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Electromagnetic waves have been widely exploited as signal, carrier, and power for wireless and wireline systems over the electromagnetic spectrum. As the classical approach, parametric interactions among localized or discrete signal processing devices are usually accomplished by electromagnetic fields or waves guided in conductor and/or dielectric bounded structures. These structures feature specific circuit functions in an electronic or photonic manner. Such electromagnetic circuits now face a number of application issues, such as geometrical complexity, power handling capability, and flexible reconfigurability, when they are used in certain large-scale electromagnetic systems, like in a massive multiple-input and multiple-output (MIMO). In this work, we propose and present an unconventional approach to realize a desired interaction or operation among devices. Such an interaction relies on wave or field interferences induced by a set of coherent antenna array over their near-field region where signal processing can be accomplished spatially. Fundamental functions and operation mechanisms of the proposed spatial signal processing approach are discussed and demonstrated in this work. It is worth mentioning that the proposed approach is universally applicable to all physical wave devices and systems, such as acoustic and electromagnetic waves. [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]

In this paper, a guided-wave structure, the half-mode composite waveguide (HMCW) is proposed and presented. Similar to the conventional mode composite wave- guide (MCW), the HMCW also has an inner and outer waveguides, each working in its half-mode operation, respectively. In the HMCW structure, the signal propagates in the inner waveguide with quasi- $\text{TE}_{0.5-0}$ mode and along the outer waveguide with the quasi-TEM mode. The HMCW’s half-mode operation principle, impedance, loss, and propagation characteristics including higher order modes are analyzed. Compared to its full-size counterpart, the HMCW only occupies half the space, when operating within the same frequency band. Simulation results show that the transmission loss of the HMCW is comparable to that of the full-size MCW. Thus, it is also suitable for both low- and high-frequency design and applications. To measure and integrate the HMCW with other planar circuits, a joint feeding network for the HMCW is also proposed. Its circuit prototype is fabricated on three layers of substrate using a multilayer substrate integration technique. This joint feeding network can simultaneously excite the inner and outer waveguides, respectively, in an independent manner. In measurements, both the inner and outer waveguides are transitioned to microtrip lines, and a good matching is achieved from 4.4 to 11.2 GHz with a relative bandwidth of 87.2% for the outer waveguide at low frequency and from 18.6 to 32.6 GHz with a relative bandwidth of 54.7% for the inner waveguide at high frequency, respectively. [ABSTRACT FROM AUTHOR]

A periodic leaky-wave antenna is reported in substrate integrated nonradiative dielectric waveguide technology. Periodical change of substrate permittivity along the waveguide channel is used to perturb the propagating LSE11 mode. The hosting substrate is perforated following a periodicity to realize the perturbation. Thus, the antenna structure is very easy to implement and suitable for millimeter-wave applications. The antenna scan performance and leakage rate is dependent on the periodicity and size of the perturbation. Guidelines for choice of the parameters along with the condition for radiation of only one beam over the frequency range of interest are discussed. The developed antenna on Alumina substrate shows a good scan performance from −35° to 7° over the frequency range 96 to 108 GHz with a gain better than 10 dBi. [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]

This communication presents a leaky-wave antenna (LWA) in substrate integrated nonradiative dielectric (SINRD) waveguide. An SINRD waveguide being a periodic structure, the bandwidth of the fast-wave frequency band can be controlled by changing the periodicity of the hole array. As a result, a fast or a slow scanning is possible by appropriate choice of the periodicity without changing the substrate parameters. Leakage characteristics of an SINRD waveguide for different parametric variations are discussed. Measurement results are provided. [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 wideband planar dielectric rod antenna with substrate integrated non-radiative dielectric (SINRD) waveguide feed, is presented in this communication for W-band and up-millimeter-wave applications. The antenna and its feeding structure are integrated into a single layer substrate, which decreases the fabrication cost and integration complexity. Simulated and measured results show that the antenna has a wide bandwidth. Due to the structure of the SINRD guide which is shielded on top and bottom of the substrate, the proposed antenna is suitable for multilayer structure techniques such as LTCC or on-chip antenna. This antenna presents numerous features such as broad bandwidth, relatively high and stable gain, use of high dielectric constant substrate, and substrate-oriented end-fire radiation. The proposed antenna is suitable for gigabyte chip-to-chip communications. Measured bandwidth of the antenna is 10 GHz (93–103 GHz) while a relatively flat gain of 9.5 \pm 1~dB is obtained over the bandwidth of interest. [ABSTRACT FROM PUBLISHER]

