and 2 GHz respectively.

A compact eighth mode circular substrate integrated waveguide (EMSIW) self-octaplexing antenna is proposed for sub-6 GHz communication systems in this paper. The designed antenna consists of coaxial fed eight EMSIW cavity resonators arranged in circular fashion. Each EMSIW cavity resonator utilizes the fundamental TM010 mode of the circular SIW cavity. The designed antenna operates at eight distinct frequencies of sub-6 GHz frequency spectrum. Isolations better than 23 dB is obtained among the different ports of the designed antenna. Moreover, each frequency band of designed antenna exhibits independent tunability without affecting the other frequency bands. Each resonator of the designed antenna can be tuned to any frequency between 3-5 GHz. The self-octaplexing antenna operates at 3.35, 3.58, 3.73, 3.91, 4.09, 4.32, 4.61 and 4.96 GHz with respective gains of 4.53, 4.62, 4.67, 4.74, 3.83, 3.89, 3.42, 3.55 dBi. The proposed antenna exhibits high inter-port isolation, good radiation characteristics and compact dimensions which makes it suitable candidate for sub-6 GHz communication systems.

The deployment of Ka-band radar necessitates addressing increased losses due to rain and free-space propagation, in addition to achieving low sidelobe levels (SLL). Substrate integrated waveguide (SIW) slot antennas, with their high-power handling capability and low loss, present a practical solution for Ka-band radar applications. However, previous SLL reduction methods for SIW longitudinal slot array antennas involves high design complexity or degrade the antenna’s radiation efficiency. In this work, we introduce a novel SLL reduction method for an SIW longitudinal slot array antenna using only one design variable—slot offset—to map electric field amplitude to a reference distribution. Our method effectively reduces SLL while maintaining radiation efficiency. The proposed antenna was fabricated and measured, showing good agreement with simulations. Compared to previous methods, our approach is simpler, advancing SIW slot array antenna design and SLL reduction.

In this paper, methods for improving frequency selectivity in filter antennas by employing controllable radiation nulls (RN) are reviewed. Radiation nulls in the Gain graph help in improving the rejection of out-of-band frequencies. The majority of the designs reviewed in this paper use substrate-integrated waveguide (SIW) technology. Some of the methods of generating RNs include: loading filtenna with slots or shorting pins, using proper design of multi-signal path between source and load, employing electric and magnetic mixed-coupling, embedding filtering structures, parasitic elements, employing filtering action in the feed network. Certain designs achieve more than two radiation nulls which give even better selectivity.

With the development of millimeter-wave radar systems, substrate-integrated waveguide (SIW) slot antennas have been widely used. This paper presents a computational approach for calculating the equivalent normalized admittance of slot in low sidelobe SIW longitudinal slot antennas. In contrast to the existing methods, this method takes into account the impact of the N-slots coupling on the admittance. Through this method, fitting functions for resonant length and conductance are obtained, which describe the relationship between the resonant length, resonant conductance, and offset of slots. Moreover, based on the two fitting functions, a low sidelobe SIW longitudinal slot linear antenna is designed for millimeter-wave radar applications at 77 GHz. This antenna consists of a transition from the standard WR-12 waveguide to the SIW and a set of radiating slots. The simulation results indicate an impedance bandwidth of 4.8% and a gain of 13.2 dBi. The sidelobe level in the H-plane is below −28 dB, which meets the desired specifications and confirms the accuracy of the presented method. [ABSTRACT FROM AUTHOR]

An Artificial Neural Network (ANN) based Substrate Integrated Waveguide Band Pass Filter (SIW BPF) is proposed in this paper. A Feed Forward Back Propagation Neural Network (FF-BP NN) is utilized to optimize the filter dimensions. The Gradient Descent with Momentum and Adaptive Learning Rate algorithm is used to train the network at a learning rate of 0.01. The high pass characteristics of the SIW is converted into band pass by incorporating U slots on its top plane. Defected Ground Structure (DGS) is utilized in the bottom plane to improve the impedance matching. To validate, the prototype is fabricated using RT/Duroid 5880 and tested. The proposed filter has a center frequency at 14.68 GHz with a wide pass band from 12.92 to 16.43 GHz with a 3-dB Fractional Bandwidth (FBW) of 24%, return loss more than 20 dB and insertion loss of about 1.9 dB within the pass band. The filter has a small dimension of about 0.63 $ \lambda _g^2 $ λ g 2 , where λg is the guided wavelength at the center frequency. This filter offers wide passband, smaller size, low insertion loss, good return loss and it is useful in Ku-band satellite communication applications. [ABSTRACT FROM AUTHOR]

