MOEMS variable optical attenuator with improved dynamic characteristics based on robust design

The design and preliminary data of a novel microoptoelectromechanical systems variable optical attenuator (VOA) driven by a pair of V-beam electrothermal actuators is described. This VOA deploys a face-to-face arranged pair of 45/spl deg/ tilted mirrors in front of two coaxially aligned lensed fibers to form retro-reflection planar light path for attenuation. The initial insertion loss is 0.7 dB at 1550 nm and the maximum dynamic range of attenuation is 50 dB, respectively. The polarization-dependent loss is measured as 0.15 dB at 20-dB attenuation. The dynamic attenuation deviation is less than /spl plusmn/0.36 dB at 20-dB attenuation with respect to 20-G shock of periodical mechanical vibration at 1 K Hz, in which it complies with requirements of the Telcordia GR1221 regulations.     

Asymmetric Tuning Schemes of MEMS Dual-Shutter VOA

A dual-shutter MEMS variable optical attenuator (VOA) is designed for advanced tuning functions such as linear attenuation relationship and simultaneous coarse and fine tunings. The mechanism behind is to take advantage of the additional shutter to render one more degree of freedom for attenuation adjustment. Although dual-shutter VOAs with asymmetric functionalities have been reported before, these intrinsic capabilities owing to asymmetry have not been extensively investigated. In experiment, the fabricated VOA device has demonstrated a linear tuning over a 20-dB range with respect to the driving voltage of one shutter, and it has also realized simultaneously coarse tuning (2.5 dB/V) and fine tuning (0.1 dB/V) by the two shutters. Ideally, the tuning can start from any available working point, linear to any controlling parameter, at any slope of linearity, and with any tuning resolution. Theoretical attenuation model has also been developed to provide a roadmap for the VOA design and choice of working point. An interesting finding is that over a certain range the linear attenuation can be obtained by moving a fixed aperture rather than by reducing the aperture size, which greatly relaxes the difficulty of shutter position control. The measured results match well with the theoretical data, implying the possibility of developing a look-up table to locate the shutter positions quickly. The dual-shutter VOA accomplishes these features without the need of high-precision control systems and therefore gives a structure-based rather than a control-system-based solution, clearly advantageous over the previously developed VOAs.     

Submicrosecond speed variable optical attenuator usingacoustooptics

A novel variable optical attenuator (VOA) is introduced that can provide high dynamic range and high-resolution all at fast submicrosecond speeds. The VOA design exploits an in-line one-to-one imaging optical architecture operating with Bragg-mode acoustooptic Bragg cells. Optical attenuation is achieved via frequency and drive voltage control of the Bragg cells, leading to flexible and precise attenuation-level settings. VOA demonstrated a 45-dB dynamic range with a 175-ns switching time. Other measured parameters include 1.14-dB/MHz resolution, 1.56-dB polarization dependent loss, and an excess loss of 3.55 dB     

Wide Temperature Range Operation of a 1.55-$mu$m 40-Gb/s Electroabsorption Modulator Integrated DFB Laser for Very Short-Reach Applications

We present the uncooled operation of a 1.55- mum 40-Gb/s InGaAlAs electroabsorption modulator (EAM) integrated distributed-feedback (DFB) laser within a temperature range of 95degC (-15degC to 80degC ). To the best of our knowledge, this is the largest temperature range reported so far for such a 40-Gb/s EAM integrated DFB laser. We designed the EAM to operate at high speed by reducing the electrical parasitics, and we achieved a 3-dB frequency bandwidth of over 39 GHz for an EAM length of less than 150 mum. We demonstrated a 2-km single-mode fiber (SMF) transmission at 40-Gb/s over a wide temperature range of -15degC to 80degC by adjusting only the bias voltage to the EAM while keeping the modulation voltage swing constant at 2.0 V when the temperature changed. We achieved a dynamic extinction ratio of over 8.2 dB and a 2-km SMF transmission with a power penalty of less than 2 dB over a wide temperature range.     

基于3 μm-SOI的波分复用/解复用器与电吸收型VOA的单片集成

波分复用/解复用器与可调光衰减器的是光通信系统中的重要元器件。为了得到制备工艺简单、响应速度快的二者的单片集成芯片,并且考虑到其与其他不同光器件的集成可能性,在绝缘体上硅材料制作了16通道、信道间隔200 GHz的阵列波导光栅复用/解复用器与电吸收型可调光衰减器的单片集成。该器件的片上损耗小于7 dB,串扰小于-22 dB。电吸收型VOA在20 dB的衰减量下的功耗为572 mW （106 mA,5.4 V）。此外,该器件可以实现光功率的快速衰减,在0~5 V的外加方波电压下,VOA上升及下降时间分别为50.5 ns和48 ns。     

A 2.7-V SiGe HBT variable gain amplifier for CDMA applications

A monolithic SiGe HBT variable gain amplifier with high dB-linear gain control and high linearity has been developed for CDMA applications. The VGA achieves a 30-dB dynamic gain control with a control range of 0-2.7 Vdc in 824-849 MHz band. The maximum gain and attenuation are 23 dB and 7 dB, respectively. Input/output VSWRs keep low and constant despite change in the gain-control voltage. At a low operation voltage of 2.7 V, the VGA produces a 1-dB compression output power of 13 dBm and /spl plusmn/885-kHz ACPR of -57 dBc at a 5-dBm output power.     

