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Unlike popular multiband antenna array radiation based on either electric or magnetic surface currents, the use of mutually interleaved and tightly coupled electric and magnetic currents results in an aperture-reuse space-efficient multiband radiating surface for highly integrated antenna-frontend architecture and spatial power combining design scenarios. In this work, slot and dipole modes corresponding to magnetic and electric currents are effectively interleaved and excited in a surface to develop a space-efficient dual-wideband aperture-shared radiating surface. In this case, due to an effective reuse of the antenna aperture over both frequency bands, a high aperture-reuse efficiency is achieved. First, we devise a planar magneto-electric (ME)-dipole-alike antenna and analyze it in both the frequency and time domain. The antenna is then studied by the characteristic mode theory and the findings are validated using full-wave simulations. The developed planar ME-dipole-alike antenna is used to realize a dual-wideband radiating surface in which electric and magnetic currents are mutually coupled and interlaced, which is excited by properly oriented and distributed sources on the antenna's surface. Eventually, a highly isolated dual-wideband prototype was developed and fabricated using a cost-effective multi-layer Printed Circuit Board (PCB) process that operates in the Ku-band with both impedance and gain bandwidth of approximately 42% and in the Ka-band with respective impedance and gain bandwidth of 29% and 16.32%. [ABSTRACT FROM AUTHOR]

In this article, a capacity-oriented envelope correlation coefficient (ECC) that incorporates a preferred channel model for assessing a multiple antenna system of a multiple-input-multiple-output (MIMO) mobile device is proposed. Originated from the rudimentary law of ergodic channel capacity, the ECC for multiple antennas (ECC-M) is proven to holistically reflect the impact of radiation patterns and total efficiencies of multiple antennas on channel capacity. The closed-form ECC-M expressions for Rayleigh fading channel model and ray-based spatial channel model are studied, leading to an easy-to-use ECC-M expression that approximately incorporates a realistic channel model. The correlation of the proposed ECC-M to the channel capacity is demonstrated through the Monte Carlo (MC) simulation of three four-element MIMO antenna testbeds in two channel models, showing that the antenna total efficiency and a realistic channel model involved in the ECC-M play an important role in assessing the performance of multiple antennas. It is justified that the difference in channel capacities of two multiple antenna systems is highly relevant to their ECC-Ms at high signal-to-noise ratios (SNRs). The proposed ECC-M is also experimentally validated through over-the-air (OTA) throughput measurement, revealing that the ECC-M can effectively assess the OTA performance of multiple antenna systems for MIMO terminal devices. [ABSTRACT FROM AUTHOR]

A cost-effective and accurate method for predicting over-the-air (OTA) data throughput of multiple-input and multiple-output (MIMO) wireless devices in the antenna design stage is proposed. The method incorporates passive characteristics of MIMO antennas, realistic channel model, and conductive measurement results in a computer simulation framework. With extracted relation between received power and signal-to-noise ratio (SNR) of a wireless device at antenna ports by a conductive test and measured passive characteristics of MIMO antennas, OTA throughput versus received power in a realistic channel model is obtained by the Monte Carlo simulation of Shannon’s law. The unique features of this method include: no channel emulator equipment is required; a wide variety of precoding schemes can be applied; passive characteristics of antennas are fully incorporated; and frequency-selective fading channel can be adopted. The method has been intensively validated by comparing the calculated OTA throughputs with those measured by a multiprobe anechoic chamber method under spatial channel model extension (SCME) in three aspects: spatial correlation, radiation efficiency, and mutual coupling, showing as low as 0.2–0.3 dB discrepancy in power level in most cases. The method can be used to evaluate a MIMO array antenna design of a wireless device with respect to OTA performance. [ABSTRACT FROM AUTHOR]

