Measured Radiation Efficiency Research Articles

CPW-fed dual-element metamaterial inspired multiband antenna using simple FSS for gain enhancement

This article presents a dual-element metamaterial-inspired co-planar waveguide (CPW) fed elliptical antenna using a simple compact frequency selective surface (FSS) for multiband wireless applications. The designed antenna is fabricated on a cheap FR-4 substrate (εr = 4.4) with 40 × 40×1.6 mm3 dimensions. Dual complementary split ring resonators (CSRRs) loaded in the CPW ground create multiband characteristics, which are analyzed using the quasi-static design equations and the ANSYS HFSS EM simulator. FSS has been proposed as a reflector for the antenna to increase its gain. The FSS unit cell's angular stability has been analyzed using transverse electric (TE) and transverse magnetic (TM) polarization, and it has been determined to be 60°. The FSS integrated antenna offers measured bandwidths of 2.67 – 3.38 GHz (23.66 %), 3.77 – 4.17 GHz (10.25%), 4.91 – 5.93 GHz (19.61 %), and 7.28 – 8.93 GHz (20.24 %). The FSS integrated antenna shows nearly omnidirectional radiation patterns in all resonating bands with the highest gain of 9.72 dBi and measured radiation efficiency greater than 91 % in all the bands. The reported 'antenna with FSS' is appropriate for multiband wireless technologies as it covers IEEE 802.16 WiMAX, n77 5G NR, 5G Wi-Fi, WLAN, ISM and satellite spectrums.

A Low-Profile Dual-Polarized Substrate Integrated Magneto-Electric Dipole MIMO Antenna

A magneto-electric dipole (MED) MIMO antenna with low-profile, dual-polarized, and substrate integrated properties is proposed. The antenna element is composed of four fan-shaped patches lying on the radiation plane and four vertical metal vias linking the patches and the ground. Compared with the common MED antennas, the proposed MED antenna element has a lower profile of 0.1λ. Besides, it is fed by microstrip lines via two orthogonal H-shaped slots, resulting in a broad impedance bandwidth of 40% (3-4.5 GHz) and a steady gain in the entire operational band. The ports isolation is higher than 27 dB, the cross-polarization discrimination (XPD) is higher than 37 dB, and the measured radiation efficiency is greater than 70%. Furthermore, four antenna elements are utilized to form a MIMO antenna, which can obtain better ports isolation characteristics under the condition that the element spacing is half wavelength. Finally, the MIMO antenna is simulated, fabricated and measured. The results verify the rationality of the design.

An Extremely Wideband Tightly Coupled Dipole Array With Shared-Aperture Configuration

The intent of this letter is to expand the tightly coupled dipole array (TCDA) concept in a shared-aperture configuration for high radiation efficiency and extremely wide bandwidth. Specifically, a high-band TCDA is deployed beneath the aperture of a low-band TCDA. With this configuration, the profile height keeps the same as that of a stand-alone low-band TCDA. It offers a thin λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">L</sub> /13.7 (or 1.7λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">H</sub> ) array with 23.2:1 bandwidth for active VSWR < 3, where λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">L</sub> and λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">H</sub> are the wavelengths at the lowest and highest frequencies of the operating frequency band. Although the shared-aperture configuration is profit for low profile and bandwidth extension, it causes cross-band coupling and deteriorates radiation performance. To solve this issue, the low-band TCDA is designed to be electromagnetic transparent to the high-band electromagnetic waves. The two TCDAs become immune to the cross-band interference and operate properly as in their stand-alone cases. An array prototype consisting of a 16 × 16 high-band array and an 8 × 8 low-band array is fabricated and measured. The measured radiation efficiency is demonstrated to be 77% on average across a 23.2:1 bandwidth.

