In this paper, a high-order-mode (HOM) (TE330) cavity-fed 45° linear polarized 6×6 slot array antenna is proposed. The 45° linear polarization is achieved by introducing asymmetric cross slots on the HOM cavity, resulting in low profile and wide bandwidth. The antenna array was verified using standard printed circuit board technology. Measured results show that the impedance bandwidth ( $|S_{11}|\le$ −10 dB) is 13.9% (36.98–42.92 GHz), and the peak gain is 19.3 dBi with a 3-dB gain bandwidth of 13.6%. Attributed to its simple structure, low profile, and wide bandwidth, the presented antenna is a good candidate for 5G applications.

This paper presents the design, manufacturing, and measurement of a novel substrate integrated waveguide (SIW) pedestal filtering antenna solution for use in 5G New Radio sub-6 GHz communications. Miniaturization is achieved through the use of SIW pedestal resonators and integration of the radiating element into the filter design, resulting in higher order suppression. The design generates a third order filtering response utilizing SIW pedestal resonators and a patch antenna element. The manufactured SIW pedestal filtenna achieves a 10 dB return loss bandwidth of 4.29% about a center frequency of 3.63 GHz, and a boresight gain of 3.66 dBi. Using the SIW pedestal filtenna elements, two array configurations are measured, a 1 × 1 linear array and 2 × 2 planar array. Beam-steering capability for the linear array is demonstrated in simulation, while the 2 × 2 array is shown to be suited to both dual- and single-mode operation.

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.

A substrate integrated waveguide (SIW) based self-quadruplexing antenna and its design approach in Ku-band (12–18 GHz) is presented in this paper. This consists of splitting of TE220 mode of square-shaped SIW cavity by incorporating the two diagonal arrays of metallic vias. Accordingly, four orthogonal dominant mode triangular shape SIW cavity (DMTC) resonators are formed. This methodology ensures enhanced isolation. To achieve the broadside radiation, the cavity structure is fed using microstrip lines and rectangular slots are loaded on the top layer of each DMTC. The length and position of each rectangular slot being chosen such that quad-resonances are achieved at 13, 13.5, 14.3, and 15 GHz for the respective DMTC. The equivalent circuit model of the proposed design is also developed, and the tuning of each frequency band is analyzed without affecting the others. The proposed antenna is producing high isolation (>28 dB) among all four ports and a unidirectional radiation pattern with a high front-to-back ratio (>26.8 dB).

This paper presents a miniaturized tri- and quad-band power divider (PD)based on substrate integrated waveguide (SIW). By adopting different types of modified circular complementary split-ring resonators on the top surface of SIW, multiple passbands are generated propagating below the SIW cut-off frequency. The working principle is based on evanescent mode propagation that decreases the operating frequency of the PD and helps in the miniaturization of the proposed structure. The operating frequency of the proposed PD can be individually controlled by changing the dimensions of the resonator. To verify the proposed concept, a tri-band and a quad-band PD exhibiting 3 dB equal power division at 2.41/3.46/4.65 GHz and 2.42/3.78/4.74/5.8 GHz are designed using the full-wave simulator, validated through circuit model, fabricated and experimentally verified. The measured results agree well with the simulations. The proposed PDs have good performance in terms of reasonable insertion loss, isolation, minimum amplitude and phase imbalance, smaller footprint, easy fabrication and integration. The size of the fabricated prototype is 18.3 mm × 8.4 mm, which corresponds to 0.205λg × 0.094λg, λg being the guided wavelength at the first operating frequency.

This paper describes the outcome of the “Small user TErminal multi band DIplexer” project where the goal is the validation of novel SMD-compliant planar diplexer. The real application scenario concerns an integrated multi-band radio terminal for ground-segment satellite links. The advantageous and novel approach involves the simultaneous use of three different well-established concepts: a microstrip low-pass filter, a substrate integrated waveguide high-pass filter, and the thin-film technology as manufacturing process. The proposed topology applied to a planar alumina-based design guarantees a 15 × 11.1 mm2 footprint and the best integration with surface mountable soldering process over standard PCB technology. Achieved performance and resilience to environmental toughness are suitable for consumer-oriented satellite links or man-pack applications. The designed component targets the Ku 10.7–12.75 (RX) and Ka 27.5–30 (TX) GHz bands but the layout can be easily tuned across the spectrum. The described solution has been manufactured and validated. Thermal cycling and mechanical tests have been carried out to prove the high technology readiness level of the proposed device.

This paper presents a compact multilayer substrate integrated waveguide (SIW) bandpass filter with wide stopband. The square SIW cavity resonators in multilayer substrates are horizontally and vertically coupled with magnetic coupling. By properly designing the coupling structure, the couplings between the higher-order resonant modes can be suppressed. Compared with the conventional single-layer SIW filters, the proposed multilayer SIW filter also exhibits a compact size. To verify the design concept, a double-layered SIW filter is fabricated and measured. The measured results agree well with the simulations. The measured results show that the upper stopband of the filter is extended to 2.73 times of the center frequency 8.02 GHz.

