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This brief presents a new wide stopband substrate integrated waveguide (SIW) filter with multimode suppression based on a multilayer structure. All spurious modes below TE404 of a multilayer SIW filter operating in TE101 could be effectively suppressed by moving the intercoupling slots away from the sidewall by about 1/6 of the cavity’s width. To verify it, two prototypes are designed, fabricated, and measured. The results show a small size and a wide stopband of up to 4.03 ${f} _{0}$ (${f} _{0}$ is the filter’s center frequency) with a simple design. The proposed technology could be efficient for developing wide stopband SIW filters in wireless/microwave circuits and systems. [ABSTRACT FROM AUTHOR]

In this work, we propose and demonstrate an integrated dual linearly polarized cavity-backed patch antenna, which is excited by a concurrent dual-mode substrate integrated waveguide (SIW) structure. For the first time, we have exploited the TE10 and TE20 modes of a traveling wave in a dual-mode SIW configuration to excite the horizontal and vertical polarizations of the patch antenna. The proposed methodology yields a low-profile structure with a high interport isolation thanks to the inherent symmetry of the structure. Measurement results indicate an isolation performing better than 42 dB over a 600 MHz impedance bandwidth of the antenna. Moreover, a methodology is developed to implement transitions from the dual-mode SIW to the two different TEM transmission lines for separate but concurrent excitations of the device. Detailed field and impedance analyses are presented to explain the operation principle of the proposed antenna, which are supported by an excellent agreement between the obtained measurement and simulation results. [ABSTRACT FROM AUTHOR]

An approach for implementing compact multichannel substrate integrated waveguide (SIW) diplexers is presented based on orthogonal dual modes and split-type multiband responses. By coupling multiple TE101-based bandstop single-mode cavities to TE201/TE102-based bandpass dual-mode cavities, one or both of the two passbands constructed by TE201 and TE102 modes could be split into multiple subpassbands. Additionally, by arranging two output ports at central positions of adjacent sides of the last cascaded dual-mode cavity, isolations between these two output ports can be achieved and then further improved by tiny offset locations benefitting from the orthogonal characteristics of TE201 and TE102 modes. Three experimental prototypes, including a 1 + 2 type tri-channel SIW diplexer, a 3 + 1 type quad-channel SIW diplexer, and a 2 + 2 type quad-channel SIW diplexer, are synthesized, designed, fabricated, and measured to demonstrate and validate the proposed mode-collaborative design concepts. [ABSTRACT FROM AUTHOR]

Miniaturized substrate integrated waveguide (SIW) diplexers with widely separated channel passbands using common half-mode dual-mode SIW junction-cavities are presented and developed for 5G sub-6 GHz communications and wireless systems. With this kind of half-mode dual-mode junction-cavities to eliminate the conventional T-junctions and also to produce one transmission pole in each channel passband, significant circuit miniaturization can be achieved for SIW diplexers. Additionally, by exploiting the first dual modes in the half-mode SIW junction-cavities, flexibly allocated fractional bandwidths (FBWs) for the two channels can be realized through FBW design graphs, large frequency ratios can also be accommodated, which is difficult to implement using the whole-mode SIW cavity scheme due to spurious problems. Two compact SIW diplexers with large frequency ratios are synthesized, designed, fabricated, and measured for demonstration, including a third-order direct-coupled prototype centered at 3.5 and 5.0 GHz with a frequency ratio of 1.43 based on the TE101/TE301 half-mode dual-mode junction-cavity and a fourth-order cross-coupled prototype centered at 3.5 and 5.5 GHz with a frequency ratio of 1.57 based on the TE101/TE102 half-mode dual-mode junction-cavity. [ABSTRACT FROM AUTHOR]

This article proposes and presents a fully planar endfire circularly polarized (CP) antenna with mingled three-layer substrates. It consists of a unidirectional dielectric radiator (UDR) and an antipodal linearly tapered slot antenna (ALTSA) surrounded by a UDR. The ALTSA is fed by a substrate integrated waveguide (SIW) on a thin substrate of $0.05\lambda _{0}$ , which can easily be integrated with RF subsystems. The UDR is fed by the ALTSA, which enables the UDR to enhance the original vertically polarized radiation rather than the horizontally polarized radiation from the ALTSA. Due to the polarization selectivity enhancement, an endfire CP antenna with a very thin substrate is created. An experimental prototype of the proposed antenna has been studied, designed, and measured. The measured impedance bandwidth of −10 dB covers a broadband of 29.7 GHz from 26.1 to 55.8 GHz, and the 3 dB AR bandwidth is 19.7 GHz ranging from 25.3 to 45 GHz. The measured gain is over 9 dBic from 27.8 GHz to over 32 GHz. A good performance with a small size of only $2.57\lambda _{0} \times 0.78\lambda _{0} \times 0.33\lambda _{0}$ , including the CPW-SIW transition, makes it an attractive option in the development of high gain planar endfire CP antennas and arrays for 5G and B5G applications. [ABSTRACT FROM AUTHOR]

This work devises and investigates a Fabry–Perot-styled planar unidirectional dielectric radiator (UDR) antenna fed by a thin embedded slotted substrate integrated waveguide (SIW). The proposed UDR-SIW antenna consists of two identical dielectric substrates and an embedded feeding SIW between the two dielectric substrates. This diligently mingled multilayer structure makes it possible to not only use the thick dielectric substrates to narrow down the E-plane pattern for symmetrical radiation but also facilitate its integration with RF subsystems through the thin embedded feeding SIW, thereby achieving a compact size and an effective excitation. An experimental prototype of the URD-SIW antenna is simulated, fabricated, and measured. It features a size of $2.96\lambda _{0}\,^\ast \,0.65\lambda _{0}\,^\ast \,0.33\lambda _{0}$ and a nearly symmetrical endfire radiation pattern. The antenna presents a measured impedance bandwidth of 9.4% from 26.3 to 28.9 GHz, a gain varied from 8.2 to 10.3 dBi, which is over 10 dBi from 27.7 to 28.4 GHz, and a front to back ratio over 20 dB from 27.5 to 29 GHz. The proposed UDR-SIW antenna has vertically polarized radiation pattern that is different from a conventional UDR antenna; thus, it is an appropriate candidate to replace the SIW H-plane horn in certain applications. [ABSTRACT FROM AUTHOR]

