Showing papers on "Slot antenna published in 2018"

Tapered Fed Compact UWB MIMO-Diversity Antenna With Dual Band-Notched Characteristics

Abstract: In this paper, a compact design of multiple-input multiple-output (MIMO) Antenna with dual sharply rejected notch bands for portable wireless ultrawideband (UWB) applications is presented and experimentally investigated. The proposed UWB MIMO Antenna has a compact size of 18 mm $\times$ 34 mm. The tapered microstrip fed slot Antenna acts as a single radiating element with inverted L-shaped slits to introduce notches at wireless local area network and the IEEE INSAT/Super-Extended C-bands. The mutual coupling of less than −22 dB is achieved over the entire operating band (2.93–20 GHz). At the center of notched band, the efficiency of the Antenna drops that indicates a good interference suppression performance. The performance of the MIMO Antenna in terms of isolation among the ports, radiation pattern, efficiency, realized gain, envelope correlation coefficient, mean effective gain, and total active reflection coefficient is studied.

A Novel 28 GHz Beam Steering Array for 5G Mobile Device With Metallic Casing Application

Abstract: The design of a novel practical 28 GHz beam steering phased array antenna for future fifth generation mobile device applications is presented in this communication. The proposed array antenna has 16 cavity-backed slot antenna elements that are implemented via the metallic back casing of the mobile device, in which two eight-element phased arrays are built on the left- and right-side edges of the mobile device. Each eight-element phased array can yield beam steering at broadside and gain of >15 dBi can be achieved at boresight. The measured 10 dB return loss bandwidth of the proposed cavity-backed slot antenna element was approximately 27.5–30 GHz. In addition, the impacts of user’s hand effects are also investigated.

12-Port 5G Massive MIMO Antenna Array in Sub-6GHz Mobile Handset for LTE Bands 42/43/46 Applications

Abstract: A 12-port antenna array operating in the long term evolution (LTE) band 42 (3400–3600 MHz), LTE band 43 (3600–3800 MHz), and LTE band 46 (5150–5925 MHz) for 5G massive multiple-input multiple-output (MIMO) applications in mobile handsets is presented. The proposed MIMO antenna is composed of three different antenna element types, namely, inverted $\pi $ -shaped antenna, longer inverted L-shaped open slot antenna, and shorter inverted L-shaped open slot antenna. In total, eight antenna elements are used for the $8 \times 8$ MIMO in LTE bands 42/43, and six antenna elements are designed for the $6 \times 6$ MIMO in LTE band 46. The proposed antenna was simulated, and a prototype was fabricated and tested. The measured results show that the LTE bands 42/43/46 are satisfied with reflection coefficient better than −6 dB, isolation lower than −12 dB, and total efficiencies of higher than 40%. In addition to that, the proposed antenna array has also shown good MIMO performances with an envelope correlation coefficient lower than 0.15, and ergodic channel capacities higher than 34 and 26.5 b/s/Hz in the LTE bands 42/43 and LTE band 46, respectively. The hand phantom effects are also investigated, and the results show that the proposed antenna array can still exhibit good radiation and MIMO performances when operating under data mode and read mode conditions.

Multiband 10-Antenna Array for Sub-6 GHz MIMO Applications in 5-G Smartphones

Abstract: A multi-band 10-antenna array working at the sub-6-GHz spectrum (LTE bands 42/43 and LTE band 46) for massive multiple-input multiple-output (MIMO) applications in future 5G smartphones is proposed. To realize $10\times 10$ MIMO applications in three LTE bands, 10 T-shaped coupled-fed slot antenna elements that can excite dual resonant modes are integrated into a system circuit board. Spatial and polarization diversity techniques are implemented on these elements so that the improved isolation and mitigated coupling effects can be achieved. The proposed antenna array was manufactured and experimentally measured. Desirable antenna efficiencies of higher than 42% and 62% were measured in the low band and high band, respectively. Vital results, such as the envelope correlation coefficient, channel capacity, and mean effective gain ratio, have also been computed and analyzed. The calculated ergodic channel capacities of the $10\times 10$ MIMO system working in the LTE bands 42/43 and LTE band 46 reached up to 48 and 51.4 b/s/Hz, respectively.

