Monopole-like Radiation Characteristics Research Articles

A Single-Layer Low-Profile Broadband Metasurface-Inspired Antenna With Monopole-Like Radiation Characteristics

This communication presents a novel single-layer, low-profile broadband metasurface (MTS)-inspired antenna with monopole-like radiation characteristics. To excite symmetric surface waves (SWs) propagating along an MTS consisting of an array of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$4\times4$ </tex-math></inline-formula> metal square patches, a horizontal center-fed monopole structure is used at the center of the MTS. The proposed antenna is further embedded within a square ring to improve the gain and H-plane patterns roundness at the upper-frequency band. The presented antenna achieved a −10 dB bandwidth of 32.62% (5.08–7.06 GHz) and a low profile of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.06\lambda _{0}$ </tex-math></inline-formula> ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\lambda _{0}$ </tex-math></inline-formula> is the free space wavelength at the center of the operating band) distinctive features due, respectively, to the effective excitation of different TM SW resonant modes that are close to each other and the in-phase reflection property of the MTS. The planar structure, single-layer, and low-profile merits make the proposed antenna an ideal candidate for various wireless communications systems, such as wireless local area network (WLAN) at 5.2/5.8 GHz, WiMAX at 5.5 GHz, and car to car (C2C) at 5.85–5.925 GHz.

Low-Profile Wideband Omnidirectional Antenna for 4G/5G Indoor Base Station Application Based on Multiple Resonances

A novel low-profile antenna with monopole-like radiation characteristics is proposed for 4G/5G indoor micro ceiling base station applications. The proposed antenna consists of a top loading disk, two polygonal copper sheets, which are orthogonally intersected, and a circular printed circuit board (PCB), which serves as the ground. A prototype is fabricated and measured. The proposed antenna has a very low profile of 0.057λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">min</sub> , where λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">min</sub> is the free-space wavelength at the lowest frequency of the operating band. A fractional bandwidth of 85.3% ranging from 1.6 to 3.98 GHz with |S <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sub> | <; -10 dB is achieved, which covers the 4G LTE band and 5G N78 band. The proposed antenna demonstrates consistent monopole-like radiation pattern in the whole working band, which is very suitable and well designed for indoor ceiling base station applications.

A Low-Profile Wideband Antenna With Monopolelike Radiation Characteristics for 4G/5G Indoor Micro Base Station Application

A wideband, low-profile, vertically polarized antenna with monopolelike radiation characteristics is proposed for 4G/5G indoor base station applications. The design of this antenna is based on the traditional monocone antenna with internal matching and reactive load. The structure of monocone is realized by crossed substrate, which reduces the antenna weight and improves the design flexibility simultaneously. Then, reactive loading of capacitively coupled triangle patches and shorting pins are used to reduce the height of antenna profile to 0.08 λ min, where λ min is the free-space wavelength at the lowest operation frequency. An interdigital capacitor is etched near the antenna's input to adjust the impedance matching. The proposed antenna demonstrates consistent monopolelike, omnidirectional radiation patterns within the operating band. A measured impedance bandwidth for voltage standing-wave ratio (VSWR) < 2.2 of about 81% ranging from 1.66 to 3.95 GHz is achieved, which covers 1.7–2.7 GHz 4G Long-Term Evolution band and 3.3–3.8 GHz 5G N78 band simultaneously. The proposed antenna is tailored for the ceiling micro base station in indoor distributed system.

A Conformal Band-Notched Ultrawideband Antenna With Monopole-Like Radiation Characteristics

A conformal, planar, and low-profile ultrawideband antenna with monopole-like radiation and band-notched characteristics is presented. A circular patch shorted to the ground is combined with two rectangular slots and two concentric rings, to achieve an ultrawide bandwidth from 3.8 to 8.3 GHz with a single rejection band from 5 to 6 GHz. The monopole-like radiation features, generated by combining TM $_{01}$ and TM $_{02}$ operating modes of a circular patch antenna, are maintained over the entire operating bandwidth. The antenna has only 0.046 $\lambda _{o}$ height at 3.8 GHz and is realized using polydimethylsiloxane conductive fabric composite technology making it highly flexible and physically robust. This was validated through severe bending tests with various curvatures.

