Substrate Integrated Waveguide Technology Research Articles

Band‐stop filter sensor based on SIW cavity for the non‐invasive measuring of blood glucose

Design and realisation of a substrate integrated waveguide (SIW) planar sensor for the non-invasive monitoring of blood glucose concentration (BGC) is described. The structure of the presented sensor is similar to a conventional band-stop filter. To produce a substantial and localised field enhancement in the sensing region by the SIW technology, the slots and interdigital arms on the upper conductor of the SIW cavity are utilised. Further, the fingertip is used as materials under test and its displacement and fingerprints effects are studied. The introduced sensor is then fabricated and measured. The evaluated results indicate that the developed sensor features improvement in both the fingertip positioning and fingerprints effects compared to the other work. Also, the frequency resonance shift of the proposed sensor observing the valuable enhancement of non-invasive BGC detection sensitivity is much more than the previous study.

Design and implementation of 2.5D frequency-selective surface based on substrate-integrated waveguide technology

AbstractIn this paper, the patch-type frequency selective surfaces (FSS) based on substrate-integrated waveguide (SIW) technology is proposed to improve the bandwidth (BW) and angular performance. The proposed FSS configuration overcomes the limitations of both conventional 2D and 3D FSS structures. A closely coupled cascaded mechanism is employed to combine two identical FSS elements separated by thin dielectric substrate results in incorporation of SIW technology; hence, named as 2.5D FSS. A derived equivalent circuit model is used to estimate the basic performance of proposed FSS–SIW elements, and the response of analytical expressions has been validated and final design is obtained using full-wave simulations. Two basic FSS elements viz. single square loop and a Jerusalem cross have been investigated to prove the enhancement in their BW and angular stability. The proposed technique evidently improves the BW and angular stability of FSS structures than in its established form. Besides, various important parameters that influence the performance characteristics of reported 2.5D FSSs are also studied. The important observations made on the thickness, as the thickness increases the bandstop FSS, can change to bandpass FSS. Finally, the proposed FSS structure has been fabricated and measured using free space measurement setup, to show the effectiveness of theoretical results. The measured results show good agreement with simulated results at normal and oblique incidence angle.

A Highly Sensitive Substrate Integrated Waveguide Interferometer Applied to Humidity Sensing

This letter presents a new generation of radio frequency interferometric sensors. Herein, an original, simple, and monolithic interferometer based on substrate integrated waveguide technology is introduced for the first time. In order to demonstrate its potential for measurement applications, the proposed structure has been studied as a humidity-sensing element. Its detection principle is based on the variation of the effective dielectric constant of a sensitive branch due to the variation of the humid air dielectric constant. The sensitive characteristics of the structure have been investigated in the range of 20%–70% relative humidity. An analytical model that predicts the frequency shift and estimates the humidity level is proposed. The substrate integrated interferometer can be used in many measurement applications such as dielectric material characterization and environmental detection.

Automatic Design of a CP Fan-Beam Linear Slotted Array in SIW Technology

In this paper, we present a technique for the automatic optimization of a right-hand circular-polarized (RHCP) linear slotted array in substrate integrated waveguide (SIW) technology for the so-called “last-mile”communications, in which a narrow (broad) beam is required in the elevation (azimuthal) plane. The procedure can be divided into two steps; i) the optimization of isolated single slot pairs, by means of two physics-based functionals able to minimize both slot pair back-scattering and axial-ratio, ii) the optimization of the entire linear array of slot pairs, by means of a global functional able to match the co-polar component of the synthesized aperture distribution to the target one, i.e., a uniform magnetic current distribution to radiate a narrow beam in the elevation plane. A prototype of array was optimized at 24.3GHz and measured in the bandwidth [24.1, 24.5]GHz, showing a fair agreement against full-wave simulations, thus validating the exposed techniques.

A Cavity-Backed Shorted Annular Patch (SAP) Array for Mid-Range V-Band Backhauling Applications

This paper presents a new improved gain array configuration well suited for mid-range V-band backhauling applications. The proposed solution is based on a cavity-backed shorted annular patch (SAP) antenna loaded with a parasitic patch element for gain maximization. This solution is proved by designing and measuring a 4 × 4 array which presents a reflection coefficient bandwidth covering the frequencies from 58.7 to 63.25 GHz (7.6% at 60 GHz). The experimentally validated array gain is equal to 18 dBi corresponding to 37.9% of aperture efficiency. The antenna and array configurations presented in this paper are optimized to minimize the manufacturing cost and complexity. This result is achieved through a novel beamforming network (BFN) configuration, implemented using a dual-layer substrate-integrated waveguide (SIW) technology, and partly integrated on the array aperture. The achieved results demonstrate how the performance of the cavity backed SAP array is comparable to the ones achieved with more complex and expensive solutions.