Wearable Circular Ring Slot Antenna With EBG Structure for Wireless Body Area Network

Abstract: A wearable circular ring slot antenna with electromagnetic bandgap (EBG) structure for wireless body area network application is proposed in this letter. According to the analysis of equivalent circuit model, the volume of the EBG element is miniaturized for wearable applications. The measured impedance bandwidth of the proposed antenna is observed to be 2.28–2.64 GHz, which covers the 2.4 GHz Industrial Scientific Medical (ISM) band. The measured half-power beamwidths are 60° and 54° in the H -plane and the E -plane, respectively, and the front-to-back ratios are 17 and 13 dB in the H -plane and the E -plane, respectively. The specific absorption rate calculated values for tissue in 1 g (for the U.S. standard) and 10 g (for Europe standard) are both less than the limitations. In conclusion, it is proper to use the proposed antenna in wearable applications.

Planar Millimeter-Wave 2-D Beam-Scanning Multibeam Array Antenna Fed by Compact SIW Beam-Forming Network

Abstract: A planar millimeter-wave 2-D beam-scanning multibeam array antenna fed by compact 16-way beam-forming network (BFN) in multilayered substrate integrated waveguide (SIW) technology is addressed. The BFN is formed by connecting two stacks of sub-BFNs, the E-plane sub-BFN and the H-plane sub-BFN. The H-plane sub-BFN is realized by a traditional H-plane $4 \times 4$ Butler matrix (BM). The key point of this design is to propose an E-plane $4 \times 4$ BM which realizes a planar E-plane sub-BFN. These two sets of sub-BFNs can joint directly without resorting to any connectors or connecting networks to form such a compact 16-way BFN with a reduced area of merely $3\lambda \times 12\lambda $ . After that, to be compatible with the proposed BFN, a ladder-type $4 \times 4$ slot antenna array is employed, which is comprised of four linear $1 \times 4$ slot antenna arrays. Different from traditional array, the four subarrays are distributed in separate layers for the purpose of jointing to the BFN more conveniently. Transition network are also required to connect the BFN with the antenna array. Finally, a compact 2-D scanning multibeam array antenna based on the planar SIW BFN are fabricated and measured, which would be an attractive candidate for 5G application.

Design of Triple Band Differential Rectenna for RF Energy Harvesting

Abstract: A triple band differential rectenna for RF energy harvesting applications is proposed in this paper. The rectenna is designed to operate in frequency bands of universal mobile telecommunication service (2.1 GHz), lower WLAN/Wi-Fi (2.4–2.48 GHz), and WiMAX (3.3–3.8 GHz). For designing the proposed rectenna, first a differentially fed multiband slot antenna that works as the front-end receiving unit is designed, fabricated, and tested to check its performance. It is observed that a peak antenna gain of 7, 5.5, and 9.2 dBi is achieved at 2, 2.5, and 3.5 GHz, respectively. In the next step, a triple band differential rectifier is designed using the Villard voltage doubler where interdigital capacitors (IDCs) in lieu of lumped components are used. The full rectifier circuit comprising of the rectifying unit and impedance matching circuit is fabricated and tested to check its performance in the desired bands. The peak RF-dc conversion efficiency of 68% is obtained using the three-tone measurement. In the final stage, both antenna and the rectifier circuit are integrated through SMA connecter in order to implement the proposed rectenna. Measurement of the proposed rectenna shows an approximate maximum efficiency of 53% at 2 GHz, 31% at 2.5 GHz, and 15.56% at 3.5 GHz.

