负载变化对设计二端口网络传输特性的影响

该文研究负载变化对设计二端口网络传输特性的影响,定义网络传输特性随负载变化不灵敏的二端口网络为最小失配网络。利用蒙特.卡罗方法设计了一个5阶最小失配滤波器网络,设计的最小失配滤波器传输特性在负载电阻变化时,其传输特性优于原型滤波器。计算结果证明在合理选择技术指标条件下,最小失配网络存在并可以实现。     

基于PSO的射频天线自适应阻抗匹配

由于天线的场分布的易变性容易导致阻抗失配,从而会降低功率传输效率和输出信号功率。文章提出了一种射频天线自适应阻抗匹配的粒子群方法,在射频天线和激励源中间加入无源型匹配网络,根据负载阻抗实时变化快速,通过调节网络中可变电容和电感来实现共轭匹配,射频天线负载获得最大传输功率,从而提高RFID系统读写器的最大读取距离。     

无源UHF RFID标签的低成本阻抗匹配网络设计

提出了一种符合ISO/IEC18000-6C标准的无源RFID(射频识别)标签的低成本阻抗匹配网络。该设计基于复功率波反射系数的概念,修正芯片输入阻抗,在片内添加阻抗匹配电路。通过变化芯片阻抗和天线共轭匹配及失配间切换,有效完成信号的调制反射。提出的电路结构简单,易于实现,在读写器、标签天线和芯片之间实现了功率传输的最大化,提高了芯片输入电压以及读写器对标签反射信号的识别率。采用该阻抗匹配网络的芯片基于chartered 0.35μm CMOS工艺实现。测试结果表明,在923MHz频带下,倍压电路输出可达1.47V,标签满足系统设计要求。     

一种精测低耗互易二端口网络传输效率的系统

本文介绍一种测量低损耗互易二端口网络在较大失配情况下的功率传输效率的测试系统。该系统的测量精度对被测器件的失配不敏感。如当被测网络及其给定负载的反射系数均达0.1时,对于效率约为99％的被测器件,失配误差仅有2×10~(-4),而总精度可达±0.06％。     

一种频响平坦的矩形波导失配负载

用微扰法推导了矩形波导宽边上金属薄圆片的输入反射系数幅值表示式,求得了薄圆片的最佳横向位置,在此位置圆片的反射系数幅值频响最小。报导了相当数量的测量结果,实测和理论有一定的一致性。导得的公式可用来设计全波导频宽的标准失配负载。     

新型快速波导缝隙天线设计方法

对馈电网络和天线的散射矩阵进行级联,推导了互耦条件下阵列天线输入端口散射参数和天线实际激励分布的计算方法。基于该方法,提出了一种新型快速波导缝隙天线设计方法,并设计了一副12 元宽边纵缝一维波导缝隙天线。测试结果表明,在9. 82 ~10. 21 GHz 内反射系数和副瓣电平分别优于-15 dB 和-28 dB。测试结果与计算、仿真结果吻合良好,验证了该方法的准确性和有效性。     

实现最大功率传输的阻抗变换方法研究

最大功率传输是信号传输中必须考虑的问题。正弦稳态电路中,在负载阻抗不可调节时,可以通过在电源（或含源线性一端口网络）与固定负载之间级联无源无耗二端口网络来变换负载阻抗,实现负载从正弦稳态电源（或含源线性一端口网络）获得最大功率。本文研究此类无源无耗二端口网络的最简单结构、参数关系及其适用范围。推导可以实现最大功率传输的...     

n端口网络散射参数测量中失配误差的修正方法

本文对n端口网络散射参数测量中的失配误差提出了两种修正方法——迭代法和矩阵变换法。前者适用于端接负载失配较小的场合;后者适用于端接负载失配任意的场合。对有关算式已编制了通用计算程序,并结合具体网络作了数值验证,一致性较好。     

多端口网络的广义匹配理论

本文提出了多端口网络的广义匹配理论，并给出了具体的实现方法。研究表明：多端口网络要满足全匹配，则必须牺牲端口间的传输作为付出代价。特别在Ｎ口全对称网络情况下，传输系模值得满足不等式约束│β│≤１／Ｎ－１）。此外，本文还发现三口互易网络的广义匹配由无耗转向有耗时会发生突变现象，很值得进一步探讨。     

有耗串联网络对GaAs FET信号参数和噪声参数的影响

本文详细讨论了有耗串联网络对低噪声GaAs FET的信号参数和噪声参数的影响,以及同时获得噪声匹配和功率匹配的条件。以WC606型GaAs FET为计算实例表明:在频率为12GHz,当串联电感为0.1nH,负载反射系数为0.25∠120°时,可以同时获得噪声和功率匹配。但此时最小噪声系数将增加0.2dB,而相应增益下降1.0dB。     