Multilayer Organic Multichip Module Implementing Hybrid Microelectromechanical Systems

We present the design and development of an organic package that is compatible with fully released RF microelectromechanical systems (MEMS). The multilayer organic package consists of a liquid-crystal polymer film to provide near hermetic cavities for MEMS. The stack is further built up using organic thin-film polyimide. To demonstrate the organic package, we have designed and implemented a 2-bit true-time delay X-band phase shifter using commercially available microelectromechanical switches. The packaged phase shifter has a measured insertion loss of 2.45 plusmn 0.12 dB/bit at 10 GHz. The worst case phase variation of the phase shifter at 10 GHz is measured to less than 5deg. We have also conducted temperature cycling (-65degC to 150degC) and 85/85 to qualify the packaging structures.     

Variable optical attenuator based on ion-exchange technology in glass

A thermooptic variable optical attenuator (VOA) based on the Mach-Zehnder interferometer principle was fabricated in glass by an ion-exchange technique. The thermooptical effect was reached via heating electrodes on the side of the Mach-Zehnder arms. The insertion loss of the device was 1 dB, the dynamic range was 38 dB, maximal power consumption was 138 mW, and the polarization-dependent loss (PDL) was 0.2 dB/0.6 dB at 10 dB/20-dB attenuations, respectively.     

Wideband planar lightwave circuit type variable optical attenuator using phase-generating coupler

A novel wideband planar lightwave circuit type variable optical attenuator (VOA) that incorporates a phase-generating coupler is proposed. The proposed VOA was fabricated on a 1.5%-/spl Delta/ silica-based waveguide, and obtained a low insertion loss of less than 1.2 dB and a low wavelength dependent loss of less than 0.8 dB at attenuation levels of 0 to 25 dB over the C- and L-band wavelength range.     

A low-voltage and variable-gain distributed amplifier for 3.1-10.6 GHz UWB systems

A low-voltage and variable-gain distributed amplifier is presented in this letter. This microwave monolithic integrated circuit amplifier achieves 12-dB gain with a 3-dB frequency band of 1.6-12.1GHz and 6.5-dB noise figure under the bias condition of 0.8-V supply voltage and 6.4-mW total dc power consumption. The gain-control range is from -18dB to +20dB. Resistive metal-oxide-semiconductor field-effect transistors are used as termination resistors to compensate the mismatch due to different bias conditions. From 3.1 to 10.6GHz, the maximum gain ripple of this amplifier is only /spl plusmn/1dB for the gain level between -4 and 20dB.     

MOEMS variable optical attenuators using rotary comb drive actuators

We propose a novel design of variable optical attenuator using electrostatic rotary comb actuator. Our optimized electromechanical design results in large dynamic range of 57-dB attenuation, low driving voltage of 3.6 dc V for 30-dB attenuation, fast response time of 3 ms, and excellent optical transient stability with no mechanical overshoot. The optimized layout design also contributes small device footprint of 3.2/spl times/4.7 mm/sup 2/ only.     

Binary-Weighted Digital-to-Analog Converter Design Using Floating-Gate Voltage References

An implementation of a compact and programmable 10-bits floating-gate digital-to-analog converter (FGDAC) is described. In this implementation, nonvolatile floating-gate voltage references (epots) are employed together with unity-size capacitors to obtain the binary-weighted scale factors. The FGDAC, fabricated in a 0.5- mum CMOS process, occupies 0.208 mm² of die area. The stored epot voltages drift 10_3% over the period of ten years at 25 degC and exhibit temperature coefficients of less than 37 ppm/degC. With the proposed design, INL and DNL values less than plusmn0.5LSB (LSB = 3 mV) and SFDR around 63 dB are obtained.     