Design of Frequency-and Polarization-Reconfigurable Antenna Based on the Polarization Conversion Metasurface

Abstract: A frequency- and polarization-reconfigurable antenna composed of a metasurface, a planar slot antenna, and a metallic reflector is proposed in this letter. The metasurface is made up of 64 identical patches, and all the patches are on the top surface of the substrate. In order to extend the bandwidth of the antenna, the planar slot antenna adopts a double-slot structure. The reconfiguration of frequency and polarization can be achieved by adjusting the relative positions between the metasurface and the planar slot antenna. The antenna can be reconfigured to linear polarization, and left-hand and right-hand circular polarizations. At the same time, the gain of the antenna is improved. In order to verify this method, a frequency- and polarization-reconfigurable antenna is designed. Simulation and experimental results show that the polarization reconfiguration can be achieved from 8 to 11.2 GHz (fractional bandwidth of 33.33%) by adjusting the distance among the metasurface, source antenna, and metallic reflector. The maximum gain can achieve 16.5 dBi.

A mmWave Wideband Slot Array Antenna Based on Ridge Gap Waveguide With 30% Bandwidth

Abstract: A wideband $8 \times 8$ element slot antenna array based on ridge gap waveguide feeding network has been proposed for mmWave applications. The antenna subarray consists of four radiating slots which are excited by a groove gap cavity layer. Compared with previously published works, the proposed planar antenna array has quite wide impedance bandwidth. The antenna covers a wideband of 50–67.8 GHz with 30% impedance bandwidth (VSWR < 2). Also, the antenna has only 2.5 dB gain variation over the entire bandwidth which implies also good radiation characteristics for the proposed antenna. The maximum measured gain value is about 27.5 dBi with a total efficiency of 80% for the proposed antenna within the band of interest. With this performance, the proposed antenna array is a promising candidate for mmWave communication systems.

A SAR Reduced mm-Wave Beam-Steerable Array Antenna With Dual-Mode Operation for Fully Metal-Covered 5G Cellular Handsets

Abstract: In this letter, a specific absorption rate (SAR) reduced 28 GHz beam-steering array antenna with dual-mode operation for a fully metal-covered fifth-generation (5G) cellular handset is proposed. The proposed antenna consists of two subarrays, each of which has eight rotated slot antenna elements, which are arranged on the upper frame and on the part of the back cover of the handset. The subarrays are selected according to the modes by using a switch. The proposed array demonstrates good reflection coefficients in the frequency band ranging from 27.2 to 28.2 GHz and the mutual couplings between antenna elements are less than –11.8 dB. The proposed antenna has good beam-steering properties and a hemispherical beam coverage for a millimeter-wave (mm-wave) 5G cellular handset. The calculated peak SAR values on the head phantom by the proposed structure, for the beam scan angles of 0° and 40°, are 0.53 and 0.88 W/kg, respectively, when the input power of each subarray is 24 dBm.

Ka-Band Near-Field-Focused 2-D Steering Antenna Array With a Focused Rotman Lens

Abstract: This paper presents a near-field-focused (NFF) substrate-integrated waveguide (SIW) antenna at a center frequency of 35 GHz with 2-D steerable focus. The proposed antenna is achieved by combining an NFF leaky-wave slot antenna array with a focused multibeam SIW Rotman lens. In most of the existing NFF planar antennas, the total phase distribution on the radiating aperture is separated into two parts with respect to the E-plane and the H-plane, which leads to a large error and deteriorates the NFF performance. Here, a modified NFF planar antenna synthesis method is proposed to calculate the desired phase distribution on the aperture and completely eliminate such an error at the center frequency. The linear NFF leaky-wave slot antenna is designed to scan the focal point in the H-plane with the frequency. The 15 leaky-wave slot antennas are grouped in a special topology and excited by the focused SIW Rotman lens. In this case, multiple focal points can be generated in the E-plane. Moreover, an SIW matching load is developed to improve the NFF beam performance. The whole NFF antenna is integrated into a single-layer substrate. The measured results are in agreement with the simulated ones.