声表面波器件输入及输出负载阻抗匹配研究

针对声表面波器件测量中网络分析仪的负载阻抗与射频传输线特性阻抗不匹配,导致传输线上反射波幅值较大的问题,提出一种减少传输线上反射波的负载阻抗匹配系统与方案。负载阻抗匹配方案针对声表面波器件测量中输入与输出端分别设计不同的无源负载阻抗匹配网络,使输入输出端同时达到匹配状态。负载阻抗匹配系统集成了未匹配通道与匹配通道,根据负载阻抗不同调整匹配参数。对一个中心频率为101.764MHz,带宽为30MHz的声表面波器件使用该匹配方案前后中心频率处的衰减进行测量对比,实验结果表明采用该匹配方案后在中心频率点处输入及输出反射损耗分别为-49.36dB和-38.13dB,比未采用匹配方案时分别减少了44.99dB和29.44dB。     

天线调谐器Ⅱ型阻抗匹配网络参数估算

介绍了天线调谐器Ⅱ型匹配网络的组成结构和元件配置。对于给定的网络匹配后的电压驻波比(VSWR)门限值,定量分析了匹配网络中各元件的最小取值所必须满足的取值范围,得出了合理的估算值。对于决定网络匹配范围的各元件的最大取值,则依据天线输入阻抗的范围,给出了初步的估算值。通过对以上2类参数的估算,为后续的天线调谐器调谐算法设计及整体性能指标设计提供了参考。     

Design of a wideband miniature dielectric-filled waveguide antennafor collision-avoidance radar

This article presents a theoretical and experimental study of the design of a miniaturized wideband dielectric-filled waveguide (DFW) antenna. The operational frequency is X band, i.e., 9.0⩽f⩽10.5 GHz. The desired bandwidth is 1.5 GHz. The antenna uses an air-gap matching network to reduce its high aperture reflection. In order to ease the integration with antenna circuits and to increase the bandwidth, two E-plane steps are used. The antenna is designed to have -3 dB beamwidths of 60° and 100° for the E- and H-plane patterns, respectively. An input reflection of less than -10 dB for the desired bandwidth is observed. The gain of the antenna is 7 dBi. A cross-polar level of less than -25 dB is achieved. This article discusses the mathematical model for input reflection, the design scenarios, and the experimental results     

电感性负载的非福斯特电路研究与设计

基于非福斯特电路的有源电小天线宽带匹配在工程应用领域受到广泛关注。文中以电小环天线的等效电路为负载,提出一种接地型运放管的非福斯特电路,并对其负阻抗转换性能进行了分析。经过仿真分析,在2-30MHz频段内,单级运放非福斯特电路可以实现99%的电感转换率;两级运放乘法电路能够将电路的输入阻抗匹配到50欧姆,S11在整个频段内小于-26dB。实物测试了两级运放乘法器电路,验证了接地型运放管非福斯特匹配电路可较好地提高电感性电小天线的性能。     

Microwave impedance matching strategies of an applicator supplied by a bi-directional magnetron waveguide launcher.

It is shown that a bi-directional waveguide launcher can be used advantageously for reducing the reflection coefficient mismatch of an input impedance of an applicator. In a simple bi-directional waveguide launcher, the magnetron is placed in the waveguide and generates a nominal field distribution with significant output impedance in both directions of the waveguide. If a standing wave is tolerated in the torus, which connects the launcher and the applicator, the power transfer from the magnetron to the applicator can be optimal, without using special matching devices. It is also possible to match the bi-directional launcher with two inductance stubs near the antenna of the magnetron and use them for supplying a two-input applicator without reflection.     

Input mismatch of TE11mode coaxial waveguide feeds

The reflection characteristics of the TE11mode in a coaxial waveguide antenna due to mismatch at the radiating aperture are described. Results are presented for conventional coaxial waveguide as well as waveguide whose inner conductor extends beyond the aperture plane. Coaxial wavegulde mismatch is often quite large, particularly for conditions of good pattern symmetry, and some matching is usually required. A broad-band matching technique using annular rings inside the waveguide is described for the case where there is no external conductor. Results presented show excellent agreement between theory and experiment.     

An RF electronically controlled impedance tuning network design and its application to an antenna input impedance automatic matching system

A novel design is proposed for an electronically tunable impedance unit. The prototypes include lumped elements, but no electromechanical control methods. The devices can tune many different complex impedances at minimum manufacture costs. Two antenna input impedance automatic matching systems are also presented, based on the tuning network. One includes a simplified version of the generic tuner, which can achieve good matching levels between the antenna and the power module with low losses. In a more complete version, an application specific integrated circuit control unit is developed including a complex search algorithm. In order to obtain a good matching level, both systems require a control module to select the proper tuner impedance configuration. The measurements and results of both constructed prototypes are presented. The designs were carried on terrestrial trunked radio mobile stations in the 380-400-MHz frequency band and supported high power levels (greater than 40 dBm).     

Simple adaptive matching antenna

The performance of handheld wireless devices can be affected when they are held close to parts of the human body. Deterioration can vary from person to person or even different forms or types of use. One of the problems is antenna impedance mismatch in different situations. Reported is an adaptive matching antenna realised by combining a simple monopole antenna and an oscillator with a phase-locked loop (PLL). The PLL helps to monitor return loss and to adjust the matching network automatically. It is found that the antenna can operate in the whole 2.4 GHz ISM band no matter how close it is to the human body after the adaptive matching circuit is applied.