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This letter presents a planar inverted-F antenna (PIFAs) system for Wireless Fidelity 6 (Wi-Fi 6) and Wi-Fi 6E applications with compact size and high isolation. To realize decoupling in a guided way, single-mode structure is proposed based on common mode and differential mode theory. For the demonstration, the mutual coupling between two back-to-back asymmetric PIFAs was reduced by etching two slots on the ground. The measured results show that the two PIFAs, respectively, achieve the impedance bandwidth of 5.14–6.03 GHz and 5.90–7.24 GHz, and the port isolation higher than 17.4 dB across 5.14–7.24 GHz frequency band. [ABSTRACT FROM AUTHOR]

This article demonstrates an electronically scanned reflectarray antenna based on liquid crystal (LC). The LC-based reflectarray element was designed as a periodically loading of parallel H-shaped polygons on two metal layers. To realize a tunable reflection phase and reduce the inhomogeneity effect of LC, an $8~\mu \text{m}$ -thick LC layer was designed as a varactor rather than a substrate. In simulations, the adjustable reflection-phase range of the proposed element was 180° in the frequency band 21–21.5 GHz. The design concept was verified on a reflectarray prototype containing 26 rows of the basic elements. In addition, a 32-channel control circuit was designed and fabricated for biasing. The measured results confirmed a tunable phase range of 150° at 23.8 GHz. The disagreements between the simulated and measured results are discussed, and a test process is proposed. As a proof of concept, the main beam was steered to 0°, −40°, and −60° in one plane. The result confirmed the high beam-steering capability of the proposed reflectarray with measured gains above 18 dB at 23.8 GHz. This work provides useful references for the design and measurement of LC-based reflectarray antennas. [ABSTRACT FROM AUTHOR]

A high-gain low-profile leaky-wave antenna (LWA) for vertically-polarized (VP) fixed-beam endfire radiation is proposed in this article. The LWA is composed of two back-to-back half-mode waveguides with grooves etched at the margins of both radiation edges. By etching grooves, the phase velocity of the traveling wave can be tailored to slower than the wave velocity in free space for fitting the Hansen–Woodyard condition. Compared with periodic LWAs, the proposed antenna continuously radiates at two symmetric apertures, contributing to a high endfire gain. A prototype is fabricated and tested to validate the concept. The measured and simulated results are in good agreement. A simulated gain of 14.29 dBi and a measured gain of 13.37 dBi are achieved within an antenna length of $3.05\lambda _{0}$. Moreover, a measured overlapping bandwidth of 2.74–3.17 GHz (14.3%) is realized with $S_{11} < - 10$ dB and gain variation less than 3 dB. To the best of the authors’ knowledge, the proposed VP endfire LWA realizes the highest aperture efficiency and shows great advantages in high gain, low profile, and wide bandwidth. [ABSTRACT FROM AUTHOR]

In this letter, a novel reconfigurable 0°/90° phase shifter is proposed. Compared with the conventional phase shifters, the proposed one uses fewer reconfigurable devices and becomes more compact. Two states of a meander line are used to generate the 90° phase shift, making it suitable for the 2-D beam steering 2-bit array application. A phase shifter prototype on F4B was measured to validate its design theory. Four phase states (i.e., 0°, 90°, 180°, and 270°) are realized through the combination of the phase shifter and the array radiation element. A 2 × 4 array working at 1.5 GHz was fabricated and measured to verify the performance of the proposed phase shifter. When different phase states are switched, the measured peak gain of the array varies from 10.6 to 11.2 dBi. [ABSTRACT FROM AUTHOR]

This article presents a pattern-reconfigurable saber-like antenna with low wind drag for the onboard communication application, under the requirement of upper hemispherical coverage. The compact antenna mainly consists of a segmented loop and a $\Pi $ -shaped polygon, which are closely integrated for compact size. By controlling the OFF/ON states of a p-i-n diode embedded in the segmented loop, the proposed antenna can be operated at dipole/monopole modes. An upper hemispherical coverage area can be achieved since broadside and omnidirectional patterns are obtained at dipole and monopole modes, respectively. To validate the design strategy, a prototype was fabricated and tested. A good agreement between the simulated and measured results is achieved. The measured −8 dB reflection coefficient common bandwidth of two modes is from 2.16 to 2.63 GHz with the relative bandwidth of 19.6% while keeping a smaller size of $30.5\times 32.5\times 0.6$ mm3 ($0.24\,\,\lambda _{0} \times 0.26 \lambda _{0}\times 0.005 \lambda _{0}$ , $\lambda _{0}$ is the free-space wavelength at the center frequency). We portend that the proposed design scheme, with merits of low wind drag, metal ground compatibility, and upper hemispherical coverage, has the potential for airborne application. [ABSTRACT FROM AUTHOR]

