Design and modeling of 4-bit slow-wave MEMS phase shifters

A true-time-delay multibit microelectromechanical systems (MEMS) phase-shifter topology based on impedance-matched slow-wave coplanar-waveguide sections on a 500-/spl mu/m-thick quartz substrate is presented. A semilumped model for the unit cell is derived and its equivalent-circuit parameters are extracted from measurement and electromagnetic simulation data. This unit cell model can be cascaded to accurately predict N-section phase-shifter performance. Experimental data for a 4.6-mm-long 4-bit device shows a maximum phase error of 5.5/spl deg/ and S/sub 11/ less than -21 dB from 1 to 50 GHz with worst case S/sub 21/ less than -1.2 dB. In a second design, the slow-wave phase shifter was additionally loaded with MEMS capacitors to result in a phase shift of 257/spl deg//dB at 50 GHz, while keeping S/sub 11/ below -19 dB (with S/sub 21/<-1.9 dB). The beams are actuated using high-resistance SiCr bias lines with typical actuation voltage around 30-45 V.     

A low local input 1.9 GHz Si-bipolar quadrature modulator with noadjustment

A 1.9 GHz quadrature modulator with an onchip 90° phase-shifter was fabricated using a silicon bipolar technology. This paper investigates error factors caused by a limiter amplifier. It is found that a gain enhancement technique in a phase-shifter circuit is effective in realizing an adjustment free quadrature modulator; we propose a new high-gain phase shifter circuit for this purpose. This technique employs a current mode interface and an on-chip inductor. An image-rejection ratio of over 45 dBc and a carrier feedthrough of below -40 dBc were attained at -15 dBm local oscillator power. This quadrature modulator operates at 2.7 V supply voltage. The operating frequency ranges from 1.2 GHz to 2.3 GHz. The die size of the quadrature modulator IC is 2.49 mm×2.14 mm     

一种新的电子散斑微小振动测量系统

给出了一种新的电子散斑微小振动的振幅和相位测量系统,该系统将光学相移器和正弦相位调制器置于参考光路中,因而当被测物体改变时,系统勿需重新标定。采用高精度低压压电陶瓷作为光学相移器和正弦相位调制器,易于实现计算机直接控制,使系统具有很高的抗干扰能力。实验表明,该系统可以方便地对物体的微小振动（ 振幅小于３０ ｎｍ） 进行定量分析。     

微位移器的在线测试

提出一种微位移器的在线测试方法,记录一组与微位移器位移特性相关的干涉图,截取每幅图中位置相同的一条线,建立干涉图截线法光强数学模型,然后在最小二乘法的基础上引入阻尼因子,通过几步快速迭代就可求出这组干涉图的相位主值,再通过相位解包就可得到微位移器的电压-相位曲线。并在本教研室研制的一台斐索干涉仪上进行了实验,实验结果表明:该方法克服了传统方法速度慢,精度低,标定和在线测试条纹疏密状态不一致的不足,简单易实现,运算量小,迭代次数适中,实时性强,可作为干涉测试中微位移器的在线测试方法。     

大下倾角电调基站天线移相器及馈电网络设计

采用耦合串馈移相器和遗传算法天线赋形技术,设计了一个应用于GSM1800 频段动态范围的基站天线。移相通过串馈形式获得大下倾角所需要的移相量。实验表明,该移相器在整个频段内具有良好的幅度变化和插入损耗,所计的基站天线在大下倾角范围内具有很好的上旁瓣抑制和下倾角精度。     

Aperture-coupled reflectarray element with wide range of phase delay

An aperture-coupled phase-shifter element providing a very wide range of phase delay is proposed as a unit cell in reflectarrays. A range of phase delay larger than 1600/spl deg/ has been achieved by using a U-shaped true-time delay line. Theoretical results are validated by comparing them with the measurements of two elements in a waveguide simulator, showing good agreement for both phase delay and losses.     

