Substrate Integrated Waveguide Square Research Articles

Two‐dimensional multichannel bandpass filter bank with improved fractional bandwidth and selectivity

AbstractThis letter presents a six‐channel bandpass filter bank created on substrate integrated waveguide (SIW) with improved bandwidth and frequency selectivity on the lower band. Through SIW square cavities and slant slots, a two‐dimensional multichannel bandpass filter bank with a transmission zero constructed with the SIW orthogonal resonant modes is produced. The substrate integrated square cavity approach is used to achieve the propagation of the two orthogonal‐oriented transverse electric modes, TE102 and TE201, which resonate on the same frequency and bandwidth, depending on the location of the feed ports. The bandwidth could be altered by the coupling matrix synthesis and coupling windows. Better transmission and bandpass responses are produced in each channel when the feed ports and coupling gaps are positioned and appropriately adjusted. However, a pair of slot lines are imprinted along each cavity's designated diagonal to guarantee better isolation while attaining an increased fractional bandwidth. A 3 × 3 array of six bandpass filters with a center frequency of 8.65 GHz has been built, simulated, and measured to establish the suggested technique. Low insertion loss, high return loss, high isolation, an improved fractional bandwidth, and a compact device were the proposal's advantages.

A Single-Layer Wideband Differential-Fed Filtering Antenna With High Selectivity

In this communication, a single-layer, wideband, differential-fed filtering antenna with high selectivity is proposed. The developed filtering antenna possesses a simple structure and consists of a square patch, a square substrate integrated waveguide (SIW) cavity, a pair of symbiotic stepped impedance resonators (SSIRs), and a pair of complementary split ring resonators (CSRRs). The SIW cavity formed with sparse metallized posts is embedded in the square patch, and the impedance bandwidth can be broadened by merging the TM10 mode of the square patch, excited by the electromagnetic energy escaping from the sparse posts, with the TE210 mode in the SIW cavity through differential excitation. The SSIRs are connected with both radiating edges of the square patch. And two extra in-band resonances together with an upper-edge radiation null are simultaneously generated, so the impedance bandwidth and the frequency selectivity at higher stopband can be significantly improved. The CSRRs, surrounding around the differential excitation ports, are etched into the bottom surface of the SIW cavity, and a lower-edge radiation null is produced to further sharpen the roll-off rate. By adjusting the geometrical parameters of the SSIRs and CSRRs, the positions of the two radiation nulls can be independently controlled. For verifying the design method, a prototype of the developed single-layer filtering antenna has been fabricated and tested. The measurement results are well consistent with the simulated values, indicating good performance with a large -10 dB fractional impedance bandwidth of 21.2%, a peak realized gain of 9.3 dBi, two out-of-band rejection levels more than 26 dB, and very high selectivity.

Improved HMSIW Cavity for Differential Antenna With High Common-Mode Rejection

In this letter, a differential antenna with high common-mode (CM) rejection is proposed, which consists of dual improved half-mode substrate-integrated waveguide (HMSIW) cavities and a square substrate-integrated waveguide (SIW) coupling-feeding cavity (CFC). First, a novel approach to enhance the differential-mode (DM) radiation performance by flipping the symmetrical TE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">201</sub> cavity is presented. The two E-field components excited from reversed magnetic walls are superposed in phase. Then, a pair of improved HMSIW cavities with oppositely magnetic walls is adopted to suppress the CM and enhance the uniformity of the radiation pattern on E- and H-planes. The square TE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">202</sub> CFC with four coupling holes is discussed for the DM excitation. Meanwhile, it is equivalent to a band-stop filter further to improve CM rejection under CM excitation. The four perturbation holes in the CFC for the adjacent E-field isolation are analyzed. Finally, the proposed antenna is fabricated. The measured and simulated results show good agreement. The high CM rejection (27.3 dB) is achieved through the two-step rejection of the radiator and CFC.

Dual-Band Balanced to Unbalanced Multilayer Filtering Magic-T Based on SIW Cavity

A new dual-band balanced to unbalanced (BTU) multilayer filtering magic-T (FMT) based on square substrate integrated waveguide (SIW) cavity is proposed in this letter. Degenerate TE₂₀₁ and TE₂₀₃ modes are exploited to realize the requested dual-band filtering responses and in-/out-of-phase characteristic. The requested differential-mode (DM) transmission, common-mode (CM) suppression, and port-to-port isolation can be obtained by appropriately placing the input&#x2013;output ports and coupling slots. Multiple transmission zeros (TZs) are introduced to improve frequency selectivity, and the center frequencies (CFs) can be flexibly controlled to some extent. For validation, a prototype dual-band BTU FMT operating at 11.6 and 19.1 GHz is fabricated and measured. It can be obtained that the simulated results are in good agreement with the measured ones.

