Design of electrically small ground planes for HF ground wave transmission

Electrically small spiral ground planes for a monopole and an electrically small antenna have been designed for HF ground wave transmission. Prototype ground planes have been built and tested. For the monopole, the transmission loss of the designed ground plane is 6 dB better than that of the same size ground radials. For the electrically small antenna, the transmission loss of the designed ground plane is 7 dB better than that of the same size solid ground plane at the antenna's operating frequency.     

Electrically small unbalanced four-arm wire antenna

An electrically small antenna element is presented. It is an unbalanced antenna, consisting of four wire arms arching over a groundplane. One of the wire ends is the feed, and the other three are connected to the groundplane, via a capacitance, short, and load, respectively. The resonance frequency is tuned by varying the capacitance, which can be set fixed or used to accomplish electronic tunability with a tuning range of several octaves. The momentary bandwidth of the antenna is approximately 3%. Applications are typically antennas for very small terminals in narrowband systems, or alternatively broadband systems where electronical tuning can be implemented in the antenna. The exact shape of the wires is not critical and can be chosen to conform to mechanical design requirements.     

Electrically small antenna elements using negative permittivity resonators

We show how resonators composed of negative permittivity materials can form the basis of effective small antenna elements. A quasi-static analysis of the resonant properties of a sub-wavelength negative permittivity sphere predicts that such a resonator will have a Q-factor that is only 1.5 times the Chu limit, matching the performance of other known electrically small spherical antenna designs, such as the folded spherical helix and the spherical capped dipole. Finite element simulation is used to demonstrate an impedance-matched radiating structure formed by coupling the resonator (a half-sphere above a ground plane) to a 50 ohm coaxial transmission line, where the coupling is mediated by a small conducting stub extending partially into the half-sphere. The resulting antenna has a ka<0.5, and its bandwidth and efficiency performance corresponds well to that predicted by the quasi-static analysis of the resonator.     

Polarisation and ground effects on HF receiving antenna patterns

The behaviour of receiving antennas is investigated forHF wavelengths. The polarisation characteristics of incoming waves are determined and then, taking into account ground reflections, the signal intensity at the antenna output is calculated for antennas that are small compared to the wavelength. The results are shown as a series of figures. They illustrate the importance of the link geometry and the location of the receiving site in relation to the earth’s magnetic field. The results can be used to achieve a better adaptation between antennas and ionospheric modes.     

小地板锯齿作馈源的背射式天线

本文提出一种新式宽带线极化背射天线。该天线的馈源是一种背射式锯齿天线。这种背射天线E面和H面主瓣宽度在 2 6°～ 39°之间 ;其方向图和驻波系数等主要指标带宽可达 1～ 1.6。此外这种天线还具有馈电方便、结构简单等优点。     

An extremely small transmission line antenna for DAB VHF band

This paper is to present a design method for an extremely small antenna, which is based on the traditional concept of transmission line antenna. Physically, it is composed of a short section of planar transmission line antenna and a long and slender cable. Since this slender cable can be wound and attached on the planar section, the whole apparent size is small even it is operating for DAB (Digital Audio Broadcasting) VHF band. Special techniques are applied for the purpose of impedance matching.     

Miniature circular GSM wire-patch antenna on small ground plane

A miniature stacked wire-patch antenna, on small ground plane is described. Its dimensions are only 1.2 times the radiating element. This uses the original resonance phenomenon, owing to the presence of wires, to work like a short monopole for GSM frequencies located below the fundamental cavity resonance mode. Owing to its low profile, low cost, large bandwidth and dipolar radiation pattern, this antenna is very suitable for automobile or indoor ceiling applications needing a very small ground plane     

Aperture coupled microstrip patch antenna with thick ground planein millimetre waves

The finite thickness of the ground plane is taken into account in the cavity model to analyse some aperture coupled microstrip patch antennas at millimetre-wave frequencies (60 GHz). The thickness has a strong effect on impedance matching at high frequencies owing to the ratio between the thickness and the wavelength, which increases with frequency. The calculated results are compared to those obtained by experiment for several antennas with different input impedances due to different slot lengths. Close agreement is found between the calculated and experimental results     

Naval structural antenna systems for broadband HF communications

This paper introduces the concept of multipurpose structural antenna system for shipborne installations. By combining properly shaped and loaded wire radiators together with an existing naval superstructure, such as the funnel or a big mast, it is possible to achieve a broadband high-frequency compact radiating system which permits handling both sea-wave and near vertical incidence sky-wave communications. When provided with a plurality of feeding points, the naval structural antenna may be used in multichannel mode, with a huge efficiency improvement over the conventional multichannel broadband systems requiring a combining network. Additionally it is shown that, when fed in monochannel mode, the structural antenna system exhibits focusing features with the possibility to achieve sectorial coverages. This paper demonstrates the advantage and limitation of this new system by carefully taking into account the interantenna coupling.     

电小甚低频发射天线的地损耗电阻计算与分析

针对电小甚低频发射天线辐射电阻小,地损耗影响天线辐射效率的问题,文中研究了基于解析法计算分区域均匀辐射状地网区内磁场损耗电阻、电场损耗电阻和地网区外磁场损耗电阻、电场损耗电阻的方法,根据该方法可实现对分区域均匀辐射状地网的损耗电阻计算.计算结果表明,电小甚低频发射天线的磁场损耗电阻是地损耗的主要部分;此外,在地网总长度和地网敷设区域半径不变的条件下,均匀辐射状地网并不是甚低频天线的地网敷设最佳模式.基于上述结果,提出通过分区域敷设均匀辐射状地网的方法来降低地损耗电阻,为进一步提高电小天线的辐射效率提供了一种新的途径,具有一定的理论和工程实践指导意义.     

