Radiation Efficiency Of Antenna Research Articles

Large effective length and high efficiency by embedding L-shaped radiating blocks in subwavelength grating slot waveguide

Integrated optical antennas featuring large effective lengths and high radiation efficiency (RE) are essential to chip-scale light detection and ranging technology. However, there are challenges in simultaneously achieving both large effective length and high RE in silicon photonics platforms with high refractive index contrast. For traditional silicon waveguide grating antennas based on silicon photonics, the RE is relatively low and the antenna effective lengths are constrained to several hundred micrometers because of the high refractive index contrast. In this article, an embedded grating waveguide antenna which is L-shaped radiating blocks embedded in the slot gap of a silicon subwavelength grating slot waveguide is proposed and investigated numerically. Simulation results indicate the antenna’s effective length is above 4.25 mm, and the far-field divergence angle is near 0.0197°. Using L-shaped radiation blocks can break the diffraction’s perpendicular symmetry and increase the antenna’s RE to near 0.75 at 1550 nm compared to traditional design. Meanwhile, the antenna’s field-of-view reaches around 17.5° × 48.15° (θ× ϕ) to satisfy the needs of conventional optical phased arrays.

High-efficiency single-layer corporate-feed gap waveguide based circularly polarized antenna array with compact size

A high-efficiency, single-layer gap waveguide based circularly polarized (CP) metasurface (MTS) antenna array has been proposed at Ka-band, employing a combination of printed circuit board (PCB) and machining techniques. The coupling slot parallel to the feeding ridge is proposed, which can be beneficial for designing single-layer ridge gap waveguide (RGW) networks, avoiding the traditional cavity layer and reducing the transmission loss. The MTS elements in a 4 × 4 lattice of truncated-corner patches are etched on a single substrate layer for lightweight and low-cost, validating the concept of a compact mixed design that can be easily adapted to other printed CP antennas. A 4 × 4 MTS array prototype was fabricated and tested. The impedance bandwidth and axial ratio bandwidth are 26–31.3 GHz (18.5%) and 28.2–33 GHz (15.7%), respectively. Over the entire operating bandwidth of 28.2–31.3 GHz (10.4%), antenna radiation efficiency exceeds 82%, and the maximum realized gain at 29.2 GHz is 21.2 dBi. The designed broadband MTS antenna array is efficient, compact, and suitable for certain millimeter-wave communication applications.

FSS based high gain optically transparent MIMO antenna for Sub-6 GHz 5G mid-band applications

A novel optically transparent Multi Input Multi Output (MIMO) antenna design positioned on a Frequency-Selective Surface (FSS) for gain improvement while maintaining a simple fabrication procedure. Transparent conductive materials inherently exhibit higher sheet impedance due to lower conductivity, resulting in decreased antenna gain and radiation efficiency. To address this limitation, an optically transparent FSS is incorporated beneath the MIMO structure to improve radiation characteristics. Utilizing a Malinex substrate and a conductive silver oxide sheet, the 4-element MIMO design achieves both transparency and MIMO operability. The operational bandwidth spans from 3.09 GHz to 3.7 GHz, with a percentage bandwidth of 17.96 %, ensuring port isolation of over 20 dB. With the presence of the FSS, a consistent gain enhancement of approximately 3.46 dBi is achieved, with an average gain within the band reaching 4.56 dBi. The proposed design employs a simplified fabrication process while addressing aesthetic concerns and providing a solution to the existing issue of low gain in conductive metal oxide-based transparent antennas.

A wideband end‐fire stepped slot antenna with gain enhancement and filtering capability

AbstractA wideband end‐fire stepped slot antenna with gain enhancement and filtering capability is proposed. On one hand, a parasitic dipole serving as a director is introduced in the stepped slot to improve the radiation gain of the slot antenna without increasing its physical size. It is found that a gain enhancement of about 2 dB can be achieved after adopting such approach. On the other hand, an absorptive branch possessing a nearly complementary frequency response with regard to the one of the slot antenna is in‐parallel loaded at the microstrip feedline. It allows the partial dissipation of the out‐of‐band/non‐radiated RF‐signal power of the antenna to attain both an RF‐quasi‐absorptive behaviour and filtering capability. It is found that after loading the dissipative branch, the out‐of‐band radiation efficiency of the slot antenna is reduced to less than 20%. The measured results of a fabricated proof‐of‐concept antenna prototype show a reasonable agreement with the simulated ones and verify the RF performance merits of the proposed stepped slot antenna, such as wide RF operating band covering the 3.39−4.73‐GHz range, end‐fire radiation with a front‐to‐back ratio (FBR) above 10 dB, flat radiation gain, and co‐integrated filtering functionality with RF‐quasi‐absorptive capability.