In this article, H-plane cross-polarization (X-pol) radiation of probe-fed air-filled patch antennas is substantially suppressed by introducing two or more floating metal cylinders underneath the patch, respectively. The X-pol is canceled by the radiation of induced currents on metal cylinders. The working principle of the new X-pol suppressed patch (XSP) antenna is revealed by an approximate model. The X-pol level of a typical XSP antenna can be suppressed to lower than −49 and −37 dB theoretically and experimentally for $| \theta |\le 60^{\circ }$. Two $1\times $ 8-element arrays constructed by XSP antennas and conventional patch antennas are prototyped and measured at scanning beam angles of $\theta = 0^{\circ }$ , −40°, and −65°. The measured co-polarization (co-pol) gain of the XSP antenna array is 0.7 and 0.9 dB larger than that of the conventional patch array at $\theta = -40^{\circ }$ and −65°, respectively. Besides, the beam scanning angle with −30 dB X-pol level of the XSP antenna array can be as wide as $| \theta |\le 40^{\circ }$ , while that of the conventional patch array is about $| \theta |\le 12^{\circ }$. A wide-band dual-polarized XSP antenna is also presented. The measured maximum H-plane X-pol level can be lower than −29 dB within 8.7% fractional bandwidth. [ABSTRACT FROM AUTHOR]

We investigate and present a very low-profile, high-efficiency, and high-gain 2-D leaky-wave antenna (2DLWA) implemented on a high permittivity substrate operating in the millimeter-wave range, paving the way for the seamless integration of a high-gain and high-efficiency antenna with a frontend. In contrast to the typical air-filled 2DLWA, where a perturbation of the first higher-order mode (TE1/TM1) results in highly directed broadside radiation, in the proposed antenna, the propagation and leakage of a quasi-TEM (Q-TEM) mode results in an extremely low-profile ($0.065\lambda _{0}$), high-gain (~15 dBi) antenna. In this scenario, the transverse resonance condition for a Q-TEM mode is established by employing a capacitive partially reflective surface (PRS) in a thin ($0.065\lambda _{0}$) substrate with a relative permittivity of 10.2. The proposed periodic 2DLWA, unlike the conventional uniform/quasi-uniform air-filled counterparts, radiates based on the $\mathbf {n}=-\mathbf {1}$ space harmonic operation. Due to a strong mutual interaction between the PRS and ground plane, conventional design and analysis approaches are no longer relevant in this low-profile architecture. Instead, we employ the Floquet modal expansion theory to create an equivalent circuit model (ECM) for the PRS that takes into account the contributions and mutual interactions of the Floquet harmonics as well as the ground plane effect. By employing reflecting boundaries realized with edge truncation (air trenches) in a high permittivity substrate, we show that the aperture efficiency is enhanced by 15% compared to conventional counterpart. [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]

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]

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]

Radiation efficiency of electrically small antennas largely depends on antenna geometry. However, the actual mechanism that governs the antenna radiation efficiency remains unclear, although various models have been developed since the 1940s. Extant circuit models are either intuition-based or mathematic representations of input impedance/far-field spherical mode functions for structurally simple antennas with limited uses and physical insight. In this article, a recently developed physical micromodeling circuit (MMC) model is utilized to explain the nature of radiation of an electrically small antenna of arbitrary configuration. It is theoretically discovered and experimentally validated for the first time that the radiation efficiency decisively depends on mutual radiated power associated with partial segments of the antenna. A circuital figure of merit for describing the total mutual radiated power is introduced to quantify the measure. The graphical representation of the figure of merit called the holographic radiation diagram is also proposed for illustrating the correspondence of the positive and negative radiated power and the antenna structure. The applications of the proposed theory to antenna design is demonstrated by designing a highly efficient loop antenna. The physical circuit model paves a new way of understanding electromagnetic (EM) radiation problems. [ABSTRACT FROM AUTHOR]

A generalized mesh-network equivalent model for a microstrip rectangular patch antenna (RPA), which is simple yet efficient is proposed, studied, and demonstrated in this article. The mesh-network equivalent model is established through the segmentation of RPA width and radiation parameters into $M$ sections, as well as the segmentation of RPA length into $N$ sections. A general design procedure to realize the mesh-network equivalent model is addressed and described for any number of RPA segmentations, as desired by specific applications. Subsequently, the proposed mesh-network equivalent model is used to accurately evaluate the input impedance responses at various feed positions along the length of RPA. In addition, to include the effects of a slot etched inside the RPA geometry, a generalized microstrip coupled line equivalent model is proposed, analyzed, and discussed in detail. Eventually, the microstrip coupled line model in conjunction with the proposed mesh-network equivalent model can accurately estimate the input impedance response of a slotted RPA, and has been verified for RPA with center slot, edge slot, and multiple slots as examples in this work. Two cases with multiport excitation of RPA are also analyzed and presented as a part of this work. For demonstration purposes, all these prototypes are designed, fabricated, and measured at 28 GHz. The proposed equivalent model-based results are validated by measured and simulated counterparts. Furthermore, the extension of the proposed mesh-network model to accommodate slots of smaller size inside RPA, RPA loaded with via, inverted-F antenna, and multimode operation are demonstrated and discussed through a comparison between mesh-network modeling results and simulation results. [ABSTRACT FROM AUTHOR]