A Compact, Low-Profile Simultaneous Transmit and Receive Antenna With Monopole-Like Radiation Characteristics

A compact, vertically polarized simultaneous transmit and receive (STAR) antenna with a high transmit–receive isolation level and an omnidirectional radiation pattern in the azimuth plane is presented. The proposed STAR antenna consists of transmit (TX) and receive (RX) antennas whose phase centers are collocated. The TX antenna is a monopole with top-hat loading, placed directly below the central point of the crossed loop. The RX antenna consists of a pair of orthogonal half-loops, each capacitively fed at both of its ends with a $\text{180}^\circ$ phase difference. The four ports of the RX antenna are fed with the same amplitude and relative phase values of $\text{0}^\circ$ , $\text{90}^\circ$ , $\text{180}^\circ$ , and $\text{270}^\circ$ to produce an omnidirectional radiation pattern and high isolation with the TX antenna. The STAR antenna was designed for operation in the 2.45 GHz ISM band with electrical dimensions of $D \times H=$ $0.44\lambda \times 0.15\lambda$ (diameter × height). A prototype of this antenna was fabricated and experimentally characterized. Measurement results show that the antenna has a TX/RX isolation level better than 38 dB and maintains monopole-like patterns for both TX and RX modes over a frequency range of 2.4–2.7 GHz.

Dual‐band platform‐mounted HF/VHF antenna design using the characteristic mode theory

The design of a dual-band antenna mounted on a military platform is presented. The antenna operates in both high-frequency (HF) and very-high-frequency (VHF) bands and consists of two half-loops mounted on the platform. When the two half-loops are excited differentially, they act as coupling elements exciting the platform dominant characteristic mode. This generates a horizontally polarised radiation with maximum radiation towards to zenith. Due to the presence of the platform, the antenna bandwidth is increased compared with that of an isolated antenna. When the two half-loops are excited in the common mode, they behave as an ultra-wideband antenna with monopole-like radiation in the VHF band. A diplexer is used to achieve dual-band operation, which allows the antenna operating at both bands simultaneously. A 60:1 scaled antenna prototype and its feed network is fabricated and characterised. At the lower band, the antenna exhibits an impedance bandwidth of 2.8% for a voltage standing wave ratio (VSWR) better than 2.25:1 and a directional radiation pattern with horizontal polarisation. At the higher band, the antenna exhibits a VSWR better than 2.25:1 and monopole-like radiation characteristics across 2:1 bandwidth. The impact of the presence of a realistic ground plane on the antenna performance is also studied and discussed.

A High-Isolation, Ultra-Wideband Simultaneous Transmit and Receive Antenna With Monopole-Like Radiation Characteristics

A high-isolation, ultra-wideband simultaneous transmit and receive (STAR) antenna with monopole-like radiation characteristics is presented. The proposed STAR antenna consists of a center-located monocone and a circular array of bent loops. The monocone and the array of loops are located in the near fields of each other and serve, respectively, as the transmit (TX) and receive (RX) antennas. To achieve omnidirectional, vertically polarized radiation patterns, the array factor of the bent loops is first examined. A circular top loading and four T-shaped parasitic elements are exploited to decrease the lowest frequency of operation of the antenna without increasing its occupied volume. Finally, based upon the analysis of the array factor, four directors are strategically mounted over the ground plane to enhance the omnidirectionality of the antenna in the azimuth plane. A prototype of the antenna operating in the UHF band is fabricated and measured. Experimental results demonstrate that the proposed STAR antenna achieves an isolation greater than 40 dB from 0.6 to 1.75 GHz (2.9:1 bandwidth). Furthermore, the STAR antenna is capable of maintaining consistent monopole-like radiation patterns and vertical polarization for both the TX and the RX channels across the entire band of operation.

