System-on-Packaging with Electroabsorption Modulator for a 60-GHz Band Radio-Over-Fiber Link

A system-on-packaging (SoP) with an electroabsorption modulator (EAM) for a 60 GHz band radio-over-fiber (RoF) link is described. The system consists of an EAM device, a microstrip filter, and a low noise amplifier (LNA). The microstrip filter was used to achieve impedance matching between the EAM device and the LNA and to reject the local oscillator (LO) frequency of the heterodyne system. The frequency response and the effect of the EAM bias voltage were measured for a simple RF/optical link. A 60 GHz band RoF link with 2.5 GHz intermediate frequency (IF) was prepared to measure the transmission characteristics of the 16 QAM data.     

A Passive Broadband Impedance Equalizer for Improving the Input Return Loss of Electro-Absorption Modulators

Based on the context of an electro-absorption modulator integrated laser and the industry's standard 7-pin package having a RF connector, a complete module design that incorporates a simple yet effective broadband impedance equalizer to improve the input return loss of electro-absorption modulators (EAM) is proposed. The passive broadband impedance equalizer effectively reduces the input return loss of the EAM from between -9.84 and -5.26 dB to between -11.5 and -9.35 dB over a frequency range from 4.4 to 12.2 GHz without having to add a resistor in series with the EAM or reducing the EAM absorption-layer capacitance from the value that was optimized for optimal optical performance.     

60-GHz System-on-Packaging Transmitter for Radio-Over-Fiber Applications

Using ultra-high-speed electroabsorption modulator (EAM) devices for RF/optic conversion, we fabricated system-on-packaging (SOP) transmitter (Tx) modules and characterized their performance in 60-GHz RF/radio-over-fiber (ROF) applications. Both an EAM and low-noise amplifiers (LNAs) were co-packaged with internal bias circuits into a butterfly-type metal housing. At the EAM temperature, $T {sim} {hbox{25}}~^{circ}$ C and the EAM reverse bias, $V_{R} {sim} $1.6 V was the largest RF gain obtained that was very susceptible to the change of $T$ . The impedance matching in the 60-GHz band was accomplished with both a microstrip-line bandpass filter and a 500- $Omega$ shunt resistor, which defined the 2-GHz passband of the SOP transmitter. In 60-GHz two-tone experiments, we observed that the spurious free dynamic range of an SOP module with two LNAs was 78 dB $cdot$ Hz $^{2/3}$ while that of the narrowband EAM module showed 82 dB $cdot$ Hz$^{2/3}$. In contrast, the noise figure exhibited a large reduction of up to 30 dB for the SOP module compared with the narrowband EAM module. Using the SOP Tx module, we achieved successful transmission of commercial high-definition digital CATV signals in 64-quadrature amplitude modulation (QAM) format through the 60-GHz RF/ROF link. The total throughput of the link was estimated to be 6.5 Gb/s.      

Thermal effects in monolithically integrated tunable laser transmitters

We investigate thermal effects in widely tunable laser transmitters based on an integrated single chip design. The chip contains a sampled-grating distributed Bragg reflector (SG-DBR) laser monolithically integrated with a semiconductor optical amplifier (SOA) and an electroabsorption modulator (EAM). The thermal impedance of the ridge structure is evaluated through simulation and experiment, and thermal crosstalk between sections is examined. Heating of the mirrors by neighboring sections is found to result in unintentional offsets in wavelength tuning. Thermal effects in the EAM are examined in depth. A positive feedback mechanism causes local temperature rise at the modulator input, with the potential to trigger catastrophic thermal runaway. A self-consistent finite-element model is developed to simulate the EAM temperature profile and device performance. This model is used to optimize the device, resulting in integrated EAMs that achieve a dissipated power limit in excess of 300mW.     

ALD中射频阻抗匹配器的设计与研究

阐述原子层沉积系统（ALD）中射频阻抗匹配器的设计方案。利用ADS软件对阻抗匹配网络进行仿真,通过分析ALD真空腔室内等离子体产生前后的负载阻抗变化,结合仿真结果,提出等离子体产生过程中阻抗匹配网络的控制方法。经实验验证,该阻抗匹配器和控制方法可实现阻抗匹配。     

Improved RF amplifier mounting scheme

The use of a conductive, silicone rubber-based wafer is described in conjunction with RF amplifier module installation on double-sided printed wiring boards. The new method provides for device heat sinking, device pin stress relief, and low impedance device ultrahigh frequency (UHF) ground connection for achieving cost-effective reliable device performance.     