A 45° Polarized Wideband and Wide-Coverage Patch Antenna Array for Millimeter-Wave Communication

A 45° polarized millimeter-wave (mmWave) patch antenna and arrays with wide impedance and gain bandwidth are proposed in this article. The compact antenna consists of stacked patches, one substrate integrated waveguide (SIW) back cavity, one SIW square cavity, and a feeding line. The patches and the SIW back cavity rotate 45° with respect to the SIW square cavity. For the antenna, the −10 dB impedance bandwidth is from 22.31 to 29.65 GHz, and the peak gain is greater than 5 dBi in the bandwidth from 22 to 30.5 GHz. Based on the proposed antenna, a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1\times16$ </tex-math></inline-formula> linear array is designed, fabricated, and measured. According to the experimental results, all antenna elements can realize the −10 dB impedance bandwidth from 21.7 to 27 GHz. Within 3 dB gain fluctuation, the scanning coverage of the linear array can achieve 116° in the frequency band from 22 to 26 GHz and 110° at 27 GHz. Then, an <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$8\times 8$ </tex-math></inline-formula> planar array with wide bandwidth and wide scanning coverage is proposed. The reflection coefficient can achieve less than −10 dB from 21.82 to 27.22 GHz. The main beam of the radiation pattern can be widely spatially scanned. In the bandwidth from 22 to 26 GHz, the scanning coverage within 3 dB gain fluctuation can achieve 107°. Also, at 27 GHz, the coverage can achieve 90°. Due to the outstanding performance, reliable multilayer printed circuit board (PCB) fabrication technology, and easy integration with circuits, the proposed antenna and arrays are good candidates for the fifth-generation (5G) mmWave communication systems, satellite communication systems, and so on.

Low-Profile Dual-Band Filtering Antenna With a Shared SIW Cavity

An integrated low-profile dual-band filtering antenna is proposed in this letter. By reshaping a square substrate integrated waveguide (SIW) cavity, diagonal TE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">102</sub> and TE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">201</sub> modes could be excited at two different bands. Two pairs of quarter-wavelength patches serve as the radiators in conjunction with the reshaped SIW cavity. The coupling between the cavity and patches is realized by sparse vias. By this coupling method, the original dual-mode filtering response of SIW cavity could be well maintained. A novel folded structure was proposed to reduce the aperture size achieving unsplit radiation beams for both low and high bands. With this novel configuration, the antenna radiation and filtering performance are greatly improved. A prototype has been fabricated and measured. Measured results agree well with the simulation, demonstrating good performance in terms of dual-band filtering, out-of-band rejection, radiation efficiency, and gain at two bands.

Compact Square Substrate Integrated Waveguide Filtering Power Divider With Wideband Isolation

In this letter, a new compact filtering power divider (FPD) on the square substrate integrated waveguide (SIW) with wideband isolation is proposed. As the isolation network is embedded in a square SIW cavity, good in-band isolation, compact structure, and low insertion loss can be simultaneously attained. The proposed FPD consists of the coplanar waveguide feeding line of Port 1, the capacitor, a resistor, and the square SIW cavity. TE101, TE201, and slot-line modes can realize third-order filtering response. Center frequency (f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> ) and bandwidth of the filtering response can be independently adjusted. In order to achieve out-of-band isolation, Port 2/3 is placed in the specific position to suppress the high-order modes according to the electric-field distributions of these modes. Finally, a prototype with in-band return loss of 20 dB across 5.59-6.4 GHz is designed at 5.99 GHz. The bandwidths of isolation higher than 21 dB and upper stopband attenuation higher than 20 dB are extended to 2.79f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> and 2.83f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> , respectively.

Compact wideband SIW cavity‐backed slot antenna using triple resonance and hybrid mode

A compact and wideband slot antenna backed by a square substrate integrated waveguide (SIW) cavity is presented. By exciting the dual-slotted SIW cavity with an offset coaxial feed, a transverse electric (TE)110 resonant mode along with two hybrid modes as combinations of TE110 and TE120 resonances can be generated within a close range. The triple resonances contribute to producing a wideband response while maintaining a compact antenna structure. An antenna prototype with a total size of 0.49λ 0 × 0.49λ 0 × 0.16λ 0 is manufactured and experimentally tested. Measures results show that an operating band of about 33.0% is obtained. Meanwhile, it also exhibits stable unidirectional patterns and moderate gains over the whole band.

