一种组合馈线的设计

天线馈线是天线的重要组成部分,天线馈线设计的好坏对天线性能的影响非常大。在分析了造成某工程设计的L/S组合天线方向图畸变的原因之后,应用电磁波在金属导体上传输的趋肤效应和λ/4同轴短路传输线的阻抗特性,巧妙地设计了一种L/S双频段同轴组合馈线。经测试得到的方向图验证了该设计合理且简单有效。     

Range distance requirements for large antenna measurements

The dependence of the radiation patterns and antenna gains on the measurement distance when both transmitting antenna and receiving antenna have the same order of large dimensions is discussed. The antenna under test is the transmitting antenna. The near-zone radiation patterns (Fresnel pattern) and the antenna gains of various kinds of circular aperture distributions vs the measurement distances are calculated for an arbitrary size of the receiving probe antenna. It is found both theoretically and experimentally that the near-zone measurement error of the radiation patterns introduced when the receiving antenna is of comparable or the same dimension as the transmitting antenna is smaller than the error introduced when the receiving antenna is very small. Thus, it is concluded that as a range criterion 2D²_a/λ is more appropriate than 2(D_a+D_b)² /λ for pattern measurements (D_a and D_b are linear dimensions of the transmitting and receiving antennas, and D_a⩾D_b is assumed). It is shown that the gain error for any aperture distribution obtained by using a large receiving probe antenna is greater at any range distance than the error obtained by using a small antenna such as a dipole     

Photodiode-integrated microstrip antenna array for subterahertz radiation

The radiation characteristics of subterahertz (sub-THz) electromagnetic waves emitted from an antenna array integrated with photodiodes are investigated. The element of the fabricated array antenna was a 300-GHz microstrip antenna integrating a uni-traveling carrier photodiode. It was observed that the beamwidth of a 3 /spl times/ 1 antenna array is about half that of the single microstrip antenna. We also confirmed that the radiation direction changed by 20/spl deg/ when 2/spl pi//5 of phase difference was added to the input optical signal for each antenna element. These results demonstrated that sub-THz waves emitted by each element of the array were coherently superimposed and the power combining of the sub-THz radiation occurred in the microstrip antenna array. The measured output power of each radiation element is about 120 /spl mu/W, and a total output power of 1 mW can be estimated for a fabricated 3 /spl times/ 3 array in an ideal radiation condition.     

几种多天线系统的信道容量比较

分布式天线、智能天线和扇区天线是三种能大大提高无线通信系统容量的技术,本文比较了这三种多天线系统的信道(Shannon)容量.假设每个用户在所有接收天线上的总功率相等,分析表明分布式天线和扇区天线的信道容量远大于智能天线的信道容量,而传统的观点认为智能天线在抑制干扰时要比扇区天线的性能更好,从而获得更大的系统容量.另外我们分析了分布式天线在渐近条件下的信道容量,即用户数K和载波数M都趋近无穷大,而保证α=K/M一定.分析表明在α较大时,分布式天线与比扇区天线的信道容量差趋近常数0.44比特/秒/维,但是如果考虑分布式天线的分集增益,那么分布式天线的信道容量要远大于扇区天线.     

Design of dual-polarized L-probe patch antenna arrays with high isolation

An experimental study of a dual-polarized L-probe patch antenna is presented. The antenna is designed to operate at around 1.8 GHz. A "dual-feed" technique is introduced to achieve high isolation between two input ports. The proposed antenna has an impedance bandwidth of 23.8% (SWR/spl les/2), 15% (SWR/spl les/1.5) and an isolation over 30 dB. In array designs, techniques for improving the isolation between two adjacent elements of an antenna array are also investigated. A two-element array with more than 30 dB isolation is designed and tested.     

Compact microstrip-T coupled patch antenna for dual polarisation and active antenna applications

A novel way of feeding single-layer microstrip patch antennas using electromagnetically coupled microstrip-T junctions is proposed. The measured isolation and 10 dB bandwidth of an X-band dual polarised antenna are /spl sim/32 dB and 2.1%, respectively, on an /spl epsiv//sub r/ 3.0 substrate. Since both ports of the antenna are electromagnetically coupled, the proposed antenna eliminates the need for capacitors in the RF path for active antenna applications.     

An experimental study of the insulated dipole antenna immersed in a conducting medium

The driving-point admittance and the amplitude and phase distributions of the current referred to the driving-point were measured for an insulated cylindrical antenna immersed in a conducting medium. The ratiosigma/omegaepsilon_{r}epsilon_{0}of the conducting medium was varied fromsigma/omegaepsilon_{r}epsilon_{0}= 0.036to 8.8, a range which includes a variety of media such as poor insulators, the ionosphere, plasmas, dry earth, wet earth, lake water and sea water. The antenna heightbeta hin radians was varied frombeta h=0.1throughbeta h=2piat intervals of 0.1. The thickness of the insulator was varied fromb/a = 1.25tob/a = 12.0whereais the radius of the antenna andbthe radius of the insulator. Measurements have also been made of the admittance, current and phase distributions along an insulated antenna with a conductive top load, that is, one whose tip is in direct contact with the conducting medium. It is found that when the tip of the antenna is in direct contact with the conducting medium, the current increases almost linearly as the end of the antenna is approached. This is quite unlike the decaying sinusoidal distribution on the completely insulated antenna. In a general sense, the experimental results are in fair agreement with an approximate theoretical expression for the admittance of an insulated antenna immersed in a highly conducting solution. The approximate theory is based on the driving-point admittance of a coaxial line whose outer conductor is imperfectly conducting and infinite in extent.     