In this article, a densely integrated and unified paralleled amplifier and antenna architecture is proposed and demonstrated for next-generation millimeter-wave (mmW) and terahertz (THz) front-end modules. It makes use of topologically paralleled transistors cohabitated within a compact rectangular patch antenna (CRPA) as a unified cell. This design simultaneously amplifies and radiates power without resorting to any power divider, input and output matching networks, or power combiner whatsoever, therefore, greatly reducing front-end loss, size, and complexity. Then, the unified unit cell is self-consistently distributed to form a unified planar array with active elements between array elements as power feeders. In this demonstration, the input power is sequentially amplified, radiated through each array element, and spatially added up, resulting in low on-board circuit losses and efficient radiation. In this article, we investigate and present challenges and early results of implementing this unification concept of active circuitry and antenna at mmW frequencies. Using a standard 65-nm CMOS process, a set of chips were designed, fabricated, and tested under different amplifier biasing conditions at 146 GHz for experimental demonstration. The realized low-loss, matched, and compact unified prototypes have demonstrated an amplified radiation, with power enhancement of 3.4 dB through single element and 6 dB through $2 \times 2$ layout compared to their respective passive counterparts. Moreover, frequency tuning is observed varying drain bias and self-matching is improved with increasing gate bias. Therefore, the feasibility of a unique feature in the architectural implementation of low-loss, compact, and densely integrated and topologically cohabitated mmW and THz front-end modules is confirmed. [ABSTRACT FROM AUTHOR]

The concept of a self-decoupled antenna array using the cancellation of two opposite couplings is proposed in this article. A pair of such antennas can be closely placed with inherent high isolation without using an extra decoupling structure between the antennas. A pertinent equivalent circuit model is presented to illustrate the physical mechanism of this new concept. It is found that the inductive and capacitive couplings between the antennas can be well canceled out with each other by properly adjusting the antenna dimensions. A demonstrating antenna array with a spacing of $0.024\lambda _{0}$ at the working frequency of 3.5 GHz and its counterpart array are first studied. The measured results show that although the proposed antenna array occupies a slightly larger size than its counterpart array, it presents better performance compared with its counterpart antenna array in port isolation (from 10 to 20 dB), total efficiency (from 68% to 80%), and envelope correlation coefficient (ECC) (from 0.14 to 0.04) throughout the desired frequency band of 3.3–3.8 GHz. A 3-D self-decoupled antenna array is designed to show that the proposed antenna can be in a compact form factor. Another self-decoupled array and its counterpart working at 2.14 GHz (long-term evolution (LTE) band 1) are studied through multi-input multi-output (MIMO) over-the-air (OTA) test when the arrays are integrated with an LTE module, showing significant improvement on the data throughput. [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 novel diplexer-based fully passive transponder is presented in this paper, which targets sub-6-GHz 5G-compatible internet-of-things applications. To alleviate the antenna design restrictions of traditional transponder with two separate antennas, a new architecture has been proposed with the introduction of a diplexer, which allows transponder to simply employ a dual-band antenna. In this paper, a dual-band circularly polarized omnidirectional spiral slot antenna, with enhanced bandwidth and gain performance, is designed as the transponder Tx/Rx antenna. Besides the new architecture, a diode selection criterion is proposed as well. Analytical models are derived, showing relationships between the diode’s SPICE parameters and the conversion efficiency or conversion loss (CL) of such diode-based transponders. With help of the analysis, transponder designers can easily identify diodes to implement transponders with better performance. Under the guidance of the criterion, low-barrier diode SMS7630 is chosen for verification. Measured CL results of the transponder circuitry part show a noticeable improvement over the state-of-the-art works. The complete prototype was tested with radar’s transmitting power of 25 dBm, and it presents a maximum read-out distance up to 7 m when the operating fundamental frequency is 3.5 GHz. [ABSTRACT FROM AUTHOR]