A novel planar broadband microstrip-to-waveguide transition is proposed in this paper. The referred waveguide can be either rectangular waveguide or ridged waveguide. The transition consists of an open-circuited microstrip quarter-wavelength resonator and a resonant U-shaped slot on the upper broadside wall of a short-circuited waveguide. A physics-based equivalent-circuit model is also developed for interpreting the working mechanism and providing a coarse model for engineering design. The broadband transition can be regarded as a stacked two-pole resonator filter. Each coupling circuit can be approximately designed separately using the group-delay information at the center frequency. In addition to its broadband attribute, the transition is compact in size, vialess, and is highly compatible with planar circuits. These good features make the new transition very attractive for the system architecture where waveguide devices need to be surface mounted on a multilayered planer circuit. Two design examples are given to demonstrate the usefulness of the transition: one is a broadband ridged-waveguide bandpass filter and the other is a surface-mountable broadband low-temperature co-fired ceramic laminated waveguide cavity filter. Both filters are with the proposed transition for interfacing with microstrip lines, showing promising potentials in practical applications. [ABSTRACT FROM PUBLISHER]

In this article, a multilayered substrate integrated waveguide (SIW) Butler matrix beam-forming network is proposed, designed, and demonstrated at 24 GHz for automotive radar system applications. The proposed low-cost SIW structure can be used to develop a highly integrated multibeam antenna platform in automotive radar systems and other applications. In this structure, an SIW H-plane coupler is optimized with an H-plane slit to provide the required phase shift. A class of SIW E-plane 3-dB couplers in doubled layer substrate are studied and designed as the fundamental building blocks to avoid crossovers usually required in the construction of a Butler matrix. A 4 × 4 matrix is investigated and designed, which shows excellent performance over 22-26 GHz frequency band. Two types of antenna are tested with the proposed matrix scheme. First, an antipodal linearly tapered slot antenna (ALTSA) is incorporated into the Butler matrix to verify the broadband performances. Second, a longitudinal slotted waveguide antenna array is examined to generate radiation patterns in the broadside direction. Measured results agree well with simulated counterparts, thus validating the proposed multilayer SIW design concepts. In the next sections, the use as feeding networks for providing the reconfigurability operation of an antenna will be illustrated. © 2012 Wiley Periodicals, Inc. Int J RF and Microwave CAE , 2012. [ABSTRACT FROM AUTHOR]

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]

In this article, we present an efficient technique for the accurate design of wideband substrate integrate waveguide directional couplers. By tapering the coupling section, the bandwidth of substrate integrated waveguide (SIW) directional couplers can be enlarged. Two design aspects are involved in this approach. First, the even-mode propagation constant in the tapered coupling section is accurately extracted with the help of a numerical thru-reflect-line calibration technique. Then, it is fitted into the model of a uniform dielectric-filled rectangular waveguide and thereafter extrapolated to the operation range of the odd mode. Second, equivalent circuit models of the waveguide bifurcation effects are also presented together with parametric values. Based on the results of extraction, a 90° 3-dB directional coupler is developed to validate the proposed design approach. To achieve the reverse phasing at two output ports, the prototyped 90° 3-dB directional coupler is subsequently integrated with a novel broadband fixed phase shifter developed with the SIW technology, of which a systematic synthesis procedure has been proposed in this article. Measured performance of both 90° and 180° 3-dB couplers confirms the accuracy of our proposed design approach. This kind of wide-band directional coupler can find applications in wideband power dividing/combining circuits within a single-layer platform. © 2011 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2012. [ABSTRACT FROM AUTHOR]

A technique concerning the design and implementation of substrate integrated nonradiative dielectric (SINRD) waveguide is proposed in this paper. Different from the current SINRD waveguides, this scheme of making the SINRD guide structures directly out of the conventional printed circuit boards (PCBs) or similar platforms effectively eliminates cover metallic plates. This class of SINRD waveguides can be realized without resorting to a mechanical assembly as usually is done in the case of developing conventional nonradiative dielectric (NRD) guide circuits owing to the following two facts. First, increasing the width of the dielectric strip will decrease surface electric currents more significantly in the area of NRD strip. Second, the fabrication process and practical implementation are based on the concept of the substrate integration technique. In this case, air via-slot or via-hole arrays are created or punched directly on PCBs or metallized dielectric layers in order to fulfill the basic requirements of an SINRD waveguide design. By carefully choosing the SINRD dimensions and the pattern of via-slots or via-holes, potential leakage loss caused by these metallically uncovered via-slots or via-holes can be minimized and reduced to a negligible level. Therefore, the NRD waveguides can be designed and made through various processing techniques in a simple and practical manner for millimeter-wave and terahertz applications. In this paper, simulations and measurements have verified the proposed scheme. [ABSTRACT FROM PUBLISHER]

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]

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]