Tracking antenna arrays for near-millimeter waves

A two-dimensional monolithic array has been developed that gives the elevation and azimuth of point source targets. The array is an arrangement of rows and columns of antennas and bismuth bolometer detectors on a fused quartz substrate. Energy is focused onto the array through a lens placed on the back side of the substrate. At 1.38 mm with a 50 mm diameter objective lens, the array has demonstrated a positioning accuracy of 26 arcmin. In a differential mode this precision improves to 9 arcsec, limited by the mechanics of the rotating stage. This tracking could be automated to a fast two-step procedure where a source is first located to the nearest row and column, and then precisely located by scanning. With signal processing the array should be able to track multiple sources.     

Experimental study of wideband hybrid dielectric resonator antenna on small ground plane

A wideband hybrid dielectric resonator antenna (DRA) is investigated experimentally. The proposed hybrid DRA comprises a rectangular dielectric resonator and a conductor-backed coplanar waveguide (CB-CPW) slot etched on a small ground plane. Dual resonances of the two radiators are merged to expand the antenna bandwidth. By utilising the CB-CPW structure, a back-cavity is formed underneath the slot to suppress the backward radiation. Hence consistent unidirectional radiation pattern is achieved across the matching band.     

Converting a small standard receiver into a hand-heldnarrow-aperture HF direction finder

Describes a compact HF-antenna accessory, designed for use with book-sized portable receivers. It converts the receiver for sky-wave-direction finding (DF), co-channel-interference reduction, and radio-frequency-interference (RFI) location, while being hand-carried by the user. When the system is operated in the DF mode while in motion, site-related errors in line of bearing (LOB) can be reduced by spatial averaging, and by over-sampling and excising "outliers." This approach is equivalent to increasing the effective aperture to improve resolution. Spatially averaging the LOBs permits useful DF measurements to be made in locations, so cluttered by scattering from nearby objects, as to be unsuitable with standard DF equipment. The receiving system has been designed to be as insensitive as possible to local reflections (including those from the operator's body)     

A dual-polarized slot antenna for millimeter waves

We describe a new dual-polarized slot antenna to be used with quad-optical devices such as superconductor-insulator-superconductor (SIS) mixers at millimeter and submillimeter wavelengths. The radiation and impedance characteristics of the antenna were obtained from a moment-method calculation. The antenna has an excellent radiation pattern, a low impedance, wide bandwidth, and low cross polarization     

千兆以太网数据传输技术在数字化高频地波雷达中的应用

介绍了千兆以太网数据传输技术在数字化高频地波雷达中的应用,说明了具体的实现方法,验证了在数字化高频地波雷达中应用千兆以太网数据传输技术的正确性。     

一种低成本的海事卫星移动终端天线

提出一种适用于宽带全球局域网(BGAN)地面移动终端低成本天线的设计方案.通过选用泡沫塑料和铝箔材料,采用叠层微带天线阵结构及多种展宽带宽的方法来实现天线设计,并进行了电磁仿真优化.最后对天线进行了加工试验,测试结果表明天线在整个海事卫星通信工作频带内驻波比小于1.5,增益高于14 dB,3 dB广角轴比大于21°.本文所设计的天线已成功应用于HNS9201移动终端.     

The wave antenna for transmission and reception

The traveling-wave horizontal-wire antenna over the earth is analyzed in its original form with vertical ground connections (the Beverage antenna) and with these replaced by horizontal terminations. For transmission, the electromagnetic field of an antenna with optimum length is determined, both along the surface of the earth in air and in the earth, in an accurate but simple form that takes full account of the proximity of the earth (lake, sea) on the distribution of current. For reception, the induced currents in the antenna and in the load are determined for a field incident along the surface of the earth. The two types of termination are compared and their contributions shown to be small when the horizontal wire has a length near the optimum.     

Model of HF interference for application to data transmission

Cochannel interference is not usually a Gaussian process, but it would be both theoretically and practically convenient if it could be considered to have the same effect as Gaussian noise on data transmissions. The letter describes measurements and simulations which show that this is indeed a useful approximation in evaluating the effects of HF interference on phase shift keying.     

Metamaterial-based antenna with triangular slotted ground for efficiency improvement

A metamaterial-based antenna is presented that consists of periodic electromagnetic bandgap (EBG) cells on the top plane and triangular slots on the bottom ground plane. This proposed microstrip patch antenna can yield left-handed, zeroth-order and right-handed metamaterial resonances owing to the asymmetrical periodic structure of honeycomb- like EBG. Experimentally, the efficiency of this antenna is improved by about 14.7% at the zeroth-order resonant mode as the triangular slot length on the ground plane is increased from 0 to 5.5 mm.     

An array technique for reducing ground losses in the HF range

Ground losses of HF antennas situated near the earth's surface are reduced if single antennas are replaced by small arrays of, for example, two or four closely spaced radiating elements. It is shown both theoretically and experimentally that an array spacing ofsim 0.1 lambdais sufficient to achieve significant improvement in ground-to-ground transmission efficiency. In particular in the lower HF range and for poorly conducting ground, the improvement approaches a theoretical limit equal to the number of elements in the array.