Substrate Integrated Waveguide Cavity Resonator Research Articles

Compact Tri-Band SIW Bandpass Filters With High Selectivity and Controllable Center Frequencies Using Perturbation Structure

In this paper, two compact tri-band substrate integrated waveguide (SIW) bandpass filters (BPFs) with high selectivity and controllable center frequencies are presented based on the proposed tri-mode SIW resonant cavity perturbed by metallized vias. The resonant characteristics of the tri-mode SIW cavity are first analyzed, and the impacts of some key parameters on the resonant frequency are comparatively analyzed to further elucidate the flexible controlling of the vias perturbated SIW cavity structure. For demonstrating the superiority of the proposed tri-mode SIW cavity, a prototype of tri-band SIW BPF, centered at 11.18, 12.61 and 13.33GHz, is designed using one-layer substrate. In order to further reduce the occupied size, a tri-band SIW BPF with controllable center frequencies of 11.93, 13.21 and 14.12GHz, is constructed based on electric and magnetic coupling structure using two layers substrates. Both of the proposed triband BPFs exhibit six transmission zeros (TZs), resulting in good out-of-band rejections. The measured results agree well with the simulated ones.

Flexible SIW humidity sensors based on nanodiamond sensing films

AbstractIn 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.

Low Profile Dielectric Rod Tuned Reconfigurable Band Pass Filters

A novel low profile mechanical tuning technique is introduced in this paper to change the center frequency of substrate integrated waveguide (SIW) based reconfigurable bandpass filters (BPF), by loading dielectric rods of different permittivity in resonant cavities and coupling apertures. The technique is simple, cost-effective (rods are machined from conventional substrates), and the same physical structure provides a wide frequency tuning. First, the tunability of center frequency of the SIW cavity resonator is theoretically explained and then estimated with the help of full-wave 3D EM simulator and electrical equivalent circuit. This concept is extended to the tuning of coupled resonator BPF loaded with dielectric rods followed by the analysis of maintaining constant bandwidth. Following the analysis technique, the tunability concept is studied for different arrangements of dielectric rods inside the SIW BPFs. The characteristics of the fabricated filters are experimentally validated. It is shown that center frequency tunability can be achieved by simply varying the permittivity of all the dielectric rods simultaneously. The proposed technique is further extended for obtaining wider tunability and constant bandwidth by using dielectric rods of dissimilar permittivities from a look up table. These designs demonstrate a simple and cost-effective passive tuning technique achieving high Q-factors in the range of 102–210.5, lowest insertion loss <2dB above 10 GHz, and wide tuning bandwidth in X-band. The reconfigurable filters are developed for advanced high-speed, long-distance, and fixed wireless connectivity in a rural area at a low cost. The technique can also be used for temperature compensation and overcoming fabrication uncertainty.

Near‐field sensor based on substrate integrated waveguide microstrip cavity resonator with a circular aperture

A near-field planar sensor fabricated from a substrate integrated waveguide (SIW) cavity resonator is presented. The SIW cavity resonator is a modification of a rectangular microstrip antenna. The rectangular microstrip antenna radiates from two radiating edges that produce far-field radiation, which is undesired for near-field sensing. To suppress the radiation from the edges, the microstrip antenna is modified to have conducting vias that short all four edges of the patch to the ground plane. A circular hole is placed on the patch surface in the middle of the patch to form a sensing aperture. The field is thus confined inside the cavity with leakage only allowed through a small aperture, which is used for sensing surrounding objects in the vicinity of the aperture. This cavity resonator operates in the TM21 mode of the SIW cavity. Full-wave simulations are performed and the results are consistent with the theoretical analysis as well as CAD formulas that are derived. The performance of the sensor as a near-field sensing device and as a near-field imager is explored.