Measuring Antenna Radiation Efficiency in a Reverberation Chamber and Effect of Unstirred Waves

Measuring Antenna Radiation Efficiency in a Reverberation Chamber and Effect of Unstirred Waves

Wideband frequency reconfigurable plasma antenna launched by surface wave coupler

A wideband reconfigurable plasma antenna excited by a surface wave coupler (SWC) operating at 13.56 MHz is presented in this study. The plasma antenna and SWC are designed and modeled in CST Studio. A detailed analysis of the SWC is carried out using CST Studio, and experimental measurements supplement the performance. This work explores the signal transmission capabilities of a plasma antenna excited at 13.56 MHz for the first time. A SWC is a two-port device that is modified for radiating electromagnetic waves through a plasma column produced at a frequency of 13.56 MHz with a coupling efficiency of 99%. The power port and signal port of the SWC are isolated for better coupling efficiency and to reduce interference. The return loss and isolation between the ports of the SWC at 13.56 MHz are −22 dB and −46.81 dB, respectively. The plasma antenna excited by a surface wave has a wider bandwidth than its metallic counterpart. It varies from 280 to 540 MHz for input plasma power ranging from 2 W to 10 W. In addition, a reconfigurability frequency span of 240 MHz for power ranging from 2 to 10 W is achieved experimentally. Moreover, we attained an enhanced peak gain of -5 dBi. The radiation efficiency of the plasma antenna is around 20%. The experimental results of the SWC and plasma antenna are in coherence with its simulations.

Synthesis of a Multiband Microstrip Patch Antenna for 5G Wireless Communications

This paper presents a multiband microstrip patch antenna for future 5G Millimeter Wave (mm-wave) wireless technologies. The synthesized antenna is designed to be based on the genetic algorithm (GA) optimization tool in the high frequency simulation software (HFSS). The optimized dimensions of the engineered antenna are 24 × 24 × 0.203 mm3, comprising of a ground plane. The antenna design simulated results have been implemented via (HFSS) and microwave studio (CST) tools. The proposed antenna structure is engineered using Rogers RT-Duroid 4003 substrate as a dielectric medium. The Conformist rectangular and circular patches are modified to get multiband operation in the mm-wave band 25–32 besides 40–60 GHz frequency ranges. The input reflection coefficient (S11\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\\mathrm{S}}_{11}$$\\end{document}) simulation results were compared with the measurements to check the validity of the design. The fabricated antenna radiation efficiency and gain values are also measured over the desired bandwidths. The measured gain and radiation efficiency values reached up to 9.75 dBi, 0.85%, and 10.75 dBi, 0.84%, for both bandwidths, respectively.

Effect of PIN Diode Integration on Patch Antennas for Frequency Reconfigurable Antenna Applications

PIN diodes are commonly used to design reconfigurable antennas owing to their sufficient isolation, lower cost, and ease of fabrication. This study aims to explore the effect of biasing conditions of a PIN diode radio frequency (RF) switch on a frequency-reconfigurable antenna. This approach investigates the contribution of the forward diode current and the reversed biased voltage on the shift in the operating band, the impedance matching, and the radiation efficiency of a reconfigurable antenna. The benefits and drawbacks of different approaches to modeling PIN diode RF switches are demonstrated on Ansys electromagnetic switch. The result shows a significant match between simulated and measured operating bands, impedance matching, and radiation efficiency. The proposed RF switch model can be used as a practical simulation model for implementing various reconfigurable microwave components.

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.

Metal-Loaded Acoustically Actuated Piezoelectric Antenna and Its Radiation Efficiency Limit

A metal-loading method (ML) is proposed in this paper to increase effective length, near-field magnitude and radiation efficiency for acoustically actuated piezoelectric antenna (PEA). Field-based circuit model method (FBCM) is utilized to characterize the metal-loaded piezoelectric antenna (MLPEA) by introducing antenna fields into piezoelectric equations and impedance analysis at boundary. Furthermore, current distribution within PE cylinder and on loaded metal rod is calculated by FEM method and formulated with piecewise functions. And, antenna effective length is evaluated with different loaded metal lengths and effects of the loaded metal are analyzed on antenna near-fields and radiation efficiency. All the methods are validated by measurement of a demonstrated MLPEA on a precise testing vehicle with frequency error of 0.05% and near-field magnitude error of 0.97dB. Finally, maximum increase of 4.6dB for near-field magnitude, and 10 times for radiation efficiency is obtained for PEA with loaded metal length of 0.8m. Different loss mechanisms in MLPEA are also analyzed and the radiation efficiency limit for PEA, as estimated by FBCM, is much larger than that of metallic antenna when <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ka</i> is less than 0.1, leaving far more room for radiation efficiency elevation of PEA for the-state-of-art.

