Dual-polarisation and dual-pattern planar antenna for diversity in body-centric communications

A novel dual-polarisation/dual-pattern stripline-fed annular-ring slot antenna for body-centric communication systems working in the IEEE 802.11a frequency band at 5.725-5.825-GHz is presented. A stripline feeding technique has been implemented in order to reduce the back radiation level and make the antenna suitable for wearable communication systems. The planar antenna has been designed to provide capabilities for implementation of a polarisation/pattern diversity scheme in body-centric communications. Two prototypes have been fabricated and characterised. The design criteria are described and measurements of return loss, isolation between ports, principal plane radiation patterns and radiation efficiency are shown. A measurement campaign has also been carried out to evaluate the diversity scheme performance.     

Second-order discriminant function for amplitude comparisonmonopulse antenna systems [EW antenna array]

The technique of using three receiving elements for amplitude comparison monopulse direction finders (DF) is examined. An appropriate second-order discriminant function is chosen for this technique. Simulation is then used to compare the system performance to that of the two-element system. In performance evaluation, errors coming from receiver noise, antenna pattern, amplitude imbalance, and mechanical and quantization origins are accounted for     

新型半模基片集成波导漏波天线

 为了设计一种结构简单、可靠性高的全向天线,提出了一种基于半模基片集成波导技术的漏波天线.这种天线是在半模基片集成波导结构的H壁增加4个对称振子形成的漏波辐射结构.使用电磁仿真软件对提出的天线结构进行了精确的建模,分析了介质厚度对天线带宽的影响,并对天线结构进行了优化,最后制作了天线测试样片进行实验验证.所设计的天线具有较宽的带宽和准全向辐射的特性,在7.3~9.7 GHz频段内具有良好的辐射性能,最大增益为5.8 dBi,测试结果验证了设计的有效性．     

Triple-frequency meandered monopole antenna with shorted parasitic strips for wireless application

The performance of a triple-frequency meandered-strip monopole antenna for wireless application is presented. The proposed antenna comprises of a microstrip-fed monopole with an additional meandered strip and a ground plane with three protrudent strips on the opposite side of the substrate. By adding these shorted parasitic strips to this monopole, good impedance matching for multi-band application is obtained. Tuning effects of the additional shorted strips to the different resonant modes were examined and prototype of the proposed antenna had been constructed and experimentally studied. The measured results explore a broadband triple-frequency operation covering the required bandwidths of the PCS-1900/UMTS-2100 and the 2.4/5.2/5.8 GHz WLAN standards, a near-directive radiation pattern and a good antenna gain for this design.     

Omnidirectional ADE antenna with a GO-shaped main reflector for an arbitrary far-field pattern in the elevation plane

This work presents a formulation for shaping the main reflector of a dual-reflector antenna designed to offer an omnidirectional coverage with an arbitrary radiation pattern in the vertical plane. The subreflector is generated by an axis-displaced ellipse and the main reflector is shaped to achieve a prescribed far-field radiation pattern. The shaping procedure is based on geometrical optics (GO) principles. Two distinct far-field ray structures are investigated. The GO-shaping results are validated by an analysis using the accurate method of moments technique.     

Performance of mobile phone antennas including effect of environment using two methods

The performance evaluation of a mobile terminal antenna can be done by measurements on test routes or by calculations using measured direction-of-arrival distributions and the measured or calculated radiation pattern of the antenna. Measurements on test routes require a lot of effort with completed prototypes, and, therefore, a reliable calculation-based evaluation method would be useful. In this paper, the results of these two types of evaluation methods are compared for the mean effective gain of six different terminal antennas in four environments at 2.15 GHz. The results of the two evaluation methods coincide well, as the mean and the standard deviation of the difference between the relative received powers are -0.2 dB and 0.8 dB, respectively. No significant difference in the coincidence is found between different environments or antennas.     

