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In a highly integrated analog radio-over-fiber transceiver, seamless integration of the antenna-frontend is crucial as an antenna is generally implemented on a high-κ material, which is set to highly degrade the antenna's performance. This work is concerned with the radiation behavior improvement of a planar leaky-wave antenna with an inductive partially reflecting surface (PRS) on a high-κ substrate for the development of a highly directive antenna. To begin with, we show how a thin and single-mode resonance (SMR) inductive PRS on high-κ materials in a planar leaky-wave antenna is set to provoke two resonance frequencies (i.e., PRS and cavity resonances) to converge, thereby diminishing the antenna's broadside directivity. By applying an equivalent circuit model, we explain how a multi-mode resonance (MMR) PRS can adequately be applied to address the underlying challenges. Subsequently, the leaky-wave radiation behavior of an antenna with a heterogeneous substrate is investigated and analytical equations are derived and verified with a full-wave simulation. The effects of material permittivity and thickness in a heterogeneous-cavity antenna on leaky-wave performance are investigated using these approximate yet accurate-enough equations. To justify the findings, two 9 × 9 planar leaky-wave antennas are prototyped on heterogeneous substrates based on SMR and MMR PRS and the radiation performances are compared. Our investigations reveal that in the proposed scenario, an MMR PRS can significantly enhance the antenna's broadside directivity by over 4 dBi at the resonance frequency (27.5 GHz), which is also set to improve radiation pattern compared to a SMR-based antenna. Finally, a single-fed dual-band aperture-shared antenna with a large frequency ratio (S-band and Ka-band) is developed and fabricated on a high-κ substrate based on the proposed MMR PRS. [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]

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]

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 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]

A concept of seamlessly colocated and cointegrated antennas and front-end chain circuits in the form of a unified and integrated design space is proposed, studied, and demonstrated in this paper, which strives to create future joint circuiting-radiating front-end analog functional blocks. To show the proposed concept, the building elements involving dual-function amplifier antenna are highlighted as an example and arranged in a series-connected array, each acting simultaneously as a matching circuit and transmitting antenna. In other words, a single geometrical space serves as both circuits and antennas, meaning a space overlap in which the circuit is an antenna and the antenna is a circuit. This reflects both the harmony and harmonious relationship of the circuit antenna. In this paper, the spacing between two neighboring array elements is utilized to accommodate active devices, such as transistors, in this example. As the first theoretical and experimental demonstration, this paper involves the design of patch antennas, the analysis of mutual coupling, and the placement of amplifying transistors in different operation modes. The modeling procedure for a $1 \times N$ amplifier-antenna system is presented. The proposed concept is experimentally validated by prototyping a $1 \times 2$ amplifier-antenna array at 5 GHz with rectangular patches and off-the-shell HJ-FET. An equivalent circuit network is established for the proposed dual function block. Measured results show that the experimental block has −10 dB matching bandwidth of 125 MHz at the steering angle of +30° with an amplifying gain of 11.5 dB. It is also experimentally illustrated that frequency tuning and beam steering can easily be enabled by varying the dc bias. The design of $1 \times 4$ amplifier-antenna array at 5 GHz is also discussed to generalize the proposed theory and guide the design of higher order amplifier arrays. [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]

A field-based analytical procedure is presented and developed for accurate modeling of the effective parameters of substrate integrated nonradiative dielectric (SINRD) waveguide. This modeling strategy is based on the eigenmode analysis of a dielectric substrate material perforated with air holes and enclosed between two horizontal metallic plates. From this model, it is found that the resulting effective dielectric constant of the periodic geometry of the SINRD waveguide is dependent on the direction of an electric field vector with respect to the material periodicity. In other words, the guiding parts of the SINRD waveguides act as anisotropic materials. A full demonstration for the proposed analysis is supported with simulation results using a full-wave finite-element method. The proposed model provides a scheme for the isotropization of anisotropic substrates. This is in addition to clarifying the exact regimes of operation inside the SINRD waveguide based on the guiding mechanism. Validation examples are studied based on polarization-selective coupling and effective polarization-independent coupling. A prototype is realized and measured where good agreement is achieved between simulation and measurement results. [ABSTRACT FROM AUTHOR]