A Compact, Capacitively Fed UWB Antenna With Monopole-Like Radiation Characteristics

A compact, ultrawideband (UWB) antenna occupying a cylindrical volume and providing omnidirectional monopole-like radiation is introduced. The antenna consists of two closely placed 3-D loops, two parasitic small loops, and a circular top hat. Two strip-shaped probes, each coupling with one loop, are used to feed the antenna in common mode. UWB operation is achieved by taking advantage of the magnetic coupling of the parallel-fed 3-D loops. Small electrical dimensions of the antenna are due to the special capacitive proximity feeding scheme and the presence of the top hat. A prototype with 4.1:1 bandwidth is designed, fabricated, and characterized. The antenna demonstrates a VSWR better than 2:1 and monopole-like omnidirectional radiation characteristics across this entire band. It occupies a cylindrical volume with a diameter of $0.14\lambda _{\mathrm{min}}$ and a height of $0.09\lambda _{\mathrm{min}}$ , where $\lambda _{\mathrm{min}}$ is the free-space wavelength at the lowest frequency of operation. The antenna has a $k_{\mathrm{min}}a = 0.73$ , where $k_{\mathrm{min}}$ is the wavenumber at its lowest frequency of operation. The fabricated prototype is demonstrated to have a lowest frequency of operation that is only 10% above the theoretical limits on UWB antennas. Further miniaturization of the antenna using a spherical top hat is also examined and demonstrated to be capable of reducing $k_{\mathrm{min}}a$ values down to 0.60.

A Low-Profile Dipole Array Antenna with Monopole-Like Radiation for On-Body Communications

In this paper, a low-profile dipole array antenna with monopole-like radiation for on-body communications is proposed. The proposed antenna, operating in the industrial, scientific, and medical (ISM) band, is designed with consideration of the human body effect. By placing eight planar dipole antenna elements symmetrically around the z-axis, the proposed antenna achieves monopole-like radiation characteristics with a low profile. The antenna has overall dimensions of <TEX>$0.44{\lambda}_0{\times}0.44{\lambda}_0{\times}0.013{\lambda}_0$</TEX> at 2.45 GHz in the ISM 2.45 GHz band (2.4-2.485 GHz) and a 10-dB return loss bandwidth of 4.9% ranging from 2.4 to 2.52 GHz.

A Low-Profile, Vertically Polarized Ultrawideband Antenna With Monopole-Like Radiation Characteristics

A compact, ultrawideband (UWB) antenna with an extremely low profile is presented. The antenna has consistent monopole-like radiation characteristics over approximately an 8.5:1 bandwidth. It consists of two radiators where one radiator is a smaller, slightly different version of the other one. The smaller radiator is partially embedded into the large one to avoid considerable increase in the maximum antenna height. Each radiator has two parallel loops in the shape of a bent diamond connected to the ground plane at their ends. A properly designed feed network is used to feed the larger antenna at lower frequencies while feeding the smaller one at higher frequencies to improve the consistency of the radiation characteristics of the system over a very broad bandwidth. A prototype of the proposed antenna and the feed network are fabricated and experimentally characterized. The fabricated antenna prototype has electrical dimensions of $0.26\lambda_{\min} \times 0.26 \lambda_{\min} \times 0.046 \lambda_{\min}$ at its lowest frequency of operation and demonstrates monopole-like radiation characteristics with consistent, vertically polarized, omni-directional radiation patterns over roughly an 8.5:1 (0.66–5.6 GHz) bandwidth.

A Low-Profile IR-UWB Antenna With Ring Patch for WBAN Applications

A compact ultrawideband (UWB) antenna for on- body communications is proposed herein. The antenna consists of a mono- cone and a shorted ring patch. By using a ring patch with four shorting pins, the proposed antenna operates at TM41 resonance mode in the low-frequency band and achieves a compact low-profile structure with monopole-like radiation characteristics. The antenna has overall dimensions of 64 mm × 64 mm × 7 mm (0.64 λ0 × 0.64 λ0 × 0.07 λ0at 3 GHz) in the impulse radio UWB (3.1 GHz - 10.6 GHz) band and a 10-dB return loss bandwidth of 121.1% in the range from 2.8 to 11.4 GHz. The antenna performance was simulated and measured in free space and on a homogeneous human equivalent phantom to account for the human body effect. The results show that the antenna characteristics are relatively stable regardless of the existence of a human phantom.