Compact Dual-Band MIMO Antenna With Shared Decoupling Structure for 5G Mobile Terminals

In this letter, a compact dual-band MIMO antenna, consisting of four antenna pairs, is presented for 5G mobile terminal applications. Each pair includes two tightly-arranged monopoles. By folding the L-shaped monopoles into U-shaped structures, both the 3.5 GHz band and 4.9 GHz band can share the same decoupling inductor. By adding stop-band filter on the monopole, dual-band operation can be provided by a single branch. The size of the dual-band antenna pair is merely 19×4 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . The measured -6 dB bandwidth can cover 3.4-3.6 GHz and 4.8-5.0 GHz, with port isolation higher than 12 dB. The measured radiation efficiency varies from 41% to 59% in the lower band, and varies from 38% to 62% in the upper band.

Experimental Measurement of Noise Figure and Radiation Efficiency With the Antenna Y-Factor Method at X-Band

To optimize the design of a high-sensitivity receiver, it is valuable to be able to assign noise budget contributions to various parts of the system. The system noise and aperture efficiency can be characterized using the antenna Y factor method, which has been added recently to the IEEE Recommended Practice for Antenna Measurements, Std 149-2021. We extend the antenna Y factor method by showing that it can be used to measure the noise figure of an active antenna and receiver system.With an additional measurement of the receiver noise, the antenna radiation efficiency can be determined. We demonstrate the extended antenna Y factor method experimentally at X band for antennas under test including a horn with near 100% efficiency, microstrip patch antenna with efficiency near 80%, and a patch antenna array with 40% nominal efficiency.

L Band Phased Array Feed Noise Figure and Radiation Efficiency Measurement with the Antenna Y Factor Method

The noise performance of a high sensitivity, wide-field astronomical phased array feed receiver can be characterized by measurements using the antenna Y factor method. These measurements are used to determine figures of merit for an active array receiver. Antenna elements for the Advanced L Band Phased Array Camera for Astronomy (ALPACA) were measured using the antenna Y factor method to determine the active array and receiver noise figure, the antenna loss, receiver equivalent noise temperature, and radiation efficiency of the system over its 500[Formula: see text]MHz operating bandwidth. The completed ALPACA instrument will feature a fully cryogenic design with both the low-noise amplifiers and array elements cryogenically cooled. The uncooled performance measurements from the antenna Y factor method are used to extrapolate the elements cryogenic radiation efficiency and antenna loss showing that it is expected that the elements will contribute less than 1 K to the overall system noise temperature. These results validate the antenna Y factor method to measure key antenna parameters such as the antenna radiation efficiency and show that the instruments front-end array and electronics meets expected performance targets.

A Christmas Tree-Shaped Quadband Compact Antenna with Triple Slots for Various Wireless Technologies

A compact, coplanar waveguide (CPW)-fed multiband antenna is developed and analyzed in this paper for quad-band applications. Christmas tree-like monopole antennae with three symmetric slots are designed on a low-cost FR4 epoxy substrate with the overall dimensions of 0.312λ 1 × 0.364λ 1 × 0.0083λ 1 where λ 1 is the wavelength corresponding to the lower cut-off frequency. Three rectangular-shaped slots of different dimensions are etched on the three triangular-shaped stacked patches to enhance the current carrying path due to which the proposed antenna resonates at the required frequency bands. Different antenna parameters such as reflection coefficient (S 11), gain, radiation efficiency, surface current, radiation pattern, group delay and magnitude response of transfer function (S 21) are analyzed for inspecting the antenna performance. The quad-band antenna offers measured bandwidths of 3.1–3.9 GHz (22.86%), 5.46–5.98 GHz (9.1%) 9.76–11.74 GHz (18.42%) and 17.55–19.25 GHz (9.24%). The antenna shows nearly omnidirectional radiation patterns in all resonating bands with the highest gain of 4.5 dBi and measured radiation efficiency greater than 70% in all the bands. The antenna also offers stable group delay response and linear S 21 response in its operational spectrums. All these characteristics ensure the antenna’s applicability in IEEE 802.16 WiMAX band, 5.5 GHz Wi-Fi band, 5.8 GHz ISM band, terrestrial broadband, radiolocation and earth explorer satellite applications.