A new wideband ±45° dual-polarized metal loop dielectric resonator magnetoelectric antenna is proposed in this communication. The antenna consists of two orthogonal dielectric bars that support two orthogonal electric dipoles and two cross interlaced metal semi-loops that are equivalent to two orthogonal magnetic dipoles above the ground. With a legitimate combination of the electric and magnetic dipoles, a unidirectional radiation with low backward radiation and equal E-plane and H-plane radiation patterns can be achieved. The antenna can be made of a monolithic dielectric block with simple installation. To validate the new antenna configuration, a prototype is designed, manufactured, and measured. The prototype antenna using ceramic with the electrical size of $0.33\lambda _{o} \times 0.33\lambda _{o} \times 0.21\lambda _{o}$ demonstrates that an impedance bandwidth of 11.4% ($\vert S_{11}\vert < -15$ dB) in the 3.5 GHz frequency band can be achieved with the measured forward/backward ratio of better than 22 dB. The proposed antenna is suitable as antenna element for massive-MIMO array antennas, where a large number of antenna elements need to be installed in a compact space. [ABSTRACT FROM AUTHOR]

In this paper, we study a frequency-modulated continuous-wave based radio-frequency identification system, which is composed of a reader with single transmitter and multiple receiving antennas as well as multiple active backscatter tags. In particular, our contribution is twofold in this paper. First, we construct a general architecture for achieving the functionality of wireless positioning based on the principle of the switched injection-locked oscillator (SILO). Unlike the previous SILO-based schemes, some limitations on the pulsed waveform generated by the tags are overcome. In addition, only one reader set up with multiple receiving antennas is used to precisely localize tags based on the delay and direction-of-arrival estimates. Second, the developed algorithms make use of a shift invariant property among the baseband signal snapshots of intra- and/or intermodulation intervals, i.e., snapshots in one modulation period and/or sets of snapshots in multiple modulation periods. A new joint singular value decomposition based ESPRIT algorithm is developed for determining the number of multiple active tags and their positions by implementing the matrix reconstruction and stacking techniques. The proposed method has its basic foundation on the processing of received data with global fusion scheme. In this way, this method can improve the performance of parameter estimates in terms of accuracy and resolution without suffering from the pair matching problem. System simulations and experimental validations are carried out to verify the proposed system architecture associated with the signal processing technique. [ABSTRACT FROM AUTHOR]

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]

An integrated low-temperature co-fired ceramic (LTCC) coupled resonator decoupling network (CRDN) for two coupled antennas is proposed in this paper. By virtue of LTCC technology, a second-order CRDN is realized by two tightly coupled lumped-element resonators in a volume of \3.2\times \2.5\times \1.2\ \mm^3. Theoretical analysis has revealed that a wide range of mutual admittance of a CRDN can be realized by choosing appropriate I/O coupling elements while the coupled resonators can be consolidated in an LTCC device. This “one-fit-all” feature allows for decoupling a wide range of coupled antennas with different form factors for a given frequency band. To prove the concept, two LTCC CRDNs for decoupling different forms of antennas working in the 2.45-GHz band are designed, fabricated, and tested. Measurement results have demonstrated that significant improvement in isolation can be achieved within a wide operating frequency range in all cases. The presented design theory and circuit topology are general and can be applied to both symmetric and asymmetric two-element antenna arrays. [ABSTRACT FROM PUBLISHER]

A new decoupling scheme called dual-band coupled resonator decoupling network (CRDN) is presented. By properly designing the coupling coefficients between two pairs of coupled resonators, the network can effectively reduce the mutual couplings between two coupled dual-band antennas in two bands simultaneously. The new scheme is proved by a practical microstrip version of the device for two dual-band antennas working at 2.4 and 5.2 GHz frequency bands. A compact planar dual-band CRDN consisting of a pair of dual-band open-loop square ring resonators is proposed. The measured scattering parameters of two coupled antennas with and without the dual-band CRDN in free space (FS) and with hand phantom demonstrate that the isolation between the two antennas in both the low and high bands can be improved from 8 to 10 dB, respectively, to below 20 dB while maintaining a good matching performance. The total efficiency and envelop correlation coefficient for the decoupled antennas show a significant improvement as compared to the coupled antenna case. The proposed dual-band CRDN scheme is easy to be implemented in an integrated device, and is very attractive for practical multiple input and multiple output (MIMO) applications. [ABSTRACT FROM PUBLISHER]