一种K频段宽带双极化滤波喇叭天线设计

文中设计了一种K频段宽带双极化滤波喇叭天线,该天线采用阶梯型喇叭代替传统喇叭提升了天线效率,并通过在馈电波导冗余空间中引入一种T/Π型滤波结构,提升了天线带外的抗干扰能力. 仿真和实验结果表明,该双极化天线的?10 dB阻抗带宽超过5 GHz,覆盖了K/Ka频段卫星的下行频段,天线效率超过58%,并在其上行频段实现了超过33.1 dB的带外抑制,该天线可作为单元用于K/Ka频段卫星下行频段的大型阵列天线设计.     

New method of measuring phase characteristics of antenna using Doppler frequency measurement technique

This paper reports on a new method of measuring the phase characteristics of an antenna using the Doppler frequency measurement technique. With this method, the antenna being tested is rotated at a rate of f/sub sp/ around an axis through its geometrical center, and the phase characteristics of the antenna are calculated from the harmonic components of f/sub sp/ during time variations in the Doppler frequency of radio waves emitted from the antenna. Using this, we obtained three-dimensional phase characteristics of a patch antenna with a root-mean-square error of about 0.5/spl deg/, and confirmed its efficacy through experimental results.     

A Pentagonal Shaped Microstrip Planar Antenna with Defected Ground Structure for Ultrawideband Applications

A new compact pentagonal microstrip patch antenna with slotted ground plane structure, developed for use in ultrawideband applications, is studied in this article. The proposed antenna is mainly constituted by a pentagonal shaped patch antenna, a defected ground plane structure, two stubs, and four slots to improve the bandwidth. The designed antenna has an overall dimension of 30?×?17.59?×?1.6 mm³, for WIMAX/WLAN/WiFi/HIPERLAN-2 /Bluetooth/LTE/5G applications with a very large bandwidth starting from 2.66 to 10.82 GHz (S₁₁?<???6 dB). A parametric study of the ground plane structure was carried out to find the final and the optimal UWB antenna, and to confirm that the antenna has good performance and broader bandwidth. The proposed antenna prototype has been fabricated. The measured results indicate that the antenna has a good impedance matching. The antenna has an electrically small dimension with a good gain, a notable efficiency, and a wide impedance bandwidth, which makes this antenna an excellent candidate for ultrawideband wireless communication, microwave imaging, radar applications, and the major part of the mobile phone frequencies as well.

     

A new method for obtaining antenna gain from backscattermeasurements

A method is presented for determining the gain of an antenna from analysis of backscatter data of the antenna. This approach is different from those which have been presented in the past because it accounts for the presence of resonances which can occur in the antenna during a backscatter measurement. In particular, this type of resonance appears in the backscatter measurement of symmetric reflector antennas. This technique is applied to determine the gain of a Ka-band Cassegrain antenna and an X-band prime focus-fed antenna     

Millimetre-wave InP antenna for monolithic integration

A printed antenna realised on an indium phosphide wafer is presented. The antenna provides an efficient, broadband antenna solution for MMIC/OEIC systems and subsystems. The antenna is based on an aperture coupled patch architecture with the substrates layers in a hi-lo configuration. Measured results exhibit an impedance bandwidth of around 12% for VSWR<2, and a gain of 8 dBi.     

Compact Switched-Beam Antenna Employing a Four-Element Slot Antenna Array for Digital Home Applications

In this paper a compact switched-beam antenna is proposed. The antenna is composed of a four-element antenna array based on L-shaped quarter-wavelength slot antenna elements. Such an antenna element is a planar structure and presents a directional radiation pattern in the azimuth plane. Its maximum radiation direction is toward near the direction of the open end of the slot. As a result, the open ends of the four slot antennas are arranged toward $0, pi/2, pi$, and $3pi/2$ , respectively. The statuses of these antennas are controlled by some diodes. Consequently, by carefully controlling the diodes, an antenna with several switchable patterns can be achieved. To prove the concept, a 2.4–2.5 GHz switched-beam antenna for WLAN applications is designed and implemented. Its size is 52 mm in square. The antenna possesses eight directional patterns and many nearly omnidirectional patterns in the azimuth plane. The experiment results fully demonstrate the performance of the proposed design. The envelope correlations and the characteristics of the designed antenna are also discussed. Due to the compact size and low manufacture cost, such a design can be a promising solution for digital home applications to overcome multipath problems and increase the transmission data rate.      