This paper presents a stepped substrate integrated waveguide. The generalized scattering properties of the cascaded $ H $ H -plane discontinuity in a substrate integrated waveguide operating in various frequency bands are obtained using mode-matching techniques (MMT) from the respective field equations at four different step discontinuities. The scattering parameters $ (S) $ (S) obtained from the individual regions are cascaded to obtain the $ S $ S -parameters of the overall structure. The processor computation time and memory used by MMT are compared to those of commercial simulators like high-frequency structure simulator (HFSS) and computer simulation technology microwave studio (CST-MWS), and the S-parameters obtained using MMT are compared with HFSS and CST-MWS simulated and measured S-parameters. Due to periodicity in the designed structure, a filter-like property has been observed. The $ S $ S -parameters generated from mathematical formulations, simulations, and measurements show very good agreement. [ABSTRACT FROM AUTHOR]

This article presents a novel double - layered, dual band and dual polarized hybrid substrate integrated half cylindrical dielectric resonator antenna (SICDRA) for IRNSS satellite base station and various wireless applications. The SICDRA comprises of a unique top semi cylindrical dielectric resonator (DR) with top and side copper strips, circular hybrid substrate integrated waveguide (SIW) cavity and an inner circular ring type air gap cavity on upper FR4 substrate. To produce circularly polarized (CP) fields, two tilted rectangular cross slots of dissimilar size is etched in the middle layer. Also, the tilted cross slot and DR is excited through underneath microstrip feed line in the bottom of lower Rogers 5880 substrate. Due to the hybridembedded assembly, the fundamental mode TM01d excited at L5-band (1.164-1.188 GHz) and the other higher order TM02d mode excited at S-band (2.48-2.5 GHz) simultaneously. The proposed archetype has provided improved S11 < -25 dB for L5 band and < -15 dB for S-band, axial ratio (AR) more than 3 dB for L5 band. Moreover, a novel circularly arrange substrate integrated metallic and non metallic vias has boosted the realized gain at 5.63 dbic for circularly polarized L5 band and 4.81 dbi for linearly polarized S-band. The proposed structure is fabricated and tested in the anechoic chamber also. Also, the detail parametric analysis is carried out to achieve the desire results. Comparative result analysis shows proposed novel design has miniaturized DR radiating aperture, better reflection coefficient, dual polarization, improved realized gain and radiation performance compare to earlier techniques stated in the literature. [ABSTRACT FROM AUTHOR]

This manuscript introduces an innovative six-way power divider design using substrate integrated waveguide technology, specifically tailored for applications in both X-band and Cband frequencies. The utilization of SIW technology in this design offers significant advantages, including exceptional isolation between output ports, and a high level of return loss. Additionally, the design incorporates a coaxial port at its center, facilitating the analysis of the power divider's performance. This coaxial port can also serve as a feeding structure for an antenna array, adding to its versatility. The simulation results indicate that the input return loss for port 1 of the power divider exceeds 23dB, demonstrating excellent performance. Furthermore, the design has been successfully fabricated, and the measured results align with the expected performance standards, affirming its practicality and functionality. [ABSTRACT FROM AUTHOR]

A multiband, frequency reconfigurable, and bifunctional metasurface for simultaneous full-space control of Electromagnetic (EM) waves is proposed for wearable applications. The unit-cell structure contains concentric rectangular rings and empty substrate-integrated waveguides (SIWs) for miniaturisation. The miniaturised dimension of the Polydimethylsiloxane (PDMS) substrate is 18 × 18 × 1 mm³. Two varactor diodes are integrated for frequency switching operations by configuring the structure using bias voltage (forward/reverse) through the ground via the proposed surface resonates at 3.5,5.8,7.6 (On),8.1 (Off) GHz frequencies, which provide simultaneous bi-functionalities: artificial Magnetic Conductor (AMC) reflector/absorber in reflection and transmission space of operations, respectively. In reflection space, it acts as an AMC reflector by providing in-phase reflection with a radiation efficiency of >84% and unidirectional E-field patterns. However, the magnitude of absorbance is more than 96% in transmission, thereby simultaneously controlling full-space EM wave in normal incidence. The obtained simultaneous metasurface functionalities are investigated for different oblique angles of the transverse electric (TE) and transverse magnetic (TM) incident wave. The proposed surface is fabricated and experimentally validated. The features of the designed bifunctional metasurface provide a strategic platform for potential multifunctional wearable devices. [ABSTRACT FROM AUTHOR]