In this communication, a millimeter-wave (mm-wave) air-filled slot antenna with a conical beam at 60 GHz is proposed. The antenna is suitable to be integrated with various IC systems mainly because it is designed and fabricated based on bulk silicon microelectromechanical systems (MEMS) technology. The whole structure is composed of an antenna part and a waveguide to substrate integrated waveguide (SIW) converter. In the antenna part, four meander slots are arranged annularly and excited by a square air cavity. The conical radiation pattern benefits from the out-phase ${E}$ -field excited on slots. An operating bandwidth of 2.17% for S11 < −10 dB and a conical beam peak gain of 3.21 dBi are achieved. The proposed antenna shows its potentials in mm-wave indoor communication. [ABSTRACT FROM AUTHOR]

This communication presents a dual-mode dipole antenna for impedance bandwidth improvement. In our approach, an electrically small loop (ESL) resonator is properly loaded to compress the operating frequencies of first- and third-order modes. With the existence of ESL, the third-order mode shifts to its first-order mode to obtain a wide bandwidth with stable polarization and radiation patterns, due to the fact that ESL is equivalent to an orthogonal magnetic dipole at the third-order mode. To validate the design strategy, a prototype was fabricated and tested. Omnidirectional radiation pattern in H-plane is achieved over the entire operating band from 2.94 to 3.89 GHz while keeping a smaller size of $0.45\lambda _{0}\times 0.17\lambda _{0} (\lambda _{0}$ is the wavelength in free space at the center frequency). Good agreement has been obtained between measurement and simulation. [ABSTRACT FROM AUTHOR]

In this letter, a dual-beam periodic leaky-wave antenna with a low beam-squinting character is presented. It has a simple and low-profile configuration, which consists of 15 slot radiating elements and one microstrip feedline. The slot radiating element creates nulls in the pattern at forward and backward endfire. By properly arranging the radiating elements with a small separation, the higher order spatial harmonics are suppressed. Fed by an air-substrate microstrip line working on the non-dispersion transverse electromagnetic (TEM) mode, the antenna has a moderate phase constant leading to a stable endfire array factor. By integrating the almost unchanged array factor and element pattern, the dual-beam radiation pattern with reduced beam squinting is obtained. To verify the design strategy, a prototype was designed, fabricated, and measured. Over the operating bandwidth from 2.7 to 3.2 GHz, the antenna exhibits a small measured beam squint of 6.8°. [ABSTRACT FROM AUTHOR]

In this letter, a novel high-gain leaky-wave endfire antenna is proposed. By utilizing an air substrate parallel strip line, which is periodically disturbed by the radiating elements, such as the feedline, the phase constant of the antenna approaches the phase requirement of the Hansen–Woodyard (H–W) condition. By optimizing the size of the radiating element, which is dipole element, an approximately constant aperture distribution is obtained by the antenna. Thereby, with the characters similar to the H–W endfire antenna around the center frequency and moderate phase constant over the operating bandwidth, the antenna achieves a high gain, narrow beamwidth, and stable endfire radiation pattern. With the radiating aperture length of two wavelengths, the antenna generates the measured gain of 12.5 dBi at the center frequency of 5 GHz, operating bandwidth of 20.8%, and measured 1 dB gain bandwidth of 16.2%. Fabricated by metal, the antenna may be an attractive substitute for the long-distance communication applications, especially for the systems where cost and power capacity are important. [ABSTRACT FROM AUTHOR]