An orthomode transducer (OMT) design is presented and implemented for future RF and millimeter-wave applications. The novelty of the proposed OMT stems from a distinct concept of handling dual-polarized signals on the basis of a polarization-selective coupler (PSC). The theory of the PSC is developed and understood through analyzing its constituent waveguides. Such waveguides are hybrid forms of nonradiative dielectric waveguide and substrate-integrated waveguide. An equivalent circuit model is deduced for modeling dispersion characteristics of the PSC. Consequently, design methodologies supported with comprehensive theoretical study and simulation analysis for a PSC-based OMT are developed and examined. The general design of a PSC-based OMT basically depends on a dielectric slab coupler waveguide with a longitudinal periodic PEC polarizer wall in its middle. Practical limitations for this design is discussed and supported with solutions using a proposed top slot coupler instead of the dielectric slab coupler. Closed-form equations are obtained as design recipes for computing structure dimensions and bandwidth based on operating frequency and the material parameters. The proposed structure is prototyped and measured. Measured results show an acceptable agreement with simulation results. [ABSTRACT FROM PUBLISHER]

With the rapid and continuous development of new generations of wireless technologies and networks, exploring the underutilized millimeter-wave (mm-wave) band becomes inescapable. Polarization diversity has been an essential factor in the performance and capacity enhancement of various wireless systems including cellular networks. Accordingly, the design and development of dual-polarized antenna feeding structures in the mm-wave band is a must. In this paper, a compact wideband orthomode transducer design in the Ka-band is proposed and explored. The proposed architecture and design are based on a forward mode polarization-selective coupling strategy between two unconventional waveguides. These special waveguides are a combination between two types of guiding structure, namely, nonradiative dielectric waveguide and substrate-integrated waveguide. Polarization-selective coupling can be achieved in these structures due to different mechanisms by which orthogonally oriented modes are guided. Theoretical coupling levels of 0 dB are possible in the designed structure. Analytical analysis and design steps are given in detail. This analysis facilitates a complete control on the single-mode operation for each polarization. This control, besides the structure being planar, represents the main advantages of the proposed structure. Finally, a prototype is implemented and measured where an excellent agreement is achieved with the simulation results. [ABSTRACT FROM PUBLISHER]

This communication presents a high-order-mode microstrip patch antenna driven by substrate integrated waveguide (SIW) for millimeter-wave polarization-adjustable applications. Different polarization status can be yielded from variable excited signals, including vertical and horizontal linear, right-handed and left-handed circular polarizations. In the patch antenna configuration, an enlarged aperture coming from high-order mode makes it easy to be fed by orthogonal SIWs for dual polarizations. Loaded slots on the patch significantly improve the radiation patterns. The impedance bandwidth with dual resonances is originated from the SIW slot and patch modes. A Ka-band $2\times 2$ antenna array integrated with single-layer SIW feeding network is designed and tested to illustrate this technique. The results manifest that the planar integrated $2 \times 2$ antenna array features adjustable polarization with considerable gain. Furthermore, a two-layer scheme of orthogonal SIW feeding is developed, which would provide a more flexible topology for the scale-expandable array antenna with adjustable polarizations. [ABSTRACT FROM AUTHOR]

This paper proposes a robust option for developing a new class of efficient and cheap antenna array based on patch array fed by substrate-integrated waveguide (SIW) through slot apertures for wireless backhauling applications. It consists in performing the feed network in SIW and the radiating structure in microstrip technology. The microstrip lines are coupled to the slots on the top wall of the SIW. Hence, it is demonstrated that the best alternative of the costly, heavy, and bulky rectangular waveguide feeder is SIW, which provides miniaturization, cost reductions, performance enhancements, and easy integration with patch array antennas. The experimental prototype presented in this paper demonstrates the efficiency of the design method and the feasibility of creating low-cost moderate-bandwidth millimeter-wave planar $8\times 8$ patch antenna array configurations in two stacked substrates to get ultracompact antenna module. The principle of achieving such high-quality antenna array is presented in detail along with experimental verification of theoretical results to validate the design procedure and demonstration of the feasibility of implementing the array by means of relatively inexpensive compact structures. The maximum gain is around 23 dBi at 22.4 GHz, the measured impedance bandwidth is 5%, and the efficiency is around 70%. [ABSTRACT FROM PUBLISHER]