인체 표면 통신을 위한 TM31고차 모드 반원-링 인체 부착형 마이크로스트립 패치 안테나 설계

본 논문에서는 모노폴과 같은 방사특성을 갖고 인체 표면 간 통신을 위한 <TEX>$TM_{31}$</TEX> 고차 모드 반원-링 마이크로스트립 패치 안테나를 제안하였다. 제안된 안테나는 단락 핀을 이용하여 <TEX>$TM_{31}$</TEX> 고차 공진 모드를 형성하였고, 평면형임에도 불구하고 모노폴과 같은 방사특성을 갖는다. 패치안테나의 좁은 대역폭을 확장하기 위해 <TEX>$TM_{31}$</TEX> 모드 C-형 반링 패치를 반원 패치에 인접시켰으며, 소형화를 위해 half mode를 사용하였다. 인체 착용환경을 고려하여 마이크로스트립 라인을 이용하여 급전하였다. 제안된 안테나는 ISM(Industrial, Scientific, and Medical) 2.45 GHz 대역(2.4~2.485 GHz)에서 <TEX>$0.25{\lambda}_0{\times}0.46{\lambda}_0{\times}0.025{\lambda}_0$</TEX>의 크기를 갖고, 2.38~2.49 GHz에서 4.24 %의 10-dB 반사손실 대역폭을 갖는다. 인체의 영향을 고려하기 위해 2/3 근육-등가 반고체형 모의인체를 제작하고, 이를 이용하여 안테나에 미치는 인체의 영향을 분석, 검증하였다. 또한, 실제 인체 상황에서 제안된 안테나를 통해 인체 표면 간 링크의 통신 성능 분석을 위한 실험을 수행하였다. In this paper, a <TEX>$TM_{31}$</TEX> higher order mode half circular-ring microstrip antenna with monopole-like radiation characteristic for on-body communication is proposed. By using shorting vias, <TEX>$TM_{31}$</TEX> resonance mode was excited, while achieving compact low-profile antenna with monopole-like radiation characteristics. To overcome the narrow bandwidth of a patch antenna, a C-shape half ring patch with shorting vias having <TEX>$TM_{31}$</TEX> mode is closely located around a half circular patch. For size reduction, half mode is adopted. The proposed antenna has the overall dimensions of <TEX>$0.25{\lambda}_0{\times}0.46{\lambda}_0{\times}0.025{\lambda}_0$</TEX> at the industrial, scientific, and medical(ISM) 2.45 GHz band(2.4~2.485 GHz) and the 10-dB return loss is 4.24 % ranging from 2.38 to 2.49 GHz. To verify body effect, two-thirds muscle equivalent semi solid phantom was fabricated and used to measure the antenna performance. A communication link is analysed to investigate the effect of human-body movements and antenna locations.

An Electrically Small, Vertically Polarized Ultrawideband Antenna With Monopole-Like Radiation Characteristics

We present an electrically small, low-profile, ultrawideband (UWB) antenna with monopole-like radiation characteristics. The antenna is composed of a monopole bow-tie antenna reactively loaded with a cascaded system of top hats, two shorting arms, and a ring slot cut into the ground plane. The reactive loads are used to introduce two additional resonances close to each other and below the lowest resonant frequency of the bow-tie. This results in a very compact, ultrawideband antenna that utilizes the available volume inside the Chu's sphere rather efficiently. At the lowest frequency of operation, the proposed antenna has electrical dimensions of 0.085λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">min</sub> ×0.189λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">min</sub> ×0.189λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">min</sub> , where λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">min</sub> is the free-space wavelength. The antenna demonstrates a VSWR of 2.2:1 and consistent monopole-like, omnidirectional radiation patterns over a 5.5:1 bandwidth. A prototype of the antenna, which operates in the 0.6-3.2-GHz band, is fabricated and characterized using a multiprobe spherical near-field system.

A Very Low-Profile, Omnidirectional, Ultrawideband Antenna

We present a compact, ultra-low-profile, ultrawideband (UWB) antenna with monopole-like radiation characteristics. The antenna is composed of two bent diamond-shaped loops that are fed in parallel and loaded with a common capacitive top hat to reduce their lowest frequencies of operation. A series capacitor is used at the feeding terminals of one of the loops to create an additional resonance below the lowest frequency of operation of one of the loops and, hence, further reduce the lowest frequency of operation of the antenna. At the lowest frequency of operation, the proposed antenna has electrical dimensions of L × W × H = 0.22λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">min</sub> × 0.22λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">min</sub> × 0.033λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">min</sub> , where λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">min</sub> is the free-space wavelength. The antenna demonstrates a VSWR lower than 3:1 and consistent monopole-like, omnidirectional radiation patterns over a 4:1 bandwidth. A prototype of the antenna with physical dimensions of 7 × 7 × 1 cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> , which operates in the 1.0-4.0-GHz frequency range, is fabricated and characterized using a near-field system.