Fabrication of High Radiation Efficiency Dielectric Resonator Antenna Array Using Temperature Stable 0.8Zn2SiO4‐0.2TiO2 Microwave Dielectric Ceramic

AbstractArray antenna is of great significance in realizing the Sub‐6 GHz fifth‐generation (5G) mobile communication systems, however, its utilization in the base station systems implementation is limited due to high power consumption. In this paper, a high radiation efficiency 4 × 4 cylindrical dielectric resonator antenna (CDRA) array fabricated using the temperature stable 0.8Zn2SiO4‐0.2TiO2 composite ceramic is proposed. TiO2‐doped Zn2SiO4 composite ceramics are synthesized by the conventional solid‐state method. Notably, 0.8Zn2SiO4‐0.2TiO2 composite ceramic sintered at 1250 °C demonstrates excellent microwave dielectric properties with dielectric constant (εr ≈ 8.24), high‐quality factor (Q × f ≈ 35 000@8.08GHz), and the temperature coefficient of resonant frequency (TCF ≈ +4.6 ppm °C−1). Moreover, the composite ceramic CDRA array is designed by exciting fundamental HE11δ mode using the aperture coupling microstrip feeding network. The fabricated composite ceramic based 4 × 4 CDRA array has enhanced measured radiation efficiency of up to 87%, high gain of 17.85 dBi and is a promising candidate for utilization in Sub‐6 GHz 5G Base Station communications systems.

A Cosmological Fireball with 16% Gamma-Ray Radiative Efficiency

Gamma-ray bursts (GRBs) are the most powerful explosions in the universe. How efficiently the jet converts its energy to radiation is a long-standing problem, which is poorly constrained. The standard model invokes a relativistic fireball with a bright photosphere emission component. A definitive diagnosis of GRB radiation components and the measurement of GRB radiative efficiency require prompt emission and afterglow data, with high resolution and wide band coverage in time and energy. Here, we present a comprehensive temporal and spectral analysis of the TeV-emitting bright GRB 190114C. Its fluence is one of the highest for all the GRBs that have been detected so far, which allows us to perform a high-resolution study of the prompt emission spectral properties and their temporal evolutions, down to a timescale of about 0.1 s. We observe that each of the initial pulses has a thermal component contributing ∼20% of the total energy and that the corresponding temperature and inferred Lorentz factor of the photosphere evolve following broken power-law shapes. From the observation of the nonthermal spectra and the light curve, the onset of the afterglow corresponding to the deceleration of the fireball is considered to start at ∼6 s. By incorporating the thermal and nonthermal observations, as well as the photosphere and synchrotron radiative mechanisms, we can directly derive the fireball energy budget with little dependence on hypothetical parameters, measuring a ∼16% radiative efficiency for this GRB. With the fireball energy budget derived, the afterglow microphysics parameters can also be constrained directly from the data.

Q Factor-Based Electrically Small Antenna Radiation Efficiency Measurement Using the Wheeler Cap

In this letter, a small antenna radiation efficiency measurement method is presented. The method utilizes the antenna quality factor, where it is a modification of the original Q factor method, amended by the loss Q factor of the antenna instead of the radiation Q factor. The method is verified for two kinds of antennas: the first is designed to operate at 868 MHz having a series resonance input impedance, and a second at 433 MHz having a parallel resonance input impedance. The method shows very high accuracy and prevent errors that may occur when using the conventional Wheeler cap method if the stored energy is not treated explicitly, which is considering the same imaginary part of the input impedance or input admittance for series resonance or parallel resonance, respectively.

