Rain attenuation measurements over New Delhi with a microwave radiometer at 11 GHz

Rain attenuation measurements over New Delhi carried out with a microwave radiometer installed at the National Physical Laboratory (NPL), New Delhi and operating on 11 GHz for a period of more than three years are presented. For 0.01 percent of time for the period June 1977-April 1978, the attenuation exceeded for the monsoon period is 14.0 dB whereas for the whole year, it exceeds 10.4 dB. During the winter for the same percentage of time, the attenuation exceeded 1.5 dB, whereas for March-April it exceeds 0.5 dB. For the period May 1978-June 1980, it is observed that for 0.01 percent of time the attenuation for the whole year exceeds 9.0 dB. During the winter for the same percentage of time, the attenuation exceeds 1.4 dB whereas for March-April it exceeds 0.4 dB. A comparison of attenuation over New Delhi and those reported elsewhere are discussed. Yearly and worst month time ratio over New Delhi are given also as the values reported for the European region. Comparison of the attenuation distribution and the rate of surface rainfall measured with a rapid-response rain gauge are also given. The comparison shows that for the monsoon period and for 0.01 percent of time, the attenuation value exceeded for 14 dB corresponds to the surface rainfall rate of 140 mm/h. For the monsoon of 1978, 1979, comparison shows that for 0.1 percent of time, the attenuation value exceeded for 9.0 dB corresponds to the surface rainfall rate of 90 mm/h. Variation of attenuation and effective path length for various rainfall rates and elevation angles are also given.     

4×4 polymer thermo-optic directional coupler switch at 1.55μm

An integrated 4×4 polymer thermo-optic switch at 1.55 μm is demonstrated for the first time. A fibre to fibre insertion loss of 10 dB, and extinction ratios of 17.5-19.5 dB were measured. The polarisation sensitivity was typically less then 0.5 dB and the response time was less then 1 ms. The electrical power consumption was found to be 70 mW per single switch     

Fiber-Optic Polarizer Using Resonant Tunneling through a Multilayer Overlay

We demonstrate an in-line fiber-optic polarizer using resonant tunneling through a leaky multilayer overlay for the first time. Polarization extinction ratio (PER) ? 27 dB with an insertion loss (IL) ? 3 dB has been demonstrated experimentally with scope of further improvement. A simple planar waveguide model is developed to analyze the device whose predictions match very well with the experimental results. It is further shown that by properly selecting the device parameters one can achieve PER ? 68 dB with IL ? 0.2 dB for λ = 0.6328 μm and PER ? 80 dB with IL ? 1.2 dB for λ = 1.3 μm.     

三通道多普勒雷达杂波信号实时模拟器

本文采用一种新的杂波信号实时重构和调制技术,研制了三通道多普勒雷达杂波信号实时模拟器.与简单组合一系列时域数据组相比,由于对时域数据组采取了加窗、搭接等处理,使得到的杂波信号的信噪比由30dB提高到60dB以上.同时,由于采用了数字正交调制,从而有效地提高了镜频抑制度.     

Gigahertz analog repeater for fiber optic delay lines

A gigahertz analog fiber optic repeater is used to extend the achievable delay time for radar delay line applications. The repeater consists of a silicon avalanche photodiode (APD), a wide-band amplifier, and a GaAlAs laser diode transmitter. This repeater has an optical gain of 14.5 dB, a 42 dB electrical dynamic range, and a noise figure of approximately 6.5 dB. The frequency response is flat within ±2 dB over the frequency range from 10 MHz to 1.3 GHz. The nanosecond pulse fidelity is such that the subtraction between input and output pulses is 20 dB below the pulse amplitude.     

Microstructure-fibre-based optical parametric amplifier with gain slope of /spl sim/200 dB/W/km in the telecom range

A microstructure-fibre-based optical parametric amplifier with a gain slope of /spl sim/200 dB/W/km in the 1550 nm range is demonstrated, for the first time to the authors' knowledge. By using only 12.5 m-long fibre, gains were obtained of >20 dB over a bandwidth of approximately 30 nm, achieving a peak net gain of 25.4 dB.     

A Broad-Band Optoelectronic Microwave Switch

A broad-band optoelectronic switch based on an avalanche photodiode is described. The microwave signal is supplied to the switch as intensity modulation on an optical carrier wave. Switching is achieved by reverse biasing the APD for the on-state and forward biasing for the off-state. Isolation of better than 80 dB is reported over a signal frequency range of 10 MHz to 1 GHz. In the same switch, isolation greater than 60 dB is observed up to 3 GHz. A turn-on time of 400 ns was observed without special techniques for discharging the junction, the turn-off time is much shorter.     