ABSTRACT A frequency reconfigurable bandpass filter using an electronically tunable dual-mode Substrate Integrated Waveguide (SIW) resonator is presented. Four lumped capacitors as electric tuning elements are loaded near the regions of strongest electric field of TE102 and TE201 modes. The resonant frequency of these two orthogonal modes is tuned by different capacitance values of four lumped capacitors coupled to the SIW resonator. Measured results show that the proposed filter exhibits a tuning range of about 37% from 3.44 to 5 GHz with the total insertion loss variation of 1.85-5.2 dB. © 2017 Wiley Periodicals, Inc. Microwave Opt Technol Lett 59:934-937, 2017 [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]

The properties of dual mode resonance in planar SIW-based rectangular cavities are investigated and discussed. A specific mode combination of dual mode cavity presents a unique frequency response feature. With the aid of an optimization process or software, it is convenient to cascade a number of cavities with coupling apertures to form a filter. A 3-cavity pseudo-elliptic SIW filter based on H 203 & H 104 hybrid resonance is designed and fabricated on a Rogers TMM3 substrate. Measured results show that the insertion loss at the central frequency around 24 GHz is 4.58 dB and the return loss is better than 20 dB in the whole pass-band of 760 MHz. The design method can widely be used for high-density microwave integrated circuits and the mass-fabrication of such filters is made easy even when keeping development and processing costs very low. [ABSTRACT FROM AUTHOR]

This Letter proposes a balanced dual‐mode substrate integrated waveguide (SIW) filter for the first time. Based on dual‐mode square SIW cavities, perturbation vias, and balanced ports, the quasi‐elliptic differential mode response with improved selectivity as well as high‐performance common mode suppression can be obtained conveniently. Resonator number decrease and compact size can also be available. [ABSTRACT FROM AUTHOR]

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]

In the last 10 or 15 years, exciting new developments have occurred in the field of filters and multiplexers. The two words that best explain this phenomenon are “topology” and “technology.” Thus, this paper will cover new connections, new materials, and new processes. This paper summarizes what is new, describes the new devices, and avoids simply surveying the entire field. It is not possible to cover everything, and regrettably, some new and possibly exciting areas are omitted (such as filters fabricated using liquid crystal polymers, active element inclusion, extreme power devices used in accelerators), and others,\ldots, because something has to be left for the next paper! The paper does cover bandstop filters, intrinsically switched film bulk acoustic resonator, and barium–strontium–titanate filters, brand new derivations of lossy filter synthesis and dual-band filter synthesis, multimode networks, new work on optimal multiplexer (multiport network) configurations, and substrate integrated waveguide filters. In each of these areas significant new work has been recently performed and is presented in a summary format suitable for those thinking that the area of filters and multiplexers has become mature (stagnant) with nothing interesting to learn. Nothing could be further from the truth! [ABSTRACT FROM PUBLISHER]

This Letter proposes a balanced hybrid substrate‐integrated waveguide (SIW)–coplanar waveguide (CPW) bandpass filter, which combines a hybrid SIW–CPW filter and a balanced structure for the first time. High performance common mode suppression can be achieved with high quality factor, compact size, and quasi‐elliptic differential mode response. [ABSTRACT FROM AUTHOR]

An air-filled substrate integrated waveguide (SIW) made of a multilayer printed circuit board process is proposed in this paper. It is of particular interest for millimeter-wave applications that generally require low cost and low-loss performance and excellent power-handling capability. This three-layered air-filled SIW allows for substantial loss reduction and power-handling capability enhancement. The top and bottom layers may make use of a low-cost standard substrate such as FR-4 on which baseband or digital circuits can be implemented so to obtain a very compact, high-performance, low-cost, and self-packaged millimeter-wave integrated system. Over Ka-band (U-band), it is shown that the air-filled SIW compared to its dielectric-filled counterparts based on Rogers substrates RT/Duroid 5880 and also 6002 reduces losses by a mean value of 0.068 dB/cm (0.098 dB/cm) and 0.104 dB/cm (0.152 dB/cm), increases average power-handling capability by 8 dB (6 dB) and 7.5 dB (5.7 dB), and quality factor by 2.7 (2.8) and 3.6 (3.8) times, respectively. The peak power-handling capability of the proposed structure is also studied. A wideband transition is presented to facilitate interconnects of the proposed air-filled SIW with dielectric-filled SIW. Design steps of this transition are detailed and its bandwidth limitation due to fabrication tolerances is theoretically examined and established. For validation purposes, a back-to-back transition operating over the Ka-band is fabricated. It achieves a return loss of better than 15 dB and an insertion loss of \0.6 \pm \0.2 dB (\0.3 \pm \0.1~\dB for the transition) from 27 to 40 GHz. Finally, two elementary circuits, namely, the T-junction and 90^\circ hybrid coupler based on the air-filled SIW, are also demonstrated. [ABSTRACT FROM AUTHOR]