A Novel RF Test Scheme Based on a DFT Method

This paper presents a new RF testing scheme based on a design-for-testability (DFT) method for measuring functional specifications of RF integrated circuits (IC). The proposed method provides the input impedance, gain, noise figure, voltage standing wave ratio (VSWR) and output signal-to-noise ratio (SNR) of a low noise amplifier (LNA). The RF test scheme is based on theoretical expressions that produce the actual RF device specifications by utilizing the output DC voltages from the DFT chip. This technique can save marginally failing chips in production testing as well as in the system, hence saving a tremendous amount of revenue from unnecessary device replacements.     

Modeling, analysis, and design of RF LDMOS devices usingharmonic-balance device simulation

This paper describes how device simulation may be used for the modeling, analysis, and design of radio-frequency (RF) laterally diffused metal-oxide-semiconductor (LDMOS) transistors. Improvements to device analysis needed to meet the requirements of RF devices are discussed. Key modeling regions of the LDMOS device are explored and important physical effects are characterized. The LDMOS model is compared to dc and small-signal ac measurements for calibration purposes. Using the calibrated model, large-signal accuracy is verified using harmonic distortion simulation, and intermodulation analysis. Predictive analysis and a study of the structure's parasitic components are also presented. Load-pull simulation is used to analyze matching network effects to determine the best choices for device impedance matching     

Effect of gate poly-silicon depletion on MOSFET input impedance

One of the most challenging problems encountered in developing RF circuits is accurate prediction of MOS behavior at microwave signal and data frequencies. An attempt is made in this work to accurately model the device input impedance for the 1-20-GHz frequency range. The effect of device length and single-leg width on the input impedance is studied with the aid of extensive measured data obtained from devices built in 0.11-/spl mu/m and 0.18-/spl mu/m technologies. The measured data illustrates that the device input impedance has a nonlinear frequency dependency. It is also shown that this variation in input impedance is a result of gate poly-silicon depletion, which can be modeled by an external RC network connected at the gate of the device. Excellent agreement between the simulation results and the measured data validates the model in the device active region.     

Design method for fully integrated CMOS RF LNA

An efficient method for fully integrated RF CMOS LNA design is presented. A particular input matching topology enables inductor values to be selected in order to be integrated fully and to minimise the input losses. Moreover, an active device sizing method is used to achieve a 50 /spl Omega/ input impedance with a low noise factor. Simulations show a 3.0 dB noise figure at 2.45 GHz for a power consumption of 10 mW in a 0.28 /spl mu/m RF CMOS process.     

Decreasing-size distributed ESD protection scheme for broad-band RF circuits

The capacitive load, from the large electrostatic discharge (ESD) protection device for high ESD robustness, has an adverse effect on the performance of broad-band RF circuits due to impedance mismatch and bandwidth degradation. The conventional distributed ESD protection scheme using equal four-stage ESD protection can achieve a better impedance match, but degrade the ESD performance. A new distributed ESD protection structure is proposed to achieve both good ESD robustness and RF performance. The proposed ESD protection circuit is constructed by arranging ESD protection stages with decreasing device size, called as decreasing-size distributed electrostatic discharge (DS-DESD) protection scheme, which is beneficial to the ESD level. The new proposed DS-DESD protection scheme with a total capacitance of 200 fF from the ESD diodes has been successfully verified in a 0.25-mum CMOS process to sustain a human-body-model ESD level of greater than 8 kV     

应用于40Gb／s电吸收调制器的Al2O3高速热沉研究

设计制作了面向40Gb/s电吸收调制器(EAM)的高速微波过渡热沉,并进行了EAM管芯级封装测试的验证.这种基于氧化铝(A l2O3)的热沉采用共面波导(CPW)传输线以实现低损耗微波传送,以及Ta2N薄膜电阻用于EAM的阻抗匹配.采用Ti/Cu/N i/Au金属材料作为CPW传输线电极材料,从而保证CPW传输线与Ta2N电阻材料之间良好的电接触,使热沉的典型反射系数在0~40 GHz范围内均达到优于-21 dB的水平.作为验证,采用该种热沉用于高速EAM的管芯级封装,测试得到小信号调制响应带宽超过40 GHz.     

射频同轴传输线的设计仿真与加工工艺

基于SU-8和BPN紫外负性感光胶,结合微电镀工艺加工制作射频同轴传输线,以实现射频器件信号的传输与耦合。首先确定在阻抗匹配情况下同轴传输线特性阻抗为50Ω的同轴传输线的具体尺寸,然后通过HFSS仿真软件对设计的结构进行模拟仿真。通过仿真结果验证设计的可行性,采用紫外光刻技术利用SU-8光刻胶做出内导体支柱,并用BPN光刻胶做出结构,对结构进行电镀。最后将BPN光刻胶剥离,即可得到射频同轴传输线。此方法制得的同轴传输线具有介质损耗小、辐射损耗小、无色散、带宽大和抗干扰强的优点,适用于高性能射频和微波电路。另外,它的制作工艺能与其他射频和微波器件及集成电路工艺兼容,便于与射频和微波电路集成。     