基于InGaP/GaAs HBT的10Gbps跨阻放大器

采用InGaP/GaAs HBTs设计并实现了传输速率为10Gbps的跨阻放大器.在电路设计上采用两级放大器级联的形式以提高跨阻增益,在第一级采用了cascade结构,第二级采用了cherry hooper结构以提高电路的带宽和稳定性.测试结果表明,跨阻增益为40dB·Ω and 3dB带宽为10GHz.     

A novel time-based low-power pipeline analog to digital converter

A new power reduction technique for analog-to-digital converters is proposed in this paper. A novel current-mode algorithm which uses time to perform analog-to-digital conversion has been described and a 12 bit 100-ksample/s time-based pipeline analog to digital converter has been designed and simulated in standard 90-nm CMOS technology based on introduced structure. Employed circuit techniques include a continues-time comparator, bottom plate sampling, digital correction and a state machine. A time based-mechanism has been used for subtraction and amplification. Simulation results show that the pipelined ADC achieves a peak signal-to-noise-and-distortion ratio of 69.8 dB, a peak spurious-free dynamic range of 75 dB, a total harmonic distortion of 73 dB, and a peak integral nonlinearity of 0.85 least significant bits. The total power dissipation is 90 μW from a 3-V supply.     

A novel loss compensation technique analysis and design for 60 GHz CMOS SPDT switch

A novel loss compensation technique for a series-shunt single-pole double-throw (SPDT) switch is presented operating in the 60 GHz. The feed-forward compensation network which is composed of an NMOS, a couple capacitance and a shunt inductance can reduce the impact of the feed forward capacitance to reduce the insertion loss and improve the isolation of the SPDT switch. The measured insertion loss and isolation characteristics of the switch somewhat deviating from the 60 GHz are analyzed revealing that the inaccuracy of the MOS model can greatly degrade the performance of the switch. The switch is implemented in TSMC 90-nm CMOS process and exhibits an isolation of above 27 dB at transmitter mode, and the insertion loss of 1.8-3 dB at 30-65 GHz by layout simulation. The measured insertion loss is 2.45 dB at 52 GHz and keeps<4 dB at 30-64 GHz. The measured isolation is better than 25 dB at 30-64 GHz and the measured return loss is better than 10 dB at 30-65 GHz. A measured input 1 dB gain compression point of the switch is 13 dBm at 52 GHz and 15 dBm at 60 GHz. The simulated switching speed with rise time and fall time are 720 and 520 ps, respectively. The active chip size of the proposed switch is 0.5×0.95 mm².     

GaAs/AlGaAs directional coupler switch with submillimetre device length

A GaAs/AlGaAs directional coupler switch, for the first time with a device length shorter than 1 mm, has been fabricated by utilising the good controllability of molecular beam epitaxy and reactive ion beam etching. The switching voltage is as low as 5V. The extinction ratio is 17dB for a crossover state and 14dB for a straight-through state.     

A 32-element 8-bit photonic true-time-delay system based on a 288 /spl times/ 288 3-D MEMS optical switch

A large-scale three-dimensional microelectromechanical-system optical switch is used for the first time to realize a true-time-delay (TTD) beamformer for phased-array radar applications, with a capacity of 32 antenna elements and eight bits of delay. The 288 /spl times/ 288 optical switch has a median loss of 1.4 dB and all measured 82 944 paths exhibit less than 2.3 dB loss at 1310 nm. The TTD beamformer exhibits a loss variation of 1.5 dB, which is equalized using a mirror-offset technique.     

0.18 μm 3.1-10.6 GHz CMOS UWB LNA with 11.4±0.4 dB gain and 100.7± 17.4 ps group-delay

A3.1-10.6 GHz ultra-wideband low-noise amplifier (UWB LNA) with excellent phase linearity property (group-delay-variation is only plusmn17.4 ps across the whole band) using standard 0.18 mum CMOS technology is reported. To achieve high and flat gain and small group-delay-variation at the same time, the inductive peaking technique is adopted in the output stage for bandwidth enhancement. The UWB LNA dissipates 22.7 mW power and achieves input return loss (S₁₁) of -9.7 to -19.9 dB, output return loss (S22) of-8.4 to -22.5 dB, flat forward gain (S21) 11.4 plusmn0.4 dB, reverse isolation (S12) of -40 to -48 dB, and noise figure of 4.12-5.16 dB over the 3.1-10.6 GHz band of interest. A good 1 dB compression point (Pi dB) of -7.86 dBm and an input third-order intermodulation point (IIP3) of 0.72 dBm are achieved at 6.4 GHz. The chip area is only 681 x 657 mum excluding the test pads.     