A multiband reconfigurable slot antenna for wireless applications

Abstract: This research presents a novel four band frequency reconfigurable antenna for 1.6 (Global Navigation Satellite system (GNSS)), 2.5 (Lower Worldwide Interoperability for Microwave Access (WiMAX)), 5.8 (Wireless local area network (WLAN)) and 9.8 GHz (X-band) frequency bands. The antenna has a compact size of 0 . 18 λ 0 × 0.18 λ 0 × 0.0096 λ 0 at lower resonance of 1.8 GHz and is printed on FR4 material with height (h) = 1.6 mm, dielectric constant ( ( e r ) = 4.4 and loss tangent ( δ ) = 0.02. Multiband phenomenon in the antenna is achieved by etching trapezoidal slot in the radiating monopole and rectangular slots in the ground plane. Frequency reconfiguration in the proposed structure is achieved by placing PIN diode switch between rectangular slot placed in the ground plane. During OFF state, the antenna exhibit quad band with S11

A Compact Wideband Flexible Implantable Slot Antenna Design With Enhanced Gain

Abstract: In this communication, a coplanar waveguide-fed, compact, wideband dual-ring slot antenna for biomedical applications in the Industrial, Scientific and Medical frequency band is presented. This implantable antenna is designed using thin and biocompatible substrate–superstrate layers to achieve human body insulation as well as flexibility. Despite showing good antenna performances, only the realized gain value is observed to be reduced (−12 dB). To improve the antenna gain, a metamaterial (MTM) array with epsilon very large behavior has been introduced on the superstrate of the implantable antenna. Using the MTM, about 3 dB gain enhancement has been observed. Even after the introduction of the MTM superstrate, wideband characteristic and flexibility are maintained. Also, the specific absorption rate (SAR) analysis of the antenna configuration with and without MTM has been studied. A low SAR is obtained in both the cases. The fabricated antenna parameters have been measured with the in vitro test by immersing the antenna inside a single-layer tissue emulating gel, as well as, inside a chicken breast slab.

A Multibeam Cylindrically Conformal Slot Array Antenna Based on a Modified Rotman Lens

Abstract: A dual-layer multibeam conformal slot array antenna operating at a center frequency of 10 GHz is proposed in this paper. The antenna consists of a microstrip Rotman lens and a substrate-integrated waveguide (SIW) array of $10{\times} 10$ radiating slots, which is axially mounted onto a cylindrical surface with a radius of 90 mm, i.e., $3\lambda _{0}$ . The Rotman lens feeds the slot array through the coupling slots in the broad sides of the SIWs. An improved design process is introduced for realizing a conformal Rotman lens for cylindrically conformal arrays. There are unique requirements for the phase distribution and phase compensation in cylindrically conformal applications. The Rotman lens and slot antenna are built and optimized in full-wave simulation software. To validate the proposed concepts, a conformal antenna prototype is implemented and measured. The experimental results demonstrate a scanning range of ±46°, with a −3 dB crossover level between adjacent radiation beams in the E-plane and a −20 dB sidelobe level in the H-plane. The measured and simulated radiation patterns of all the scanned beams are in good agreement. This type of multibeam conformal slot array has been theoretically and experimentally studied, and it demonstrated the potential for applications in aircraft, missiles, and high-speed vehicles.

