侧向辐射的平面小天线的数值分析

在短距离移动通信中，由于系统对天线的效率和增益要求不高，人们大量使用FR4（玻璃纤维双面铜板）构造的天线，但未见损耗的分析报道。分析了一种构造于廉价的玻璃纤维电路板上的侧向辐射的小型平面天线，首次给出了天线在不同的介质损耗正切（tgδ）下的天线阻抗带宽，天线辐射效率以及方向图和天线增益的数值分析结果。     

Enhanced radiation from an electrically small radiator using an array of sub-wavelength holes

An experimental demonstration of radiation enhancement from an electrically small antenna (ESA) using an array of sub-wavelength holes engraved on a metallic plate is presented in this paper. A weakly radiating, chip inductor loaded open coplanar waveguide transmission line is used as the reference ESA. We show that an array of sub-wavelength hole loaded metallic aperture, placed near the antenna, can significantly enhance radiated power from the source. The hole array converts the high spatial reactive spectrum existing in the near-field of the antenna into a far-field propagating spectrum. The theory is validated by experiments and simulations in the microwave frequency regime. This novel radiation enhancement scheme is seen to enhance the gain of the antenna from ?8.5 to ?2.5?dBi and radiation efficiency from 13 to 33% around resonance.     

E-plane sectoral horn power divider

E-plane sectoral horn power divider design method for high-power antenna array applications is presented. In this method, power division is proportional to the cross section areas of the waveguide channels at the aperture of an E-plane sectoral horn antenna. Two different power dividers are designed and produced to be used with an X-band antenna array having 30 dB Taylor distribution. The first one employs a simple E-plane sectoral horn antenna. This straightforward application of the method might be limited with production tolerances. The second one incorporates a corrugated E-plane sectoral horn antenna, whose design is relatively complex but less sensitive to production tolerances. The produced dividers are compared based on simulations and measurements and good agreement with the theoretical expectations is observed for both types.     

Analysis and design of a Ka‐band satellite shaped offset reflector antenna for producing a contoured beam to cover the Taiwan region

Abstract

Analysis and design of a Ka‐band (20‐GHz) satellite offset‐fed shaped reflector antenna with a single feed for producing a contoured beam to cover the Taiwan region is presented. The design of this shaped reflector antenna is for future geostationary (GEO) satellite communication or DBS (direct broadcasting satellite) applications to serve the Taiwan region. The geometrical optics (GO)/aperture field (AF) method and aperture phase optimization procedures are employed for reflector surface shaping to produce the desired contoured beam. The physical optics (PO) method is used to accurately calculate the far‐field radiation pattern. Numerical simulation results show that the designed shaped reflector produces a Taiwan region converge beam and effectively reduces the antenna gain level in the nearby area of mainland China. Further reduction of the antenna gain level can be achieved by shifting the boresight direction of the satellite antenna for a certain small angle.     

A printed CPW-fed slot-loop antenna with narrowband omnidirectional features

The design of a novel CPW-fed printed slot-loop antenna with narrowband omnidirectional attributes is proposed. The antenna geometry is selected to reduce slot coupling, thus achieving both a narrow bandwidth and an omnidirectional radiation pattern simultaneously. A gain of 2.1 dBi is accomplished with high radiation efficiency. Very narrow fractional impedance bandwidths as low as 2.9% are realised with good omnidirectional radiation characteristics. A technique providing unconstrained control of the bandwidth in the range of 1.7?6.9% is described.     

Artificial Magnetic Conductor as Planar Antenna for 5G Evolution

A 5G wireless system requests a high-performance compact antenna device. This research work aims to report the characterization and verification of the artificial magnetic conductor (AMC) metamaterial for a high-gain planar antenna. The configuration is formed by a double-side structure on an intrinsic dielectric slab. The 2-D periodic pattern as an impedance surface is mounted on the top surface, whereas at the bottom surface the ground plane with an inductive narrow aperture source is embedded. The characteristic of the resonant transmission is illustrated based on the electromagnetic virtual object of the AMC resonant structure to reveal the unique property of a magnetic material response. The characteristics of the AMC metamaterial and the planar antenna synthesis are investigated and verified by experiment using a low-cost FR4 dielectric material. The directional antenna gain is obviously enhanced by guiding a primary field radiation. The loss effect in a dielectric slab is essentially studied having an influence on antenna radiation. The verification shows a peak of the antenna gain around 9.7 dB at broadside which is improved by 6.2 dB in comparison with the primary aperture antenna without the AMC structure. The thin antenna profile of λ/37.5 is achieved at 10 GHz for 5G evolution. The emission property in an AMC structure herein contributes to the development of a low-profile and high-gain planar antenna for a compact wireless component.     