A broadband and high-gain endfire antenna array fed by an air-substrate parallel strip line is proposed in this communication. It has a simple and planar structure consisting of multiple dipole radiating elements and one parallel strip line. By utilizing the center-fed dipole working between the first and third resonances as the radiating element, the antenna array could obtain stable radiating capability over a broad bandwidth. Fed by an air-substrate parallel strip line working on the TEM mode, the antenna array achieves a moderate phase constant, which is helpful for realizing stable endfire radiation. The radiating element separation is optimized to eliminate the high-order spatial harmonics, ensuring single beam radiation. Fabricated by thin copper plates, the merits of the antenna array include lightweight, low cost, and easy fabrication. According to the measured results, the antenna array has a good match and a stable endfire radiation pattern over the operating band from 4 to 10.5 GHz with the measured gain varying from 10.1 to 13.5 dBi. [ABSTRACT FROM AUTHOR]

In this letter, a monostatic and cochannel simultaneous transmit and receive (STAR) antenna with identical circularly polarized radiations of transmitting (TX) and receiving (RX) channels is designed using a thin single-layer substrate. Four concentrically arranged microstrip radiating elements are properly excited by two sets of feeding networks: the feeding network of transmitting antenna (FNT) and the feeding network of receiving antenna (FNR). To fit FNT and FNR into the same plane, the FNR consists of a compact sequential-phase structure placed at the center of the antenna, while the FNT is aligned along the side with a planar crossover junction armed. Two vital techniques, orthogonal feeding points and leakage signal cancellation based on feeding networks, are utilized for satisfactory isolation level between the TX and RX ports. The experiment results demonstrate an isolation at least 41 dB and up to 54 dB, an axial ratio better than 1.7 dB, and a realized gain of 7.2 ∼ 10.5 dBic in the 2.4 GHz WLAN band. Our design scheme may overcome the profile and cost limitations of bulky multilayered STAR antennas, and thus portends potential for the highly integrated inband duplex systems. [ABSTRACT FROM AUTHOR]

This communication presents a novel single-fed compact circularly polarized (CP) dual-layer planar inverted-F antenna (PIFA). The proposed antenna is composed of two stacked orthogonal-orientated PIFAs which can be fabricated by elaborately folding one piece of metal plate. The two PIFAs can be excited synchronously with equally allocated power by a single probe, thus a pair of orthogonal polarizations is created. Moreover, the resonant lengths of the upper and lower PIFAs are slightly different from each other to acquire 90° phase shift between the two orthogonal polarizations. Consequently, a right-hand CP radiation is achieved, and the boresight realized gain is 3.8 dBic at the center frequency. The proposed dual-layer PIFA with two quarter-wavelength resonators provides a novel solution for the compactness of CP antennas. To validate the performance of the antenna, a prototype was fabricated and measured. The measured −10 dB impedance bandwidth and 3 dB axial ratio bandwidth are 7.4% and 1.1%, respectively, with a compact antenna volume of $0.26\times 0.22\times 0.05\,\,\lambda _{0}^{3}$. The proposed antenna is a good candidate for the 433 MHz CP active radio-frequency identification reader, and it has the merits of compact size, lightweight, high efficiency, and low cost. [ABSTRACT FROM AUTHOR]

We present a high-gain, low-profile dual-polarized microstrip antenna operating in the hybridized higher order mode. The proposed antenna consists of a slot-loaded cross-shaped patch, which can be considered as orthogonally polarized radiating elements operated in the TM50mode. Moreover, the four loaded slots can effectively excite the in-phase TM10mode such that the superposition of both modes can lead to gain enhancement in the broadside direction, with suppressed sidelobes. The proposed antenna requires only a single-dielectric layer and a simple feeding method, while exhibiting good isolation between the two polarizations. We have developed a prototype, which has a total size of only 1.65 λ0× 1.65 λ0× 0.04 λ0(λ0is the free-space wavelength at the center frequency) and a measured maximum gain of 10.9 dBi. This dual-polarized microstrip antenna with the advantages of high gain, low profile, low cost, and good isolation, is envisioned to benefit many multiple-input, multiple-output and the fifth generation (5G) communication systems. [ABSTRACT FROM AUTHOR]

This communication presents a periodic leaky-wave antenna array with the advantages of a high endfire gain at the center frequency and a stable endfire radiation beam over the entire operating band. The antenna has a narrow width and consists of multiple monopoles located on the microstrip line. It can be fabricated by line-cutting copper strips. The antenna has a high endfire gain because it is a leaky-wave antenna designed based on the Hansen–Woodyard condition. With a length of $5.5\lambda _{0}$ and a width of $0.33\lambda _{0}$ , a measured endfire gain of 12.9 dBi is achieved at the center frequency of 5 GHz. Good matching and stable endfire radiation beams are achieved over the entire operating band from 4.5 to 5.5 GHz. Good agreement between the measurement and the simulation has been obtained. [ABSTRACT FROM AUTHOR]