Double-Layer Microstrip Antenna Integrated With Solar Cells

A low-profile broadband double-layer microstrip antenna is presented for green mobile communications. Eight solar cells are adopted for the top radiation structure, which can also improve the antenna performance. The antenna height is 0.071 λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> (λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> is the wavelength of 2.2 GHz in free space) with a measured −10 dB bandwidth from 1.65–2.76 GHz, so the mobile communication band from 1.71 to 2.69 GHz has been covered. Boresight radiation patterns are realized with an average gain of 8.27 dBi and measured radiation efficiency of more than 80% within the target band. This dual-function device can be a competitive candidate for green low-carbon communication systems.

Printed collinear dipole array antenna with a horizontally omnidirectional pattern for dual‐band WLAN

AbstractA dual‐band printed dipole array antenna for a wireless local area network (WLAN) application is presented. A radiation element consists of four pairs of printed dipoles, and two radiation elements are collinearly arrayed. A broadside coupling microstrip line‐based two‐sectional impedance transformer is used to feed the radiation elements in parallel. The proposed dual‐band antenna is designed to cover the dual‐frequency bands (2.4–2.48 and 5.15–5.825 GHz) which are the lower‐ and upper‐frequency bands for WLAN operation. The experimental results support the proposed design theory and also exhibit the gain values of 3.89–4.88 and 5.79–7.18 dBi at the lower‐ and upper‐bands, respectively, maintaining the omnidirectional radiation pattern. The measured radiation efficiencies at each frequency points, 2.4, 5.2, and 5.5 GHz are 87.39%, 75.43%, 69.96%, and 73.07, respectively. In addition, for mass production, the effect from a low‐cost flexible coaxial cable, and polyethylene housing on the antenna performance is also investigated in this letter.

A New Compact Triple-Band Triangular Patch Antenna for RF Energy Harvesting Applications in IoT Devices.

This work proposes a new compact triple-band triangular patch antenna for RF energy harvesting applications in IoT devices. It is realized on Teflon glass substrate with a thickness of 0.67 mm and a relative permittivity of 2.1. Four versions of this antenna have been designed and realized with inclinations of 0°, 30°, 60° and 90° to study the impact of the tilting on their characteristics (S11 parameter, radiation pattern, gain) and to explore the possibilities of their implementation in the architectures of electronic equipment according to the available space. The antenna is also realized on waterproof paper with a thickness of 0.1 mm and a relative permittivity of 1.4 for biomedical domain. All the antennas (vertical antenna, tilted antennas and antenna realized on waterproof paper) have a size of 39 × 9 mm2 and cover the 2.45 GHz and 5.2 GHz Wi-Fi bands and the 8.2 GHz band. A good agreement is obtained between measured and simulated results. Radiation patterns show that all the antennas are omnidirectional for 2.45 GHz and pseudo-omnidirectional for 5.2 GHz and 8.2 GHz with maximum measured gains of 2.6 dBi, 4.55 dBi and 6 dBi, respectively. The maximum measured radiation efficiencies for the three antenna configurations are, respectively, of 75%, 70% and 72%. The Specific Absorption Rate (SAR) for the antenna bound on the human body is of 1.1 W/kg, 0.71 W/kg and 0.45 W/kg, respectively, for the three frequencies 2.45 GHz, 5.2 GHz and 8.2 GHz. All these antennas are then applied to realize RF energy harvesting systems. These systems are designed, realized and tested for the frequency 2.45 GHz, −20 dBm input power and 2 kΩ resistance load. The maximum measured output DC power is of 7.68 µW with a maximum RF-to-DC conversion efficiency of 77%.

Biased Estimation of Antenna Radiation Efficiency Within Reverberation Chambers Due to Unstirred Field: Role of Antenna Stirring

Reverberation chambers (RCs) are now a reliable alternative to anechoic chambers to perform antenna radiation efficiency measurements. Most methods, including the two-antenna one used in this paper, are based on the evaluation of the stirred components of the scattering parameters. They are obtained by subtracting the average scattering parameters from the measured ones. This averaging is performed thanks to mechanical stirring, that is sometimes supplemented by additional stirring such as antenna stirring (which includes platform stirring and source stirring). In this paper, we present an extensive study on the role of antenna stirring in the retrieved radiation efficiency. Four measurement campaigns were successively performed: without antenna stirring, with platform stirring only, with source stirring only, and with a combined stirring of both antennas. Performing only source stirring or platform stirring leads to a biased estimation of the radiation efficiency. Therefore, we showed that the stirring of both antennas is mandatory in order to obtain an unbiased estimation of the radiation efficiency.

