宽带毫米波矢量调制器MMIC 设计

矢量调制器由于在毫米波频段内具有的多级幅度和360^o相位控制的特点,在毫米波直接载波调制和相控阵雷达系统应用中具有十分重要的作用。文中采用平衡式矢量调制器结构,对影响该调制器宽带平衡响应的关键参数进行了分析。通过研究Lange 耦合器的耦合系数和均效应管开关管的尺寸对宽带平衡性能的影响,提出了一种宽带矢量调制器的设计方法。基于该设计方法,采用单片电路的实现方式,利用商用砷化镓70 nm mHEMT 工艺设计了一款工作在40 GHz ~80 GHz 的宽带毫米波矢量调制器微波单片集成电路。结果表明:在整个40 GHz 的带宽范围内,所设计的矢量调制器具有优于正负4^o的相位偏差和优于正负0. 4 dB 的幅度偏差。     

基于微带倒相器的新型宽带3dB分支线耦合器

设计了一种宽带的微带线3dB分支线耦合器,并给出了理论分析。该模型结构简单,易于实现,通过级联两级分支线耦合器及加入超宽带微带倒相器,增加了带宽。仿真结果表明,在0.7~1.26GHz频带范围内,该耦合器回波损耗大于20dB,隔离度大于19dB,两平分端口幅度不平衡性小于1.23dB,相位不平衡小于,具有良好的性能。实验结果与仿真结果相符。     

矢量调制器研究及干扰抵消器改进

为了分析矢量调制器对干扰抵消器性能的影响,基于测量矢量调制器幅度相位的方法研究了其特性。在实测数据的基础上分析了双极性电调衰减器的缺陷对矢量调制器和干扰抵消器性能的影响,并提出了引入可调移相器的改进方法。理论分析和实验数据表明文中提出的方法有助于提高干扰抵消器的抵消性能。     

基于GaAs工艺的新型I-Q矢量调制器芯片设计

在传统的单平衡式I-Q矢量调制器的基础上,提出了一种新颖的I-Q矢量调制方法。通过采用180°模拟移相器替代传统的双相调制器和衰减器,从而降低了插入损耗并减小了芯片面积。最终,本文采用0.25μm GaAs PHEMT工艺,设计出了一款K波段单片集成的I-Q矢量调制器。实测结果表明:在21~23GHz频带内,该芯片实现了0到360°的连续变化的相位调制,其幅度调制深度大于20dB,插入损耗小于11.2dB。     

毫米波矢量调制器及其在有源相控阵天线中的应用

矢量调制器芯片作为一种可以同时对载波进行相位和幅度调制的新型电路,能够替代传统的数字移相器和数字衰减器用在有源相控阵系统中.先设计了一款工作在Ka波段毫米波单片矢量调制器,在片测试结果显示可以实现- 12～-40 dB的幅度调制与360°的相位调制.然后设计了一个Ka波段1×8阵有源相控阵天线,改变矢量调制器的控制电压...     

基于矢量和的微波光子移相器研究

基于矢量和（vectorsum）原理,利用50：50光纤耦合器、可变光延时线（VDL）、可变光衰减器（VOA）构建了微波光子移相器。以宽带光为载波有效地解决了合波处光波相位不同引起的微波信号不稳定的问题;利用马赫-曾德（M—Z）LiNbO3调制器在不同工作电压下的反相调制特性,设定调制器的不同偏置电压,同时配合调节两支...     

电感补偿高方向性的微带定向耦合器

定向耦合器作为一种重要的微波元件在微波电路与微波集成电路中有着广泛的应用。在传统的微带线定向耦合器设计中,奇偶模之间不同的相位速度导致了较低的隔离度。目前提高方向性的手段大多采用电容加载或者再注入的补偿手段,其实现方式均属于对相位速度的补偿。介绍了一种采用对称的电感加载结构进行相位速度补偿的微带线定向耦合器,为了提高微带定向耦合器的方向性,通过对微带线定向耦合器的4个端口进行感性加载,实现了微带定向耦合器窄带的低损耗和高方向性的电气指标,通过实物制作与测试,证明了方法可以实现。     