A multimode substrate integrated waveguide based s elf‐hexplexing antenna for mobile terminal applications

A low-profile self-hexplexing antenna based on the multimode substrate integrated waveguide (SIW) cavity is presented for mobile terminal applications. It has three feeding ports, each of which can generate two resonant modes. Taking the advantage of the truncated SIW resonant cavity, the footprint of the antenna remains compact in the multiple functional mode scenario. The proposed antenna operates at six different modes, namely TM10 mode at 3.55 GHz, TM01 mode at 4.85 GHz, TE110 mode at 2.45 GHz, TE220 mode at 5.6 GHz, TE110 mode at 3.4 GHz and TE120 mode at 5.35 GHz. Good agreement is achieved between the simulated and measured antenna performance. The excitation and field distribution of each mode is analyzed. Keeping the structure miniaturized, the proposed antenna realizes hex-band characteristics without excessive feeding ports. It can be used for Microwave Access (WIMAX), the 5th Generation Mobile Communication Technology (5G) and Wireless Local Area Network (WLAN) applications, which is suitable for mobile handheld multiband terminals.

A substrate integrated waveguide (SIW) based self-quadruplexing antenna for Ku-band applications

AbstractA 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 (&gt;28 dB) among all four ports and a unidirectional radiation pattern with a high front-to-back ratio (&gt;26.8 dB).

Compact filtering power divider using mixed quarter‐ and eighth‐mode substrate integrated waveguide resonant cavities with flexible design

In this paper, a series of filtering power dividers (FPDs) employing quarter-mode substrate integrated waveguide (QMSIW) and eighth-mode substrate integrated waveguide (EMSIW) resonant cavities have been first demonstrated. The proposed prototypes possess the merits of extremely miniaturized dimensions and relatively low insertion loss. Based on the detailed analysis and investigation of electromagnetic features and feeding types corresponding to the miniaturized SIW resonant cavities, two-order mixed QMSIW and EMSIW FPDs with electric coupling or magnetic coupling topologies are presented. In addition, multi-layered structures are implemented to decrease the footprints of the FPDs further. To attain a higher-order design and enhance the out-of-band rejection, a four-order multi-layered FPD with cross coupling mechanism is finally developed. For demonstration and verification, seven prototypes of the proposed FPDs operating at 4.8 GHz are meticulously designed, fabricated, and measured. All experimental results are in reasonable agreement with the simulated ones.

Substrate integrated waveguide based cavity‐backed bowtie‐slot antenna‐triplexer

In this article, a design of planar cavity-backed antenna-triplexer is proposed for WLAN/WiMAX/ISM band at 5.2/5.5/5.8 GHz. The substrate integrated waveguide (SIW) technology is employed to realize a planar cavity-backed antenna-triplexer. The proposed geometry entails two SIW cavity resonators where a bowtie-shaped smaller cavity is inserted inside the larger rectangular one. The rectangular cavity consists of two bent-transverse slots those are excited by two different microstrip feedlines and the Bowtie-like slot inside the Bowtie cavity, excited by a coaxial feed. The antenna generates three different resonances at 5.2, 5.5, and 5.8 GHz simultaneously with flat gain characteristics. By exciting cavity modes (TE110) by Port2/Port3 and a patch mode (TM010) by Port 1 simultaneously, average isolation of better than 23 dB is accomplished among the three input ports. To validate the proposed idea, the design is fabricated and experimentally tested. The measured responses show a good matching with the simulations. Moreover, the antenna shows front to back ratio better than 18 dB and simulated gain values of 7, 5.45, 4.75 dBi at the three resonances.

Compact filtering crossover design based on SIW quintuple‐mode resonators

AbstractA compact filtering crossover utilizing substrate integrated waveguide (SIW) quintuple‐mode resonator (QMR) technology is proposed for the first time. Benefiting from this technology, the proposed crossover firstly breaks the status quo that SIW crossover filtering response is only concentrated in single passband, thereby extending the applications of the SIW crossovers. In design, the QMR is derived by embedding metal‐via holes in the conventional SIW resonant cavity, thus to produce quintuple resonant modes featuring with specific electric distributions. Next, by dividing these modes into two groups, a triple‐mode bandpass filter (BPF) channel and a single‐mode dual‐band BPF channel are both realized. To implement two flat passband channels, there are two SIW cavities cascaded. And also, the isolation between two channels is implemented by employing the orthogonal characteristic. In this way, a crossover is implemented. The proposed design method can be a good candidate for developing SIW multi‐band filtering crossovers. For verification, an example circuit has been designed, fabricated, and measured.