This article presented a compact bandpass filter with wide-stopband performance. Two substrate integrated waveguide (SIW) cavities and a short-circuited coplanar line introduced between the two cavities are used to realize a compact third-order bandpass filter. The passband is generated by combining the resonant frequency of TE101 mode of the SIW cavities and the fundamental resonant frequency of the short-circuited coplanar line. The size of the proposed filter reduces significantly in comparison with conventional third-order SIW filters. Moreover, the center frequency (CF) and the bandwidth of the filter can be controlled by adjusting the structural parameters of the filter. In addition, the first higher-order mode TE102 of the SIW cavity is suppressed by minimizing the coupling of TE102 mode in order to obtain wide-stopband performance. The proposed filter is designed, fabricated, and measured, and the simulation and measurement results show a good agreement. The filter exhibits compact size, low loss, and a rejection higher than 20 dB up to 1.94f0.

A high-isolation diplexer based on a dual-mode substrate integrated waveguide (SIW) resonator is proposed in this paper. Based on the theory of the dual-mode resonator, the miniaturized diplexers are designed by using the SIW dual-mode resonators. The superior isolation of the diplexers is obtained because the two operating modes of the dual-mode SIW resonators are not directly coupled and there is no interference with each other. In order to further improve the isolation of the circuit, the number of the order of the diplexer is added. Equivalent circuits are given to analyze and design the dual-mode high-isolation diplexers. Detailed analyses are given according to the equivalent circuits. The dual-mode third-order and fourth-order diplexers are designed and fabricated. The measured results agree well with the simulated ones. The total sizes of the fabricated third-order and fourth-order diplexers are 1.78λg × 2.64λg and 1.79λg × 3.63λg, respectively.

This paper presents center frequency and bandwidth switchable substrate integrated waveguide filters loaded with PIN diodes. The diodes are added in the slot on the surface of the resonators to switch the resonant frequencies and the coupling coefficients. Although the introduction of the slot causes extra radiation loss, it is small and acceptable. The proposed center frequency switchable filter has four center frequency switchable states of 1.78, 1.82, 1.88, and 1.91 GHz, while the bandwidth only changes ±0.64%. The bandwidth switchable filter has two states with 3 dB bandwidths of 70 and 103 MHz at a center frequency of 2.08/2.09 GHz. The measured performance of the fabricated filters shows good agreement with the simulation.

This paper reports a novel fourth-order quasi-elliptic bandpass filter (BPF) based on capacitive-loaded eighth-mode substrate integrated waveguide (CLEMSIW) cavities. The CLEMSIW cavity is constructed by the conventional eighth-mode SIW with two dielectric substrates and three metal layers; a metal via is employed to connect the middle and bottom metal layers. The middle metal layer achieves a large loading capacitance to shift the resonance frequency. The proposed filter is designed in a quadruple scheme, and two controllable finite-transmission zeros can be realized. For the demonstration, a prototype with a center frequency of 1 GHz and a fractional bandwidth of 10% was designed, fabricated, and measured. The measured results agree well with simulated ones. The proposed filter has advantages of ultra-compact size, high selectivity, and good stopband performances.

A novel design of compact and light-weight horn mounted cylindrical dielectric resonator antenna (CDRA) fed by substrate integrated waveguide (SIW) resonator has been investigated for high gain and multiband applications. SIW resonator contains two closely spaced longitudinal slots of equal length and unequal width to excite the CDRA. These slots are responsible for introducing triple resonating bands. The excited mode in dielectric resonator by longitudinal slots is EH11δ mode. The achieved impedance bandwidths are 65, 180, and 240 MHz at resonant frequencies 9.78, 10.58, and 11.84 GHz, respectively, for |S11| <−10 dB. Copper-taped horn enhances the gain of antenna more than 2 dB for all resonating bands. The measured peak value of gain is 9.3 dBi at ~11.84 GHz.

This paper describes the design and characterization of a compact substrate integrated waveguide (SIW) fed antenna for the 122 GHz industrial, scientific, and medical band. The use of a single RO4350B substrate layer and the SIW feeding ensure a low-cost fabrication. Two versions of the antenna are presented differing in antenna gain and size. For measurement purpose, a transition from rectangular waveguide to SIW is introduced. Measurements of the radiation pattern have been performed and show good agreement with the numerical results for both antennas and an antenna gain up to 7.14 dBi.

In this paper, two new feed network designs for single layer and double layer slotted waveguide array antennas are presented. A microstrip to substrate integrated waveguide transition is applied to the single layer antenna. The aperture coupling mechanism is used in order to find the optimum feed network for double-layer structure and to obtain stable radiation characteristics over the frequency band. The prototypes of the proposed antennas have been fabricated and tested. The measured results were compared very well with the simulation results obtained from CST microwave studio and showed low side lobe level at the center frequency of 11.5 GHz for the low-profile 4-channel slotted waveguide arrays.

A new single-feed aperture-coupled, X-band microstrip patch antenna array with circular polarization (CP) is designed. CP is achieved using indented microstrip patches fed through the slots on a substrate integrated waveguide. The antenna has the high radiation efficiency more than 90% over the operating frequency. Impedance bandwidth (VSWR < 2) and axial ratio bandwidth (AR < 3 dB) of 11.8, and 10.9% is attained, respectively. Good agreement is achieved between simulated and measured results.