High Gain, Broadband and Dual-Polarized Substrate Integrated Waveguide Cavity-Backed Slot Antenna Array for 60 GHz Band

Abstract: In this paper, a compact substrate-integrated waveguide (SIW) cavity-backed slot antenna array with high gain, broadband, and dual-polarization performances is proposed for 60-GHz applications. An enhanced 17.1% impedance bandwidth was achieved by cutting semi-circle edges on the conventional slot radiator. A simplified SIW feed network is aperture-coupled vertically and constructed on a double-layered structure to implement the dual-polarization operation. By adopting innovative techniques on both radiating element and double-layered SIW feed networks, a high-gain, broadband, and dual-polarized $8\times8$ antenna array was designed on three-layered printed circuit board that allows for mass production. This configuration also resolves the trade-off between the bandwidth and gain of the existing 60-GHz dual-polarized antenna array. Its feasibility is proved by obtaining a measured gain in the range of 19.7–22.3 dB and an enhanced impedance bandwidth of 17.1% over 55.7–66.1 GHz for both horizontal and vertical polarizations. With advantages of high-gain, broadband, and dual-polarization performances in a low-cost low-profile structure, the proposed antenna array is a promising candidate for millimeter-wave wireless systems.

Trident-shape strip loaded dual band-notched UWB MIMO antenna for portable device applications

Abstract: In this paper, a novel compact dual band-notched ultra-wideband (UWB) multiple-input multiple-output (MIMO) antenna of size 22 × 26 × 0.8 mm 3 is proposed for portable devices. The antenna comprises of two stepped slot UWB antennas fed by 50 ohms microstrip line, T-shape slot and narrow slot. Dual band-notches from 5.4 to 5.86 GHz and 7.6–8.4 GHz are achieved by loading trident-shape strips on microstrip line. A T-shape slot is used on the ground plane to enhance impedance matching characteristics and to minimize mutual coupling above 4 GHz. To improve isolation further at 3–4 GHz, a narrow slot is used on ground. The proposed antenna is giving a good bandwidth ranging from 3.1 to 11.8 GHz with |S 11 | > 10 dB and mutual coupling larger than 20 dB in the entire operating band except at two rejected bands. The simulation and measurement results demonstrate that the antenna is more suitable for portable device applications.

A Flexible Dual-Band Antenna With Large Frequency Ratio and Different Radiation Properties Over the Two Bands

Abstract: The coexistence of microwave and millimeter-wave technologies becomes the inexorable trend of future wireless communication systems. The corresponding components of the system are required to cover these two frequency bands simultaneously. However, it is difficult for the existing dual-band antenna configurations to achieve a frequency ratio larger than 3. In this paper, a novel topology is proposed to solve this problem. For the desired dual-band operation, a signal routing approach is proposed to guide the microwave/millimeter signals to the specific elements, respectively. The classical aperture coupling mechanism is deliberately utilized to block the millimeter-wave signal from feeding to the microwave antenna element and route the millimeter-wave signal into the millimeter-wave antenna element. Meanwhile, the substrate- integrated waveguide (SIW)-based millimeter-wave antenna element has the high-pass nature to reject the microwave signal. Therefore, the antenna elements for microwave and millimeter-wave bands can be designed separately with a high flexibility. First, a dual-band antenna was implemented to support 5.8 and 30 GHz simultaneously by integrating an annular-ring antenna element and an SIW slot antenna element. Furthermore, different radiation properties at the two bands can be easily realized owing to the high flexibility of the proposed approach. For validation, these two antennas were fabricated and measured.

An Integrated SIW Cavity-Backed Slot Antenna-Triplexer

Abstract: A low-profile antenna-triplexer is realized using a substrate integrated waveguide (SIW) technology for radio altimeter/WLAN/ISM band applications. The antenna is composed of two SIW cavity resonators where a smaller cavity is nested inside the larger one. The larger cavity is excited by using two distinct microstrip feedlines, while the smaller one by a coax probe. The antenna produces three distinct resonances around 4.18, 5.2, and 5.8 GHz simultaneously employing one annular slot and two transverse slots. By exciting cavity modes (TE110/TE 120) and the patch mode (TM10) simultaneously, an average isolation of better than 23 dB is accomplished among three input ports. As compared to the conventional counterparts, the proposed geometry is simple to realize in a compact space. To validate the proposed idea, the design is experimentally tested, and the measured responses show a good agreement with the simulations. Moreover, the antenna shows a front-to-back ratio better than 19 dB and measured gain values of 6.56, 4.2, and 5.85 dBi at three resonances. The proposed design is compact, easy to fabricate, and capable to integrate with planar circuits.