In-flight experiment for combined planar antennas and solar cells (SOLANT)

An in-flight experiment to validate advanced solar antenna structures (SOLANT) in space is presented. Two different antennas have been designed and manufactured, one for global positioning system (GPS) reception and one for S-band beacon transmission. Both units use slot aperture radiators embedded in identical mechanical structures. The GPS antenna has been designed to generate an omni-directional radiation pattern with righthanded circular polarisation thus fulfilling NavStar specifications. The S-band beacon antenna is based on a four-element circularly polarised array providing 6 dBic of gain. These antennas are integrated within two solar panels, which form the upper layer of the antenna structure. The two panels are identical, make use of gallium arsenide (GaAs) solar cells arranged in two strings and provide a peak power of 10 W each. The SOLANTs were launched, fixed to a Cosmos payload adapter and remained operative for 2 years, well beyond their expected lifetime. This study summarises the design and performance tests performed prior the launch and during the orbital operation.     

Reconfigurable angular diversity antenna with quad corner reflector arrays for 2.4 GHz applications

The authors propose a reconfigurable angular diversity antenna, constructed with quad corner reflector arrays and switching control, that can provide effective polarisation. With switches in the control unit of the base station, a high radiation gain antenna to provide cross-pair polarisations for receiving operations, as well as an omni-directional radiation pattern for transmitting, has been reconfigured. Simulation and measurement results including frequency responses, radiation patterns and three-dimensional polar plots demonstrate the design of an antenna. Diversity measurements with correlation and root mean square (RMS) error vector magnitude (EVM) are presented in order to evaluate the proposed antennas. The angular diversity technique can be applied to wireless local area network (WLAN) and multiple-input and multiple-output (MIMO) systems.     

High-frequency surface wave radar based on a sea floating antenna concept

The concept of sea floating antenna array is to replace a conventional coastal receive unit by a sea floating array, constituted of a set of receive buoys. Waves and wind introduce movements of buoys in the array which generate disturbances in the array radiation pattern. In this paper, compensation methods for vertical and horizontal displacements are presented. This paper introduces algorithms for both displacements which are tested following different sea states. Then, these algorithms can be combined in series, providing a simple method to optimise the radiation pattern of the deformed array.     

卫星天线一体化轴系驱动机构研究

导航卫星天线指向驱动机构是实现卫星星间链路天线高精度、长寿命可靠指向的核心部件。根据驱动机构需经历的发射段力学环境，入轨后真空、高低温等约束条件及星间链路天线的高精度、长寿命的特殊要求，提出了在步进电机、谐波减速器、编码器串装和一体化轴系的基础上，提高驱动机构精度和寿命的设计方法。理论分析了驱动机构预紧轴系受力状态及其影响因素，并进行了驱动机构轴系预紧力、启动转矩等效试验和使用寿命试验，分析了所设计驱动机构的负载特性；对驱动机构轴系的锁紧螺母进行结构改进，使驱动机构轴系的受力得到了较好的优化。为验证所设计驱动机构及其改进方法的正确性，在地面开展了不同热环境下精度和寿命等测试试验，最终验证了该导航卫星天线驱动机构能够满足天线在特殊环境下高精度、长寿命在轨稳定运行的要求。机构轴系预紧力的分析和试验验证工作具有一定的工程指导意义。     

Method of determining the phase center of an antenna using polarization measurements

A method of determining the single or partial phase center of an antenna using polarization measurements at two points of the radiation field in the antenna for zone is proposed. The method is based on a determination of the directions of the Poynting vector at these points. An example of the determination of the phase center of an antenna with a known axis is given. Translated from Izmeritel'naya Tekhnika, No. 4, pp. 55–57, April, 1998.     

Short backfire antenna with microstrip Clavin feed

A single short backfire antenna has an enclosed structure with no sharp projections and approximately 15 dBi gain, making it attractive for handheld radio monitoring and other man-portable applications. However, a microstrip patch fed short backfire antenna had a broad E-plane radiation pattern main lobe, leading to a loss of gain and low aperture efficiency. The antenna was studied using a commercially available Method of Moments software. Adding eight parasitic wires inside the cavity of a short backfire was found to narrow the E-plane radiation pattern main lobe, making it more like the H-plane radiation pattern and increasing the peak gain by 1.5 dB. A single proof of concept antenna was built at 1.49 GHz, which had a bandwidth of 2.3%, aperture efficiency of 78% and was shown to have equalised principal plane main lobes.     