A pseudo-heterodyne fiber optical gyro, using integrated optics

A hybrid fiber-optical gyro using a novel scheme for pseudo-heterodyne detection is presented. The large bandwidth of integrated optical phase modulators allows for the use of a triangular-wave for dynamical biasing of the interferometer, while still being able to choose the modulation frequency to be the eigenfrequency of the fiber-loop. It is shown that this, together with the use of a dual-channel approach, minimizes both bias and scale factor errors. It is proposed that the fourth harmonic can be used to keep the modulation index of the applied triangular-wave phase modulation at the correct height and thus guarantee a good scale factor linearity     

A small-baseline approach for investigating deformations on full-resolution differential SAR interferograms

This paper presents a differential synthetic aperture radar (SAR) interferometry (DIFSAR) approach for investigating deformation phenomena on full-resolution DIFSAR interferograms. In particular, our algorithm extends the capability of the small-baseline subset (SBAS) technique that relies on small-baseline DIFSAR interferograms only and is mainly focused on investigating large-scale deformations with spatial resolutions of about 100/spl times/100 m. The proposed technique is implemented by using two different sets of data generated at low (multilook data) and full (single-look data) spatial resolution, respectively. The former is used to identify and estimate, via the conventional SBAS technique, large spatial scale deformation patterns, topographic errors in the available digital elevation model, and possible atmospheric phase artifacts; the latter allows us to detect, on the full-resolution residual phase components, structures highly coherent over time (buildings, rocks, lava, structures, etc.), as well as their height and displacements. In particular, the estimation of the temporal evolution of these local deformations is easily implemented by applying the singular value decomposition technique. The proposed algorithm has been tested with data acquired by the European Remote Sensing satellites relative to the Campania area (Italy) and validated by using geodetic measurements.     

A novel multilevel coherent optical system: 4-quadrature signaling

A novel multilevel coherent optical system is proposed. It is based on the exploitation of the property that the electromagnetic field propagating in a single-mode optical fiber can be represented by a four-dimensional vector whose components are the phase and quadrature terms of the two polarization components of the electrical field. This allows a wider use of the resources of the electromagnetic field for information transmission in order to obtain a spectrally efficient modulation format with a limited end. The net performance gain with respect to multilevel amplitude and phase modulation (N-APK) and N-PSK increases with an increase in the number of levels N. For instance, for N=32 the gain is 1.6 and 7.7 dB with respect to N-APK and N-PSK systems. The effect of laser phase noise on the system performance is evaluated     

An analysis of an N-port microstrip planar disk devicewith an arbitrarily located short circuit post of arbitrary radius

An analysis technique is presented which allows the performance of a multiport microstrip planar disk device with an arbitrarily located internal short circuit (S/C) post of arbitrary radius to be predicted. The analysis approach does not rely on the determination of eigenvalues and yields analytical expressions which are ideal for CAD implementation. The technique allows the electromagnetic fields at the periphery of the disk to be dramatically altered by an appropriate choice of post size and offset. Since the operation of N-port devices is dependent on the peripheral fields, this technique offers a potentially very powerful design tool for the production of planar disk devices     

铁氧体锁式可变极化移相器的设计和研究

本文介绍了一种适用于电捷变雷达的铁氧体锁式可变极化移相器的设计机理,利用仿真技术证明了其移相和变极化的互易性,并提供了典型器件的具体设计方法。     

Characterization of highly dispersive materials using compositecoaxial cells: electromagnetic analysis and wideband measurement

In this work, theoretical modeling and experimental characterization of composite coaxial-line cells are made for accurate dielectric measurement. The coaxial cells are designed such that highly dispersive materials can be characterized over a wide band of frequencies. In addition, a transmission line matrix (TLM) algorithm with a new type of node is proposed for electromagnetic analysis of the complex composite geometry of the measurement cells. Such a hybrid-mode simulation allows the electrical performance of the proposed cells to be determined for a variety of complex permittivity measurements. The proposed node in the cylindrical coordinate not only accommodates cylindrical coaxial discontinuities in the cell, but also describes the frequency-dependent properties of material. Experiments on a network analyzer were done with a number of APC-7 coaxial cells and various liquid samples to verify the wideband characteristics of the technique. It is found both theoretically and experimentally that the sample volume can be adjusted to ensure a wideband sensibility of the S-parameters. A sensitivity factor is also defined to characterize the frequency response of the coaxial cells. Such an electromagnetic analysis (direct problem) can be used in extracting unknown dielectric characteristics of a material (inverse problem) based on a recently proposed generic approach     