In this communication, dual-fed wideband circularly polarized (CP) patch antennas based on the single-layer printed circuit board (PCB) process and the substrate integrated waveguide (SIW) technology are proposed. Firstly, a patch antenna fed by an SIW coupler is developed to achieve a measured 3 dB axial-ratio (AR) bandwidth of 21% (from 38 GHz to 47 GHz). Then, by introducing second-order inductive windows, an improved CP patch antenna is developed. The measured results show that the 1 dB gain bandwidth is expanded from 3 GHz to 9 GHz while the overlapped bandwidth of AR and reflect coefficient is maintained. Finally, a 2 \times 2 CP array is developed with a dual-polarized patch array. By carefully selecting the resonant frequency of the patches, a wide gain bandwidth is achieved. Moreover, by compensating the major error that deteriorates the AR bandwidth with a specially-designed coupler, the measured 3 dB AR bandwidth reaches as wide as 22.8%. The measured peak gain is 12.35 dBi. [ABSTRACT FROM PUBLISHER]

A class of directional couplers based on the substrate integrated waveguide (SIW) technique for compact three-dimensional (3-D) integrated circuits is proposed and studied in this work. Backward and forward couplers as well as strong coupling-defined forward couplers are presented and developed. They are composed of two joined SIW sections such that the common wall between them is made of a portion of the broad side of the first SIW and the narrow side of the second SIW. This perpendicular topology is arranged and formed through the use of a LEGO-like interconnect between the two SIW structures. Different coupling geometries developed with a low-cost printed circuit board process are studied. Design considerations and measured results at Ka-band are presented and discussed. To achieve respectively weak backward and forward directional couplings, Schwinger and multihole-type directional couplers are introduced first of all, which make use of coupling slots arranged around the center of the SIW broad wall. For each of those structures, a wideband 20-dB directional coupler is fabricated and measured for demonstration purposes. To achieve a strong coupling, a Riblet-type directional coupler is proposed and examined. Subsequently, a 3-dB coupler is demonstrated together with a 0-dB coupler, offering a wideband and very efficient transition between the perpendicularly arranged SIWs. The proposed directional couplers can be used at millimeter-wave frequencies for probing and the design of compact 3-D integrated circuits and systems such as polarimetric imaging radiometer or antenna array feeding networks. [ABSTRACT FROM PUBLISHER]

Substrate integrated waveguide (SIW) cavity backed dual-band triangular-ring slot (TRS) antennas are proposed for planar integration. First, a low profile dual band 45^\circ linearly polarized (LP) antenna is designed and analyzed. The dual-mode TRS is proposed and developed by simultaneously exciting the mode of the slot and the mode of the patch inside the slot. To minimize the antenna size, the lowest mode (TE110 mode) of the SIW cavity is adopted to excite the TRS. The -10 dB impedance bandwidth at the higher band is 5.9%, 58.3% wider than that of the conventional SIW cavity backed slot antenna. The interactions of the SIW cavity, the slot mode and the patch mode are analyzed with circuit models and verified by full wave simulations, which provides a new insight into the SIW cavity backed antennas. Then, by exciting a pair of the 45^\circ LP antennas with an SIW coupler, a circularly polarized (CP) dual band antenna with a small frequency ratio of 1.26 is developed. The two antennas are fabricated and tested, and the measured and simulated results agree well. [ABSTRACT FROM PUBLISHER]

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]

An approach for the bandwidth enhancement of a polarization rotating frequency selective surface (FSS) based on the substrate integrated waveguide (SIW) technology is proposed in this communication. Compared with the previously reported polarization rotating FSS, the passband bandwidth of the proposed FSS is enhanced from 4.6% to 7.2% by introducing a triple-mode SIW cavity resonator as the periodic element. Meanwhile, better frequency response selectivity of filtering performance is achieved. The proposed FSS is made up of a periodic array of the novel triple-mode SIW cavity resonators with two orthogonal slots on the front and back surfaces for polarization rotation. The triple-mode SIW cavity resonator is achieved by placing a metallic via at the center of a dual-mode SIW cavity resonator. Bandwidth enhancement of the FSS is achieved by simultaneously exciting and properly merging together these three modes in the SIW cavity resonator. A prototype designed at Ka-band was fabricated and measured. Good agreement between the measurement and simulation results has been achieved. [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]