In this article, using a novel structure, simulated and measured microwave characteristics from substrate integrated waveguide photodetector (SIWPD) are obtained and compared with the conventional microstrip waveguide photodetector. A Ka-band microstrip to rectangular waveguide multilayer transition for OC-768/STM-256 optical systems is designed and fabricated. Attenuation constant results shows that by replacing substrate integrated waveguide (SIW) instead of conventional microstrip in waveguide photodetectors, operation frequency can be increased. Microwave fields in the proposed structure show a good transition from quasi-TEM mode to TE10 mode in multilayer structure. The multilayer structure is considered to separate SIW and DC bias of the photodetector. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 2204–2207, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24528 [ABSTRACT FROM AUTHOR]

In this article, a direct synthesis and dimensional design method for narrowband waveguide bandpass filters with a general dispersive coupling element is proposed. Comparing with the dispersion-less filter synthesis approaches, the general dispersive coupling matrix (DCM) that incorporates unique dispersive characteristics of a physical realization is introduced to provide an accurate description of the filter to be designed. Moreover, the DCM can describe not only strong dispersive coupling elements for realizing transmission zeros (TZs), but also dispersive resonators. A DCM consists of a frequency-invariant part and a dispersive part. For a given dispersive part, by iteratively remedying the characteristic polynomials, the frequency-invariant part for an equal-ripple response can be directly obtained. Consequently, according to the synthesized frequency-invariant coupling matrix, the filter dimensions can be designed only by electromagnetic (EM) simulation of each individual coupling element at the center frequency. Two design examples are presented, including a four-pole filter with two TZs and an eight-pole filter with four TZs. The examples are validated either by hardware prototyping or by EM simulation, demonstrating the effectiveness, accuracy, and generality of the proposed synthesis and design framework. [ABSTRACT FROM AUTHOR]

We present a multifilament current method (MFCM) to accurately and efficiently determine the cutoff wavenumbers (cutoff frequencies or eigenfrequencies) of homogeneous anisotropic material-filled metallic waveguides with arbitrary shapes. A set of $z$ -directed filamentary line sources placed outside of a waveguide are responsible for generating the simulated fields within the anisotropic material-filled waveguide in light of the derived 2-D anisotropic dyadic Green’s functions. Instead of solving an excitation-free eigenvalue problem, a substantial line source presented as an excitation is incorporated into the MFCM to formulate an eigenmode analyses technique without spurious eigenmodes. The internal field intensity response versus free space wavenumber are subsequently simulated, and a high magnitude response can be observed when an eigenmode is excited. In this case, the cutoff wavenumbers of physical eigenmodes are revealed by maximum locations of simulated field intensity response. Several numerical examples with different configurations on a waveguide are investigated. The simulated results are compared with those obtained from commercial software packages and an excellent agreement is achieved. In addition, the study of the oscillating phenomenon on magnitudes of filamentary sources and the ill-conditioning issue of constructed impedance matrix with respect to the placement of filamentary sources are also discussed. [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]

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]

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]

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]

A broadband Nolen matrix in substrate integrated waveguide (SIW) technology is proposed and studied in this paper. Being serial feeding networks, Nolen matrices usually introduce significant phase dispersion in their standard form, thus limiting effective bandwidth. In this work, broadband frequency operation is achieved with adequate coupler delay compensation, resulting in a more “parallel” matrix topology. Consequently, H-plane couplers with continuous aperture are preferred in the proposed design as opposed to the cross-couplers previously used in the “serial” configuration. The SIW couplers and phase shifters of a balanced amplitude 4\,\times\,4 Nolen matrix are designed at 77 GHz for radar applications. The resulting matrix that combines these elementary building blocks is fabricated and measured, and measured characteristics are in good agreement with theoretical and simulated predictions. This first design achieves excellent results over a 11.7% frequency bandwidth centered at 77 GHz. This modified Nolen matrix combines advantages of standard Nolen and Butler matrices and may be used as a building block for generalized orthogonal matrices. [ABSTRACT FROM PUBLISHER]

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]

The propagation and loss characteristics of the substrate-integrated rectangular waveguide (SIRW) at microwave and millimeter-wave bands are investigated. The results further verify that the substrate-integrated rectangular waveguide has nearly the same waveguide characteristics as conventional rectangular waveguides, and it can be analyzed as a rectangular waveguide with effective width of the SIRW. The insertion loss of SIRW and its equivalent rectangular waveguide agree well with each other. However, it is observed that the derivation of the propagation characteristics of the SIRW and its equivalent rectangular waveguide indicates the frequency dependency. At the X-, K-, and Ka-bands, the effective width of the equivalent rectangular waveguide given by the empirical formula [7] should be slightly increased in order to obtain the propagation characteristic that agrees better with that of the SIRW, about 2%. In addition, at the U-band, when the effective width of the equivalent rectangular waveguide is increased 5% or so, the propagation constant of the rectangular waveguide in the whole band agrees well with that of the rectangular waveguide. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 46: 588–592, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21059 [ABSTRACT FROM AUTHOR]