Advanced Filtering Solutions in Coaxial SIW Technology Based on Singlets, Cascaded Singlets, and Doublets

The use of singlets, cascaded singlets, and doublets in a coaxial substrate integrated waveguide (SIW) technology is proposed in this paper, with the aim of implementing low-loss filters with very compact size and highly selective symmetric, asymmetric as well as dual-band responses. Singlets based on coaxial SIW resonator structures with source-load coupling are presented and studied. Then, different filter examples based on $N$ cascaded singlets are designed, fabricated, and measured at 7.5 GHz, with up to $N$ transmission zeros that can be easily located below and above the passband. Moreover, the application of doublets based on a dual-mode coaxial SIW resonator with source-load coupling for achieving extremely compact dual-band filters is presented, and two examples with different bandwidth configuration for each channel are designed, demonstrating the flexibility of the proposed coaxial SIW structure. The obtained experimental results of the differently implemented filters show a good agreement with simulations, thus confirming the interesting potential application of these structures for the design of very compact devices with advanced filtering responses.

Design of wide band-pass substrate integrated waveguide (SIW) filters based on stepped impedances

A full-wave design technique of n-order Chebyshev stepped impedance band-pass filters in substrate integrated waveguide (SIW) is presented for the first time. The structure of the filter is based on including elliptic patterns etched on the SIW top surface to synthesize Chebyshev transfer functions. The band-pass response is obtained from the high-pass characteristic of the SIW line together with the behavior of the elliptic patterns, which implement the impedance inverters needed to control an upper cut-off frequency in the response of the filter. The synthesis technique is applied to the design of a sixth-order Chebyshev stepped impedance band-pass SIW filter. It is shown that the use of elliptic patterns instead of circular patterns can increase the spurious free range of the filter. In addition, when exponential microstrip-to-SIW transitions are integrated into the design process, a reduction in size and improvement in return loss are achieved, as compared to a base-line filter (sixth-order Chebyshev stepped impedance band-pass filter) designed with transitions separately. Electromagnetic (EM) simulation and measurements results have shown the effectiveness of the proposed design technique to carry out high-performance band-pass filters in SIW technology.

Design of a Novel Quarter-Mode Substrate-Integrated Waveguide Filter With Multiple Transmission Zeros and Higher Mode Suppressions

This paper presents a novel quarter-mode packaged bandpass filter with four transmission zeros (TZs) in substrate-integrated waveguide (SIW) technology. The filter has an insertion loss of 2.85 dB at 30 GHz and fractional bandwidth of 20%. The design methodology of the TZs was first demonstrated to increase the attenuations of the filter stopband. The quarter-mode SIW resonators were analyzed with high-mode suppression by properly setting their feed points. The packaged filter was consistent between the simulation and measurement results and offers the advantages of compact configuration and easy integration with other devices. Mode suppressions of up to 110 GHz were also provided. The proposed concept is attractive for designing miniaturized and high-performance-packaged filters for 3-D millimeter-wave transceiver systems.

Review on Design of Frequency Selective Surfaces based on Substrate Integrated Waveguide Technology

The spectacular development of frequency selective surfaces (FSS) as a spatial filter, absorbers and reflectors made them feasible for the aerospace and defence applications. The intervention of substrate integrated waveguide (SIW) technology into FSS results in the improvement of unit cell structures and better performance by isolating them from inter-element interference. Such FSS structures with SIW cavities upholds the FSS properties and improves their selectivity and performance. Considering the diversity in applications of introducing SIW cavity technology into FSS, the aim of this paper is to furnish a study on the glimpse of EM design techniques to analyze this type of structures. Design topologies of narrowing bandwidth, dual resonance, the design of FSS with sharp sideband edges and frequency selective polarization rotating structures are presented. Further, a novel design for improving the bandwidth of reflective FSS is discussed based on SIW technology. Fabrication techniques pertaining to this type of structures are presented in brief.