X波段交直流分离的MEMS开关的设计与研究

介绍了一种带直流驱动电极交直流分离的MEMS开关,研究了影响开关阈值电压的因素,运用缩腰设计、尺寸优化等方法降低开关的阈值电压;运用阻抗匹配方法降低开关的反射损耗;利用等效电感的设计提高所需频段的隔离度。使用Coventor和HFSS软件模拟,设计的开关阈值电压小于20V,在X波段插入损耗低于0.1dB,反射损耗低于-25dB,谐振点处隔离度高于40dB。     

Analysis of RF MEMS switch packaging Process for yield improvement

Radio frequency microelectro-mechanical systems (RF MEMS) switches offer significant performance advantages in high-frequency RF applications. The switches are actuated by electrostatic force when voltage was applied to the electrodes. Such devices provide high isolation when open and low contact resistance when closed. However, during the packaging process, there are various possible failure modes that may affect the switch yield and performance. The RF MEMS switches were first placed in a package and went through lid seal at 320degC. The assembled packages were then attached to a printed circuit board at 220degC. During the process, some switches failed due to electrical shorting. Interestingly, more failures were observed at the lower temperature of 220degC rather than 320degC. The failure mode was associated with the shorting bar and the cantilever design. Finite element simulations and simplified analytical solutions were used to understand the mechanics driving the behaviors. Simulation results have shown excellent agreement with experimental observations and measurements. Various solutions in package configurations were explored to overcome the hurdles in MEMS packaging and achieve better yield and performance     

Reconfigurable 16-channel WDM drop module using silicon MEMSoptical switches

A reconfigurable 16-channel 100-GHz spacing wavelength-division-multiplexed drop module for use at 1550 nm was demonstrated using silicon microelectromechanical system (MEMS) optical switches and arrayed waveguide grating routers. Through-channel extinction was greater than 40 dB and average insertion loss was 21 dB, Both drop-and-retransmit of multiple channels (11-18 dB contrast, 14-19-dB insertion loss) and drop-and-detect of single channels (>20-dB adjacent channel rejection, 10-14-dB insertion loss) were implemented     

A 95-dB linear low-power variable gain amplifier

An all-CMOS variable gain amplifier (VGA) that adopts a new approximated exponential equation is presented. The proposed VGA is characterized by a wide range of gain variation, temperature-independence gain characteristic, low-power consumption, small chip size, and controllable dynamic gain range. The two-stage VGA is fabricated in 0.18-/spl mu/m CMOS technology and shows the maximum gain variation of more than 95 dB and a 90-dB linear range with linearity error of less than /spl plusmn/ 1 dB. The range of gain variation can be controlled from 68 to 95 dB. The P1dB varies from - 48 to - 17 dBm, and the 3-dB bandwidth is from 32 MHz (at maximum gain of 43 dB) to 1.05 GHz (at minimum gain of - 52 dB). The VGA dissipates less than 3.6 mA from 1.8-V supply while occupying 0.4 mm/sup 2/ of chip area excluding bondpads.     

一种雪花型MEMS单刀五掷开关的研究与设计

针对MEMS单刀多掷(SPMT)开关插入损耗及隔离度较差的问题,设计了一种基于雪花型功分器的单刀五掷(SP5T)MEMS开关,通过雪花型功分器实现信号的均衡分配和低损耗传输.通过设计H形上电极结构,有效减小开关弱接触,增强开关接触稳定性,实现信号的高隔离.采用HFSS仿真软件,对开关的插入损耗、隔离、驱动电压和应力分布...     

高隔离度宽频带MEMS双膜桥开关

利用一种新型双边加直流驱动电极的电容耦合式MEMS并联膜开关与直接接触式并联膜开关进行级联,形成MEMS双膜开关.通过对其尺寸和结构的优化,降低开关阈值电压,Coventor软件模拟表明,开关的阈值电压小于20V;通过对其匹配设计改善开关的高频性能,HFSS软件模拟的结果表明,在DC～20GHz整个频带内,开关的插入损耗优于-0.1dB,反射损耗低于-30dB,隔离度低于-20dB,在 谐振点处隔离度能达到-40dB.     

一种S波段平衡式限幅低噪声放大器的设计

介绍了一种小型化平衡式限幅低噪声放大器。该放大器采用Lange桥平衡结构,在实现低噪声的同时,保证了小电压驻波比;在3.0～3.5GHz频带内,噪声系数小于1.3dB,输入输出驻波系数小于1.3,增益大于27dB,平坦度±0.6dB以内,输出1dB压缩点大于12dBm。该放大器能够承受最大5W的连续波功率输入,且大功率输入时的驻波系数小于1.3。     

A silicon bipolar transmitter front-end for 802.11a and HIPERLAN2 wireless LANs

A 5-GHz transmitter front-end for 802.11a and HIPERLAN2 wireless local area networks was implemented in a low-cost 46-GHz-f/sub T/ silicon bipolar technology. The transmitter includes a digitally controlled linear-in-dB variable-gain up-converter and a three-stage linear power amplifier. At a 3-V supply voltage, the front-end exhibits a 23.5-dBm output 1-dB compression point, 35-dB maximum power gain, and 30-dB dynamic range. The dB-linear gain error is lower than /spl plusmn/0.8 dB. The transmitter is able to comply with the stringent error vector magnitude requirement of the standard up to a 19-dBm output power level.