This paper presents a high-gain, wideband series-fed antenna designed for 5G millimeter-wave (MMW) applications. The structure employs a substrate-integrated-waveguide (SIW)-based power splitter and metamaterials (MMs). The power divider functions effectively at 27.5 GHz, exhibiting an impedance bandwidth from 26.9 to 28.6 GHz. The series-fed dipole is assembled on the SIW-based power splitter, incorporating four dipoles with varying lengths and spacing. The dipoles are connected in series on both sides, running in parallel through a microstrip line. Effectively combining the resonances of the series-fed dipoles and the SIW results in a broad impedance bandwidth, ranging from 26.9 GHz to 34.75 GHz. The design has a gain extending from 9 to 10.5 dBi within the operating bandwidth. To improve gain performance without a substantial increase in antenna size, 11 × 6 MM unit cells were positioned in front of the antenna. As a result, the proposed antenna achieves a maximum gain of 14.1 dBi at 30.5 GHz while maintaining an operational bandwidth of 7.85 GHz. Additionally, due to the arrangement of the two MM-based series-fed dipoles, the antenna exhibits symmetrical dual-beam E-plane radiation at ±20° and 28 GHz in the end-fire direction. The developed system was experimentally validated and an excellent agreement between the simulated and measured data was demonstrated. [ABSTRACT FROM AUTHOR]

Major constraint in leaky wave antenna (LWA) is open stop band. In this paper study of different techniques used by researchers to remove the open stop band problem has been done. Different characteristics of leaky wave antenna with the design of substrate integrated waveguide is also discussed. This paper explain theory and design of the unit cell and array of leaky wav antenna in different frequency range i.e. X-band, Kuband and higher frequency range. Study of various techniques to achieve high beam scanning and higher gain has been done. [ABSTRACT FROM AUTHOR]

This paper describes a substrate integrated waveguide (SIW) filter built on an Fr4-Epoxy substrate with a dielectric constant 4.4 and a height of h=1.6mm. SIW-based devices have piqued the interest of researchers in recent years due to their low loss, small size, and low cost. The goal is to simulate and realize a SIW filter for C-band applications. The designed filter is analyzed using the reflection coefficient S11 and electric field distributions. We used the HFSS simulator. According to the findings, there is a high degree of agreement between the simulated and realized filters. The results also show that the filter has a very good response. It also shows a bandwidth of 6.3GHz around the C-band frequencies. This filter's pass-band ranges from 5.39 to 6.83GHz, with an insertion loss of 4.2dB and a return loss of 45.49dB. [JJCIT 2023; 9(2.000): 166-174]

In this paper, a directivity‐enhanced planar slot antenna (PSA) backed by substrate integrated waveguide (SIW) cavity is proposed to solve the problem of maximum gain direction bias. According to the radiation principle of slot antenna, the reason for maximum gain direction bias is explained and the solution has been given. Ulteriorly, the problem of frequency bias caused by changing the directivity is also explained by resonance modes and solved by introducing the metal via. An example with 5.8 GHz which has the maximum gain of 5.28 dBi and the total thickness less than λ/4 is given. After structural optimization and measurement, the maximum radiation direction of improved antenna is 0° from the normal direction of antenna surface, and it maintains the good radiation performance and small size of the traditional PSA backed by SIW cavity. [ABSTRACT FROM AUTHOR]

A novel dual-band bandpass filter (DB-BPF) based on SIW dual-mode resonant cavity is proposed in this study. This resonant cavity works in the degenerate mode TE102 mode and TE201 mode. The two modes of operation are coupled by opening a window between the resonant cavities, and the passband frequency of the DB-BPF is adjusted by controlling two degenerate modes. This filter works at 9 GHz and 9.5 GHz and has a 3-dB fractional bandwidth of 2.2% and 3.5% GHz, respectively, and has three transmission zeros (TZs) which improve out-of-band rejection and isolation between high-passband and low-passband. The return loss in the high-passband and low-passband is below 13 dB; the insertion loss of the high-passband and low-passband is 2.32 dB and 3.16 dB, respectively. The measured results agree well with the simulation results, which proves the feasibility of the design method. [ABSTRACT FROM AUTHOR]