基于光纤干涉仪的相位调制器半波电压的测量

基于相位调制干涉仪解调微波光链路的数学模型 ,提出了通过链路的S21增益峰值计算得到相位调制器半波电压的方案。 实验表明,此方法测得的相位调制器半波电压和厂家提供的数据相符合。把测得的相位调制 器半波电压应用在实际的光链路系统,增益仿真曲线和实验结果也相吻合 。在实验中,实现调制信号相位-幅度转换的光纤干涉仪由2个保偏 耦合器加特定跳线构成。实验结果表明,本文方案是一种结构简单、操作容易且具较高实 用价值的相位调制器半波电压测量方法。     

宽带数字调制器设计实现

针对现代数字通信系统中广泛使用的宽带数字调制,分析了其矢量合成原理,并采用统一的FPGA硬件平台、算法软件实现、IF/RF矢量调制器来实现。文中给出了实现电路原理,对实际的幅度与相位不平衡给出补偿解决办法。最后给出了多进制相移键控(MPSK)调制器测试数据,其性能优良,可以满足多频段扩跳频数据传输要求。     

OLCR系统中滤除衰减直流分量的BD结构设计

设计了由环形器、耦合器、衰减器和平衡探测器组成的平衡探测(BD)结构的OLCR系统,分析了衰减直流分量产生的原因以及耦合器相位特性在BD结构中的作用。对参考臂中光耦合效率与反射镜角度和位置关系进行了仿真,结果表明耦合效率主要受反射镜偏转角度影响。实验测试了非平衡和平衡结构下参考臂的输出光功率,对噪声的均方根值和信噪比进行了分析,同时还测试分析了两种结构下的干涉信号。实验结果表明,OLCR系统的BD结构在滤除衰减直流分量的同时还能抑制噪声信号和放大交流分量,结构简单有效。     

Low cost wideband I-Q vector modulator

One of the applications of QPSK modulators is to control the amplitude and phase of an RF signal, working as a vector modulator. Recently there are several monolithic commercial circuits that can be easily used to frequencies of >4 GHz. First, the input signal must be decomposed into two quadrature components, which is usually done in a 3 dB 90° hybrid coupler. Using microstrip techniques, this I-Q vector modulator exhibits narrowband characteristics, due to the degradation of the hybrid performances with frequency. The authors show how the working bandwidth can be extended up to an octave by means of a versatile control system as described here, as an alternative to a new design of the RF stage     

一种提高RFID系统中耦合器定向性的方法

微带的定向耦合器是一些RFID系统中的关键性部件,功能一般是分离存在于信道中reader输出的信号和从天线接收的tag信号。定向耦合器的性能直接影响了系统所能辨识tag信号的能力,系统一般要求性能比较良好的定向耦合器。但是由于微带型定向耦合器其本身的奇偶模不平衡性,定向性一般不高。这里介绍一种新型的改进方法,通过调节耦合端的高阻抗线长度和宽度,使得定向性得到很大的提高。     

一种基于微带均衡器结构的定向耦合器的研究

提出了一种新颖的基于微带均衡器结构的宽频带高定向性微带线定向耦合器,并对该结构进行了理论分析、设计、制作和测量。该结构的新颖之处是通过对耦合度随频率的变化曲线进行均衡得到宽频带特性。该结构采用三电容补偿的微带线定向耦合器结构,并通过在耦合端集成微带均衡器结构实现。测量结果显示,该结构在2.5～3.5GHz工作频带内的耦合度随频率的变化范围约为1dB,隔离度低于-34dB,较之传统结构的微带线定向耦合器均有大幅的提高。测量结果很好地验证了设计方法的正确性。     

Transient Analysis of a Directional Coupler Using a Coupled Mlcrostrip Slot Line in Three-Dimensional Space (Short Paper)

In recent MIC techniques, double-sided MIC has been studied because its advantages in propagation characteristics are greater than that conventional MIC's. A coupled microstrip slotline is one of them. Its application to various circuit elements has often been discussed. But the coupled microstrip slotline is essentially three-dimensional structure, so the analysis demands a rigorous three-dimensional treatment. Also, the recent high-speed pulse technique demands analysis in the time domain. The present paper treats a directional coupler using the coupled microstrip slotline in three-dimensional space and time. The results of the directional coupler analysis is presented with the complicated time variation of the three-dimensional electromagnetic field. So, the mechanism of the directional coupling phenomena that is produced by the propagation characteristics of the even and odd modes is presented in the time domain, In particular, the instantaneous diagram of the Poynting vector details the energy flow in the transient process. For the analysis of the characteristics of the complex microwave device, these results present the utilities of the various field distributions that are obtained by the three-dimensional vector analysis in the time domain.     