Low insertion loss and low dispersion penalty InGaAsP quantum-well high-speed electroabsorption modulator for 40-Gb/s very-short-reach, long-reach, and long-haul applications

We present a metal-organic-chemical-vapor-deposition-grown low-optical-insertion-loss InGaAsP/InP multiple-quantum-well electroabsorption modulator (EAM), suitable for both nonreturn-to-zero (NRZ) and return-to-zero (RZ) applications. The EAM exhibits a dynamic (RF) extinction ratio of 11.5 dB at 1550 nm for 3 Vp-p drive under 40-Gb/s modulation. The optical insertion loss of the modulator in the on-state is -5.2 dB at 1550 nm. In addition, the EAM also exhibits a 3-dB small-signal response (S21) of greater than 38 GHz, allowing it to be used in both 40-Gb/s NRZ and 10-Gb/s RZ applications. The dispersion penalty at 40 Gb/s is measured to be 1.2 dB over /spl plusmn/40 ps/nm of chromatic dispersion. Finally, we demonstrate 40-Gb/s transmission performance over 85 km and 700 km.     

Waveguide-to-microstrip transition with integrated bias-T

A novel device, a waveguide-to-microstrip transition with an integrated bias-T, is presented. The substrate-based planar structure comprises a waveguide E-probe, shaped as a radial line. The probe couples the RF field of a full-height waveguide to a microstrip line or directly to an active component, e.g., a transistor or diode in a mixer or direct detector. The radial probe is connected on its wide side to another port via a specially shaped high impedance line that provides RF/DC isolation. This port can then be used to inject DC and/or extract IF signals. The design of the presented structure was done using CAD (3-D EM simulation) and an X-band device was produced and fully characterized. The measured performance is in excellent agreement with the simulations; the device has return loss better than -20 dB, insertion loss less or equal to -0.15 dB and isolation for the bias-T line better than -20 dB. RF bandwidth for the transition is 30% of the central frequency.     

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。     

140 GHz GaAs double-Read IMPATT diodes

CW GaAs double-Read IMPATT diodes for D-band frequencies are designed and tested. For reproducible RF impedance matching, the module encapsulation technique is applied. Ohmic losses of the active device are reduced by a titanium-Schottky contact instead of an alloyed ohmic n ⁺-contact. At 144 GHz 100 mW RF power with a conversion efficiency of 5% is realised     

全固态高效率射频电源

射频电源作为微电子设备如刻蚀机、溅射台和PECVD等的核心部件,其性能的好坏直接关系到整个设备的性能。固态射频电源采用E类MOSFET功率放大器,通过适当的阻抗匹配网络,最终的射频电源在500 W的额定功率下,功率转换效率可以达到84%,微电子设备真空腔室内的等离子体启辉时,其阻抗变化范围很大且速度很快。目前匹配速度最快的MKS的自动匹配器(在允许匹配范围内匹配到50Ω时用时3~5 s)也很难实时跟上,所以固态射频电源必须能够承受500 W功率的反射至少3~5 s。经过实验后,本固态射频电源完全可以承受500 W功率的全反射30 s左右。     

Demonstration of a dual-depletion-region electroabsorption modulator at 1.55-/spl mu/m wavelength for high-speed and low-driving-voltage performance

We demonstrate a novel structure of electroabsorption modulator (EAM) at a 1.55-/spl mu/m wavelength: the dual-depletion-region EAM. After an n/sup +/ delta-doped layer was inserted into the thick intrinsic region (550 nm) of a tradition p-i-n modulator, the tradeoff between driving-voltage and electrical bandwidth performance can be released effectively. This new structure can also release the burden imposed on downscaling the width or length of high-speed EAM with low driving-voltage performance. The microwave and electrical-to-optical measurement of this novel device with traveling-wave electrodes show very convincing results.     

RF and IF ports matching circuit synthesis for a simultaneousconjugate-matched mixer using quasi-linear analysis

A quasi-linear two-port approach between RF and IF ports to design a simultaneous conjugate-matched mixer is presented in this paper. Conventionally, mixer design is treated as a nonlinear three-port device problem. Nonetheless, with the exception of the large-signal local oscillator (LO) that exists at the LO port, the input RF and output IF signals that exist at the RF and IF ports, respectively, are small signals. Consequently, mixers can be approximated as bilateral quasi-linear two-port circuits with a time-variant transfer function between the RF and IF ports, in which the LO port of the mixer is treated as part of the two-port network. With this approximation, it can be shown mathematically that the optimum source and load matching networks required for attaining simultaneous conjugate match at the RF and IF ports are actually time invariant, thus implying that it is possible to synthesize these optimum impedance values. This proposed mixer design technique, together with the equations derived, are verified with block-diagram simulation and experimental measurements of two 2.4-GHz RF/420-MHz IF double-balanced diode mixers