Differentially Fed Dual-Polarized 2-D Multibeam Dielectric Resonator Antenna Array Based on Printed Ridge Gap Waveguide

In this article, a differentially fed dual-polarized dielectric resonator antenna (DRA) subarray excited by a substrate integrated waveguide (SIW) cavity is proposed. A #-shaped slot etched on the top wall of the SIW cavity is used to achieve the differential excitation due to the intrinsic field distribution of TE120 mode in the SIW. Based on the proposed antenna subarray, a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$2\times $ </tex-math></inline-formula> 2 dual-polarized 2-D multibeam DRA antenna array with simple structure is designed, fabricated, and measured, which can achieve high cross-polarization discrimination (XPD) in the direction of maximum radiation. To reduce substrate loss, the printed ridge gap waveguide (PRGW) technology is used to feed the SIW cavity. Two orthogonal PRGW Butler matrices are placed at different layers so as to realize 2-D beamforming scanning with dual-polarization. The SIW cavity is placed in the air gap of PRWG, which can increase the stability of the antenna structure. By cleverly combining the SIW cavity and PRGW structure, the proposed multibeam antenna array has the advantages of high XPD and high radiation efficiency. Measured results show that an impedance bandwidth of 10% (28.5–31.5 GHz) and a peak gain of 11.8 dBi are obtained. Also, the measured XPDs are 28.3 dB at the center frequency and larger than 19.2 dB over the band of operation. Besides, the measured radiation efficiency of 67% is achieved for both the polarizations at 30 GHz.

Magnetoelectric Dipole Antennas Loaded With Meta-Lens for 5G MIMO Pattern Diversity Applications

This communication presents a unique design of a dual-polarized wideband passive beam-switching antenna at millimeter-wave (mm-wave) bands for multiple-input–multiple-output (MIMO) pattern diversity applications, which exhibits low correlation between the ports and a broad tilt bandwidth (BW). A magnetoelectric (ME) dipole fed by a printed ridge gap waveguide (PRGW) as a quasi-TE source is considered as the elementary antenna in the Ka-band. To achieve beam deflection in each quadrant, a four-port MIMO prototype consisting of four ME-dipoles, positioned perpendicular to each other, is integrated with a meta-lens that consists of three layers of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$12\times12$ </tex-math></inline-formula> dual-polarized split-ring resonators (SRRs) offset from the center of each antenna. The beamforming structure is able to generate four fixed beams, one in each quadrant at an elevation angle of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\sim 40^{\circ }$ </tex-math></inline-formula> with respect to the broadside direction by exciting each port sequentially, while the other ports are terminated. Moreover, the proposed orthogonal structure contributes to low correlation between the four ports, while achieving dual-polarization, which highlights the suitability of the antenna for 5G mm-wave applications. The measured results from a fabricated prototype demonstrate a −10 dB impedance BW of 40% over 24–36 GHz, tilting BW of 32.2%, and a peak gain of 13.4 dBi at 29 GHz, while an isolation better than 30 dB is achieved over the whole frequency band. Moreover, a measured radiation efficiency in excess of 85% is obtained, due to the use of the low-loss PRGW feedlines.