An all-metal end-fire leaky-wave antenna is proposed in this letter. The proposed antenna has a centipede-like structure, which consists of a feeding microstrip line and several periodical radiation elements. The all-metal antenna utilizes air medium to intrinsically realize the end-fire array factor. By periodically exciting radiation branch elements, the proposed antenna achieves end-fire radiation with vertical polarization. Compared with previous researches, the proposed antenna has higher end-fire gain and a compact all-metal structure, which contributes to fabrication convenience and low dielectric loss. A prototype of the proposed end-fire antenna is fabricated and tested. The measured results are consistent with full-wave simulation results. The length of the whole leaky-wave array is about 4.13 λ°, and the measured gain is 11.61 dBi in the end-fire direction at 5 GHz. [ABSTRACT FROM AUTHOR]

In this paper, a millimeter-wave air-filled slot antenna is presented based on bulk silicon microelectromechanical systems micromachining technology. The antenna is suitable for system-in-package application by utilizing this silicon micromachining technique. To achieve high radiation efficiency in millimeter-wave band, three gold-plated silicon layers are bonded together to realize an air-filled slot antenna. The air-filled structure has the advantages of reducing transmission loss and enhancing the radiation gain. To mitigate the discontinuity between silicon and air, the proposed antenna employs a patch to feed the air-filled structure that also broadens the impedance bandwidth. Owing to the micromachining technique and the air-filled structure, the antenna can be easily integrated with integrated circuit without suffering from dielectric loss. The measured impedance bandwidth of the proposed antenna is 56.3–63.4 GHz, and the measured peak gain is 7.8 dBi at 60 GHz. [ABSTRACT FROM PUBLISHER]

In this communication, an all-metal standing wave antenna array is proposed based on the microstrip transmission line. By alternatively blocking the microstrip line every half wavelength, the symmetrical equivalent magnetic currents are broken for effectively radiating. By properly tuning the blocking positions along the microstrip line, a broadside pattern is achieved with high gain. The proposed antenna is scalable along one direction to a certain level to acquire the directivity as high as about 15 dBi. More importantly, the proposed antenna array has the potential to be built only by metal without any dielectrics. The all-metal structure has the merits of being low-cost, light weight, easily fabricated, and having no dielectric losses. Based on this idea, a five-segment linear array with a center feed is designed and tested. The measured bandwidth is from 7.83 to 8.81 GHz (980 MHz, 11.78%), and the measured gain is ranging from 9.1 to 12.47 dBi. [ABSTRACT FROM AUTHOR]

This communication proposes a compact single-feed dual-mode antenna for active radio-frequency identification (RFID) tag application. The proposed antenna consists of a slotted patch on an FR4 substrate, a feeding microstrip line, and a foam spacer with a volume of only 60\;\textmm \times 50.3\;\textmm \times 6\;\textmm ($0.48{{\lambda}_0} \times 0.40{{\lambda}_0} \times 0.048{{\lambda}_0}$, where ${{\lambda}_0}$ is the wavelength at the center frequency). It operates as a dipole in free space and as a patch when placed on a metallic surface. A prototype that can provide an impedance bandwidth of 390 MHz (2.28–2.67 GHz) in free space and 470 MHz (2.32–2.79 GHz) on a metallic surface is built and measured. The measured radiation patterns, peak gains, and radiation efficiencies in these two scenarios are provided. [ABSTRACT FROM PUBLISHER]

A wideband printed dipole with V-shaped ground branches is proposed, which is designed for multiple-input multiple-output (MIMO) antennas. It is based on a dipole with an integrated balun, and V-shaped ground branches are introduced to improve the impedance matching. The bandwidth of this element reaches 62.3% (2.30–4.40 GHz), which covers all three WiMAX bands (2.30, 2.50, and 3.30 GHz) and the 2.40 GHz WLAN band. Based on this element, a quad-element MIMO antenna is designed and fabricated. By reusing the V-shaped ground structure between adjacent elements, the size of this quad-element antenna is only $0.31 \lambda \times 0.31\lambda \times 0.01\lambda $. Meanwhile, a bandwidth of 60.6% (2.30–4.30 GHz) is achieved, in which the ${{\rm{S}}_{11}} < - 10\;{\rm{dB}}$, ${{\rm{S}}_{12}} < - 10\;{\rm{dB}}$, and ${{\rm{S}}_{13}} < - 13\;{\rm{dB}}$. Directional radiation patterns with 2.1 dBi average gain are attained, which are very stable throughout this band. This antenna system can be suitable for multielement MIMO devices such as wireless routers and adapters. [ABSTRACT FROM PUBLISHER]

