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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

E-plane out-of-phase junction is proposed for three-dimensional (3-D) substrate integrated waveguide (SIW) circuits and systems. Its fabrication is made with low-cost printed circuit board (PCB) process and Lego-style planar building blocks. The proposed structure is validated through the simulation and measurement of an experimental E-plane junction operating from 30 to 40 GHz (28% bandwidth). Over this broadband frequency range, the fabricated prototype shows excellent performances with measured return loss, insertion loss and phase imbalance of better than 16 dB, 0.46 dB, and \pm 3^\circ, respectively. An integrated wideband dual-polarized array feed is designed and demonstrated on the basis of the proposed E-plane junction. The fabricated array achieves measured isolation of larger than 26 dB and return loss of better than -10.6~dB, with gains of 14 and 14.6 dBi at 35 GHz, respectively, for the vertical and horizontal radiation patterns. [ABSTRACT FROM PUBLISHER]