Substrate Integrated Waveguide Filtering Slot Antenna for Ka-Band Satellite Communications

This paper proposes a substrate integrated waveguide (SIW) filtering slot antenna. Based on four SIW cavity resonators and a slot locating on the last resonator, a filtering antenna was designed, targeting the near 20 GHz satellite communication band. Simulated in the Ansys-HFSS commercial software, it exhibits a - 10 dB impedance bandwidth of 1.5 GHz and a flat gain of 5.5 dBi in the operating frequency band. Besides, the filtering antenna has good selectivity at passband edges and features such as compact size, low profile, and low cost, making it suitable for Ka-band satellite ground terminals.

A wide stopband multilayer substrate integrated waveguide bandpass filter with suppression of higher-order mode coupling

AbstractThis 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.

Designing of Novel Eighth-Mode Forth-Order Substrate Integrated Waveguide Band-Pass Filter with High Selectivity

A fourth-order Substrate Integrated Waveguide (SIW) filter has been presented in this research work. The four Eighth-Mode (EM) SIW cavity resonators have been electrically coupled and source to load coupling has been achieved by a slight modification of the eighth-mode resonator cavity. Here a 87.5% size reduction has been achieved using the EMSIW, which plays a significant role in achieving miniaturized structure. The operating center frequency is 13.5 GHz with a 3dB bandwidth of 0.5 GHz. The Rogers-5880 substrate has been utilized with relative permittivity of 2.2. The results show that the filter has three transmission zeros on either side of the pass-band, which gives high selectivity and a high out of band rejection.

Frequency Reconfigurable Antenna Based on Substrate Integrated Waveguide for S-Band and C-Band Applications

A novel frequency reconfigurable antenna based on substrate integrated waveguide (SIW) for S-band and C-band applications is proposed. The antenna employs a SIW resonant cavity structure with a rectangular-ring slot and a long slit etched on the top surface. An extra via post is introduced to adjust the resonance frequency of the low-frequency mode independently without affecting the impedance matching of the high-frequency mode or decreasing the gain. Several PIN diodes are symmetrically placed along the rectangular-ring slot to attach the patch to the top surface. The working state of PIN diodes is controlled by a simplified bias structure. A prototype was fabricated and measurements show the proposed antenna has a bandwidth of 18 MHz in S-band low-frequency mode and 322 MHz in C-band high-frequency mode. Good agreements between the simulated and measured return losses, as well as radiation patterns, are observed.

3.4/4.0 GHz Tunable Resonant Cavity in SIW Technology Using Metal Post and PIN Diode on a Low-Cost Biasing Network for 5G Applications

This paper presents a dual-band resonant cavity in Substrate Integrated Waveguide (SIW) technology to operate in the range from 3.3 GHz to 4.2 GHz, spectrum considered for the Fifth Generation (5G) network. The cavity was designed to operate at 3.4 GHz and 4.0 GHz. To achieve different states, a jumper and a PIN diode switch are considered as switching elements, connecting and disconnecting the bottom and the upper walls of the SIW resonant cavity through a metal post inserted inside its internal volume. A fitting equation is proposed to predict the maximum resonance frequency caused by the insertion of a single metal post inside the internal volume of the SIW resonant cavity and a new low-cost biasing network is designed on a thin dielectric substrate allocated on the upper wall of the SIW resonant cavity, using transmissions lines and a single capacitor, reducing the final cost and the insertion losses. Good agreement was observed among the fitting equation, computational electromagnetic simulations, and experimental results, validating the proposed methods.

Miniaturised substrate integrated waveguide cavities in dual‐band filter and diplexer design

The contribution of this study is to develop a miniaturised substrate integrated waveguide (SIW) cavity resonator with two evanescent-mode resonances. The circuit area of the developed dual-frequency SIW cavity is only 9.2% that of its conventional SIW cavity counterpart. A dual-band filter is implemented from using two miniaturised SIW cavity resonators. The two-passband frequencies can be independently controlled. Two transmission zeros are created by the two sides of each passband for enhancing the signal selectivity. A diplexer is also designed from using the proposed SIW cavities. A dual-band filter and a diplexer are built for experimental verification. Agreements between measured and simulated data are observed. To the best of the authors' knowledge, the designed dual-band filter and diplexer have achieved the best circuit area efficiency in the categories of dual-band SIW cavity filters and diplexers.