With the change in lifestyles, emerging stress and physical parameters of the environment, health-related issues have affected many people worldwide. An important indicator of serious illness is the abnormality in respiration rate. This abnormality leads to asthma, obstructive sleep apnea (OSA) and heart-related diseases. This leads to having more accurate and robust healthcare monitoring and diagnosis facilities. The respiration rate and vital signs are detected through electromagnetic (EM) waves using different antennas. Different types of previous antennas (parabolic, horn, yagi-uda, helical and patch) used for respiration monitoring are studied and compared with the proposed antenna. The limitations of currently used antennas include the bulky size of setup and less directional beam, which may interfere with other devices leading to errors. Substrate integrated waveguide (SIW)-based leaky-wave antenna (LWA) is proposed with better results than current antennas available for respiration monitoring. Experimental work is carried out for the validation of simulated results. The proposed antenna has a gain of 9.72 dB with angular width or approximately HPBW 37.5°. The simulated s11 of the antenna is −16 dB, and the measured s11 is −22.97 dB. VSWR shows antenna radiation efficiency is approx 97%. An experimental setup using VNA is used to detect respiration monitoring in real-time; the system could detect the respiratory activity of the subject with a confidence interval accuracy of 93% and an average error of 7%. [ABSTRACT FROM AUTHOR]

In this paper, flexible substrate integrated waveguide (SIW) resonators have been designed and fabricated on polyimide substrates for humidity sensing applications. The proposed SIW resonant cavity allows the resonator to obtain the maximum humidity sensitivity and meet the demand for flexible microwave sensing detection. Meanwhile, the humidity response performance can be further significantly enhanced by introducing nanodiamond (ND) sensing material. Three prototypes of ND-coated SIW sensors with different bending radii are measured to analyze their humidity sensing performance. The experimental results demonstrate that the proposed ND-coated SIW sensor with the minimum bending radius can achieve a maximum humidity sensitivity of 1.09 MHz/% relative humidity (RH) in the high RH region (>75.3% RH) and a low humidity hysteresis of 1.8% in the range of 11.3–97.3% RH. This study provides a promising candidate to realize flexible microwave sensors with excellent sensing performance. [ABSTRACT FROM AUTHOR]

This paper presents a new design of a reconfigurable miscrostrip patch antenna based on a substrate-integrated waveguide (SIW). The antenna is resonant at the millimeter-wave (mmWave) 5G spectrum. The tuning technique consists of using a nematic liquid crystal (K15). An adjustable frequency band from 30.191 to 32 GHz is obtained, giving a tunable range of Δfr = 1.809 GHz. The maximum gain and efficiency reach the values of 7.61 and 9.07 dBi and 93 and 94%, respectively. The proposed SIW antenna loaded with liquid crystal was fabricated and tested. The experimental results correlated well with the simulation; however, the measured reflection coefficient plot shows a shift of the tuning range of 284 MHz, which is an acceptable outcome compared to simulation. A new approach of adopting the magnetic field as a technique to tune the resonance frequency has been used. The structure is characterized by its design simplicity, compactness, and fabrication process. The proposed antenna proves that the liquid crystal improves the performance of the antenna in the Ka band for 5G applications and satellite communication systems. [ABSTRACT FROM AUTHOR]

In recent years, Split-Ring Resonators (SRRs) and Complementary Split-Ring Resonators (CSRRs) have gained significant attention for their unique electromagnetic properties, such as negative permeability and negative permittivity, making them promising candidates for advanced microwave devices. This paper presents the design and analysis of a substrate-integrated waveguide (SIW) filter using CSRR structures for miniaturization. The improved CSRR unit can be easily integrated on the surface of the SIW, making it an ideal candidate for the design of compact SIW filters. In this paper, an improved CSRR-loaded SIW filter is designed and analyzed based on its equivalent lumped parameter model. A filter with a center frequency at 22.6 GHz is designed. Several transmission zeros (TZs) are also realized to improve the skirt selectivity of the filter. The design process involves theoretical analysis and electromagnetic simulations to optimize the dimensions of the CSRR resonators to achieve the desired filter characteristics. The measured and simulated results show good agreement, confirming the effectiveness of the proposed improved CSRR-loaded SIW filter. The successful implementation of the improved CSRR-loaded SIW filter demonstrates its potential for achieving miniaturization and enhanced performance in advanced microwave applications. [ABSTRACT FROM AUTHOR]