Design of a compact orthogonal fed self‐diplexing bowtie‐ring slot antenna based on substrate integrated waveguide

In this article, a novel design of compact cavity-backed slot antenna based on substrate integrated waveguide (SIW) technology is presented for dual-frequency communication services. A single layer printed circuit board is applied to implement the proposed antenna. The bowtie-ring slot engraved on the SIW square cavity is excited using two orthogonal microstrip feed lines to operate at two distinct frequencies (6.62 GHz and 11.18 GHz). The proposed antenna allows each of these frequencies to be designed independently. A prototype of the proposed cavity-backed antenna that radiates at both 6.62 GHz and 11.18 GHz is fabricated and measured. The port isolation better than 29.3 dB is achieved by utilizing the transmission zeros (TZs), which are produced due to the orthogonal feed lines, TE110 mode and coupling between the TE120 and TE210 modes. The measured peak gains of the proposed diplexing antenna are 5.77 dBi and 5.81 dBi at lower and upper resonating frequencies, respectively. The proposed dual-frequency antenna exhibits the front-to-back-ratio (FTBR) and cross-polarization level greater than 26 dB and 21 dB, respectively, at both resonating frequencies.

Compact Quarter-Mode Substrate-Integrated Waveguide Dual-Frequency Millimeter-Wave Antenna Array for 5G Applications

A compact linearly polarized quarter-mode substrate-integrated waveguide (QMSIW) dual-frequency millimeter-wave antenna is presented in this letter. The antenna has two unequal-sized quarter-mode parts of two square substrate-integrated waveguide (SIW) cavities for two operating bands. Each quarter can be tuned independently. The two quarters are realized within one layer of substrate laminate and are placed in a back-to-back configuration, sharing the same row of metalized vias, which makes the structure very simple and compact. For the demonstration, a QMSIW dual-frequency antenna simultaneously operating at 28 and 38 GHz bands was designed for fifth-generation (5G) applications. Compared with a traditional full-mode SIW slot antenna, our element design merits in an antenna footprint miniaturization of 53.5%. A four-element corporate-fed antenna array was also designed, fabricated, and measured. Good agreement between the measured and simulated results is obtained. The measured peak antenna gains of 9.5 dBi and 11.0 dBi are obtained for the lower and upper bands, respectively.

Compact triple‐band filter with adjustable passbands on one substrate integrated waveguide square resonant cavity

AbstractA new compact triple‐band bandpass filter (BPF) with adjustable passbands based on only single substrate integrated waveguide (SIW) square resonant cavity is proposed in this letter. The first six resonant modes (the perturbed TE101′ mode and TE102′ mode, the perturbed TE201′ mode and TE202′ mode, the perturbed TE301′ mode and TE302′ mode) of the SIW cavity are controlled to constitute the three corresponding passbands by elaborately introducing metallic vias in the design. The three center frequencies and passband bandwidths can be effectively adjusted by only changing the location and sizes of these perturbations. For demonstration, a prototype SIW triple‐band BPF is designed, fabricated, and tested. Measured and simulated results are in good agreement, verifying the feasibility of the design concept.

A Differential Dual-Polarized SIW Cavity-Backed Slot Antenna

A compact, low-profile, and dual-polarized differential slot antenna with high isolation and high common-mode rejection is presented in this communication. The antenna is composed of a cross-shaped slot backed by a square substrate integrated waveguide (SIW) cavity. The two differential pairs of grounded coplanar waveguide are used for the excitation of the differential signals. These differential signals excite the diagonal TE120 and TE210 modes of the SIW cavity. The proposed antenna offers a differential gain of 7.4 dBi with a front-to-back ratio of 22 dB. A prototype of the designed differential antenna is fabricated as a proof of concept. The experimental results show that the proposed antenna is a good candidate for various ${X}$ -band applications.

A High-Sensitivity Microfluidic Sensor Based on a Substrate Integrated Waveguide Re-Entrant Cavity for Complex Permittivity Measurement of Liquids.