It is a challenging and tough task to achieve and tune multiple frequencies for handset antennas in a small area. In this communication, we have proposed a novel modes controlling method to build and tune the handset antenna. By combining different modes of an open slot and different monopole branches, a hepta-band, covering GSM850, GSM900, DCS, PCS, UMTS, LTE2300, and LTE2500, handset antenna is achieved in a small area of 8\,\times\,60 mm^2. The most essential merit of the proposed antenna is that the related modes can be added step by step, according to the operating bands. The modes for the lower and upper bands can be easily tuned and optimized. We have also built a prototype of the proposed antenna to validate the design strategy. The tested results include reflection coefficient, radiation patterns, efficiency, and gain. [ABSTRACT FROM PUBLISHER]

This communication proposes a wideband differential-fed slot antenna that works in its dominant mode (\lambda/2 mode). The antenna has a near omnidirectional radiation pattern with vertical polarization, which is designed for near-ground wireless sensor node applications. A compact integrated T-slot balun and a loop to T-slot feeding structure are introduced to realize the differential feeding; the bandwidth is expanded to 30.7% (2.2 GHz–3.0 GHz) with a 3.8 dB peak gain. A detailed matching method without using lumped elements is proposed, which can be applied to various types of RFIC chips. A prototype is built and measured. Its differential impedance, antenna patterns, and gain are consistent with the simulation results. [ABSTRACT FROM PUBLISHER]

In this communication, a circularly polarized (CP) antenna is proposed for satellite communication applications. The proposed antenna consists of two parts. One part is in-phase-fed folded monopoles with omnidirectional CP radiation pattern, and the other part is sequential-fed L-shaped monopoles with broadside CP radiation pattern. By combining the two parts as a pattern diversity antenna, upper hemispherical coverage with left-handed circular polarization (LHCP) is achieved in a small volume of 0.38\lambda\times 0.38\lambda\times 0.071\lambda (\lambda is the free-space wavelength). A prototype of the proposed antenna operating at 1.575 GHz has been built and tested. The measured overlapping bandwidth for both the two patterns with -10-dB impedance bandwidth and 3-dB axial-ratio (AR) is 6.7% (1.515–1.62 GHz), also with high port isolation. In addition, the AR and gain coverage over the upper hemisphere is discussed in detail. [ABSTRACT FROM PUBLISHER]

This communication presents a compact monopole-fed slot-loop hybrid antenna for wideband wireless communications. The wideband characteristic is achieved by coupling three different resonant modes of the proposed slot-loop hybrid antenna, namely, a loop mode for the lower band, a slot mode for the middle band and a monopole mode for the higher band. The proposed antenna is built and tested to verify the design strategy. The measured impedance bandwidth (\vertS11\vert<-10\ dB) ranges from 1.82 GHz to 5.68 GHz (102.9%) with stable performance, including bi-directional radiation pattern, vertical polarization and gain. The proposed slot-loop hybrid antenna also shows the merits of compact dimension, low cross-polarization and low cost. [ABSTRACT FROM PUBLISHER]

In this communication, a dual-polarized diversity antenna with azimuthally omnidirectional patterns is designed inside a slender and low-profile columnar structure. The proposed antenna is composed of a cavity-backed notch for horizontal polarization and a folded slot for vertical polarization. The most important contribution of this communication is to reduce the antenna dimension, maintain high port isolation, broaden impedance bandwidth, and generate azimuthally omnidirectional radiation patterns. The overall volume of the proposed antenna is 42\times 12\times 12\ mm^3 (0.336\lambda0\times 0.096\lambda0\times 0.096\lambda0). A prototype of the proposed antenna is built and measured for 2.4-GHz wireless local area network (WLAN) applications to validate the idea. [ABSTRACT FROM PUBLISHER]