Reduced-size microstrip patch antenna for Bluetooth applications

A novel reduced-size microstrip rectangular patch antenna for Bluetooth operation is presented. The proposed antenna operates in the 2400-2484 MHz ISM band. Although an air substrate is introduced, the antenna occupies a small volume of 33.3/spl times/6.6/spl times/0.8 mm. The gain and the impedance bandwidth of the antenna are predicted using a commercial finite-element method software package. The predicted results show good agreement with measured data.     

Amplitude aperture-distribution control in displaced-axistwo-reflector antennas

A design method for improving the efficiency and reduction of sidelobes in displaced-axis two-reflector antennas is presented. The method is based on an analysis of the geometrical-optics field transformation in the displaced-axis two-reflector arrangement. The principal difference of the displaced-axis antenna from the Cassegrain/Gregory two-reflector antenna is pointed out. While decreasing the level of illumination of the subreflector edge in the Cassegrain/Gregory antenna leads to decreasing the sidelobe levels, and, respectively, the efficiency of the antenna system, in the displaced-axis antenna, decreasing the level of illumination of the subreflector leads to an increased level of sidelobes and an essentially nonuniform amplitude distribution in the aperture. The aperture-amplitude-distribution dependence of the illumination level of the subreflector edge in displaced-axis antennas is much stronger than in Cassegrain/Gregory antennas     

A compact antenna for ultrawide-band applications

A novel compact and ultrawide-band (UWB) antenna is presented in this paper. The basis for achieving such an UWB operation is through proper magnetic coupling of two adjacent sectorial loop antennas in a symmetrical arrangement. A large number of coupled sectorial loop antennas (CSLA) with different geometrical parameters are fabricated and their measured responses are used to experimentally optimize the geometrical parameters of the antenna for achieving the maximum bandwidth. Through this optimization process an antenna with a VSWR of lower than 2.2 (S/sub 11/<-8.5 dB) across an 8.5:1 frequency range is designed. The maximum dimension of this antenna is smaller than 0.37/spl lambda//sub 0/ at the lowest frequency of operation and provides an excellent polarization purity. Furthermore, the antenna exhibits a relatively consistent radiation pattern. Modified versions of the CSLA are also designed to reduce the overall metallic surface and weight of the antenna while maintaining its wide-band characteristics. This allows modifying its dimensions to design low frequency light-weight UWB antennas.     

Surface Impedance and the Efficiency of Horizontal-Dipole Extremely Low Frequency (ELF) Antenna Arrays

The effective conductivity of a potential antenna site is a measure of the field strength that an antenna built on the site would radiate. Only in special cases, however, is this same measure suitable for characterizing the power that the antenna would dissipate. It is shown that in the case of a current-sheet antenna built on a horizontally stratified half-space, a measure that characterizes both the radiation and dissipation properties of the site is the complex surface impedance. This same measure remains substantially valid for an antenna composed of separate cables and for inhomogeneous half-spaces of not too great lateral variation. The most reliable methods of measuring the surface impedance are theE/HandH/Imethods, provided both include the measurement of the phase of the ratio.     

Finite-difference time-domain analysis of integrated ceramic ball grid array package antenna for highly integrated wireless transceivers

This paper presents a study of the integration of an antenna in a ceramic ball grid array package for highly integrated wireless transceivers. The study has been carried out on an 11/spl times/11.66 mm/sup 2/ small microstrip antenna in a thin 48-ball ceramic ball grid array package with the finite-difference time-domain (FDTD) method in C band. The impedance and radiation characteristics of the antenna are examined. More importantly, the loading effects of the complementary metal-oxide-semiconductor (CMOS) chip and bond wires on the performance of the antenna are investigated. It is found that the loading generally increases the impedance bandwidth but decreases the radiation efficiency of the antenna. To minimize detrimental loading, the shield of the antenna from the CMOS chip is considered. A new design has been realized. The new antenna achieves impedance bandwidth of 4.65%, radiation efficiency of 63%, and gain of 5.6 dBi at 5.52 GHz.     

Multifunction single-package antenna system for spin-stabilized near-synchronous satellite

An antenna system is described for a spin-stabilized satellite with its axis normal to the orbital plane. Three antennas in a compact lightweight package comprise the antenna system: a switched-beamX-band transmitting antenna, an omnidirectionalX-band receiving antenna and an omnidirectional VHF telemetry antenna. The first is a cluster of eight circularly polarized horns pointed radially outward every 45 degrees about the spin axis. An eight-throw solid-state waveguide switch turns on that horn currently pointing most nearly to earth. This is accomplished by providing the switch with electrical signals from a logic circuit operating on information from earth sensors. The second antenna is a circularly polarized biconical horn located above the cluster of transmitting horns. Its sense of polarization is opposite that of the transmitting antenna, and a filter in the transmission line to the receiver insures the required isolation. The third antenna is obtained by feeding across the gap between the twoX-band antennas and exciting the external surfaces to radiate in a linearly polarized mode. Total weight of the three-antenna package is less than4frac{1}{2}pounds; it occupies a volume less than 10 inches square by 8 inches high above the top panel of the satellite.