The concept and feasibility of deploying higher-order space harmonics (HSHs) in 1-D periodic leaky-wave antennas (1-D periodic LWAs) is proposed, studied, analyzed, and demonstrated in this article. This can lead to the creation of multiband multibeam antennas (MBMBAs) with the capability of wide scanning ranges. To show the proposed concept, the excitation and flexibility of odd (n ε [−1, −3]) and even (n ε [−2, −4]) HSHs based on the analysis of a Brillouin diagram along with the effect of unit-cell geometrical structures of substrate integrated waveguide (SIW) for different propagating media are investigated. The proposed analysis is experimentally validated by prototyping and measuring a 1-D periodic LWA in SIW technology in which two HSHs (n ε [−1, −2]) are utilized for achieving a dual-band multibeam LWA with wide scanning range capability. In addition, a triple-band multibeam LWA design based on this concept is also analyzed and demonstrated where we take advantage of the characteristics of four HSHs (n ε [−1, −2, −3, −4]). Furthermore, the band edge issue of different stop-bands of HSH is also examined, and a method is proposed and used to address this issue where we use a quarter wavelength technique to overcome the matching problem at different frequencies related to different stop-bands of various HSHs (n ε [−1, −2, −3, −4]). Another design of a SIW-based 1-D periodic LWA is also discussed to extend and generalize the proposed concept in solving the mismatch issues of HSHs focusing on broadside radiation of the n = −2 space harmonic. The measured results are found to agree very well with their simulation and analysis counterparts. [ABSTRACT FROM AUTHOR]

In this work, directly perforated substrate integrated waveguides (SIWs) in the form of periodic air holes are studied with a focus on the electromagnetic shielding effect by examining its bandpass and stopband filtering characteristics. Two different configurations of the air-filled holes are considered for this electromagnetic bandgap structure, which are called shielded and unshielded cases. In both the scenarios, the relationship between the center frequency of the bandgap and the structural material and geometric parameters is established and used for the bandgap investigation. In addition, the impact that the shielding of the air-filled holes yields on the loss of the structure is systematically examined. Finally, equivalent circuits for both the cases are formulated and experimentally verified up to 30 GHz. [ABSTRACT FROM AUTHOR]

Loading effects of radiating discontinuities have been explored to increase the phase constant’ frequency sensitivity of leaky-wave antennas (LWAs), based on which a quasi-uniform transversely slotted substrate integrated waveguide LWA featuring rapid beam-scanning and its hexagonal array have been proposed and investigated for millimeter-wave applications. The design concept is simply based on the use of a short period of unit cells and a long transverse slot with a sharp inductive reactance, and it has been theoretically elaborated and effectively validated by both full-wave and circuit-based simulations. A taper design with −25 dB Taylor amplitude distribution is implemented for the proposed LWA to have a low sidelobe radiation. For practical system applications, a hexagonal array consisting of six proposed LWAs is developed to provide an omnidirectional coverage in the azimuth plane while remaining the rapid frequency-driven beam-scanning in the elevation plane. Both the measured and simulated results are in an acceptable agreement with respect to the LWA block and the associated hexagonal array in terms of circuit and radiation performances. The proposed antenna will be a good candidate to be applied for prospective millimeter-wave systems such as autonomous driving and flying. [ABSTRACT FROM AUTHOR]

In this article, a class of mode composite transmission line called mode composite sandwich slot line (MCSSL) is proposed, studied, and demonstrated. The MCSSL is composed of two substrate integrated waveguides (SIWs) and a sandwiched quasi-slot line. Structural parts of the two SIWs inherently serve as the two conductors of the quasi-slot line. The SIW supports the TE10 fundamental mode propagation, whereas the quasi-TEM mode is supported by the quasi-slot line. Two types of transition structures are proposed in this article, which enable an easier integration of the studied MCSSL with other transmission lines. An MCSSL-based antenna is designed and fabricated to theoretically and experimentally demonstrate its advantages and feasibility. It has been shown that the MCSSL features the physical and electrical characteristics of a joint structure (or structure sharing) in connection with a mode composite with planar structures, and it can find applications in broadband and multiband circuits and antenna developments. [ABSTRACT FROM AUTHOR]

A wideband high-efficiency millimeter-wave (mm-wave) circularly polarized (CP) array which is constituted by novel planar substrate integrated waveguide (SIW)-fed S-dipoles is presented in this communication. The proposed mm-wave CP S-dipole consists of two rotational symmetric curved arms and is fed differentially through aperture coupling, which features simple configuration and excellent performance. Detailed analysis is given to explain the operating principles of this element. It is noted that superior element performance including a wide impedance bandwidth of 43%, a wide 3 dB axial ratio (AR) bandwidth of 36%, and 1 dB gain bandwidth of 38% is achieved by the planar SIW-fed S-dipole. By feeding 64 in-phase S-dipole elements through a full-corporate SIW feeding network, a planar wideband highly efficient mm-wave $8 \times 8$ CP array is realized. To verify the design concept, a prototype operating at Ka-band is fabricated and measured. The measurement results indicate that the proposed array achieves a wide overlapped bandwidth of 27.6%, a high antenna gain of 25.2 dBic, and a high aperture efficiency of 89.9%. Attributed to the planar and robust array structure as well as its excellent performance, the presented array is a good candidate for various mm-wave applications. [ABSTRACT FROM AUTHOR]

Ideally, the orthogonal port can be effective to eliminate the TE102/TE201 spurious passband of a fundamental substrate integrated waveguide (SIW) filter using the orthogonality. However, it was not feasible in practical applications because the orthogonality of TE102/TE201 is deteriorated by the orthogonal port. Here, we propose an approach to repair the orthogonality which makes the practical orthogonal port work as the ideal one and thereby avoid the TE102/TE201 spurious passband in an SIW filter. The repair is achieved using ports’ offset almost without affecting the fundamental passband. A guideline of using the proposed technique to design a wide stopband filter based on square SIW resonators is provided. Four SIW filters with three, four, five, and six resonators, respectively, are then experimented. The measured results agree with the expectations well. An empirical equation is finally given to initialize the critical ports’ offset to facilitate the design. Compared with counterparts, the proposed technique uses a much simpler design, obtains better performance, and can be more easily implemented in practical applications. [ABSTRACT FROM AUTHOR]