A novel null scanning patch antenna operating at 2.4 GHz is presented. Unlike the existing reconfigurable techniques, the even and odd modes of a shorted patch are adopted to first achieve a broadside pattern and pattern null on broadside. Continuous null scanning is achieved by combining these two modes with different exciting powers. The mechanism of null scanning is discussed from both theoretical analysis and simulated/measured results. A rat-race switching network is used to excite the two modes and simultaneously obtain high port isolation. A prototype is fabricated and tested. The measured results verified the null scanning capability of the proposed design. [ABSTRACT FROM PUBLISHER]

In this communication, we have proposed a compact planar antenna for isotropic radiation pattern in a wide operating band. The proposed antenna consists of four sequential rotated L-shaped monopoles that are fed by a compact uniform sequential-phase (SP) feeding network with equal amplitude and incremental 90^\circ phase delay. Based on the rotated field method, a full spatial coverage with gain deviation less than 6 dB is achieved in a wide operating band from 2.3 to 2.61 GHz, also with well-impedance matching. A prototype of the proposed antenna has been built and tested. The measured results, including the reflection coefficient, gain, and radiation patterns, are analyzed and compared with the simulated results. [ABSTRACT FROM PUBLISHER]

This paper presents the successful design and physical realization of a wideband MNG-TL dipole antenna. An artificial mu-negative transmission line (MNG-TL) structure is realized by employing periodically loaded parallel-plate lines. It is known that the current reversal, which occurs at frequencies much beyond the dipole natural frequency, disturbs the omnidirectional radiation pattern in the azimuth plane. The MNG-TL has a unique property to support a zero propagation constant (\beta =0) with non-zero group velocity at the zeroth-order resonance. Due to the unique property of an infinite wavelength, the current distribution of the dipole antenna can be improved. Furthermore, the MNG-TL dipole is also useful to achieve a wide impedance bandwidth. A prototype of the proposed MNG-TL dipole is fabricated and measured. It can provide a wide effective bandwidth of about 1.55 GHz (1.85–3.40 GHz) with VSWR 2:1 (S11< -10 dB) impedance matching and stable omnidirectional radiation patterns in the azimuth plane. [ABSTRACT FROM PUBLISHER]

A substrate integrated waveguide (SIW)-fed circularly polarized (CP) antenna array with a broad bandwidth of axial ratio (AR) is presented for 60-GHz wireless personal area networks (WPAN) applications. The widened AR bandwidth of an antenna element is achieved by positioning a slot-coupled rotated strip above a slot cut onto the broadwall of an SIW. A 4\, \times \,4 antenna array is designed and fabricated using low temperature cofired ceramic (LTCC) technology. A metal-topped via fence is introduced around the strip to reduce the mutual coupling between the elements of the array. The measured results show that the AR bandwidth is more than 7 GHz. A stable boresight gain is greater than 12.5 dBic across the desired bandwidth of 57–64 GHz. [ABSTRACT FROM PUBLISHER]

A compact monopole-slot antenna with polarization diversity is proposed for wireless local area network (WLAN) applications. Dual polarization is provided by a ground-folded monopole and a slot cut from the folded ground. The total volume of the proposed antenna is only 50\,\times\,16\,\times\,16 mm^3\ (0.4 \lambda0 \times 0.128 \lambda0 \times 0.128 \lambda0). However, low mutual coupling is achieved due to the orthogonal modes of current distribution on the ground. A prototype of the proposed antenna is built and tested. The obtained results include the S parameters, radiation patterns and radiation gain. The results from our presentation match with the simulation and demonstrate an isolation better than -36 dB in the required band. [ABSTRACT FROM PUBLISHER]

An 18-port compact antenna cube is proposed in this paper. The cube, which has a volume of 0.76\,\times\,0.76\,\times\,0.76 \lambda0^{3}, provides 18 individual channels and is ideal for multiple-input multiple-output (MIMO) wireless communications. On each of the total six faces of the cube, a three-port tri-polarization antenna is installed. All antennas adopt a metal backing configuration, so the ground of all antennas forms a well shield Faraday cage, in which other functional circuits can be installed. Experimental measurements were carried out to evaluate the performance of the antenna cube in different MIMO scenarios. The results show that MIMO systems with the proposed compact antenna cube outperform those with dipole antennas which occupy the same number of RF channels but with much larger space. When a vertical 3-dipole array, a horizontal 3-dipole array and a dual polarization antenna are used in the user end (UE), respectively, the capacity of the global selected MIMO systems with antenna cube is about 2.7, 4.6, and 2.9 bits/s/Hz more than the full MIMO systems with a vertical 3-dipole array as the access point (AP) antennas. It is 1.9, 3.9, and 2.0 bits/s/Hz more than the full MIMO systems with a vertical 5-dipole array as AP antennas. The performance differences between the MIMO systems using global and simplified selection circuits are small. [ABSTRACT FROM PUBLISHER]