Design and Development of Low-Profile Multi-Band Antenna Fed by SIW Cavity Resonator Using Twin Apertures

AbstractA novel design of compact, linearly polarized and low-profile planar antenna which is electrified by Substrate Integrated Waveguide (SIW) resonator has been developed for multi-band applications of X-band spectrum. Radiating patch has been excited through two closely spaced longitudinal apertures of identical length but non-identical width, incorporated in SIW resonator. These apertures are responsible for multiple operating bands. The achieved fractional bandwidths are 1.29 %, 0.49 % and 1.60 % having resonant frequencies at 10.07 GHz, 10.85 GHz and 11.82 GHz respectively for |S11| ≤ -10 dB. The measured peak gain for first, second and third operating band is 6.54 dB, 6.86 dB and 7.68 dB respectively. The proposed antenna is a highly selective antenna for various applications of X-band microwave spectrum. This band has been particularly selected for military communication because it provides a trade-off between the characteristics (i. e. interference and rain resilience, data rates and remote coverage) of different frequency bands which are particularly suited to the needs of military users. It is very much suitable for secure communication i. e. to deny unauthorized access to sensitive unclassified information and prevent disruption of telecommunication. A comparative analysis of antenna’s parameters has been examined by Ansys HFSS and results are verified through experimental outcomes.

Design of wideband four‐way filtering power divider based on SIW loaded square patch resonator

A new design of wideband four-way filtering power divider (FPD) based on substrate-integrated waveguide (SIW) loaded square patch resonator is presented. The wideband operation is realised by utilising the TM 20 mode of the patch and the TE 110 mode of the SIW cavity resonator. Afterwards, the selectivity is obtained by adding four open-ended coupling lines to each side of the square patch. Besides, an extra isolation network is introduced between each output port. To verify the design concept, a prototype of the proposed FPD operating at 3.55 GHz with a fractional bandwidth of 21.3% is fabricated and measured. Results indicate that the input return loss is >10 dB and the insertion loss is 0.3 dB and 3°, respectively. Both simulated and measured results are in good agreement.

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.

Design of highly compact reconfigurable filters with tunable reactive loading

A compact and electronically tunable substrate integrated waveguide cavity resonator is presented in this work. The SIW cavity resonator is loaded symmetrically with stubs on the two sides which are terminated through varactors. By changing the capacitance along the loaded stubs the resonant frequency has been varied. Parametric analyses carried out in this work show a large potential tuning range along with the total resonator size of less than 3/4 λg. The resonator is created on a single layer printed circuit board with integrated biasing network. A two pole filter is realized using the tunable resonator and measured tuning bandwidth of 8.51% at center frequency of 2.55 GHz is demonstrated. The insertion loss is measured between 2.7 and 4.8 dB for the whole range and the return loss is less than 13.5 dB. The technique also allows the real-time fine tuning of coupling coefficient of the two resonators which can easily be extended to the realization of higher order filters. The proposed filter is an excellent candidate for miniaturized RF front-ends where tuning is essential for better spectrum control.

An Integrated SIW Cavity-Backed Slot Antenna-Triplexer

A low-profile antenna-triplexer is realized using a substrate integrated waveguide (SIW) technology for radio altimeter/WLAN/ISM band applications. The antenna is composed of two SIW cavity resonators where a smaller cavity is nested inside the larger one. The larger cavity is excited by using two distinct microstrip feedlines, while the smaller one by a coax probe. The antenna produces three distinct resonances around 4.18, 5.2, and 5.8 GHz simultaneously employing one annular slot and two transverse slots. By exciting cavity modes (TE110/TE 120) and the patch mode (TM10) simultaneously, an average isolation of better than 23 dB is accomplished among three input ports. As compared to the conventional counterparts, the proposed geometry is simple to realize in a compact space. To validate the proposed idea, the design is experimentally tested, and the measured responses show a good agreement with the simulations. Moreover, the antenna shows a front-to-back ratio better than 19 dB and measured gain values of 6.56, 4.2, and 5.85 dBi at three resonances. The proposed design is compact, easy to fabricate, and capable to integrate with planar circuits.