A longitudinally slotted TE20-mode-driven substrate integrated waveguide (SIW) leaky-wave antenna (LWA) with low side-lobe and low cross-polarization is proposed and presented for millimeter-wave applications. In this work, a pair of long slots is etched symmetrically on the top broadside of an SIW working in the TE20 mode. With the odd-symmetry of TE20 mode field distribution, the even-symmetrically etched long slots paired along the centerline of the SIW have aperture fields of the same direction, thereby resulting in a constructive superposition of radiation. Thanks to these long slots with a meandering shape that is designed according to a specific aperture amplitude illumination (e.g., −35 dB Taylor line-source distribution) and their even-symmetry with respect to the centerline of the SIW, both low side-lobe and low cross-polarization are simultaneously achieved. Two meandering schemes with respect to the centerline of the SIW are adopted and, thus, two types of the designed LWAs are developed. For experimental prototypes of the proposed LWAs, a 3 dB directional coupler and a 90° phase shifter are combined together to excite the desired TE20 mode of the SIW. The proposed two types of LWAs are modeled, simulated, and fabricated. Both the simulated and measured results are in a good agreement. [ABSTRACT FROM AUTHOR]

In this article, we first discover and investigate the pattern diversity of electromagnetic fields within an antisymmetrically biased twin-ferrite-loaded substrate integrated waveguide (SIW) structure. A special scenario is identified in which two separate guided-wave channels can be created exclusively for each direction of wave propagation within the same ferrite-loaded SIW body. A detailed theoretical foundation is formulated and presented to develop the so-called “nonreciprocally dual-channelized waveguide (NDW)” in this article. Next, this NDW structure is used to devise and demonstrate a fully integrated fundamental nonreciprocal building element called “nonreciprocal mode-converting waveguide (NRMCW),” which manifests modal nonreciprocity. In other words, this ferrite waveguide interchangeably converts TE10 and TE20 modes within the SIW, only in one direction. A fundamental approach to design such a unidirectional mode-converting device is proposed through unsymmetrical perturbation loading inside an NDW. Furthermore, a class of four-port circulator is devised and demonstrated for the first time, in which the operation mechanism is based on the one-way mode conversion. The measurement results of the proposed circulator are in agreement with those of the simulation and mathematical models, thereby validating the theoretical foundation and the concept of “NRMCW. ” [ABSTRACT FROM AUTHOR]

In this work, a class of antisymmetrically biased ferrite-loaded substrate integrated waveguides (SIWs) is studied in detail along with the definition of three main regions of operation. With focus on one of those newly defined regions, a nonreciprocal mode waveguide (NRMW) is introduced for the first time and its related design procedure is explained and illustrated. Furthermore, a fundamental approach is proposed and devised for developing a fully integrated structure called nonreciprocal mode-converting waveguide (NRMCW). This ferrite-based device is capable of effectively converting TE10 mode into TE20 mode only in one direction, thereby suggesting that the original mode be preserved in the reverse direction. In other words, the mode conversion, in this case, is unidirectional, which has never been reported so far. To substantiate the usefulness of the proposed structure and physical mechanism, a class of circulators is designed, fabricated, and demonstrated on the basis of the introduced NRMCW, thus validating the formulated theory of NRMCW in this work and providing an application example of such devices. Both theoretical and experimental results are presented in support of the claims made in this work regarding the proposed circuit concept and its related foundation work. [ABSTRACT FROM AUTHOR]

This letter presents a possibility of increasing the radiation efficiency of double-sided leaky-wave antennas (LWAs) by using the substrate integrated slab waveguide (SISW). The idea originates from the fact that double-sided LWAs usually operate on the second mode, and the attenuation constant of the second mode in the SISW is smaller than that in the standard substrate integrated waveguide (SIW). This inherently leads to an increase of antenna radiation efficiency, as less power is dissipated by the traveling wave. In order to prove this concept, two antennas have been designed with the same characteristics (central frequency of 28 GHz, pointing angle of 50°, and beamwidth of 10°), one based on SIW and the other based on SISW. Our experimental verification yields 64% radiation efficiency for the SIW LWA and 80% radiation efficiency for the SISW LWA, thus proving the theoretical and simulated predictions. [ABSTRACT FROM AUTHOR]

Enabling the dual-polarization feature in microwave components is proposed and demonstrated based on polarization-selective coupling (PSC). The PSC structure consists of two waveguides which are fused together in parallel. When one of the waveguides is excited by dually polarized wave, the vertical polarization remains in the excited waveguide while the horizontal polarization is fully coupled to the other one. The six-port junction is the fundamental module for developing interferometric transceivers. This junction is presented in this paper in a new form. In the new form, the six-port junction applies its functionality on two orthogonal polarizations simultaneously. This allows the implementation of a polarization-inclusive remote sensing application. The dually polarized six-port junction is invented by adding the dually polarized feature to each of its constituent components, namely, the power dividers, the hybrid 3-dB couplers, and the circularly bent phase shifters. These components are analytically studied and reinvented to be dually polarized using the aforementioned PSC. The dually polarized six-port junction is prototyped and measured. The simulated and measured results are found to be in a good agreement. [ABSTRACT FROM AUTHOR]

This paper presents an E-band substrate integrated waveguide (SIW) dual-polarized antenna system, which consists of an orthomode transducer (OMT) and a dual-polarized horn antenna. On the basis of a two-layer substrate design, the function of OMT is realized by utilizing an SIW section to excite TE10 mode for the vertical polarization, a quasi-coaxial stripline to excite quasi-TEM mode for the horizontal polarization. And also, a slot line transition is placed at the common port of the two structures for impedance matching with the ridge SIW dual-polarized horn antenna. In this way, the dual-polarized horn antenna is designed with an exponential ridge structure simultaneously for better impedance matching and higher efficiency of the antenna. To verify the functionality of the proposed integrated OMT-antenna structure, an experimental prototype is fabricated and measured, and a good agreement is found between its simulation and measured results. Over the frequency range of 83–87 GHz, return loss better than 10 dB at all ports and cross-polarization less than −25 dB are obtained. The maximum antenna gain is about 14 dBi for the horizontal polarization and 15.2 dBi for the vertical polarization. It is believed that the proposed OMT-antenna design is suitable for ultrahigh capacity millimeter-wave backhaul applications in future wireless communication systems. [ABSTRACT FROM PUBLISHER]