W-band filters play a crucial role in modern millimeter-wave communication and radar systems, finding applications in 5G/6G networks, automotive radar, and passive imaging. With the growing demand for higher data rates and efficient wireless communication, W-band filter development has gained significant attention in recent years. Various design techniques and fabrication technologies have been explored for improved performance and integration possibilities. This paper presents a planar substrate-integrated waveguide (SIW) dual-mode cavity filter as a solution to the challenges faced by previous designs in terms of integration, size, and cost. The dual-mode cavity coupling principle and design parameters are analyzed to optimize the filter's performance. A W-band 4th-order dual-mode filter prototype is designed and fabricated on a 0.127-mm-thick RO5880 substrate, and a finline waveguide-to-microstrip transition structure is employed for compatibility with the test instrument. Simulation and experimental results demonstrate that the proposed filter exhibits low insertion loss, good in-band standing wave performance, and improved out-of-band suppression. Moreover, a visible high-frequency out-of-band transmission zero is implemented to enhance the steep roll-off characteristics in the high-frequency out-of-band region. [ABSTRACT FROM AUTHOR]

A compact microstrip to substrate integrated waveguide transition feed tapered slot antenna array (1 × 4) with the elliptical patch is proposed and analyzed. The new approach is presented, employing a parasitic patch in the flared aperture to generate more radiation in the end-fire direction and improve field coupling between the arms. It boosts gain while maintaining overall size and low-frequency performance without using electrically thin dielectric substrates. To validate the designed approach, the proposed structure is fabricated and measured. The measured results show that the array provides impedance bandwidth of 40%, peak measured gain of 9.14 dBi, and radiation efficiency is 90% over the 8.5–12.5 GHz frequency band. A four-way feed network is also fabricated with the insertion loss of −6 ± 0.9 dB; the reflection coefficient is below −15 dB over the desired frequency range and only ±4° phase imbalance. The overall dimension of antenna array is 50 × 54 × 0.813 mm3 or ~1.6λ × 1.8λ × 0.027λ at 10 GHz. [ABSTRACT FROM AUTHOR]

A terahertz band (0.1–10 THz) has the characteristics of rich spectrum resources, high transmission speed, strong penetration, and clear directionality. However, the terahertz signal will suffer serious attenuation and absorption during transmission. Therefore, a terahertz antenna with high gain, high efficiency, and wide bandwidth is an indispensable key component of terahertz wireless systems and has become a research hotspot in the field of antennas. In this paper, a high-gain broadband antenna is presented for terahertz applications. The antenna is a three-layer structure, fed by a grounded coplanar waveguide (GCPW), using polytetrafluoroethylene (PTFE) material as the dielectric substrate, and the metal through-hole of the dielectric substrate forms a substrate-integrated waveguide (SIW) structure. The metal fence structure is introduced to reduce the coupling effect between the radiation patches and increase the radiation bandwidth and gain. The center frequency is 0.6366 THz, the operating bandwidth is 0.61–0.68 THz, the minimum value of the voltage standing wave ratio (VSWR) is 1.00158, and the peak gain is 13.14 dBi. In addition, the performance of the designed antenna with a different isolation structure, the length of the connection line, the height of the substrate, the radius of the through-hole, and the thickness of the patch is also studied.

This paper presents a high‐power and sharp‐skirt‐selectivity bandpass filter with flexible transmission zero (TZ) and bandwidth. The proposed filter consists of three cascaded dual‐mode resonant cavities and a bandstop resonant structure. The dual‐mode resonant cavity is composed of a substrate‐integrated waveguide structure and a mushroom metal structure, which can implement a controllable bandwidth and generate a TZ for sharp skirt selectivity. Meanwhile, the middle dual‐mode resonant cavity is an oversized waveguide structure to improve power capacity. Moreover, the integrated bandstop resonant structure is used to generate another flexible TZ. The effect of different dimensional mushroom metal structures and bandstop resonant structures are also analyzed in detail. Finally, the proposed structure is fabricated and tested. Simulation results show that the proposed filter has an insertion loss of −1 dB at the passband 8.9–10.7 GHz with two TZs on both sides of the passband. Additionally, the proposed filter can obtain an 11 MW power capacity. Compared with the traditional filters, the proposed filter possesses high‐power and sharp skirt selectivity characteristics, and its position of TZ and bandwidth can be properly adjusted. [ABSTRACT FROM AUTHOR]