A Third-Order SIW-Integrated Filter/Antenna Using Two Resonant Cavities

Abstract: A third-order substrate integrated waveguide (SIW) integrated filter/antenna is presented in this letter. The filter/antenna is composed of two cavity resonators with a slot antenna in the second cavity. The slot antenna excites two modes in the slot cavity, creating a third-order filtering response while preserving the radiating characteristics. A transmission zero can be arbitrarily placed below or above the passband. The filter/antenna operates at a center frequency of 3.71 GHz and has an 8.29% fractional bandwidth with a 5.10 dBi antenna gain.

A Dual-Band Frequency Reconfigurable MIMO Patch-Slot Antenna Based on Reconfigurable Microstrip Feedline

Abstract: In this paper, a novel microstrip feedline-based dual-band frequency reconfigurable multiple-input multiple-output (MIMO) patch-slot antenna design is presented. The antenna has a planar structure and comprises four symmetrically placed rectangular patch antenna elements. A dual-purpose hexagonal-shaped defected ground structure (DGS) is introduced into the ground plane for antenna size reduction and isolation enhancement. The overall size of the antenna is compact with total substrate area of $120\times 60\times1.6$ mm3 and is printed on FR4 substrate. Varactor diodes are integrated within feedline to achieve frequency reconfigurability. The proposed antenna design exhibits a wide continuous dual frequency reconfigurable characteristic from 1.3 to 2.6 GHz with isolation of more than 12 dB for entire band. The proposed design is verified by presenting the simulation and measured results of S-parameters, radiation pattern, efficiency, and envelope correlation coefficient (ECC), and displaying good agreement. ECC of less than 0.2 between the ports is achieved. The compact size and dual-band frequency reconfigurable characteristics make the proposed design potential candidate for wireless handheld devices and other multiband MIMO applications.

A Digital Multibeam Array With Wide Scanning Angle and Enhanced Beam Gain for Millimeter-Wave Massive MIMO Applications

Abstract: A novel full-digital multibeam array with wide scanning angle and enhanced beam gain is proposed for millimeter-wave massive multiple-input multiple-output applications. The array consists of 16 dual exponentially tapered slot antenna (DETSA) elements. Each element is integrated with a radio frequency receiver, an intermediate frequency chain, and an analog-to-digital converter (ADC). The H-plane radiation pattern of the proposed DETSA is very wide to enable the beam scanning in the azimuth plane. The beam gain is further enhanced by employing a 1-D multilayered planar lens that transforms the spherical wave into a plane wave in the E-plane for increasing the beam gain and keeping the phase compensation unaltered in the H-plane. Meanwhile, the planar lens is optimized to guarantee the wide scanning angle. In addition, all the signals received by the 16 independent channels are converted to a digital signal via ADC simultaneously and then used for synthesizing the multibeam patterns in the digital domain. Furthermore, the calibration and the verification of the synthesizing weights are discussed in detail. The measured results show that a scanning coverage of ±40° in the H-plane (or in horizontal plane) and an estimated maximum gain of 24.8 dBi with a gain tolerance of 3 dB can be achieved by the proposed 16-element array with a 1-D lens.