In this study, a novel non-invasive and contactless microwave sensor using a square substrate integrated waveguide (SIW) re-entrant cavity is proposed for complex permittivity measurement of chemical solutions. The working principle of this sensor is based on cavity perturbation technique, in which the resonant properties of cavity are utilized as signatures to extract the dielectric information of liquid under test (LUT). A winding microfluidic channel is designed and embedded in the gap region of the cavity to obtain a strong interaction between the induced electric field and LUT, thus achieving a high sensitivity. Also, a mathematical predictive model which quantitatively associates the resonant properties of the sensor with the dielectric constant of LUT is developed through numerical analysis. Using this predictive model, quick and accurate extraction of the complex permittivity of LUT can be easily realized. The performance of this sensor is then experimentally validated by four pure chemicals (hexane, ethyl acetate, DMSO and water) together with a set of acetone/water mixtures in various concentrations. Experimental results demonstrate that the designed sensor is capable of characterizing the complex permittivities of various liquids with an accuracy of higher than 96.76% (compared with the theoretical values obtained by Debye relaxation equations), and it is also available for quantifying the concentration ratio of a given binary mixture.

Novel rat‐race coupler of arbitrary power division design using resonant substrate integrated waveguide cavity

AbstractThe contribution of this letter is to propose a novel rat‐race hybrid coupler of arbitrary power division design. The rat‐race coupler's arbitrary power division design is approached by using a resonant square substrate‐integrated waveguide (SIW) cavity. The employed SIW cavity is operated under the resonance of the combined TE102 and TE201 modes. Due to the nature of the square cavity, these two modes are termed degenerate modes which possess the same resonance frequencies but exhibit distinct field distributions. Theoretically, the cavity can be excited by an arbitrary combination of these two degenerate modes, and each of the modes' power is solitarily extracted by an SMA probe located at an adequate position. The microstrip together with the perpendicularly oriented slot are used to resonate the cavity with a designated combination of the degenerate modes. Sample experiments are conducted on 3 dB and 10 dB coupling designs with the circuits' performance evaluated by the coupling precision, isolations, and phase imbalances.

Linearly Polarized and Circularly Polarized Wideband Dipole Antennas With Reconfigurable Beam Direction

Linearly polarized (LP) and circularly polarized (CP) dipole antennas with switchable beams are presented. The beam-switchable reconfigurability is realized by electronically controlling the state of switches on the side apertures of a square substrate integrated waveguide (SIW). Four wide dipoles are loaded in front of the four apertures. To generate one desired unidirectional radiation beam, the corresponding aperture is switched ON, which excites the corresponding dipole. Meanwhile, the other three apertures are switched off and perform as electric walls in the SIW. In this way, the other three dipoles work as reflectors of the excited dipole. Wide bandwidths and good directional radiation patterns can be obtained. Two fully functional LP and CP antenna prototypes with more than 47% bandwidths are developed and tested. The measurement result demonstrates antennas with measured gains of approximately 4.5 dBi and radiation efficiencies of approximately 80% over the operating band. Owing to the symmetrical antenna structures, the two designs are capable of switching the radiation beam at every 90° in the azimuth plane with identical patterns. In addition, the proposed designs possess compact antenna sizes, i.e., $0.51\lambda _{0}\times 0.51\lambda _{0}\times 0.39\lambda _{0}$ for the LP antenna and $0.95\lambda _{0}\times 0.95\lambda _{0}\times 0.46\lambda _{0}$ for the CP antenna, where $\lambda _{0}$ represents the free-space wavelength at the center frequency of 2.2 GHz.

Novel Substrate Integrated Waveguide Filtering Crossover Using Orthogonal Degenerate Modes

A novel substrate integrated waveguide (SIW) filtering crossover is presented based on the orthogonal degenerate TE201 and TE102 modes in SIW square cavities. By arranging the feeding ports and coupling windows at the cavity center, excellent transmission and isolation responses can be achieved successfully. In addition, the bandwidth of the crossover can be easily controlled using the well-established coupling matrix synthesis method, and the maximum bandwidth is determined by the acceptable isolation levels. A prototype operating at 20 GHz was designed and fabricated to verify this concept, and the measured results are in excellent agreement with the simulation results.

Ultrawideband SIW-Fed Lens Antenna

An ultrawideband K-/Ka-band lens antenna for future satellite communication systems is presented. It consists of an extended hemispherical dielectric lens that is fed by a square substrate-integrated waveguide (SIW) and therefore offers a low-cost alternative to horn antennas. The design procedure is explained, and the antenna performance is presented. A sophisticated test fixture is developed to excite the square SIW. The measured ${S}$ -parameters and far-field patterns validate the concept and exhibit more than 13 GHz bandwidth.