This paper presents a new wideband waveguide substrate integrated waveguide (SIW) coupler with maximum deviation of ±0.5 dB in a 7.5–12.25 GHz bandwidth (48% fractional bandwidth). Proposed coupler consists of the standard WR90 waveguide and single layer/double clad SIW printed circuit board (PCB) which is placed crosswise on the waveguide. Proposed three port coupler (isolated port was ended with match load) has a two coupling level (average of coupling in 8–12 GHz frequency range) of 43.2 and 58.3 dB, which is correspond with the hole diameter of 3.5 and 3 mm, respectively. The main contribution of this work is based on the hybrid techniques of SIW and RWG for coupler design in the high power microwave application. Validation of the simulation results with measurement one proves that the proposed X‐band waveguide to SIW coupler is a good candidate for use in high power industrial/commercial applications. [ABSTRACT FROM AUTHOR]

In order to minimize antenna complexity and improve gain, a new compact size low profile SIW-cavity-based frequency reconfigurable antenna is presented for IoT, WLAN, and 5G applications. The proposed antenna miniaturization is achieved by incorporating SIW cavity using metallic vias. The reconfiguration mechanism is accomplished by etching a circular ring slot and a C-shaped slot at the top metallic layer of the substrate. The frequency switching mechanism from low to high state is provided by eight PIN diodes. The diodes are placed in a symmetrical order along circular ring slot. All the diodes are switched on simultaneously to achieve low-frequency state operation. However, the off state of the diodes shifts antenna operation from low to high-frequency state. The antenna is fabricated on a small size substrate with an overall electrical size of (0.4λ* 0.4λ).The proposed antenna resonates at frequencies 2.4, and 3.45 GHz with 220 MHz and 470 MHz bandwidth respectively in low-frequency state. In high-frequency state, the antenna resonates at 5.8 GHz with 200 MHz bandwidth. The proposed antenna achieves peak gain of 6.3, 6.7, and 5.9 dBi in the three bands, and stable radiation patterns are attained in the working frequency band of the antenna. [ABSTRACT FROM AUTHOR]

In this paper, a miniaturized quarter‐mode substrate integrated waveguide (QMSIW)‐based self‐multiplexing antenna is designed to achieve high isolation in terms of small‐frequency ratios. First, the cross‐shaped slot is introduced to split the antenna into four parts with different dimensions, equivalent to four QMSIWs with different frequencies. By adjusting the slot position parameters, the QMSIW can be adjusted independently. Second, the antenna placement is optimized by adjusting the position of the slot and applying the frequency spacing technique. The designed antenna operates in four similar frequency bands (4.8, 5.15, 5.5, and 5.8 GHz). The isolation of adjacent units is more remarkable than 35.1 dB, while the isolation of relative units is more excellent than 22.7 dB. The structure of the proposed planar antenna is simple and suitable for handheld microwave devices. [ABSTRACT FROM AUTHOR]

A triple-band substrate integrated waveguide (SIW) with dielectric resonator antenna (DRA) for fourth-generation (4G) and fifth-generation (5G) applications is proposed and analyzed in this paper. Loading SIW with DRA allows for a wide bandwidth, low losses, and fabrication ease. The proposed antenna can transmit and receive data independently by covering LTE Band 3 at 1.8 GHz, LTE Band 8 at 2.6 GHz, and 5G n77 at 3.7 GHz. A U-shaped cut is applied to achieve the targeted multi-resonance frequencies. The antenna obtains high bandwidths of up to 19.50% with 4.9 dBi gain and 81.0% efficiency at 1.8 GHz, 6.58% bandwidth with 4.4 dBi and 72.7% efficiency at 2.6 GHz, and 8.21% bandwidth with 6.7 dBi and 73.5% efficiency at 3.7 GHz. The simulated and measured results agree well. The proposed antenna is feasible for 4G and 5G applications. [ABSTRACT FROM AUTHOR]