波束扫描反射阵列天线偏焦特性

针对波束扫描反射阵列天线在大角度扫描时增益下降及方向图恶化等问题,提出通过馈源偏焦来改善反射阵列天线的扫描性能。采用方形贴片结构设计了一款工作在X频段的反射阵列天线。研究馈源在15°,30°,45°扫描角的纵向偏焦以及10°,20°和30°扫描角的横向偏焦对波束扫描反射阵列天线性能的影响。测试结果显示,在扫描角度较小时,横向偏焦引起波束指向的改变,波束宽度变化不大。减小馈源纵向偏焦尺寸,旁瓣电平减小,中心频率处的增益提高,尤其是在较大的扫描角度时效果更加明显,有利于提高波束扫描反射阵列天线的大角度扫描能力。     

Broadband printed circularly-polarised aperture antenna array for millimetre-wave gigabit applications

A simple and successful design of a printed aperture antenna array is presented in view of high-speed millimetre-wave wireless access applications. The antenna element design is based on a broadband travelling- wave aperture antenna for circularly-polarised radiation. For the antenna array design, the sequential rotation scheme is employed for improving the co-polarised gain and axial ratio. The presented antenna array is designed in the 40?48 GHz band and implemented with a 5mil-thick RT/Duroid-5880 PCB. Promising performances are achieved, including a return loss (,10 dB) bandwidth of 32%, an axial ratio (,3 dB) bandwidth of 25%, and a co-polarised gain (flatness , 3 dB) bandwidth of 32% with a maximum gain of 11dBic.     

Evaluation of gain enhancement in improved size microstrip antenna arrays for millimetre-wave applications

A number of microstrip antenna arrays have been designed based on the improved size patch elements with different substrate heights to evaluate the gain enhancement in practical measurements. Initially, microstrip patch antenna arrays (MPAAs) have been designed, analysed and tested at 10 GHz frequency and then the optimised high gain (∼21 dBi) array is fabricated and tested at 60 GHz-band frequencies. It has been found that the loss emergence due to the long feeding transmission line (TL) network severely degrades the antenna gain in large MPAAs on the thicker substrates. However, the gain can be significantly enhanced in large MPAAs by employing relatively thinner substrate but it shrinks the return loss (S11) bandwidth (BW) and increases the side lob level (SLL).     

Panel gap cover for millimetre-wave antenna

The reflector of the 10 m diameter, millimetre-wave, South Pole Telescope has been equipped with reflecting covers over the gaps between panels. The covers are thin metal strips that lie on the surface of the panels, with spring clip retainers that engage steps in the panel edges. Covering the gaps reduces thermal noise from the reflector by 2 K at the expense of increasing the surface profile error by 11 m rms.     

Contoured beam reflector antenna for wireless applications

Wireless coverage in urban, suburban, and light industrial areas is a challenging problem for cellular network planners. This is mainly due to scattering from buildings and structures but also because area specific demographic features such as parks, streets, and sports arenas require specialized coverage. A contoured beam reflector antenna is a simple and effective solution for this problem, providing excellent control in both planes of the radiation pattern and a very sharp taper at the edge of coverage. The problem of wireless coverage planning using existing base-station antenna types is discussed, and a potential solution for these problems using contoured beam reflector antennas is demonstrated by examples. The implementation of this solution is made possible by using an inexpensive manufacturing technique involving a reconfigurable mould and a foam extrusion process     

Broadband element for high-gain single-layer printed reflectarray antenna

The design of a broadband reflectarray exploiting a non-conventional shape radiating element to assure a large gain bandwidth is proposed. The element shape presents sufficient degrees of freedom to compensate for the frequency variation of the differential spatial phase delay even when single-layer printed patches are employed.     

120 GHz millimetre-wave antenna for integrated photonic transmitter

A planar slot antenna on an Si substrate for a photonic millimetre-wave transmitter that operates at a frequency of 120 GHz has been designed and characterised. By integrating a uni-travelling-carrier photodiode with the antenna, emission of millimetre-wave signals with a power of 250 μW has been demonstrated experimentally     

Selectivity-improved E-plane filter for millimetre-wave applications

Measurements on a Ka-band selectivity-improved E-plane filter prototype are compared with computed predictions and are found to be in excellent agreement. The measured insertion loss is 1.5 dB, and the bandwidth is 180 MHz centred at 32.8 GHz. These prototype measurements confirm that this design has the potential for significantly improving the performance of filter components in the millimetre-wave frequency range.<>     

A beam steering antenna for X-band high power applications

There is a considerable interest in the antennas which have high power handling capacity with beam steering functionality. The design of narrow side waveguide slot-array antenna for high power applications is introduced in this paper. An approach to achieve a uniform radiation slot waveguide antenna is presented. The large scale array antenna can be composed of such antenna cells. Moreover, it is possible to realize beam steering in the azimuth direction by adjusting the broad wall dimension of the waveguide. Besides, this slot waveguide antenna is expected to have high power handling capacity in vacuum environment, because there is no dielectric or electric field enhancement inside the antenna.     

Design and performance of a microstrip reflectarray antenna

Microstrip reflectarray antennas present an alternative to conventional directive antennas in that they are flat, inexpensive, easy to install and manufacture, conformal to the mounting surface, easy to package, and they possess high power and beam steering capabilities. For the first time, a comprehensive, experimentally verified design procedure for the microstrip reflectarray is presented. In this design procedure, the microstrip reflectarray has been shown to be an effective linear array capable of beam switching and dual polarization. The design procedure also allows the array to be fed from a feed-horn offset at any given angle to the plane of the array. The design procedure is well suited for CAD programs     

Reconfigurable patch antennas for steerable reflectarray applications

Reconfigurable reflectarrays have been designed with patch elements which can vary the reflected phase by varying the height of the patches. These patches have been designed using a periodic method of moments simulation. Reflectarrays incorporating elements of varying heights have been built and tested. The first design is a 33 element array comprised of stacked patches which operates at 7.31 GHz. The second design is a 120-element dipole array over a ground plane which operates at 5.2 GHz. Microelectrical, mechanical systems actuation technology could be used to implement these designs and a potential concept is suggested.     