Plasmonic resonance effects for tandem receiving-transmitting nanoantennas

A nanoplasmonic "transceiver" was assembled to examine the efficiency of coupled plasmonic antennas and their resonance interactions. In particular, plasmonic focusing receiver antenna coupled to transmitting annular antenna having a short central plasmonic wire was measured. The receiver collected incoming radially polarized light and efficiently focused and coupled it to a rear side transmitter comprised of a short resonant plasmonic wire and annular aperture. Transmission spectra exhibited a substantial signature of the wire Fabry-Perot resonances. The wire antenna crossection was improved by nearly 3 orders of magnitude by the focusing antenna system.     

Design and optimisation of a high-frequency EMC wideband horn antenna

A new approach for the design of high-frequency electromagnetic compatibility (EMC) broadband double-ridged horn (DRH) antennas is presented. In this approach, first a conventional DRH antenna at 1-18 GHz frequency band is considered. Using a thorough sensitivity analysis of different structural parameters of the 1-18 GHz DRH antenna, several modifications are applied to this antenna to overcome its deficiencies especially in its radiation pattern at higher frequencies. The final achieved design is then scaled up in the frequency to arrive at a design suitable for higher frequency ranges. A wideband DRH antenna for 18-40 GHz frequency band is then designed using this approach. The lower frequency ratio of 1:2.2 in the new antenna as opposed to the 1:18 ratio in the conventional antenna permits us to choose the best frequency window for the scaling up process. Besides, an optimisation technique is employed to further improve the antenna performance to meet the design goals over the entire new frequency band, that is, to have a single main lobe directed along the horn axis without any deterioration, and to have acceptable broadband gain with the minimum of 10 dB, and voltage standing wave ratio (VSWR) of less than 1.5. The final design which is more compact compared with the other commercial antennas has been used to make a prototype antenna. Measurements show that the built prototype meets the design goals very well     

Ant Colony Optimisation-based radiation pattern manipulation algorithm for Electronically Steerable Array Radiator Antennas

A new algorithm for manipulating the radiation pattern of Electronically Steerable Array Radiator Antennas is proposed. A continuous implementation of the Ant Colony Optimisation (ACO) technique calculates the optimal impedance values of reactances loading different parasitic radiators placed in a circle around a centre antenna. By proposing a method to obtain a suitable sampling frequency of the radiation pattern for use in the optimisation algorithm and by transforming the reactance search space into the search space of associated phases, special care was taken to create a fast and reliable implementation, resulting in an approach that is suitable for real-time implementation. The authors compare their approach to analytical techniques and optimisation algorithms for calculating these reactances. Results show that the method is able to calculate near-optimal solutions for gain optimisation and side lobe reduction.     

Effect of Wire Space and Weaving Pattern on Performance of Microstrip Antennas Integrated in the Three Dimensional Orthogonal Woven Composites

A conformal load-bearing antenna structure (CLAS) combines the antenna into a composite structure such that it can carry the designed load while functioning as an antenna. Novel microstrip antennas woven into the three dimensional orthogonal woven composite were proposed in our previous study. In order to determine the effect of the space between the conductive wires on the antenna performance, different space ratios of 1.7, 2.3 and 4.6 were considered in the design. Simulation results showed that when the space ratio increased, the frequency shift and return loss of the corresponding antenna became larger. And the antenna had relatively good performance when the space ratio reached 1.7. Two types of antennas were designed and fabricated with the ratio of 1.7 and 1 respectively and both of them obtained agreeable results. It was also demonstrated by the experimental that the orthogonal structure patch antenna had similar radiation pattern with the traditional copper foil microstrip antenna. However, the interlaced patch antenna had large back and side lobes in the radiation pattern because the existence of the curvature of copper wires in interlaced coupons lowered the reflective efficiency of the ground.     