Design of a Relocatable Antenna Element Module for a Ku-Band Reconfigurable Array with Low Mutual Coupling

In this study, a modular array antenna with low mutual coupling is proposed for operation in a Ku-band (12–18 GHz) reconfigurable array, which consists of a ground frame board, element blocks, spacing blocks, and connecting rods. The modular element blocks can be freely mounted at any positions on a 46 × 9 grid on the ground frame board. The proposed modular array structure can be used to easily check the performance of different array structures by changing the element positions due to its low mutual coupling characteristics. An expanded view of the proposed array antenna structure is also provided, showcasing how the antenna modules, ground modules, base ground, ground frames, and aluminum rods have been constructed. The value of mutual coupling measured between the adjacent elements is less than -22.9 dB in the E-plane and -18.5 dB in the H-plane. Moreover, the measured radiation efficiency and gain patterns of the active element are shown.

Miniaturized MIMO Antenna Array with High Isolation for 5G Metal-Frame Smartphone Application.

In this paper, a highly isolated multiple-input multiple-output (MIMO) antenna array is proposed for fifth-generation (5G) metal frame smartphones. The eight identical small-sized inverted F-shaped folded slots are etched on the metal frame as a MIMO antenna. The bandwidth of the antenna can be adjusted by changing one of the short branches of the antenna. The bandwidth of the antenna can reach the N79 band (4.4~5.0 GHz). By carefully arranging the positions of the eight antenna elements, ideal spatial diversity can be successfully achieved to mitigate the coupling between the antenna elements effectively. What is more, a small combination slot of C-shape (0.0078 × 0.047λ2) and vertical I-shape (0.12 × 0.004λ2) between each antenna element is introduced to improve the element isolation of the MIMO antenna system. The proposed MIMO array has been simulated, fabricated, and measured. The results show good impedance matching (return loss > 6 dB) and high isolation (>22 dB). Due to the decent element isolation, the envelope correlation coefficient (ECC) between each antenna element is below 0.049. It can provide a reliable anti-interference performance for the MIMO antenna system. In addition, the measured radiation efficiencies of the MIMO antenna system are higher than 50%. The interaction of the hand model with the MIMO antenna system is also investigated, including the specific absorption rate (SAR).

Two-Dimensional Millimeter-Wave Beam-Switching Antenna Using an ELC Meta-Lens

A 2-D beam switching dipole antenna working at 60 GHz is proposed. To realize this, a folded electric-field coupled (ELC) resonator is designed to achieve a high-refractive-index medium in the band of 57–64 GHz. By integrating an array of ELC resonators in the off-center of a printed dipole antenna in the E- and H-planes forming high-refractive-index medium lenses (metalenses) in each plane, the main beam direction is manipulated to generate 2-D beam switching at 60 GHz. In the final configuration, six slabs each containing three folded ELC inclusions are incorporated vertically in front of the dipole antenna in the azimuth plane to tilt the radiation beam by 25° in the H-plane. In addition, a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$2\times5$ </tex-math></inline-formula> array of folded ELC resonators is added into the elevation plane of the antenna substrate to deflect the radiated beam in the E-plane by 20°. The measurement results confirm that the radiated beam is tilted by 25° and 20° in the H- and E-planes, respectively, over a frequency band of 57–64 GHz. The measured antenna gain is 10.7 dBi at 61 GHz, the measured reflection coefficient is below −10 dB over 57–64 GHz, and the measured radiation efficiency of the antenna is 82% at 60 GHz.

High‐gain and low‐cost circularly polarized antenna array for 5G MMW applications

A high-gain, low-cost empty substrate integrated waveguide (ESIW)-fed circularly polarized (CP) antenna array is demonstrated for millimetre-wave 5G applications in this letter. The ESIW is formed by metallized FR4 printed circuit boards. By stacking the metallic aluminium z-shaped radiating slots atop the ESIW feeding network, CP radiation is achieved. The proposed 1 × 8 antenna array offers a high measured gain of 17.8 dBic and high measured radiation efficiency of 89.1%. The measured impedance bandwidth for |S11| ≤ −10 dB and measured axial ratio (AR) bandwidth for AR ≤ 3 of the proposed 1 × 8 array are 11.4% (36.5–40.9 GHz) and 7.8% (37–40 GHz), respectively.