Dual-Polarized Antenna Fed by a Quasi-Planar Orthomode Transducer With Different Radiation Patterns

In this paper, a millimeter-wave (mmW) dual-polarized antenna with different radiation patterns is proposed. The antenna consists of a planar lens, a rectangular horn antenna, and a quasi-planar orthomode transducer (OMT) which provides two polarizations. The quasi-planar OMT with good isolation is based on the substrate-integrated waveguide technology, and it can be co-planar integrated with other mmW planar circuits seamlessly. A planar lens is designed on a quad-layered substrate and it has the priority of polarization selective that only takes effect on the horizontal polarization (H-pol). Consequently, high gain with the narrow beam in H-pol and low gain with wide beam in vertical polarization (V-pol) are achieved. To verify the idea, the proposed antenna is designed, fabricated, and measured, achieving a high gain of 26.4 dBi in H-pol, and a wide beamwidth in V-pol. This kind of antennas can be applied to make a balance between the range and coverage in communication and radar applications. In addition, the proposed quasi-planar OMT has potential applications in fifth-generation mmW wireless communications.

SIW Multibeam Antenna Based on Modified Horn Beam-Forming Network

A simple multibeam antenna fed by a modified horn beam-forming network (BFN) is realized in substrate integrated waveguide technology. Compared with Rotman lens fed multibeam antenna, such an antenna has the merits of a simple architecture and design process. The modified horn BFN applied here is developed from a traditional horn BFN by adding multiple lateral feeds to perform the beam scanning property. The operation principle, design method, and performance of the multibeam antenna are illustrated sequentially. Fabrication and measurement are conducted to test the consistency between simulation and experiment.

Compact 2-D Scanning Multibeam Array Utilizing the SIW Three-Way Couplers at 28 GHz

A compact two-dimensional (2-D) scanning multibeam array operating at 28 GHz in a substrate integrated waveguide technology is proposed, designed, simulated, and fabricated in this letter. To achieve better compactness, three-way couplers, instead of traditional Butler matrices, are applied here to form 2-D scanning beam-forming network. By doing so, the occupied area can be significantly reduced. After joining to the radiation portion, a 2-D scanning multibeam array allows for 3 × 3 beam steering in two orthogonal planes is fabricated and measured to test whether the measured results agree well with the simulation.

Enhanced Cavity Sensor in SIW Technology for Material Characterization

This letter presents an enhanced solution for low-cost sensors for the determination of the dielectric permittivity and the loss tangent of materials, based on substrate-integrated waveguide (SIW) cavities. The novelty consists in a slight, yet fundamental, modification of the standard sensor topology. The typical structure is based on an SIW resonant cavity with a hole in the middle and a pipe passing through, which contains the material under test. The modification consists in adding a metal sheath that partially covers the walls of the pipe. The metal sheath enhances the penetration of the electromagnetic field into the pipe, thus increasing the sensitivity of the device. Simulation and measurement results of various liquids demonstrate the advantage of the proposed structure.

Highly selective bandpass filter using substrate integrated waveguide technology for FMCW radar application

AbstractA bandpass filter using substrate integrated waveguide technology is proposed in this paper for ISM band frequency (5.7–5.9 GHz) application. Metallic inductive posts are used for the realization of the filter. The proposed structure provides pass band from the frequency range of 5.72 GHz to 5.84 GHz with the insertion loss of 0.7 dB and return loss more than 25 dB. Frequency tuning is carried out from the frequency range of 5.65 GHz to 6.06 GHz with the variation of pass band bandwidth from 88 MHz to 222 MHz. All the simulations are carried out by high frequency structure simulator based on FEM method software. Proposed bandpass filter is fabricated and measured result indicates better performance. It will be utilized in the system developed at CSRTC for the suppression of higher order harmonics in frequency modulated continuous wave radar at the frequency from 5.725 GHz to 5.875 GHz.

Miniaturized Band Pass Filter in Substrate Integrated WaveguideTechnology

Miniaturization is an important criteria in the selection of devices for next generation communication systems. A novel miniaturization technique for an inductive post filter is investigated in this paper. Miniaturization is not so popular in inductive post Substrate Integrated Waveguide (SIW) filter and so considerable amount of research is to be done in this domain. A band pass filter in SIW technology using inductive posts is realized and further analyses are carried out. The insertion loss in the pass band is found to be 0.5 dB and the return loss is 22 dB. In this paper, we investigate the use of slow wave technology for miniaturization. Unlike the conventional SIW, the slow wave SIW topology requires a double layer substrate with internal metallized vias introduced in the bottom layer connected to the bottom conductive plane. The number of rows of internal metallized vias was chosen based on a parametric study. The proposed miniaturization technique shows that the SIW filter is 21.6 % and 34.6 % miniaturized in size and area respectively. The response of the filter covers Ka band and hence is suitable for satellite communication application. A quality factor of 506 is achieved for the miniaturized filter.