Compact wideband multi-layer cylindrical dielectric resonator antennas

Homogenous dielectric resonator antennas (DRAs) have been studied widely and their bandwidth have been reached to the possible upper limit. A new non-homogenous DRA, multilayer cylindrical DRA (MCDRA), is designed and fabricated to achieve wider bandwidth. The antennas consist of three different dielectric discs, one on top of the other. Two different excitation mechanisms are studied here. As much as 66% of impedance bandwidth with a broadside radiation pattern has been demonstrated using a 50 Omega coaxial probe placed off the antenna axis. More than 32% of impedance with a broadside radiation pattern has been achieved when the antenna is excited by an aperture coupled 50 Omega microstrip feedline. Mode analysis is carried out to investigate the natural resonance behaviours of the MCDRA structure.     

Aperture-coupled asymmetrical c-shaped slot microstrip antenna for circular polarisation

A novel aperture-coupled, asymmetrical C-shaped slot, square microstrip antenna is proposed for circular polarisation (CP). A narrow and asymmetrical C-shaped slot, microstrip antenna is fed at the centre using an aperture coupling to obtain a CP operation. The compactness of the antenna is easily obtained by inserting a C-shaped slot. Wide CP radiation is achieved simply by making the C-shaped slot asymmetrical. With this antenna, the measured 3 dB AR bandwidth is around 3.3% and the 10 dB return loss bandwidth achieved is 16.0%. The overall antenna size is 0.48λo x 0.48λo x 0.092λo at 2.4 GHz. The proposed slot microstrip patch technology is useful to design compact, broadband, circularly polarised antennas and arrays.     

Investigation of anisotropic negative permeability medium cover for patch antenna

A more directional and higher gain patch antenna with an anisotropic negative permeability medium (NPM) cover is proposed. The patch antenna operates at the frequency where the permeability of split-ring resonator (SRR) is negative, and then the sideward radiation can be forbidden. It leads to a significant enhancement of designing the high gain antenna. We investigate numerically and experimentally the performance of the antenna when NPM composed of SRR is placed above the patch antenna. The measured result has a good agreement with the simulation. Compared with the conventional antenna, the result shows that the beam of antenna with the NPM cover becomes more convergent, half-power beamwidth is smaller by almost 30deg in the H-plane and 10deg in the E-plane and the gain is higher by 4.03 dB. Moreover, NPM cover can have applications in the other types of antenna such as monopoles, dipole antennas, leak-wave antennas and aperture antennas.     

测量距离对大型圆口径天线方向图影响的研究

本文运用互易原理导出了圆口径分布的天线近区辐射方向图与测量距离的关系。以圆口径指数型分布为例,计算了在不同测量距离下的辐射特性,从而研究了测量距离对天线方向图旁瓣特性的影响,给出了第一旁瓣测量误差与测量距离的关系曲线。最后,用5m环焦天线测量结果验证了理论分析和计算的正确性。     

Effect of Weaving Direction of Conductive Yarns on Electromagnetic Performance of 3D Integrated Microstrip Antenna

A three-dimensionally integrated microstrip antenna (3DIMA) is a microstrip antenna woven into the three-dimensional woven composite for load bearing while functioning as an antenna. In this study, the effect of weaving direction of conductive yarns on electromagnetic performance of 3DIMAs are investigated by designing, simulating and experimental testing of two microstrip antennas with different weaving directions of conductive yarns: one has the conductive yarns along the antenna feeding direction (3DIMA-Exp1) and the other has the conductive yarns perpendicular the antenna feeding direction (3DIMA-Exp2). The measured voltage standing wave ratio (VSWR) of 3DIMA-Exp1 was 1.4 at the resonant frequencies of 1.39 GHz; while that of 3DIMA-Exp2 was 1.2 at the resonant frequencies of 1.35 GHz. In addition, the measured radiation pattern of the 3DIMA-Exp1 has smaller back lobe and higher gain value than those of the 3DIMA-Exp2. This result indicates that the waving direction of conductive yarns may have a significant impact on electromagnetic performance of textile structural antennas.     