Substrate effect and structure optimization of fabric-based circularly polarized dipole antenna for radio frequency energy harvesting

Radio frequency energy harvesting on textiles is seen as a method of enabling sustainable battery-free operation for wearable devices, while few works have clarified the influence of fabric properties on antenna performance. To prepare successfully a fabric-based circularly polarized antenna for radio frequency energy harvesting, this paper will clarify the effect of key fabric characteristics (such as dielectric properties and fabric thickness) on antenna performance by a finite element simulation. The simulated results showed the antenna resonant frequency is inversely proportional to the half square of the fabric’s dielectric constant, and the antenna radiation efficiency and gain are inversely proportional to the square of its dielectric loss tangent and thickness. Then, for the typical fabric substrates, the structure parameters of the existing circularly polarized antenna are optimized to work in the expected working frequency band, and the dominating structure parameter of the antenna in performance was identified. The optimized antenna prototype has excellent performance. The antenna has a bandwidth of 350 MHz and a maximum transmission distance of 190 cm. The received signal strength indication per unit area is 2.35 mW/cm2 and the output voltage is 1.19 mV/cm2 at a distance of 100 cm. It is concluded that the flexible size-minimized wide bandwidth circularly polarized radio frequency energy harvesting antenna screen-printed on fabric was derived from a commercial circularly polarized antenna with fiber-reinforced epoxy plate (FR4) substrate, and the critical geometrical and material parameters of the fabric substrate for this antenna performance as well as the affecting mechanism were identified.

Design of an applied method with graphite structure for suppression of surface electromagnetic waves between array antennas

In this study, a method of combining graphite structure and electromagnetic bandgap to reduce the mutual coupling of electromagnetic waves in array antennas is proposed. This structure is designed according to the special physical properties of graphite for the emission of electromagnetic waves, transmission theory, as well as the inductance and capacitive properties of the electromagnetic bandgap structure to dissipate surface currents. The proposed multi-input and multi-output (MIMO) antenna was designed and measured with two radiating elements on a substrate. The results show that the effects of mutual coupling between radiating elements are reduced by 30 dB at the operating frequency of 3.34 GHz. By placing this structure, all antenna components, including gain, patterns, and radiation efficiency, are improved. Calculations showed that antenna components: gain and antenna radiation efficiency increased by 1.2 dB and nearly 24%, respectively. To confirm the good performance of the graphite structure, all components of the MIMO antenna, including the envelope correlation coefficient, diversity gain, mean effective gain, channel capacity loss, and total active reflection coefficient, were investigated. The results showed the desired values, which indicate the very good performance of the graphite structure on all the basic characteristics of the antenna.

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.

Reduction of mutual coupling in a microstrip array antenna with circular polarization in the C-frequency band using a combination of DGS and EBG methods

In this study, in the first stage, an antenna with circular polarization was designed with the technique of cutting the corners of radiation patches. Then a hybrid structure with DGS and EBG methods was presented. For this purpose, the designed structure of the combination of DGS and EBG, which was designed to reduce mutual coupling, was placed between the radiating elements of the antenna. This method is implemented on a microstrip antenna. The reduction of the coupling of this structure is based on the creation of a magnetic band gap. All simulation was performed numerically by CST Microwave Studio software. The simulation results showed that this structure, unlike previous structures, improves all the characteristics of the antenna, such as the antenna gain, antenna radiation efficiency, and antenna envelope correlation coefficient. Also, the resonant frequency of the antenna is 6.35 GHz, which reduces the coupling by 36.5 dB by placing the designed structure between the radiating elements of the antenna.

A W‐band dual‐beam low side‐lobe level antenna with shared slotted waveguide arrays

AbstractA W‐band dual‐beam low side‐lobe level antenna with a shared slotted waveguide radiating layer was designed by the authors. The proposed antenna consists of a symmetrical dual ports feed network layer located on two sides of the antenna, a novel shared symmetrical 4 × 32 slotted waveguide array radiation layer, and a bottom layer. The compact slot distance was adjusted to achieve deflection of the radiation pattern and reduce the radiation grating lobes. Good antenna radiation efficiency and port isolation were obtained by optimising the position of the slots at the radiation layer. A low side‐lobe level (SLL) was obtained using Taylor distribution was used in the design of the offset of each slot. The optimised antenna was fabricated and measured. Based on measurement results, the designed antenna has a 24.8 dBi far‐field gain, −17/–25.5 dB E/H plane side lobe level, and 19.8° beam deflection at 94 GHz. The performances of the two ports were in good agreement with each other, and the measured isolation was above 14.5 dB at 94 GHz.