Dual-Band Annular Slot Antenna Loaded by Reactive Components for Dual-Sense Circular Polarization With Flexible Frequency Ratio

Abstract: This paper proposes a new design of dual-band reactively loaded annular slot antenna for dual-sense circular polarization radiation. Two concentric annular slots excited by a common microstrip feedline are employed to realize dual-band operation. Each slot can radiate a circularly polarized (CP) wave with a specified sense at its one or one-and-a-half wavelength resonance, given that an appropriately valued reactive component, i.e., capacitor or inductor, is introduced at a pre-determined location. A small frequency ratio (FR) can be achieved between the two oppositely sensed CP bands when a capacitor and an inductor are loaded, respectively, onto the inner and outer annular slots. Contrarily, two oppositely sensed CP bands that possess a large FR can be yielded when an inductor and a capacitor are loaded onto the inner and outer annular slots, respectively. For experimental verification, two antenna prototypes with FRs of 1.63 and 2.41 have been designed, fabricated, and measured. The measurement results exhibit a good agreement with the simulated ones. Details of design concerns and experimental results are presented and discussed.

A Self-Triplexing SIW Cavity-Backed Slot Antenna

Abstract: In this letter, a new design of self-triplexing slot antenna using substrate integrated waveguide (SIW) technique is demonstrated for multiband communication systems. The proposed antenna operates at triple frequency bands (around 6.53, 7.65, and 9.09 GHz) simultaneously utilizing a slot inserted on the top of the SIW cavity and is excited by three separate microstrip lines. By properly optimizing the antenna parameters, an isolation of better than 19 dB is realized between any two input ports, which helps to achieve self-triplexing property. The proposed triplexing antenna preserves simplicity, compactness, and a planar configuration that makes it suitable for highly integrated handheld devices. To demonstrate the significance of the proposed work, the antenna is prototyped, and experimental results show a close agreement with simulations. Moreover, the proposed antenna exhibits the measured gain of 3.1, 4.7, and 3.9 dBi at resonant frequencies with stable radiation patterns.

A Substrate Integrated Cavity Backed Filtering Slot Antenna Stacked With a Patch for Frequency Selectivity Enhancement

Abstract: A patch is proposed to stack above a substrate integrated cavity (SIC) backed filtering slot antenna to enhance antenna frequency selectivity The antenna is composed of a slot radiator backed by an SIC, a stacked patch, and a microstrip feed line Two parallel slots are cut onto the top broad wall of the SIC, which is excited by a microstrip line through a nonresonant short slot on the center of the bottom broad wall The stacked patch is positioned right above the SIC supported by a piece of substrate slab for gain enhancement Compared with the traditional SIC-backed slot antenna, the proposed antenna achieves higher frequency selectivity as well as enhanced bandwidth and gain The field distribution and parametric study are conducted to exhibit the operating mechanism of the antenna more clearly Compared with the conventional SIC-backed slot antenna, the antenna prototype operating at 10 GHz, as example, achieves wider 10 dB impedance matching bandwidth of 867%, higher gain of 72 dBi, better frequency selectivity of 09/045 at the lower and upper edges of the operation band, and lower maximum cross-polarization levels of −23/−22 dB in E- and H-planes within the 3 dB beam range, respectively

Bandwidth and Gain Improvement of an L-Shaped Slot Antenna With Metamaterial Loading

Abstract: A metamaterial-based wideband and high-gain circularly polarized (CP) mushroom antenna is proposed and analyzed in this letter. The proposed antenna consists of a $4 \times 4$ mushroom-cells array and an L-shaped slot coupling-fed layer. The metamaterial-based mushroom cells are adopted to adjust the axial ratio (AR) to realize wideband CP and high gain. With the optimization, the proposed dielectric-filled mushroom antenna is with a low profile of $0.08{\lambda _0}$ ( ${\lambda _0}$ is the operating wavelength in free space) while covering an area of $60\,{\text{mm}} \times 60\,{\text{mm}}$ only. The measured impedance bandwidth of the proposed antenna is 48.2% (5.2–8.5 GHz), and the measured 3 dB AR bandwidths are 35.5% (5.8–8.3 GHz). Moreover, the antenna performed a stable high gain which is better than 10.5 dBic from 6 to 7.5 GHz across the CP region.