A Small Dual-Band CPW-Fed Monopole Antenna for GSM and WLAN Applications

A unique and miniaturized dual-band coplanar waveguide (CPW)-fed antenna is presented. The proposed antenna comprises a rectangular patch that is surrounded by upper and lower ground-plane sections that are interconnected by a high-impedance microstrip line. The proposed antenna structure generates two separate impedance bandwidths to cover frequency bands of GSM and Wi-Fi/WLAN. The antenna realized is relatively small in size <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$(17\times 20\ {\hbox{mm}}^{2})$</tex></formula> and operates over frequency ranges 1.60–1.85 and 4.95–5.80 GHz, making it suitable for GSM and Wi-Fi/WLAN applications. In addition, the antenna is circularly polarized in the GSM band. Experimental results show the antenna exhibits monopole-like radiation characteristics and a good antenna gain over its operating bands. The measured and simulated results presented show good agreement.

A COMPACT MICROSTRIP SLOT ANTENNA WITH A PAIR OF INVERTED L-STRIPS AND ELLIPTICAL-ARC-SHAPED STUB FOR WLAN/WIMAX APPLICATIONS

A novel compact microstrip slot antenna applied to WLAN/WiMAX applications is presented. The proposed antenna consists of a trapezoid and ellipse slot, a pair of symmetrical inverted L-strips, an elliptical-arc-shaped stub and a monopole radiator. By adjusting the dimensions and positions of these structures, the antenna can efiectively generate three difierent resonances to cover the WLAN/WiMAX bands while maintaining small size and simple structure. Based on this concept, a prototype of the proposed antenna has been successfully fabricated and measured. The experimental and numerical results show that the antenna has impedance bandwidth with 10dB return loss of 360MHz (2.33{2.69GHz) and 2630MHz (3.24{5.87GHz), which can cover both the WLAN 2.4/5.2/5.8GHz bands and the WiMAX 2.5/3.5/5.5GHz bands. In addition, good monopole-like radiation characteristics with su-cient antenna gains are obtained over the operating bands.

Frequency-Reconfigurable Monopole Antennas

A novel coplanar-waveguide (CPW) bandpass filter using short-circuit slotlines and varactor diodes is introduced. This bandpass filter, when integrated with a CPW wideband antenna, produces frequency agility with a wideband mode and a continuous narrowband mode. The design of another CPW filter based on a square-ring resonator with switches is also shown and applied to a wideband antenna, making it reconfigurable. Both filters are based on controlling two stop bands far enough apart so that there is a passband between them. When the stop band frequencies are altered using switches or varactors, the passband is altered. Complete working and design principles along with simulated S-parameter results of the filters are presented. The simulated and measured reflection coefficients of the antennas incorporating the filters are also shown. Good monopole-like radiation characteristics are observed for both antennas. The filters are small in size and can be incorporated in any CPW antenna design to make it reconfigurable. The benefits of the novel varactor filter antenna over the switch filter antenna are also described.

A NOVEL TRI-BAND PRINTED MONOPOLE ANTENNA WITH AN ETCHED ∩-SHAPED SLOT AND A PARASITIC RING RESONATOR FOR WLAN AND WIMAX APPLICATIONS

A novel tri-band printed monopole antenna with an etched \-shaped slot and a parasitic ring resonator is proposed for satisfying wireless local area network (WLAN) and worldwide interoperability for microwave access (WiMAX) applications simultaneously. The proposed antenna comprises a rectangular radiation patch with an arc- shaped edge and an embedded \-shaped slot on the top and a parasitic ring resonator on the opposite side. The measured results show that the impedance bandwidths of the proposed antenna, deflned by voltage standing wave ratio (VSWR) • 1:5, are 350MHz (2370{2720MHz), 680MHz (3390{4070MHz) and 1080MHz (4920{6000MHz), which cover the required bandwidths for both WLAN (2400{2480MHz, 5150{5350MHz, 5725{5825MHz) and WiMAX (2500{2690MHz, 3400{3690MHz, 5250{5850MHz) applications. Furthermore, good monopole-like radiation characteristics with moderate peak gains are obtained over the operating bands.