In this paper, an inductor-loaded slow-wave substrate integrated waveguide (SIW) is presented and studied. The proposed structure features a number of unique propagation properties. First of all, the inductance value imposed along the transverse direction will affect the phase velocity and cutoff frequency of the waveguide simultaneously. Second, the inductance value in the longitudinal propagating direction will only affect the phase velocity but make no difference on the cutoff frequency. Based on the aforementioned characteristics, the size of structure could be controlled by separately tuning the loaded inductor along the transverse direction and longitudinal propagating direction. More importantly, it is released on the interrelationship between the phase velocity and cutoff frequency in the proposed guiding-wave structure. The feature will be beneficial to the design of leaky-wave antenna and matching circuits for SIW circuits. Finally, experimental results demonstrate that with the increasing of loaded inductance, a reduction of 35% in cutoff frequency is achieved compared with the conventional SIW counterpart. The phase velocity is also reduced by 35% with the increasing of the loaded inductor, which contributes to a miniaturized longitudinal dimension for a given electrical length. [ABSTRACT FROM AUTHOR]

This paper proposes a novel dual-mode substrate integrated waveguide (SIW) filter technique. Based on the conventional dual-mode SIW structure, further investigation is performed. Multiple transmission zeros can be obtained at one side or both sides of the passband for an SIW cavity. Therefore, flexible design and high performance response can be available for dual-mode SIW filter. A dual-mode SIW bandpass filter with quasi-elliptic response and a dual-mode SIW diplexer with asymmetric channel response are simulated, fabricated, and measured to demonstrate and verify the novel property. [ABSTRACT FROM PUBLISHER]

In this paper, mode composite waveguide (MCW) is proposed, which consists of inner and outer wave-guiding duo structures. The outer structure acts as a rectangular coaxial line suitable for lower frequency operation for its compact size, while the inner structure works as a rectangular waveguide suitable for higher frequency operation thanks to its simple structure and low loss. The MCW can propagate signals in the inner waveguide with TE10 mode and/or the outer waveguide with TEM mode depending on frequency to achieve optimal performance for both low- and high-frequency operations. In this paper, the fundamental waveguide parameters and higher order modes of the duo waveguides are examined. The proposed MCW prototypes are fabricated on a triple-layer PCB structure using the emerging substrate integration techniques. The MCW is fabricated and measured through the proposed microstrip line to the inner and outer waveguide transitions, and an MCW simultaneous feeding circuit is also presented. For this simultaneous feeding circuit, the good matching is achieved from 7.5 to 10.5 GHz for the low-frequency operation and from 25 to 39 GHz for the high-frequency operation, respectively. [ABSTRACT FROM PUBLISHER]

A class of slow-wave substrate integrated waveguide (SIW) structures patterned with microstrip polyline is presented, theoretically studied, and experimentally validated, which demonstrates some interesting slow-wave propagation effects. The slow-wave SIW (SW-SIW) enables the size reduction of a physically large circuit without sacrificing its performance. A size reduction of 40% of the lateral dimension is achieved with reference to that of the conventional SIW counterpart at the same cutoff frequency. Meanwhile, the phase velocity of the waveguide is also reduced by 40%, resulting in a smaller longitudinal dimension for a given electrical length. Both lateral and longitudinal effects give rise to a total size reduction, largely extending the operation range of SIW structures in the low-frequency region, which has often been restrained by a physical dimension-related cutoff frequency. Also, a transmission line-based two-dimensional (2-D) equivalent-circuit model is proposed and deployed for the modeling and analysis of the slow-wave mechanism. The results from the equivalent-circuit model agrees very well with that from the full-wave simulations. Furthermore, a broadband microstrip to SW-SIW taper with good return loss is designed for measurement verification. Using the proposed SW-SIW structure, the size of conventional SIW-based microwave circuits such as power splitters, couplers, and filters can be further reduced in addition to the existing size-reduction techniques. [ABSTRACT FROM AUTHOR]

This letter proposes a novel in-line ports dual-mode substrate integrated waveguide (SIW) filter. By virtue of additional perturbation vias, for the first time, in-line ports can also realize flexible and high-performance responses in dual-mode SIW filter as good as the commonly used orthogonal/angled ports. With flexible ports configuration but without deterioration of flexibility or performance, dual-mode SIW filter can be more suitable for system circuits. [ABSTRACT FROM AUTHOR]

This paper proposes and presents a class of substrate integrated waveguide (SIW) power dividers/combiners based on a modified Wilkinson architecture. The proposed design consists of a ring-type circuit of \(1.5~\lambda _{g}\) length with three waveguide ports. Impedance variation without affecting cutoff frequency and integration of isolation resistance are the two major limitations in connection with the design of SIW Wilkinson structures. Central ring part with different thickness ensures different impedance in the first proposed scheme while the half-mode SIW in the second option. As for the second limitation, the optimal configuration of integrating the isolation resistance is studied. A version without resistance is also examined using a broad-wall series slot. To validate the proposed concept, a bilayered circuit with standard Printed circuit board prototype was fabricated and measured. A table summarizing performances of all the proposed circuits shows a bandwidth of around 25% at the 10 dB reference. A negligible additional insertion loss is observed. The proposed design techniques are found useful at millimeter-wave frequencies where reduced physical dimensions make a circuit configuration suitable for low-cost implementation. This concept is also valid for rectangular waveguide counterparts. [ABSTRACT FROM AUTHOR]

