12 Gb/s GaAs PHEMT跨阻抗前置放大器

采用0.5 μ m GaAs PHEMT工艺研制了一种单电源偏置光接收机跨阻抗前置放大器.放大器-3dB带宽约为9.5GHz;在50MHz~7.5GHz范围内,跨阻增益为43.5±1.5dB Ω ,输入输出回波损耗均小于-10dB;带内噪声系数在4dB~6.5dB之间,由此得到的最小等效输入噪声电流密度约为17.6pA/ Hz ;输入12Gb/s NRI伪随机序列时,放大器输出眼图清晰,眼开良好.     

An auto-gain control transimpedance amplifier with low noise andwide input dynamic range for 10-Gb/s optical communication systems

This paper describes a 10-Gb/s transimpedance amplifier (TIA), fabricated in a 0.1-μm-p-HEMT technology. To improve the optical overload characteristics, an automatic gain control (AGC) circuit is included. The measured results show excellent performance, transimpedance of 63.3 dBΩ (1.46 kΩ), bandwidth of 8.0 GHz, and equivalent input noise current density of 6.5 pA/rtHz. When the bit error rate is 10^-9, the minimum sensitivity and the optical overload are -21.2 dBm, +4.3 dBm, respectively, using a 0.8 A/W pin photodiode (PD). The power dissipation is about 0.5 W from a single -5-V supply. The die area is 1.3×1.6 mm²     

HEMT太赫兹探测器响应度和NEP的检测与分析

在0.8～1.1 THz内,对AlGaN/GaN高电子迁移率晶体管(HEMT)太赫兹探测器的响应度和噪声等效功率进行了具体测试和分析。在太赫兹波辐射下,HEMT太赫兹探测器源漏端产生能被栅压灵敏调控的直流光电流。该型探测器在300 K和77 K下的电流响应度分别为83 mA/W和4.1 A/W,电压响应度分别为4 kV/W和50 kV/W,噪声等效功率分别达到22 pW/Hz0.5和1 pW/Hz0.5。采用两种较为典型的测量方法,通过对实验结果的比较,确定了影响该类型探测器的响应度和噪声等效功率的主要因素,并提出了增强响应度和降低噪声等效功率的具体措施。     

Very High Sensitivity Heterodyne Detection of X-Band Radiation with Neon Indicator Lamps

Very high sensitivity with simple inexpensive commercial neon glow lamps designed for indicator-lamp applications is observed at X band in synchronous detection. Typical minimum detectable signals with 10-nW-order local-oscillator powers are 10/sup -17/ W /spl dot/ Hz/sup -1/ or lower. This is equivalent to 10/sup -22/ W /spl dot/Hz/spl -1/ with 1-mW local-oscillator power. As such lamps can be used without damage in high microwave fields, they can be used in principle with appropriate local-oscillator power levels to reach ideal microwave noise equivalent power (NEP) limits. The low NEP and noise figure result from the high responsivities of such devices which are due to high internal signal gain. Experimental results correlate well with the enhanced-ionization collision-rate detection model.     

2.5Gb/s CMOS低噪声有源电感反馈跨阻放大器

分析各种结构前置放大器性能的基础上,给出了一个应用于2.5 Gbit/s光纤通信系统的,基于CMOS工艺的共栅结构跨阻放大器。为了减小输入等效噪声电流和提高带宽,采用了有源反馈和有源电感代替传统结构中的电阻反馈。测试结果表明,该电路具有61.8 dB的跨阻增益,2.01 GHz的带宽,输入等效噪声电流为9.5 pA/Hz～(1/2),核心电路功耗仅为3.02 mW。     

Tuned front-end design for heterodyne optical receivers

A theoretical analysis of the noise performance of optical receivers with front-end tuning, suitable for wideband coherent systems, is presented. An algorithm for choosing the values of the tuning components in the front end so as to minimize the thermal noise output power has been developed. This theory is applied to the well-known simple parallel and serial tuning configurations and also to three more advanced designs. It is shown that any tuning is better than none in the wide-bandwidth designs considered and that the more advanced designs yield up to 12-dB reduction in thermal noise power. Two of the designs can be implemented with discrete components and should yield shot-noise-limited detection with 50-100 μW of local oscillator power in receivers with 5-GHz bandwidth. The practical problem of equalizing the front-end response is considered, and it is shown that good performance can be expected using realizable components     