Backward directional coupler for weak coupling of double-sided microstrip lines using longitudinal double-slots

A backward directional coupler for double-sided microstrip lines is presented. Aligned microstrip lines are coupled via two parallel slots in the common ground plane. This design works well for weak coupling smaller than 20 dB and has some advantages over the single-slot coupler. Geometrical dimensions of the proposed coupler design are presented for coupling values of 20, 25 and 30 dB, together with measurements for a 30 dB coupler.     

A design of wideband 3-dB coupler with N-section microstrip tandem structure

New design equations and a 3-dB microstrip coupler example for N-section tandem connected structure with wide bandwidth are presented. The proposed four-port S-parameters and equations are obtained from a port reduction method. The designed microstrip 3-dB coupler not only does not need high impedance lines, but also uses tight coupling gaps differently from conventional couplers such as Lange couplers, parallel coupled line couplers, etc. The measured data agrees well with the expected data, which show a wide bandwidth of 42%, an amplitude imbalance of /spl plusmn/0.5 dB, a phase unbalance of 1.0/spl deg/, and isolation characteristics of 15 dB at the band of 3.6 to 5.5 GHz.     

An 800-MHz monolithic GaAs HBT serrodyne modulator

An 800-MHz monolithic mixed-signal serrodyne modulator IC has been developed in a GaAs/AlGaAs HBT HI₂L process optimized for digital applications. This 3×2.8 mm, 2000+ transistor chip consists of a 7-b phase accumulator driving a vector modulator, implemented as a pair of balanced mixers, 5-b switched attenuators, buffer amplifiers, and central circuits. The balanced mixer's LO leakage and 3-1 products are typically 25 dB below the carrier at the nominal operating point, with all other products better than -50 dBc. Over a 32-dB control range, the 5-b switched attenuator typically achieves worst-case amplitude and phase errors of 1.5 dB and 1.5°, respectively, from 50-250 MHz. DC-level variations versus attenuator-state limit the spurious response of an 800-MHz Composite DDS based on this serrodyne modulator to -20 dBc. Post-fabrication modeling indicates that a 5°C thermal gradient across the IC may be responsible for this undesired dc-level variation. This first generation chip consumes 2.5 W of dc power and clocks to speeds in excess of 925 MHz     

A new analytic design technique for two- and three-way warped modecombine directional couplers

An analytic technique of designing ultra-wideband warped-mode two way and three-way microwave directional couplers is presented. With this matrix method it is possible to design couplers for any level of coupling by choosing a warping angle appropriate to the desired output amplitudes. The design technique involves obtaining a wave propagation matrix in analytical form as a function of the taper parameter, which in turn is a function of distance along the coupler length. The line parameters and the forward scattering matrix are then determined from the wave propagation matrix at any distance from the beginning of the coupler. The method is demonstrated for couplers using microstrip coupled comblines. The computed and the measured performances of a two-way and a three-way microstrip combline are presented for equal power splitting. These couplers were found to work between 1.5 and 8.5 GHz     

Multiconductor Couplers

Analysis of electromagnetic fields of interdigitated couplers and derivation of propagation parameters such as the line impedances and wavelengths for even and odd modes resulted in designs of couplers with an arbitrary number of strips. Calculations were carried out on two-, three-, four-, and six-strip couplers and showed that results for two- and four-strip couplers were consistent with available published data. The three-strip coupler, which was designed and fabricated, achieved 3-dB coupling with a simpler configuration than Lange's interdigitated coupler and with characteristics consistent with calculated data. Coupling as tight as 1.5 dB was achieved by a six-strip coupler which was designed with a part of the ground plane of the microstrip substrate removed. This coupler can be used as the middle part of a three-section coupler for which test data shows a wide range of balanced coupling, from 2.5 to 12 GHz, with a coupling unbalance of less than /spl plusmn/0.6 dB. It was concluded from the calculation that couplers with more than six strips would not be very practical.