A novel balanced filter realized in the form of substrate integrated waveguide (SIW) is proposed and studied in this paper. Based on the inherently horizontal and vertical symmetry of the SIW, this filter presents inherently high-performance balanced property with advantages of no identical pair requirement, being free from the limitation of symmetrical topology, easy and flexible design, high common-mode (CM) suppression, and robust CM suppression when comparing with conventional counterparts. Several prototypes are designed, fabricated, and measured to verify the expected properties. [ABSTRACT FROM AUTHOR]

A Butler matrix-fed two-dimensional (2-D) scan linearly polarized 2 \times 2 microstrip ring antenna array (MRAA) is proposed and validated in low-cost substrate integrated waveguide (SIW) technology for Ka-band applications. The highly efficient, compact, and passive beam forming network (BFN) consists of SIW cruciform couplers as coupling unit, and its special topology is well adapted for feeding planar arrays. The wideband and high radiation efficiency antenna elements are aperture-coupled through slots etched on the top of a high permittivity SIW feed substrate. Such four antenna elements are used to construct 2 ~\times 2 MRAA and to form four fixed beams, one in each quadrant at an elevation angle of 20^\circ from the broad side array axis. A triangular grid arrangement is chosen to avoid grating lobes in the visible space. A 50-\Omega grounded coplanar waveguide (GCPW) to SIW transition is used to avoid spurious input feed radiation loss. The array is measured to exhibit 3-dB beam width of 30^\circ in both of the orthogonal planes, radiation efficiency of 70% for each port, and stable radiation pattern bandwidth of 7.6% at 26.5 GHz. The physical size of the demonstrated 2 \times 2 array is 2.86\lambdao\times 2.86\lambdao\times 0.22\lambdao. [ABSTRACT FROM PUBLISHER]

A compact single-layer substrate integrated waveguide (SIW) monopulse network for Ku-band tracking system applications is investigated and demonstrated in this work. The feeding network and the monopulse comparator are integrated into a substrate with a structure size of 8.2\lambda0\times 9\lambda0 at center frequency while 32 output ports are welded perpendicularly for connecting active transmit/receive modules. The optimal design of a 3-dB coupler with metallic slots and phase shifter with dual steps is presented. The relative frequency bandwidth (\vert S11\vert, \vert S22\vert, and \vert S33\vert<10\ \ dB) of the network is 6%, in which the phase imbalance of all ports is less than 5.5° [root mean square (rms)], the power imbalance is about 0.5 dB (rms). The insertion losses are about 3–5 dB and the isolations between the three channels are all better than 25 dB. The good performances of this SIW-based monopulse network are validated by measurements, showing the advantages of low cost, light weight, easy fabrication, etc. It presents an excellent candidate for Ku-band tracking systems or up-band millimeter-wave systems. [ABSTRACT FROM PUBLISHER]

In this paper, a novel planar bandpass filter is proposed, designed, and implemented with a hybrid structure of substrate integrated waveguide (SIW) and coplanar waveguide (CPW), which has the advantages of good passband and stopband performance inherited from SIW and miniaturized size accompanying with the CPW. Additional design flexibility is introduced by the hybrid structure for efficiently controlling the mixed electric and magnetic coupling, and then planar bandpass filters with controllable transmission zeros and quasi-elliptic response can be achieved. Several prototypes with single and dual SIW cavities are fabricated. The measured results verified the performance of the proposed planar bandpass filters, such as low passband insertion loss, sharp roll-off characteristics at transition band, etc. [ABSTRACT FROM AUTHOR]

In this paper, a substrate integrated waveguide power divider is proposed on the basis of a recombinant topology that provides in-phase power division with an odd or even number of branches. The aim is to generate different types of power distribution to control sidelobe level in the antenna array. In this study, several power-divider designs were designed to demonstrate and validate the design approach. Each design consists of a cascade of steps and nfurcations, which were initially designed based on sinusoidal basis functions. These designs were simulated using the High Frequency Structure Simulator (HFSS) and shown to closely match the performance estimated using the basis functions. A substrate with thickness of 0.508 mm and dielectric constant of 2.94 is used. A three-way power divider with a binominal output taper is optimized and fabricated, showing good results in the bandwidth of interest from 72 to 81 GHz. Measurement results for a 3 \times 8 slot array antenna designed in conjunction with the proposed feeding network are presented and discussed. This design can be used to build up rectangular waveguide structures. The novel structure is expected to be useful in building sub-arrays of antenna in the development of millimeter-wave automotive radar systems. [ABSTRACT FROM PUBLISHER]

For emerging millimeter-wave wireless applications at W- and E-bands, active components including LNA and power amplifier are preferably fabricated or surface-mounted on the materials of a high dielectric constant (such as CMOS and MHMIC). On the other hand, antennas or radiating elements should be developed on relatively low-dielectric constant substrates for the enhancement of gain and bandwidth. Therefore, the development of a wideband transition from high-to-low dielectric constant substrates becomes necessary because the use of wire bonding schemes brings up packaging, interconnects, and manufacturing problems at millimeter-wave frequencies. This paper presents a novel integrated wideband transition of substrate integrated waveguide (SIW) on high-to-low dielectric constant substrates. The transition is made of a single-layer structure, which consists of a tapered high-dielectric constant substrate that connects two SIWs. Because of the waveguide-based structure of the transition, it has a self-shielded configuration, and its interference is minimum. Simulated and measured results show that the bandwidth of the proposed transition covers almost the entire W- and E-bands with low insertion loss. [ABSTRACT FROM AUTHOR]

The concept of substrated integrated waveguide (SIW)-fed horn and antipodal linearly tapered slot antenna (ALTSA) are jointly used to design a low-cost, high-gain, and efficient planar dielectric-loaded antenna for ultra-wideband gigabyte wireless services, which are demonstrated over E- and W-bands. SIW is used to feed the proposed antenna. To increase the gain of the antenna, a dielectric-loaded slab is used in front of the antenna and works as a dielectric guiding structure. The SIW feed, the proposed antenna, and the loaded dielectric are all integrated in a planar single layer substrate, resulting in low cost and easy fabrication. Low-cost printed circuit board (PCB) process is utilized to fabricate the antenna structure with rectangular and elliptical shaped loaded dielectrics. Measured bandwidth of the antenna covers both E- and W-bands (70–110 GHz). Measured gain of the single-element antenna is \14\pm \0.5 dBi, while the measured radiation efficiency of 84.23% is obtained at 80 GHz. Wideband SIW power dividers are used to form a 1\,\times\,4 array structure. Measured gain of the 1\,\times\,4 array antenna is \19\pm \1 dBi, while the measured radiation pattern and gain are almost constant within the wide bandwidth of the antenna. [ABSTRACT FROM AUTHOR]