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]

ABSTRACT Integrated frequency-modulation continuous-wave radars are attractive to a wide range of industrial and commercial applications. The design considerations unique to such an integrated radar front end are studied in this work. Theoretical models as well as experiment results are presented, which verify the effectiveness of the proposed design approach. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:1907-1912, 2013 [ABSTRACT FROM AUTHOR]

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]

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]

Substrate integrated waveguide (SIW) technology provides an effective solution for the low-cost and high-performance interconnect and packaging of microwave and millimeter wave systems. In this paper, Ka-band four-degree bandpass filters having asymmetric frequency response, which are required in the design of transmit and receive diplexers for high rejection between neighboring channels, are proposed and realized on an SIW platform. The filters are self-packaged due to the fact that a conductor-backed coplanar waveguide is used to directly excite the filters. Higher-order resonant mode is used to achieve the required negative coupling on the basis of a single-layer SIW. The proposed filters, having the same center frequency of 35 GHz and pass bandwidth of 1.3 GHz, are fabricated on a conventional Rogers RT/Duroid 6002 substrate with thickness of 0.508 mm by using a low-cost printed circuit board process. Measured results of those filters, which exhibit high single-sided selectivity and minimum in-band insertion loss of about 1.25 dB, agree well with simulated results. [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 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]

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]

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]

Substrate integrated waveguide (SIW) matching terminations or loads are proposed for low‐cost integration in SIW circuits and systems. The principles of narrowband and broadband SIW terminations are demonstrated and discussed. Both narrowband and broadband terminations are optimised, fabricated and measured over the frequency range of 6–15 GHz. Relative frequency bandwidths (|S11| < 20 dB) of the narrowband and broadband terminations are 7.6 and 42.6%, respectively. Good agreement between the measured and simulated results validates the feasibility of the proposed design strategies of SIW terminations. [ABSTRACT FROM AUTHOR]

A novel technique to design substrate integrated waveguide (SIW) resonator with harmonic suppression is proposed. The spurious band arising from the harmonics is designed as well as the fundamental passband. The bandwidth of the spurious band is designed to be zero to realise harmonic suppression. At the same time, the fundamental properties of the SIW are almost not affected, and no additional circuit area is required. The harmonic suppression and the fundamental passband can be designed independently of each other. An SIW resonator with harmonic suppression and an SIW filter with wide stopband are fabricated and measured to verify the proposed technique. The results agree with expectation well. [ABSTRACT FROM AUTHOR]

The substrate integrated waveguide (SIW) is exploited for the broadband determination of the complex dielectric permittivity of lossy material. The effective measurement frequency covers the passband of the fundamental mode in the SIW. This method is an operative technique for characterising the material in millimetre‐waves. [ABSTRACT FROM AUTHOR]

The microstrip patch antenna (MPA) with frequency stability versus temperature is proposed as the ice sensor for de-icing of aerodynamic systems. The operation principle is based on the fact that the formation of ice layer is set to disturb the near fields, thus shifting the resonant frequency. To mitigate the uncertain temperature effect, a thermal stability (TS) strategy is implemented, making the sensor only susceptible to the ice loading effect and enabling stable performance within a large temperature range from − 40∘C to + 80∘C. The proposed ice sensor is in turn interrogated wirelessly by a transmitting (Tx) antenna. Due to the frequency shift, the received signal strength (RSS) is modulated as a function of ice-thickness, allowing for remote ice detection and quantification. Two common types of ices, namely rime and clear ices, are investigated. The ice samples were generated and characterized under different weather conditions in our cold chamber and wind tunnel at Anti-icing Materials International Laboratory (AMIL) with the University of Quebec at Chicoutimi (UQAC). Experimental results show the feasibility of the proposed approach for different real-world scenarios. In particular, the sensor demonstrates the best measurement capability in the case of clear ice with full coverage, achieving the sensitivity of 75 mV/mm. [Display omitted] [ABSTRACT FROM AUTHOR]