The gain bandwidth constraint of sequential-rotation arrays (SRAs) has been an open issue since it was first pointed out in 1989. This paper reveals the reason, provides some useful conclusions and proposes an optimum design. Firstly, a first-order analytical formula is derived for the array factor (AF) of the 4-element sub-SRA. The formula embraces the polarization properties of the antenna elements. The AF is found to be dependent on the elements' polarization properties and frequency, which is not found in conventional regular arrays. Based on the theoretical results and full-wave simulations, these dependencies are analyzed in detail. Secondly, an optimum design is proposed to enhance the gain bandwidth: to constitute SRA with elliptically polarized elements (this type of SRA is denoted as EP-SRA) rather than the conventional circularly polarized elements (this type of SRA is denoted as CP-SRA). Detailed design guidance is presented for this new method. Finally, as an example, a CP-SRA and an EP-SRA are designed and tested for comparison. According to the example, by employing EP-SRA, the 1 dB AF bandwidth is improved by 80%, the measured 1 dB/3 dB gain bandwidth is enhanced by 114%/76%. In fact, the conventional CP-SRA and LP-SRA (SRA with linearly polarized elements) are two special cases of the proposed EP-SRA. [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]

A decoupling technique for a symmetric four-element compact array is proposed. A dummy array terminated with optimum reactive loads is introduced to cancel the mutual couplings between the four radiating elements. A theory that leads to a general design procedure is developed. The technique is demonstrated by three practical design examples, including a compact and low-profile “cheese-cake” antenna array. Calculated channel capacities demonstrate that the performance of a 4-by-4 MIMO communication system that uses the cheese-cake array can be significantly improved as compared to the system using its coupled counterpart. This technique provides a promising approach to the design of a compact four-element array for a MIMO communication system. [ABSTRACT FROM PUBLISHER]

In this article, an effective design method is presented to design a miniaturized UWB antenna with four band-notches. By carefully integrating C-shaped slots, L-shaped open circuit stub, and T-shaped parasitic strip onto the primitive miniaturized antenna, four band-notches (VSWR > 2) could be achieved at 3.38-3.65 GHz, 4.95-6.05 GHz, 7.42-7.78 GHz, and 8.1-8.9 GHz to reject WiMAX, WLAN, X-band satellite communication, and ITU 8 GHz band signals. Simulated and measured results show that this antenna could operate from 3.15-11.1 GHz (VSWR < 2), and maintain omnidirectional directivity patterns at H-plane. Moreover, the proposed antenna has a very compact size of 18.6 × 22 × 1.5 mm3. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:1202-1206, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27546 [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 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]

Significant advances in the development of millimeter-wave and terahertz (30–10 000 GHz) technologies have been made to cope with the increasing interest in this still not fully explored electromagnetic spectrum. The nature of electromagnetic waves over this frequency range is well suited for the development of high-resolution imaging applications, molecular-sensitive spectroscopic devices, and ultrabroadband wireless communications. In this paper, millimeter-wave and terahertz antenna technologies are overviewed including the conventional and nonconventional planar/nonplanar antenna structures based on different platforms. As a promising technological platform, substrate-integrated circuits (SICs) attract more and more attention. Various substrate-integrated waveguide (SIW) schemes and other synthesized guide techniques have been widely employed in the design of antennas and arrays. Different types of substrate-integrated antennas and beamforming networks are discussed with respect to theoretical and experimental results in connection with electrical and mechanical performances. [ABSTRACT FROM PUBLISHER]

A 24-GHz microstrip array antenna is developed on a single-layer electrically-thin substrate to provide a cost-effective solution for automotive applications. By etching two straight slots close to and parallel with the non-radiating edges, the impedance bandwidth of a conventional rectangular microstrip patch is enhanced without affecting its radiation characteristics. To demonstrate the effectiveness of the proposed technique, an 8\,\times\,8 planar array with a specified sidelobe level of 25 dB in both the E-plane and H-plane is studied and prototyped on the commercial substrate RT/duroid 5880 with a thickness of 0.25 mm. The measured impedance bandwidth for VSWR less than 2 is about 1.8 GHz, which corresponds to a relative bandwidth of 7.5%. In addition, the measured gain is 22.5 dBi at the center frequency while it is higher than 21 dBi over a frequency band of 1 GHz. Finally, the measured sidelobe level is 20 dB in the E-plane and 18 dB in the H-plane. [ABSTRACT FROM PUBLISHER]