A concept of simultaneous electric (E) and magnetic (H) 2-D tuning is presented, demonstrated, and applied for the first time through the theoretical and experimental studies of parameter-agile substrated integrated waveguide (SIW) devices. First of all, a two-dimensionally tuned SIW cavity is introduced as a building block. Considering only electric tuning with varactor diodes, no more than 1.3% of total tuning range is accomplished, while for simultaneous electric and magnetic tuning, it is extended to 7.9% with an unloaded Q factor of better than 130. Using 0.05–0.1-pF surface mount capacitors, a total tuning range of as much as 20% is experimentally achieved at 12 GHz. Another characteristic of significant interest is that the proposed 2-D tuning not only allows changing frequency, but also simultaneously optimizing other key parameters such as the return loss or unloaded Q factor. Second, the dual-tuned SIW cavity resonator is further accommodated to demonstrate parameter agile two-dimensionally tuned bandpass filter at 12 GHz. The proposed concept of 2-D tuning theoretically and experimentally demonstrates a simultaneous frequency and bandwidth tuning of bandpass filter. This filter can perform both frequency-tunable constant bandwidth, and constant-frequency variable-bandwidth operations. Third, a cavity backed slot antenna using the proposed dual tuning is demonstrated. The tuning not only achieves a higher frequency range, but the antenna return loss is optimized to improve the overall efficiency. [ABSTRACT FROM PUBLISHER]

This communication presents a low-cost 77-GHz switched-beam slot antenna array driven by a Butler matrix. In the proposed configuration, four broadband couplers are combined and crossovers are effectively avoided. In this case, the overall circuit and beamforming network losses are considerably reduced. A 4\,\times\,4 planar SIW Butler matrix is designed and demonstrated for integrated beamforming network applications, which exhibits about 7 degrees phase error and \pm 0.75~dB coupling imbalance over 11% bandwidth. This experimentally prototyped matrix is integrated with a four-array slot antenna on the same substrate. An alternating displacement of the slots in subsequent radiating waveguides is proposed to save the arrangement of the input ports and to achieve broadband performances. Measured radiation patterns are in good agreement with simulated counterparts over the proposed 77-GHz frequency range. [ABSTRACT FROM PUBLISHER]

A class of three-dimensional planar arrays in substrate integrated waveguide (SIW) technology is proposed, designed and demonstrated with 8 \times 16 elements at 35 GHz for millimeter-wave imaging radar system applications. Endfire element is generally chosen to ensure initial high gain and broadband characteristics for the array. Fermi-TSA (tapered slot antenna) structure is used as element to reduce the beamwidth. Corrugation is introduced to reduce the resulting antenna physical width without degradation of performance. The achieved measured gain in our demonstration is about 18.4 dBi. A taper shaped air gap in the center is created to reduce the coupling between two adjacent elements. An SIW H-to-E-plane vertical interconnect is proposed in this three-dimensional architecture and optimized to connect eight 1 \times 16 planar array sheets to the 1 \times 8 final network. The overall architecture is exclusively fabricated by the conventional PCB process. Thus, the developed SIW feeder leads to a significant reduction in both weight and cost, compared to the metallic waveguide-based counterpart. A complete antenna structure is designed and fabricated. The planar array ensures a gain of 27 dBi with low SLL of 26 dB and beamwidth as narrow as 5.15 degrees in the E-plane and 6.20 degrees in the 45^\circ-plane. [ABSTRACT FROM PUBLISHER]

This paper presents and demonstrates a class of 3-D integration platforms of substrate-integrated waveguide (SIW). The proposed right angle E-plane corner based on SIW technology enables the implementation of various 3-D architectures of planar circuits with the printed circuit board and other similar processes. This design scheme brings up attractive advantages in terms of cost, flexibility, and integration. Two circuit prototypes with both 0- and 45^\circ vertical rotated arms are demonstrated. The straight version of the prototypes shows 0.5 dB of insertion loss from 30 to 40 GHz, while the rotated version gives 0.7 dB over the same frequency range. With this H-to-E-plane interconnect, a T-junction is studied and designed. Simulated results show 20-dB return loss over 19.25% of bandwidth. Measured results suggest an excellent performance within the experimental frequency range of 32–37.4 GHz, with 10-dB return loss and less than \pm4^\circ phase imbalance. An optimized wideband magic-T structure is demonstrated and fabricated. Both simulated and measured results show a very promising performance with very good isolation and power equality. With two 45^\circ vertical rotated arm bends, two antennas are used to build up a dual polarization system. An isolation of 20 dB is shown over 32–40 GHz and the radiation patterns of the antenna are also given. [ABSTRACT FROM PUBLISHER]

Due to the low atmospheric absorption over W-band, numerous applications are expected, which should be developed at low cost. Short wavelength makes the dimension of antennas in this frequency range small, which usually requires sophisticated and expensive fabrication process. This communication presents a class of integrated wideband pyramidal horn antennas which can be made of low-cost multilayered printed circuit board (PCB) process. The proposed horn antenna radiates along the broadside to the substrate and uses substrate integrated waveguide (SIW) as its feeder. Transverse slot on the top metallic surface at the end of SIW is deployed to drive the horn antenna. Metalized via holes are used to synthesize the horn walls. The opening of the horn antenna is discretely flared from the bottom to the top layer. Measured bandwidth of the antenna is 35 GHz (70–105 GHz) while a relatively constant gain of 10 \pm 1 dB is obtained over most of the bandwidth. [ABSTRACT FROM PUBLISHER]