MEMS variable optical attenuator using low driving voltage for DWDMsystems

A silicon microelectromechanical system (MEMS) variable optical attenuator with fibre connection is reported. The device requires only 8 V driving voltage. It has only 1.5 dB insertion loss, but 45 dB dynamic range, 37 ms response time, and 0.9 dB wavelength dependence loss over the C-band (1528-1561 nm)     

五位RF MEMS开关延迟线移相器

设计并研制了一种6～11GHz、超宽带5位RF MEMS开关延迟线移相器,器件实现了5位延迟:λ、2λ、4λ、8λ、16λ。该器件采用微带混合介质多层板技术,分4层制作,尺寸为45mm×20 mm。整个器件包括20个RFMEMS悬臂梁开关,用60～75V的静电压驱动。6～11GHz频带内,对32个相移态的测试结果表明:一般回波损耗S11<-10dB,各状态平均插入损耗为-8～-10dB;中心频率处,器件可实现的最大延迟位时延为1680ps,总时延为3255ps。     

Laminated polarizers exhibiting high performance over a wide rangeof wavelength

A laminated polarizer exhibiting high performance over a wide range of wavelengths has been fabricated for the first time. The polarizer consists of alternate layers of laminated silica film and metal-included semiconductor ultra-thin film as the transparent and absorptive layers, respectively. Extinction ratios of greater than 50 dB with insertion losses of less than 0.4 dB have been obtained over the wavelength range of 0.8-1.55 μm. At the wavelength 0.98 μm where previously no viable laminated polarizer had been available, the extinction ratio is as high as greater than 60 dB and the insertion loss less than 0.3 dB     

An efficient all-fiber variable optical attenuator via acoustoopticmode coupling

A novel broad-band variable optical attenuator is realized using acoustooptic mode coupling on a cladding etched single-mode fiber. Broad-band coupling bandwidth with low attenuation ripples is achieved by matching both the group index and dispersion parameter between the core and the LP₁₁^cl cladding modes. A single-section device exhibits a 10-dB dynamic range with attenuation ripples of <0.5 dB over a spectral range of >100 nm, a response time of 20 μs, an insertion loss of 0.3 dB, and a maximum power consumption of only 3.4 mW. Attenuation of 22 dB is obtained for a cascaded two-section device     

0.18 μm 21-27 GHz CMOS UWB LNA with 9.3 ± 1.3 dB gain and 103.9 ± 8.1 ps group delay

A 21-27 GHz CMOS ultra-wideband low-noise amplifier (UWB LNA) with state-of-the-art phase linearity property (group delay variation is only ± 8.1 ps across the whole band) is reported for the first time. To achieve high and flat gain (S₂₁) and small group delay variation at the same time, the inductive series peaking technique was adopted in the output of each stage for bandwidth enhancement. The LNA dissipated 27 mW power and achieved input return loss (S₁₁) of 213 to 220.1 dB, output return loss (S₂₂) of 28.2 to 230.2 dB, flat S21 of 9.3 ± 1.3 dB, reverse isolation (S₁₂) of 252.7 to 273.3 dB, and noise figure of 4.9?6.1 dB over the 21-27 GHz band of interest. The measured 1 dB compression point (P_1dB) and input third-order intermodulation point (IIP3) were 214 and 24 dBm, respectively, at 24 GHz.     

Polarization-insensitive InP-based MQW digital optical switch

A polarization-insensitive InP-based p-i-n multiple-quantum-well switch is demonstrated for the first time. Polarization-insensitive switching and loss are achieved. Crosstalk and loss measurements across a wavelength range of 20 nm centered at 1.55 μm are reported. A crosstalk of better than -13 dB is achieved for both TE and TM polarizations across the 1.54-1.56-μm wavelength range with a switching voltage of -7 V. A low on-chip loss of less than 3 dB is achieved for both TE and TM across the above wavelength range, with a compact switch structure which is 3 mm long     

Vertically coupled microring resonators using polymer wafer bonding

A new technique is presented to make vertically coupled semiconductor microring resonators that eases the fabrication process with devices more robust to ring-to-waveguide misalignments. Single-mode microring optical channel dropping filters are demonstrated for the first time in this configuration with Qs greater than 3000 and an on-resonance channel extinction greater than 12 dB. A 1×4 multiplexer/demultiplexer crossbar array with second-order microrings was also made and exhibited channel-to-channel crosstalk lower than 10 dB