Balanced bandpass filter with tunable centre frequency based on substrate integrated waveguide technology

A mechanical tuning balanced bandpass filter based on substrate integrated waveguide (SIW) dual-mode resonant cavity is presented. It can be accomplished by placing two metallised via-holes with open-loop slots on the top layer which affect the TE102 and TE201 modes of the square SIW cavity, respectively. Direct source-load couplings have been utilised to achieve the high selectivity of the differential mode (DM) passband and improve the DM out of band rejection. A planar module of 60 × 60 mm2 has been fabricated on RO5880 substrate with a dielectric constant of 2.2 which verify the design concept.

Wideband Quasi-Omnidirectional Planar Inverted F-Antenna for Compact Wireless Systems

A new type of planar inverted F-antenna has been conceived and demonstrated using a fully planar structure to provide quasi-omnidirectional-type radiations over a wide operating bandwidth. Miniaturized segmented substrate integrated waveguide technology has been extended with some modifications to accommodate two distinct modal geometries in a single structure. The new approach has been systematically studied, and their equivalent circuits have been developed. A prototype has been experimentally tested in C-band revealing quasi-omnidirectional radiations with 1.3 dBi peak gain and 48.5% matching bandwidth. This miniaturized wideband omnidirectional antenna should find potential applications in compact wireless transceiver systems occupying 0.45λ0 × 0.2λ0 real estate.

Ultrathin design and implementation of planar and conformal polarisation rotating frequency selective surface based on SIW technology

The design of novel ultra-thin polarisation rotating frequency selective surface based on substrate integrated waveguide (SIW) technology has been presented. The primary function of the structure is to select the linear polarisation from the impinging electromagnetic wave on it and to rotate the wave into the 90° counter-clockwise direction in the given frequency band. The proposed array consists of periodic Y-shaped slot elements surrounded by SIW cavities. The structure shows a relative bandwidth of 8% with impedance matching better than −10 dB and a very good insertion loss of 0.3 dB. It also offers co-polarisation below −20 dB in the passband. The proposed structure is very thin (0.055 λ 0 ) compared to the existing SIW-based frequency selective polarising rotators. Also, the conformal analysis of the proposed structure has been carried to study its behaviour for real-time applications when used on curved surfaces. Finally, to prove the efficacy of proposed structure, a prototype has fabricated and measured its performance. A very good agreement is observed between the experimental and simulated results.

Beamforming Networks for antenna array, useful inWiFi applications

In this paper several types of beamforming networks have been presented, this proposal can be used for an array antenna, which are used in several types of WiFi applications, IEEE 802.11b/g/draft-n. The first design corresponds to a 4x4 Butler Matrix for a resonance frequency at 2.45 GHz, depending on the port through which the signal is excited, it will be possible to obtain several variations in phase at the output ports (45°, 135°, -45° and -135°), the proposed Butler matrix has been optimized from a generalized matrix scheme, reducing the size through a simple overlap of multiple transmission lines to l/4 at the central frequency. The second design corresponds to a Rotman lens with a characteristic resonance frequency of 5.8 GHz, with a maximum focal angle of 30°, for this design has been used geometric optics concept, and the last design has been made for a frequency of 5.8 GHz using a slot array designed with Substrate Integrated Waveguide technology.

A Wideband Correlation and Detection Module Based on Substrate-Integrated Waveguide Technology for Radio Astronomy Applications

A wideband (30% relative bandwidth) correlation and detection module based on substrate-integrated waveguide (SIW) technology intended for a radio astronomy polarimeter is presented. The SIW circuit is a six-port network with two input ports that are correlated in two hybrid couplers and their corresponding output signals are routed to Schottky diode detectors, which are designed using microstrip technology and assembled within the same system. The designed SIW structure includes hybrid couplers, power dividers, a 90° phase shifter, and 90° bends, providing a real implementation of a functional system with improved bandwidth performance from 35 to 47 GHz. Experimental results are in concordance with simulations, and they validate the module operation for the proposed application.