An efficient modes analyses technique for isotropic or anisotropic material filled 2D metallic waveguides with an arbitrary contour using the multifilament current method (MFCM) is presented. The ideal PEC boundary of a 2D waveguide is replaced by a shell with a high conductivity and electrical small thickness. The thin lossy shell not only can well approximate the boundary condition of PEC waveguide wall therefore without altering the initial waveguide modes, but also can let the external excitation penetrate through to excite the inside modes, resulting in a high internal field intensity at the frequency of each mode. In this case, the modes are revealed by the peaks of field intensity responses, and the spurious modes which existed in traditional source‐free modes determination techniques can be completely avoided. Based on this idea, a generalized impedance boundary condition (GIBC) is formulated to represent the lossy waveguide wall and further utilized in the MFCM for simulating the internal field intensity over frequency. Three different configurations of a 2D waveguide are considered. The computed modes are compared with that obtained from commercial software, and an excellent agreement is achieved, yet an competitive advantage on simulation performances is observed by using the proposed technique. [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]

To achieve broadband performances in the millimeter-wave range, antipodal linearly tapered slot antenna (ALTSA) designs with new combined substrate integrated waveguide (SIW) and regular coplanar waveguide (CPW) feeds are presented and studied. This feed structure eliminates the fabrication of air bridges in direct CPW-fed tapered slot antennas (TSAs). Two millimeter-wave design techniques are introduced for the selected 41–61 GHz and 90–120 GHz frequency ranges, demonstrating very good impedance match and nearly constant gain, beamwidth, and cross-polarization levels over bandwidths of 39% and 28%, respectively. The design procedure is validated by comparing simulated results with measurements performed on a 21–31 GHz (38% bandwidth) prototype. Very good agreement between measured and calculated performance characteristics is obtained with only cross-polarization levels slightly higher than predicted. The structural design parameters and dimensions of all three designs are given. [ABSTRACT FROM AUTHOR]

A novel six-port network based on half-mode substrate integrated waveguide (HMSIW) is proposed. In this design, a HMSIW hybrid 3 dB coupler and a -90° phase shifter are designed as fundamental building block of six-port network. By combining four HMSIW couplers and one phase shifter, a HMSIW six-port network at 29-32 GHz is constructed. The six-port network is fabricated and measured. Measurement results agree well with simulation, and show good balance and phase relationship between ports. [ABSTRACT FROM AUTHOR]

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]

A simple method for a Q-band planar triple-mode filter with quasi-elliptic function response is proposed in this letter. This filter is implemented using a high-order mode cavity with substrate-integrated waveguide (SIW) technology and standard printed circuit board (PCB) process. By adopting an orthogonal input and output feed-line and introducing some perturbation, transmission zeros are generated on both sides, which have significantly improved filter selectivity and out-of-band rejection. This triple-mode resonator is then combined with a circular dual-mode cavity to obtain a highly selective filter in Q-band with better stopband rejection. Both of the two filters are fabricated and measured. Low insertion loss and sharp sideband characteristic are observed, which is in good agreement with simulation. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 600–603, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24114 [ABSTRACT FROM AUTHOR]

Computer-aided-design models are developed and used for the characterization of ferroelectric materials at microwave frequencies, which aim at measuring the dielectric properties of BST-0.5 thin films on alumina substrates. Complex dielectric constant, voltage tunability, and K-factor are deter- mined for the ferroelectric materials with a series of BST/alumina coplanar waveguides (CPWs) and interdigital capacitors (IDCs) of different list film thicknesses. Propagation constants are extracted through measurements for CPWs using a multiline thru-reflect-line calibration technique from 1 to 16 GHz. IDC capacitance is measured at different bias points ranging from o to 35 V over the frequency range of 1-10 GHz. Conformal mapping models are deployed to interrelate circuit measurements with the BST film intrinsic properties. Dielectric constants of approximately 500-700 and loss tangents of approximately 0.07 are typically obtained at low frequencies for the BST films investigated in this study. BST voltage tunability is typically 15% at 35 V and 6 6Hz. [ABSTRACT FROM AUTHOR]

A novel optical ridge waveguide using calcium barium niobate (CBN) with a high electro-optic coefficient on silicon substrate is proposed for the design and realization of the next-generation hybrid modulators with short length and low driving voltage. To overcome the etching difficulty of CBN, the design of a waveguide, including an elevated CBN layer based on etched silicon dioxide, is presented. Fabrication of a thick 2.5-mCBN layer is performed using pulsed laser deposition. Deposited silicon dioxide on the sides and top of the CBN reduces the waveguide loss as low as 3.44 dBcm, measured using a cutback method. Good agreement between the mode profiles of the simulation and measurement is obtained. [ABSTRACT FROM AUTHOR]