A Low-Complexity Full-Duplex Radio Implementation With a Single Antenna

Abstract: This paper presents a novel low-complexity full-duplex radio design, which only uses a single patch antenna without any duplexer or circulator for passive suppression of self-interference, and a computationally efficient technique for linear digital cancellation. The proposed full-duplex design is tested for IEEE 802.11g Wireless Standard on the WARP (v3) software-defined radio implementation platform. It is shown that this design provides a total suppression of 88 dB, which is sufficient for low-power or short-range full-duplex communication. The dual polarized slot coupled patch antenna used in our design provides an interport isolation as high as 60 dB in 2.4 GHz band. Additionally, the digital domain cancellation utilizes a frequency domain-based estimation and reconstruction approach, which not only offers up to $61\%$ reduction in the computational complexity but also provides a $5-7$ dB better digital cancellation performance in highly selective channel conditions, as compared to the time-domain-based techniques. The proposed full-duplex implementation can be easily applied in OFDM-based wireless systems, such as IEEE 802.11, which is the considered air interface in this paper.

A Triband Circularly Polarized Strip and SRR-Loaded Slot Antenna

Abstract: In this communication, a simple and compact multiband circularly polarized (CP) slot antenna loaded with metallic strips and a split-ring resonator (SRR) is proposed. The multiband operation is obtained via exciting the SRR and copper strips by the microstrip-fed square slot antenna. The SRR resonates at 1.83 GHz, while the strips and the slot antenna provide resonances at 2.5 and 3.1 GHz. Resonant modes of loaded SRR and strips combined with the fundamental mode of the slot produce CP waves at the resonance frequencies of the proposed antenna. The proposed antenna allows for independent tuning of different bands via the use of the tilted strips and the SRR. Also, the sense of polarization at the resonance frequencies can be controlled by changing the orientation of the strips and the SRR with respect to the slot. The proposed antenna is fabricated on an FR-4 substrate of dimension $50 \times 50 \times 1.56$ mm3. Antenna performances in terms of 10 dB return loss bandwidth, 3 dB axial ratio bandwidth, gain, and efficiency are validated experimentally and are in a good agreement with the simulated results.

60 GHz Substrate-Integrated Waveguide-Based Monopulse Slot Antenna Arrays

Abstract: This communication presents a new kind of substrate-integrated waveguide (SIW) slot antenna array with 1-D and 2-D monopulse radiation patterns. First, a new SIW magic-tee is developed, which exhibits a wide phase/amplitude balance bandwidth. Then, the magic-tee is extended to a new comparator which is used to feed the antenna with 2-D monopulse radiation pattern. Based on the proposed magic-tee and the comparator, 1-D and 2-D monopulse slot antenna arrays with $4\times 4$ elements are designed and measured, respectively. The experimental results show that the arrays exhibit good monopulse performance. More importantly, compared with their former counterparts, the monopulse performance of the arrays exhibits merely slight degradation over a much wider bandwidth due to the wide phase/ amplitude balance bandwidth that the comparators achieved.

Compact and Low-Cost 3-D Printed Antennas Metalized Using Spray-Coating Technology for 5G mm-Wave Communication Systems

Abstract: This letter presents a design of two compact, light, rigid, and low-cost three-dimensionally (3-D) printed millimeter-wave antennas for a fifth-generation (5G) communication system. The proposed antennas consist of a radiating slot that is surrounded by a rectangular cavity and corrugations, which boost the gain performance of the antennas. Furthermore, the proposed antennas are fabricated using 3-D printing technology, and they are metalized using novel, simple, and low-cost techniques, which utilize the commercial conducive spray-coating technology. The proposed antennas operate at a 28 GHz band, where the first design is fed by a waveguide to prove the performance, whereas the second design is fed by a microstrip line to demonstrate the ability to be integrated into a compact structure. Measurement results show a wide impedance bandwidth, which enables the proposed antenna design to be a strong candidate for 5G applications.