A new temperature compensation method is proposed and demonstrated in this paper for cavities and filters realized in substrate integrated waveguide (SIW). The SIW structures largely preserve the well-known advantages of conventional rectangular waveguide, namely, high Q and high power capacity, and have the advantages of microstrip lines, such as low profile, small volume, and light weight. In this paper, we demonstrate that by an adequate selection of substrate properties, SIW cavities can provide self-temperature drift compensation. The compensation is achieved by using an appropriate ratio between the coefficient of thermal expansion and the thermal coefficient of the permittivity. The theoretical prediction is confirmed by an experimental investigation using inductive post filters. Three commercially available substrates are used to design cavities at 10 GHz with the Roger TMM10 substrate providing a close fit to the required characteristics for temperature compensation. The results for the cavity show a stability of 2 ppm/^\circC in calculation and 8 ppm/^\circC in measurement. A SIW fourth-order Chebyshev filter, centered at 10 GHz with 1-GHz bandwidth, has also been designed. The measured frequency drift is 9.1 ppm/^\circC and the bandwidth variation is \pm \0.13\\% over the temperature range of -\40\ ^\circC to +\80\ ^\circC. [ABSTRACT FROM AUTHOR]

In this paper, a low-cost integrated 60-GHz switched-beam smart antenna subsystem is studied and demonstrated experimentally for the first time based on almost all 60-GHz substrate integrated waveguide (SIW) components including a slot antenna, 4\,\times\,4 Butler matrix network, bandpass filter, sub-harmonically pumped mixer, and local oscillator (LO) source. In this study, an antenna array, a Butler matrix, and a bandpass filter are integrated and fabricated into one single substrate. Instead of using a 60-GHz LO source, a 30-GHz LO source is developed to drive a low-cost 60-GHz sub-harmonically pumped mixer. This 30-GHz LO circuit consists of 10-GHz SIW voltage-controlled oscillator and frequency tripler. Following the frequency down-conversion of four 60-GHz signals coming from the 4\,\times\,4 Butler matrix and a comparison of the four IF signals executed in the digital processor based on the maximum received power criterion, control signals will be feed-backed to drive the single-pole four-throw switch array and then the beam is tuned in order to point toward the main beam of the transmit antenna. In this way, the arriving 60-GHz RF signal can be tracked effectively. All designed components are verified experimentally. The proposed smart receiver subsystem that integrates all those front-end components is concluded with satisfactory measured results. [ABSTRACT FROM PUBLISHER]

This paper presents an innovative broadband millimeter-wave single balanced diode mixer that makes use of a substrate integrated waveguide (SIW)-based 180^\circ hybrid. It has low conversion loss of less than 10 dB, excellent linearity, and high port-to-port isolations over a wide frequency range of 20 to 26 GHz. The proposed mixer has advantages over previously reported millimeter-wave mixer structures judging from a series of aspects such as cost, ease of fabrication, planar construction, and broadband performance. Furthermore, a receiver front-end that integrates a high-performance SIW slot-array antenna and our proposed mixer is introduced. Based on our proposed receiver front-end structure, a K-band wireless communication system with M-ary quadrature amplitude modulation is developed and demonstrated for line-of-sight channels. Excellent overall error vector magnitude performance has been obtained. [ABSTRACT FROM AUTHOR]

A novel class of low-cost, small-footprint and high-gain antenna arrays is presented for W-band applications. A 4 \times 4 antenna array is proposed and demonstrated using substrate-integrated waveguide (SIW) technology for the design of its feed network and longitudinal slots in the SIW top metallic surface to drive the array antenna elements. Dielectric cubes of low-permittivity material are placed on top of each 1 \times 4 antenna array to increase the gain of the circular patch antenna elements. This new design is compared to a second 4 \times 4 antenna array which, instead of dielectric cubes, uses vertically stacked Yagi-like parasitic director elements to increase the gain. Measured impedance bandwidths of the two 4 \times 4 antenna arrays are about 7.5 GHz (94.2–101.8 GHz) at 18 \pm 1 dB gain level, with radiation patterns and gains of the two arrays remaining nearly constant over this bandwidth. While the fabrication effort of the new array involving dielectric cubes is significantly reduced, its measured radiation efficiency of 81 percent is slightly lower compared to 90 percent of the Yagi-like design. [ABSTRACT FROM PUBLISHER]

This paper presents an integrated radio and radar system using a single transceiver platform towards millimeter-wave applications. In the proposed system, wireless communication and sensing functions are fully integrated and sequentially arranged in the time domain so that they can operate independently (functional reconfiguration) and also jointly (functional fusion). For this proof-of-principle study, a system prototype is developed in the 24-GHz ISM band using the emerging substrate integrated waveguide (SIW) technology, which has been demonstrated as an attractive low-cost and high-efficiency development scheme for microwave and millimeter-wave systems. Experimental results show a very promising system performance. In addition to high-precision range detection with its radar mode, the present system has proved to have a great capability of wireless radio communication at a data rate of up to 50 Mbps for both binary-phase-shift-keying (BPSK) and quadrature-phase-shift-keying (QPSK) signals. [ABSTRACT FROM AUTHOR]

Integration of an optical waveguide array using four waveguides in a Mach–Zehnder (MZ) structure and a two-layer low-loss substrate integrated waveguide (SIW) structure is presented to propose a new class of electrooptical phase modulators. In the proposed SIW modulator, synthesized rectangular waveguide in planar form is used as “electrodes” to guide millimeter-wave signals instead of conventional coplanar waveguide (CPW) for an electrooptical modulator, thus providing low-loss non-TEM mode propagation. In this study, two layers of a lithium niobate (LiNbO3) substrate for creating a high field interaction between the millimeter-wave and optical signals are considered and studied. Fabrication of the proposed structure by titanium diffusion in an LiNbO3 substrate as the optical waveguides and laser micromachining of the SIW via-holes has been done. The validation of our simulated results is also performed by the measurement of CPW-to-SIW transitions in the LiNbO3 substrate. Optical loss of 0.8 dB/cm at the wavelength of 1550 nm is obtained for an MZ structure using an optical waveguide array consisting of four waveguiding channels. In addition, it is shown that 5-GHz bandwidth over a 60-GHz operating frequency range can easily be obtained for the proposed modulator. [ABSTRACT FROM AUTHOR]