A folded loop-inverted F reconfigurable antenna for mobile phone applications is designed and the obtained results are discussed in this communication. It is shown that loop antenna mode and an inverted F antenna (IFA) mode are controlled by only one p-i-n diodes with simple bias circuit. The impedance can be matched by adopting a matching bridge for both the loop and IFA modes. In a compact volume of 60\,\times\,5\,\times\,5 mm^3, the proposed antenna operates in hepta-band, including GSM850, GSM900, GPS, DCS, PCS, UMTS and WLAN, with the return loss lower than 6 dB. A prototype of the proposed antenna is fabricated, measured, and obtained results including return loss, efficiency and gain, are presented. [ABSTRACT FROM PUBLISHER]

A wideband antenna with a reconfigurable coplanar waveguide (CPW)-to-slotline transition feed is proposed for pattern diversity applications. The feed provides three modes -CPW feed, left slotline (LS) feed and right slotline (RS) feed- without extra matching structures. Changes between modes are controlled by only two p-I-n diodes. Features of the proposed switchable feed include compact size and simple bias circuit. The equivalent transmission line model is used in the analysis of the proposed design. A prototype of the proposed antenna is fabricated, tested, and the obtained results including reflection coefficient, radiation patterns and gains, are present. A measurement of channel capacity is carried out to prove the benefit of pattern diversity when using the proposed antenna in both line-of-sight (LOS) and non-line-of-sight (NLOS) communication scenarios. [ABSTRACT FROM AUTHOR]

In this letter, an internal folded reconfigurable loop antenna for mobile handset applications is designed, built, and tested. Two operating states with different frequencies are obtained by switching the shorting pins of the loop. The bandwidth of the proposed antenna has been increased by adopting a matching bridge. In a compact volume of 60\times 5\times 5~\mm^3, the proposed antenna operates in heptaband, including GSM850, GSM900, GPS, DCS, PCS, UMTS, and WLAN, with the return loss lower than 6 dB. The efficiency and gain with the p-i-n diodes with their bias circuit are also measured and analyzed. [ABSTRACT FROM PUBLISHER]

A conformal switchable antenna system mounted on a cylindrical surface is proposed, simulated, prototyped and measured. The antenna system is composed of several tri-polarization antennas operating at 2.4 GHz band. It is shown that this antenna system realizes a quasi-isotropic pattern without any nulls over a complete spherical surface. Specifically, it is shown that by using three tri-polarization antennas and switching among them, a complete spherical coverage could be achieved without any nulls and with a power gain larger than 2.5 dBi over more than 90 percent of a spherical surface surrounding the antenna system. Furthermore, it is shown that the performance of the antenna system does not deteriorate with the increase in the diameter of the mounting cylinder, thus facilitating the implementation of the proposed design in many applications including telemetry, satellites, and aircraft. Both simulation and experimental results of the radiation patterns are presented in this paper. [ABSTRACT FROM AUTHOR]

A novel compact wideband antenna, which adopts a multi-state switchable matching circuit, is proposed in this paper. The design of the switchable matching is systematically studied and a two-step iterative procedure is used to obtain optimized values for both the bandwidth division between the various stages and the matching circuit components in each stage. Without loss of generality, a meander line monopole, with dimensions of 80\,\times\,10\,\times\,10 mm^3, is used as the radiator in the proposed wideband antenna design. To validate the proposed new design, a four-state matching circuit controlled by four PIN diodes is fabricated and measured. The reflection coefficient of the prototype antenna is found to be better than -7.3 ~dB, and the peak gain is higher than -3 ~dBi across the 470–770 MHz bandwidth for the Integrated Services Digital Broadcasting-Terrestrial (ISDB-T) application. [ABSTRACT FROM PUBLISHER]