Compact membrane-supported bandpass filter for millimetre-wave applications

The design and testing of a new configuration of micromachined bandpass filter for millimetre-wave applications is presented. The design is based on image parameter representation of identical symmetrical cells connected in cascade. The measurements demonstrate transmission losses lower than 1 dB and very good agreement with the electromagnetic simulations.     

Tunable bandstop MEMS filter for millimetre-wave applications

The design and realisation of original millimetre-wave tunable bandstop filters using MEMS (micro-electro-mechanical-systems) technology for millimetre-wave applications is presented. The tunable behaviour is achieved by using MEMS switches. The overall structures, including the MEMS switches, have been manufactured using dielectric membrane in order to minimise the dielectric losses. Experimental validations are reported and validate the proposed topology: the bandstop frequency is shifted by approximately 3.5 GHz in V-band when the switches are actuated     

Multiple-polarization microstrip reflectarray antenna with highefficiency and low cross-polarization

This paper presents the study and prototype demonstration of the concepts of antenna focusing, cross-polarization reduction, and multiple-polarization capability of a planar microstrip reflectarray antenna. A square patch with two equal microstrip delay lines connected to its two orthogonal feeding points is used as the antenna element of the planar reflectarray. The length of the delay lines, which varies from patch to patch, is schematically designed to focus the plane wave to the feed point. The measured overall efficiency of the prototype antenna is above 50% in the normal operating band, and in some frequency ranges the efficiency has reached 70%. The experimental patterns show that the measured cross polarization due to special arrangement of the delay lines is quite low at the direction of the main beam. X-polarization and Y-polarization measured data show that the antenna is suitable for multiple-polarization applications (dual linear and dual circular). Surprisingly, the antenna has achieved approximately greater than 7% of gain bandwidth (-3 dB gain drop). These results demonstrate the feasibility of such an antenna for radar and communication system applications     

一种Ka波段宽带折合式平面反射阵天线设计与实现

基于反射面天线技术提出了一种工作于Ka波段的宽带折合式平面反射阵天线(Folded Reflectarray Antenna,FRA)。该天线的主、副反射面均采用平面反射面的设计方案,基于双层贴片单元结构设计并实现了主反射面,并通过尺寸变换型单元来实现相位补偿、极化扭转以及大通带特性,副反射面采用双层极化栅来实现对单一极化波的透射。利用电磁仿真软件Ansys HFSS与CST MWS对天线结构进行分析设计,并加工出实物。仿真与实测结果表明,该天线3 dB增益带宽达到了20%,波束宽度在6°以内,在33～40 GHz的通带范围内,天线实测增益达到了26 dBi以上。     

Parallel plate waveguide antenna for point-to-multipoint communication at millimetre-wave frequencies

Simulation and measurement results for a parallel plate waveguide antenna designed for a point-to-multipoint communication system at millimetre-wave frequencies is presented. The antenna consists of a waveguide feed, an H-plane horn, an enclosed parabolic reflector, a rectangular waveguide containing irises, and corrugated baffles. Half power beamwidths between 4.9/spl deg/-6.0/spl deg/ in elevation and 58/spl deg/-79/spl deg/ in azimuth are achieved for a bandwidth of 13%. The gain varies between 19 and 20 dBi for the frequency range between 21 and 25 GHz. The manufactured antenna is very compact with a size of 200/spl times/147/spl times/50 mm.     

CMOS IMPATT impedance and design parameters for millimetre-wave applications

This article describes lateral CMOS IMPATT diodes designed, monolithically integrated and fabricated in 0.18?µm CMOS technology. IMPATT diode impedance and avalanche frequency were confirmed in a measurement from 40?MHz to 110?GHz. Avalanche tuning range measured from 24?GHz to 44?GHz with maximum IMPATT negative resistance of 120?Ω at 38?GHz with 28?mA bias current. Furthermore, selection of the process technology and the impact of n-well impurity concentration are discussed. This device showed wide tuning range in the millimetre wave range and with the low cost of the CMOS technology used, these devices appear well suited for use in millimetre-wave applications.     

Theory and design considerations for a new millimetre-wave leaky groove-guide antenna

A transverse equivalent network is presented for a new type of leaky-wave antenna based on the groove guide and suitable for millimetre waves. Employing this network, the antenna's performance characteristics are explained and systematic design considerations are deduced.     

GaAs-loaded metal waveguide components for high-speed low-VSWR optoelectronic millimetre-wave switching

A new approach to fast optoelectronic microwave and millimetre-wave switching is reported. The concept is based on a metal waveguide section containing a thin slab of semi-insulating GaAs. Modulation or switching is achieved by wave attenuation across a laser-induced photoconductive plasma wedge generated within the GaAs slab via edge excitation. First experimental results in the 30?35 GHz range are presented.     

Pulsed silicon double-drift IMPATTs for microwave and millimetre-wave applications

The letter describes silicon double-drift IMPATT diodes designed for operation at microwave and millimetre-wave frequencies. These devices have delivered pulsed-power outputs of 16 W with 12.3% efficiency in the X band, 11 W with 14% efficiency in the KU band, and 6.4 W with 5.3% efficiency in the Ka band. These results, when combined with the demonstrated high reliability of silicon IMPATTS, should lead to the wide application of double-drift devices in pulsed-radar systems.