A planar W-band monopulse antenna array is designed based on the substrate integrated waveguide (SIW) technology. The sum-difference comparator, 16-way divider and 32 \times 32 slot array antenna are all integrated on a single dielectric substrate in the compact layout through the low-cost PCB process. Such a substrate integrated monopulse array is able to operate over 93 \sim 96 GHz with narrow-beam and high-gain. The maximal gain is measured to be 25.8 dBi, while the maximal null-depth is measured to be -43.7 dB. This SIW monopulse antenna not only has advantages of low-cost, light, easy-fabrication, etc., but also has good performance validated by measurements. It presents an excellent candidate for W-band directional-finding systems. [ABSTRACT FROM PUBLISHER]

A traveling-wave electrooptical modulator that makes use of a mode coupling mechanism between a substrate integrated waveguide (SIW) and coplanar waveguide (CPW) is proposed for millimeter-wave (mmW) radio-over-fiber applications. In this structure, SIWs are added at the input/output ports of conventional modulators from which mode conversion and signal transfer take place between lossy CPW traveling-wave electrodes and low-loss mmW SIW terminals. Such a gradual coupling from SIW to CPW in the modulation path creates a nonuniform field overlap integral and gives the ability of using the modulator at higher frequency. A laser micromachining technique for a transparent \LiNbO3 substrate and a titanium in-diffusion technique for achieving a good optical field confinement are used to fabricate the SIW and optical waveguide, respectively. The bending structure of the SIW, fabrication of pad resistors, and broadband transitions are considered in the proposed modulator. 7-GHz bandwidth was measured for the proposed modulator at 60 GHz. [ABSTRACT FROM AUTHOR]

In this paper, a planar 180^\circ phase-reversal T-junction and a modified magic-T using substrate integrated waveguide (SIW) and slotline are proposed and developed for RF/microwave applications on the basis of the substrate integrated circuits concept. In this case, slotline is used to generate the odd-symmetric field pattern of the SIW in the phase-reverse T-junction. Measured results indicate that 0.3-dB amplitude imbalance and 3^\circ phase imbalance can be achieved for the proposed 180^\circ phase-reversal T-junction over the entire X-band. The modified narrowband and optimized wideband magic-T are developed and fabricated, respectively. Measured results of all those circuits agree well with their simulated ones. Finally, as an application demonstration of our proposed magic-T, a singly balanced mixer based on this structure is designed and measured with good performances. [ABSTRACT FROM AUTHOR]

Two types of substrate integrated waveguide (SIW) long slot leaky-wave antennas with controllable sidelobe level are proposed and demonstrated in this paper. The first prototype is able to achieve an excellent sidelobe level of -27.7~dB by properly meandering a long slot etched on the broadside of a straight SIW section from the centerline toward the sidewall then back. But it is known that an asymmetrically curved slot would worsen the cross-polar level. To overcome this drawback, a modified leaky-wave antenna is proposed, which has a straight long slot etched on the broadside of a meandering SIW section. It yields an outstanding sidelobe level of -29.3~dB and also improves the cross-polar level by more than 11 dB at 35 GHz. Experimental results agree well with simulations, thus validating our design. Then, a two-dimensional (2-D) multibeam antenna is developed by combining such 14 leaky-wave antennas with an SIW beamforming network (BFN). It has features of scanning both in elevation orientation by varying frequency and in cross-plane direction by using the BFN. Excited at ports 1–10 of such a 2-D multibeam antenna at 35 GHz, angular region of 86.6^\circ in azimuth can effectively be covered by 3 dB beam-width of ten pencil beams. Varying frequency from 33 GHz to 37 GHz, the angular region of 37.5^\circ and 38.9^\circ in elevation can be covered by 3 dB beam-width of those continuous scanning beams excited at ports 6 and 8 respectively. [ABSTRACT FROM AUTHOR]

In this paper, an X-band low phase-noise voltage-controlled oscillator (VCO) using a novel electronically tunable substrate integrated waveguide (SIW) resonator is proposed and developed for RF/microwave applications on the basis of the substrate integrated circuits concept. In this case, the resonant frequency of the SIW cavity resonator is tuned by different dc-biasing voltages applied over a varactor coupled to the cavity. Measured results show that the tuning range of the resonator is about 630 MHz with an unloaded Q U of 138. Subsequently, a novel reflection-type low phase noise VCO is developed by taking advantage of the proposed tunable resonator. Measured results demonstrate a frequency tuning range of 460 MHz and a phase noise of 88 dBc/Hz at a 100-kHz offset over all oscillation frequencies. The VCO is also able to deliver an output power from 6.5 to 10 dBm. This type of VCO is very suitable for low-cost microwave and millimeter-wave applications. [ABSTRACT FROM AUTHOR]

A compact bandpass filter exhibiting an ultra-wide out-of-band rejection is studied and developed. A combination of electromagnetic bandgap (EBG)-loaded half-mode substrate integrated waveguide (HMSIW) and composite right/left-handed (CRLH) HMSIW is used in this development. The proposed filter operates below the characteristic cutoff frequency of HMSIW. The CRLH HMSIW loaded with EBG structures is investigated first. The filter with a miniaturized size is then implemented with two slots etched on HMSIW to reduce coupling effects between EBG structures and interdigital capacitors. Defected microstrip structure (DMS) as feed lines are used to obtain an ultra-wide out-of-band rejection. Measured results show that this effective stopband can cover up to 10.3 times the design center frequency for a rejection level of 20 dB. The filter exhibits high selectivity, good stopband performance, and compact size. [ABSTRACT FROM PUBLISHER]

In addition to microstrip line and basic grounded coplanar waveguide (GCPW) line circuits with perfect magnetic conductor (PMC) package, we further study the PMC package for a real component—a fifth order bandpass filter designed based on substrate integrated waveguide (SIW) with transitions to GCPWs. In particular, a simplified design of the PMC package is proposed for such a hybrid circuit. A fabricated SIW-GCPW filter was characterized without a lid, and with a traditional smooth lid, a modified smooth lid, a complete PMC lid and a simplified PMC lid. Both simulated and measured S-parameters show that the filter outband rejection using the proposed simplified PMC lid is better than the traditional and existing lids. [ABSTRACT FROM PUBLISHER]