This article presents a fundamental strategy for accurately modeling the mutual coupling of arbitrary order in any large-scale electromagnetic structures and high-density integrated chips such as antenna array elements and coupled circuit elements. The proposed method starts from the modeling of the first-order mutual coupling, and it consists of two main steps. First of all, an equivalent circuit model describing low-order mutual coupling (adjacent coupling) is characterized and established, of which each parametric value is accurately extracted by making use of a numerical calibration technique. Then, the circuit model for high-order mutual coupling (crossover or crosstalk coupling) is generated from the lower order models, and it can further be used for the modeling of mutual coupling of any higher order. The accuracy and efficiency of the proposed method are demonstrated by three different kinds of structure including a linear phased array antenna, a finite periodic electromagnetic structure, and a planar low-pass filter. This novel approach represents an easy, fast, and effective characterization of arbitrary-order mutual coupling. It can find applications in the modeling of mutual coupling between any circuit elements and building blocks such as antennas, resonators, and even small discontinuities, and it promises to be helpful for the analysis and iterative design of microwave circuits and antenna arrays. © 2010 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2011. [ABSTRACT FROM AUTHOR]

A novel bandwidth enhancement technique for phase-reversal Franklin-type antennas is proposed. Impedance bandwidth enhancement is achieved by combining several coupled modes of the antenna structure through periodic loading provided by radiating crossover dipoles. This technique is explained by the theory of periodically loaded transmission lines. Radiation pattern bandwidth enhancement is achieved by exciting the antenna in its center so as to suppress beam squinting by superposing the tilted beams of two resulting sub-arrays on either side of the feed. An offset parallel stripline (OPS) phase-reversal antenna using these bandwidth enhancement techniques is demonstrated theoretically and experimentally at 35 GHz. The antenna is printed on a thin substrate suspended over a micro-machined conductor-backed cavity for unidirectional radiation. The overall fractional bandwidth of the antenna is increased from 3% to over 11% compared to the conventional design and the antenna efficiency exceeds 80%. [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]

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]

A new phased-array driver module for a two-antenna array is proposed in this paper. This driver, designed using a six-port phase discriminator, automatically controls the phase of one antenna-array element in order to maximize the received power. The results for a phased two-antenna array operating at 2.45 GHz are presented and discussed. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 46: 346–349, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20983 [ABSTRACT FROM AUTHOR]

Presents a study which discussed a novel top-sleeve monopole antenna in parallel plates. Role of a coaxially fed monopole to microwave devices and communication antennas; Results and discussion; Conclusion.

A novel configuration of millimeter-wave planar array antenna based on low-temperature cofired ceramic (LTCC) technology is investigated. The configuration exploits the three-dimensional (3-D) integration feature of LTCC by incorporating a novel quasi-cavity-backed patch (QCBP) element using a pair of grid-like conductor walls and a mixed feeding network configuration. A proposed LTCC planar array antenna consisting of 16 by 16 elements is designed, manufactured and tested. Good agreement is achieved between the theoretical performance and the measured results. [ABSTRACT FROM AUTHOR]

The growing complexity of satellite and mobile communication systems means that there are increasing needs for antenna arrays with multiple-beam capability. Conventional beamforming-network (BFN) configurations can be realized by different types of transmission lines, such as a microstrip line or waveguide. However, each of these has its own obvious defects. As part of a new generation of high-frequency integrated circuits, called substrate integrated circuits (SICs), substrate-integrated-waveguide (SIW) technology combines the benefits of both planar transmission-line and non-planar-waveguide technologies. It presents an excellent solution for the design and implementation of high-frequency beamforming networks, including for use at millimeter wavelengths. This paper overviews the state-of-the-art of substrate-integrated-waveguide techniques in the design and realization of innovative beamforming networks, and multibeam antenna arrays for low-cost satellite and mobile systems. Different classes of substrate-integrated-waveguide-based structures are theoretically and experimentally studied and demonstrated, to offer unprecedented performance and opportunities for specific space-and ground-based applications. [ABSTRACT FROM PUBLISHER]