Split Ring Antennas and Their Application for Antenna Miniaturization

This paper investigates the miniaturization capability of split ring array antennas embedded in a low-permittivity dielectric substrate, in comparison with the same-sized high-permittivity dielectric resonator antennas (DRAs). In order to understand the miniaturization performance, a size-fixed dielectric substrate with different split ring arrays is studied. The simulation results show that the miniaturization capability increases with decreased unit cell resonant frequency and/or increased unit cell induced permeability. Miniaturizations as high as 25.54 times that of a high-permittivity DRA are obtained with split rings, etched on a dielectric substrate having a low permittivity of 2.2. Furthermore, this excessive miniaturization does not come at the expense of excessive deterioration of the antenna impedance bandwidth, gain, and radiation efficiency. Consequently, the miniaturized split ring arrays still provide high gains over wider bandwidths. This inference is further verified by comparing the miniaturization and other antenna performance parameters with three other modified split ring configurations. To experimentally verify this work, a split ring antenna was fabricated and tested, and good agreement between the simulated and measured results was observed. The results of this study indicate that adding resonant metallic inclusions into low- permittivity DRAs significantly increases their miniaturization capability, without overly deteriorating the performance.

A Novel Integrated UWB Sensing and 8-Element MIMO Communication Cognitive Radio Antenna System

In this article, a cognitive radio (CR) integrated antenna system, which has 1 sensing and 24 communication antennas, is proposed for better spectrum utilization efficiency. In the 24 communication antennas, 3 different operating band antennas are realized with an 8-element MIMO configuration. The sensing antenna linked to port 1 is able to sense the spectrum that ranges from 2 to 12 GHz, whereas the communication 8-element MIMO antennas linked with ports 2 to 9, ports 10 to 17 and ports 18 to 25 perform operations in the 2.17–4.74 GHz, 4.57–8.62 GHz and 8.62–12 GHz bands, respectively. Mutual coupling is found to be less than −12 dB between the antenna elements. Peak gain and radiation efficiency of the sensing antenna are better than 2.25 dBi and 82%, respectively, whereas the peak gains and radiation efficiencies of all communication antennas are more than 2.5 dBi and 90%, respectively. Moreover, diversity characteristics of the MIMO antenna are assessed by parameters such as DG, ECC and CCL. It is found that ECC and CCL are less than 0.42 and 0.46 bits/s/Hz, respectively, and also DG is more than 9.1 dB.

Efficiency-Driven Design for Planar Antennas With Lossy Materials

This article demonstrates a design strategy for improving the radiation efficiency of a planar antenna made of a layered conductor of MXene with modest conductivity on a lossy PDMS substrate. New methods to reduce the conductor loss and the dielectric loss are proposed. On the one hand, the conductor loss is minimized by identifying the location of high current density on the antenna radiator, and then accordingly altering its shape to redistribute the surface currents as uniformly as possible. On the other hand, the dielectric loss is reduced by employing a folded ground plane with elevated edges. This ground plane structure reduces the concentration of the electric field in the dielectric substrate and thus minimizes the power dissipation due to dielectric loss. The improvement techniques are implemented starting from a standard U-slot microstrip antenna. The method demonstrates to improve the radiation efficiency significantly by an average of 14% for a microstrip antenna fabricated using MXene conductor with a sheet resistance of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$2 {\Omega }$ </tex-math></inline-formula> /square and a lossy PDMS substrate. Importantly, the proposed method can preserve the overall antenna size and the operating frequency band. The optimized antenna exhibits a high radiation efficiency of 71% and offers a wide impedance bandwidth of 56% covering operation for the 5 GHz WLAN band.

Wideband and Efficient 256-GHz Subharmonic- Based FMCW Radar Transceiver in 130-nm SiGe BiCMOS Technology

This article proposes a fully integrated single-channel bistatic frequency-modulated continuous-wave (FMCW) radar transceiver (TRX) that operates at a center frequency of 256 GHz. The main focus of this work is to realize a wideband and efficient radar TRX that offers high resolution of target detection in the short-range FMCW radar sensing application. The radar TRX chip is designed and manufactured using the 130 nm silicon–germanium (SiGe) bipolar complementary metal-oxide-semiconductor (BiCMOS) technology which offers heterojunction bipolar transistors (HBTs) with <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$f_{\mathbf {T}}/f_{\mathbf {MAX}}$ </tex-math></inline-formula> of 300/500 GHz. The transmitter (TX) of the radar TRX is based on a fundamentally operated multiplier-by-8 chain architecture that offers a 3-dB bandwidth of around 65 GHz with a saturated output power of −5.4 dBm. On the other hand, the receiver (RX) is based on a subharmonic architecture that provides a conversion gain (CG) of 10.4 dB with an average noise figure (NF) of 23.5 dB. This TRX is realized with two integrated on-chip folded dipole antennas. The antenna offers high antenna gain and radiation efficiency due to the use of the selective localized backside etching (LBE) technique. This chip consumes 305 mW of power from a 3.3-V supply and occupies a silicon area of 3.3 mm2. The radar range measurement is performed in an anechoic chamber, and it shows the maximum dynamic range (DR) of around 34 dB at 1-m range of the target.

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.