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。     

Phaseless characterisation of compact antenna test ranges

Antenna characterisation and radar cross section measurements can be conveniently and successfully carried out by means of a compact antenna test range (CATR), whose performance is primarily assessed in terms of quiet zone size and field uniformity. CATR characterisation and diagnostics are usually performed by means of (amplitude and phase) field measurements in the quiet zone and are of timely interest either on CATR installation or on its periodic reassessments performed by manufacturers and/or users. This paper addresses CATR characterisation from amplitude-only data, an attractive topic because of the application of CATRs to the millimetre or sub-millimetre wave ranges. The approach is based on an appropriate strategy retrieving the missing quiet zone phase and facing the issue of the large electrical dimensions of the CATR. To take into account the characteristics of the collimating system as well as to keep as low as possible the number of unknowns to be sought for, it exploits the Jacobi-Bessel expansion of the aperture field. The performance of the algorithm has been tested through a wide numerical analysis against synthetic data generated by GRASP8-SE whose full version is routinely employed for CATR design. The main results related to a Gregorian dual offset reflector CATR, modelled on that proposed in the literature by Pistorius et ah, and to a single offset reflector CATR, inspired by the one available at the Queen Mary & Westfield College, London (UK), are reported.     

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.     

Design of square patch antenna with a notch on FR4 substrate

Simulation and measured results of a square patch antenna with a notch to search their possible application on modern communication systems including WiMax systems are presented. The antennas are designed on an FR4 substrate and the notch angle is varied under different conditions. It is found that on varying the notch angle from 180° to 164°, antennas resonate at a single frequency but on reducing the notch angle further, antennas start resonating at two frequencies with improved bandwidth. The optimum performance of an antenna is obtained when the notch angle is set to 151°. Different radiation parameters of the antennas under varying conditions are analysed and their possible applications in modern communication systems are investigated.     

Two-element superdirective array antenna composed of high-T c superconducting small helical radiators

Superconductors offer the potential for achieving highly efficient small and/or superdirective array antennas. This paper describes the design and reports experimental results for a two-element superdirective array antenna fabricated with YBaCuO superconducting material. 0.05λ helical radiators and quarter-wave matching and branch circuits were designed for an array antenna with a 0.09λ radiator spacing, to obtain a superdirective radiation pattern at 900 MHz. The array antenna thus fabricated realized good impedance matching and higher radiation efficiency than a Cu antenna, and a unidirectional radiation pattern at 80 K and around 900 MHz.     

Analysis on the platform-tolerant radio-frequency identification tag antenna

A new passive radio-frequency identification (RFID) tag antenna for the ultrahigh frequancy band is proposed. It consists of a modified inductive feed and a radiating slotted copper trace (SCT). A ground plane is used in the design to make the tag antenna platform-tolerant. The radiating SCT is investigated first, and its return loss, antenna efficiency and radiation pattern characteristics are studied. The read range, differential radar cross section, input impedance and current distribution of the RFID tag that employs the SCT antenna are simulated, and reasonably a good agreement between the simulated and measured results is obtained.     

Effect of conductive yarn crimp in radiation patch 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 conductive yarn crimp on electromagnetic performance of 3DIMAs are investigated by designing, simulating and experimental testing of two microstrip antennas with different patch woven structures: one woven in plain weave pattern with most yarn crimp and the other woven orthogonally without yarn crimp. The measured voltage standing wave ratio (VSWR) of the crimp free 3DIMA was 1.05 at the resonant frequency of 1.31 GHz; while that of the crimped 3DIMA was 1.78 at the resonant frequency of 1.41 GHz. In addition, the measured radiation pattern of the crimp free 3DIMA in its radiating patch has smaller back lobe and side lobes than those of the crimped 3DIMA. This result indicates that yarn crimp may have a negative impact on electromagnetic performance of textile structural antennas.     

Directional field enhancement of dielectric nano optical disc antenna arrays

This paper presents a discussion on the directive field enhancement of dielectric disc antenna arrays in optical band. The property of dielectric material is addressed, and field modes in a cylindrical resonator are discussed. It is identified that the fundamental mode of HE_11δ generates the far field with a higher directivity than other modes. More effective field enhancement in the radiation direction could be achieved by using multiple-disc antenna arrays. Simulation examples indicate that the directivity of a disc antenna array varies with the disc spacing. The maximum directivity is observed when the disc spacing is approximately equal to the half of the vacuum wavelength. The maximum directivity can be improved significantly when the disc number is increased.