Time-domain optical response of an electrooptic modulator usingFDTD

A time-domain analysis of an LiNbO₃ electrooptic modulator using the finite-difference time-domain (FDTD) technique is performed. This allows for the calculation of optical modulation and the time-domain optical response of an electrooptic modulator. The electromagnetic fields computed by FDTD are coupled to standard electrooptic relations that characterize electrooptic interactions inside the embedded Ti diffused LiNbO₃ optical waveguides. The electric field-dependent change in the index of refraction inside these optical waveguides and resulting minute phase shifts imparted to optical signals propagating along the device are determined in time, allowing for the simulation of optical intensity modulation. This novel approach to LiNbO₃ electrooptic modulators using a coupled FDTD technique allows for previously unattainable investigations into device operating bandwidth and data transmission speed     

基于电介质超表面的双频带双偏振通道波前调控

随着微纳加工技术的发展,超表面在亚波长尺度对电磁波的多维度调控展现出传统光学器件难以比拟的优势。基于电介质硅纳米柱结构构建了具有双频带响应的超表面,利用微结构对不同偏振入射光反射系数的差异,通过构建梯度几何相位实现了双波长下的异常反射;同时设计了超表面灰度成像阵列,在近红外波段实现了对正交偏振态和双波长入射具有不同响应的正负灰度图像。文中提出的超表面设计为基于超表面的多功能集成技术的发展奠定了基础。     

A production ready, 6-18-GHz, 5-b phase shifter with integratedCMOS compatible digital interface circuitry

A producible, high-yield, monolithic 6-18-GHz, 5-b phase shifter with integrated standard CMOS compatible digital interface circuitry has been developed for use over the -55 to +90°C temperature range. Differential phase shift is achieved using high-pass and low-pass filter structures. The integrated digital interface circuitry produces complementary outputs that are used to bias the phase-shifter bits. The integration of the digital interface circuitry, made with microwave FETs, reduced the phase-shifter bit control bias lines by a factor of 2. The phase shifter was fabricated at both Raytheon's and Texas Instruments' GaAs foundries in production quantities using a standard microwave process. Complete on-wafer RF tests were performed to screen the phase-shifter circuits and determine electrical yield. The phase shifter has an r.m.s. phase error <10° from 6.5 to 18 GHz, maximum insertion loss of 14 dB, and an r.m.s. amplitude error <0.8 dB over the 6-18-GHz band     

Analysis of Transmission Lines With Arrester Termination, Considering the Frequency-Dependence of Grounding Systems

The paper proposes a modeling technique to analyze the response of a transmission line terminated by a lightning arrester connected to a grounding system buried in a lossy ground. In this technique, the transmission line is modeled in the frequency domain with the aid of Baum–Liu–Tesche equations, while the grounding system to which the arrester is connected is treated using a general electromagnetic approach. The electromagnetic approach is based on the solutions to Maxwell's equations obtained by using the method of moment in the frequency domain. The arrester nonlinearity is included in the frequency-domain analysis using the arithmetic operator method. To examine the performance of the proposed modeling technique, numerical results are presented for a single-conductor transmission line connected to a typical lightning arrester. The results are first compared for a simple grounding configuration of a vertical rod with those obtained using the well-known electromagnetic transient program, showing the validity of the proposed technique. The generality of the technique is then demonstrated by studying the results of a more complex case of a typical grounding grid. It is shown that the early time responses of the lightning overvoltages are affected by the harmonic impedance of the grounding system.      

Calculation of the radiation of a waveguide-horn antenna excited by short electromagnetic pulses

A method for the numerical calculation of the electromagnetic field radiated into free space by a waveguide-horn antenna excited by short ultra-wideband electromagnetic pulses (UWB EMPs) is described. Calculations are based on the method of nonstationary waveguide equations, which was proposed earlier, and the concept of a virtual electromagnetic waveguide. It is shown that the proposed approach allows calculation of the “forward radiation field” with control of the error in the obtained results and ensures a high accuracy of calculations.     

The anti-circuit concept for the characterization of activecircuits using electromagnetic simulations

The anti-circuit is introduced as a new concept in network theory. A new technique based thereupon, for the combination of electromagnetic field simulations of planar circuits and the analysis of complex active circuits is proposed. This technique allows the incorporation of passive lumped elements as well as the passive metallization of active components into electromagnetic simulations and provides a simple interface for active and nonlinear simulations