Edge-fed cavity backed patch antennas and arrays

A new edge-fed patch antenna that mitigates spurious radiation issues when thick substrates are used to create the antenna is presented. The radiator can be classified as an edge-fed cavity backed patch. Here, a thin substrate is used to develop the microstrip feed line, thereby ensuring the track widths are small and subsequently decreasing spurious feed radiation. The patch radiator utilises the thick substrate employed in the cavity ensuring reasonable return loss bandwidth can be achieved. A single element and a 2 x 2 array have been designed, fabricated and tested using the proposed technique and it has been shown that significant reduction in pattern distortion and increase in gain can be achieved compared to conventional edge-fed microstrip patch configurations. Because of the thin tracks used to feed the radiators, the new technique is very applicable to large arrays of microstrip patches where the area consumed by the distribution network must be minimised to ensure good radiation performance.     

Super Compact UWB Monopole Antenna for Small IoT Devices

This article introduces a novel, ultrawideband (UWB) planar monopole antenna printed on Roger RT/5880 substrate in a compact size for small Internet of Things (IoT) applications. The total electrical dimensions of the proposed compact UWB antenna are 0.19 λ_o × 0.215 λ_o × 0.0196 λ_o with the overall physical sizes of 15 mm × 17 mm × 1.548 mm at the lower resonance frequency of 3.8 GHz. The planar monopole antenna is fed through the linearly tapered microstrip line on a partially structured ground plane to achieve optimum impedance matching for UWB operation. The proposed compact UWB antenna has an operation bandwidth of 9.53 GHz from 3.026 GHz up to 12.556 GHz at −10 dB return loss with a fractional bandwidth (FBW) of about 122%. The numerically computed and experimentally measured results agree well in between. A detailed time-domain analysis is additionally accomplished to verify the radiation efficiency of the proposed antenna design for the ultra-wideband signal propagation. The fabricated prototype of a compact UWB antenna exhibits an omnidirectional radiation pattern with the low peak measured gain required of 2.55 dBi at 10 GHz and promising radiation efficiency of 90%. The proposed compact planar antenna has technical potential to be utilized in UWB and IoT applications.     

Antenna systems for the “Aryabhata’ mission

The onboard and ground antenna system employed in theAryabhata mission for telemetry and telecommand operations are described. The onboard antenna system common to telemetry and telecommand frequencies consists of four monopoles fed in turnstile configuration and generates a near isotropic pattern with worst dips of the order of −10 dB over approximately 0.2% of the total radiation sphere area. The ground antenna system consists of a high gain (16 dB) telecommand antenna and a telemetry array of eight medium gain Yagis (gain 22 dB).     

Directional emission of surface-enhanced Raman scattering based on a planar-film plasmonic antenna

A planar-film plasmonic antenna for surface-enhanced Raman scattering (SERS) with good emission directivity (divergence angle < 3°) was realized on a Kretschmann prism configuration with Raman-active analytes as emitters. The simulated results of finite-difference time-domain method show the emission efficiency, the directivity and the gain of the planar-film antenna were expected to be 50%, 300 and 22 dB, respectively. Angle-resolved spectroscopy was used to characterize its properties in SERS. The experimental results show that the SERS signal of analytes was remarkably enhanced when a laser excited this planar-film plasmonic antenna at the resonance angle. Meanwhile, the radiation of SERS was concentrated in a small region in space. The planar-film antenna with high gain coefficient can be a promising light harvesting and emitting device. The good emission directivity allows high collection efficiency. This advantage opens up interesting prospects in the applications for plasmon-enhanced spectroscopy and single-phonon detections.     

Method for Realizing the Possibilities of the Dulkyn Low-Frequency Gravitational-Wave Detector

A system is proposed for self-compensating low-frequency noise in the Dulkyn pentagonal laser-interferometer low-frequency gravitational-wave detector. For a signal-to-noise ratio at the output of the optical part of the scheme of no better than 10^–7, the system makes it possible to operate in real time after roughly 25 periods of a detected gravitational-wave signal. With the orbital motion of the Earth this will make it possible to implement an antenna (a response of the detector to gravitational radiation) having an artificial aperture and a radiation pattern width of a few minutes of arc.