Experimental linewidth-insensitive coherent analog optical link

We constructed an experimental linewidth-insensitive coherent analog optical link. The transmitter utilizes an external electro-optic amplitude modulator and a semiconductor laser. The receiver consists of a heterodyne front-end, a wideband filter, square law detector and narrowband lowpass filter. We performed experimental measurements and theoretical analyses of the spurious-free dynamic range (SFDR), link gain and noise figure for both the coherent AM and the direct detection links; we investigated the dependencies of the foregoing parameters on the received optical signal power, laser linewidth, IF bandwidth, and the laser relative intensity noise (RIN). By selecting a wide enough bandpass filter, we made the coherent AM link insensitive to laser linewidth. The coherent AM link exhibits a higher SFDR than the corresponding direct detection link when the received optical signal power is less than 85 μW. The noise figure for the coherent link is greater than that for the direct detection link under all conditions investigated. For received optical signal powers greater than 4 μW, the link gain for the direct detection link is greater than that for the coherent AM link. The following are the link parameters that have been achieved for the coherent AM link investigated: SFDR=88 dB·Hz^2/3, link gain=-25 dB and noise figure=78 dB; this performance has been obtained with a received optical signal power of 85 μW, and a local oscillator power at the photodetector of 228 μW. The link performance can be further improved by auxiliary subsystems such as a balanced receiver and impedance matched transmitter and receiver ends; and/or by using better optical and electrical devices like higher power lasers, linearized optical modulators, low-noise and high gain RF amplifiers, and optical amplifiers,     

基于AlGaN/GaN HEMT太赫兹探测器的340 GHz无线通信接收前端

利用天线耦合AlGaN/GaN HEMT太赫兹探测器的自混频和外差混频效应,分别设计并测试了340 GHz频段直接检波式和外差混频式接收机前端。通过接收机信噪比的测量和接收功率的定标,得到了两种接收机的等效噪声功率。直接检波模式下探测器的响应度约为20 mA/W,直接检波模式和外差混频模式下接收机的等效噪声功率分别约为?64.6 dBm/Hz1/2和?114.79 dBm/Hz。在相同的载波功率和接收信号带宽条件下,当本振太赫兹波功率大于?7 dBm时,外差混频接收的信噪比优于直接检波的信噪比。当本振功率大于0 dBm时,外差混频接收机表现出优良的解调特性,其信噪比高出直接检波接收机的信噪比10 dB以上。     

Temperature Dependence of High Frequency and Noise Performance of Sb-Heterostructure Millimeter-Wave Detectors

The temperature dependence of the microwave and noise performance of zero-bias Sb-heterostructure backward diodes for millimeter-wave detection have been investigated experimentally. Both the junction capacitance and junction resistance were found to decrease with decreasing temperature, while the intrinsic cutoff frequency and sensitivity are observed to increase as the temperature is lowered. A simple physical model that captures these effects is described. The directly measured voltage sensitivity at 50 GHz for a 2times2 mum ² device increased from 3650 V/W at room temperature to 7190 V/W at 4.2 K. The measured noise equivalent power (NEP) decreased from 4.2 to 0.2 pW/Hz^1/2 as the temperature was lowered from 298 K to 4.2 K when driven from a 50- Omega source. Based on the measured RF sensitivity, S-parameters, and noise spectrum, a NEP of 0.3 pW/Hz^1/2 is projected for room-temperature operation at zero bias using a conjugately matched RF source     

Enhanced Plasma Wave Detection of Terahertz Radiation Using Multiple High Electron-Mobility Transistors Connected in Series

We report on enhanced room-temperature detection of terahertz radiation by several connected field-effect transistors. For this enhanced nonresonant detection, we have designed, fabricated, and tested plasmonic structures consisting of multiple InGaAs/GaAs pseudomorphic high electron-mobility transistors connected in series. Results show a 1.63-THz response that is directly proportional to the number of detecting transistors biased by a direct drain current at the same gate-to-source bias voltages. The responsivity in the saturation regime was found to be 170 V/W with the noise equivalent power in the range of ${hbox{10}}^{-7}~{hbox{W/Hz}}^{0.5}$ . The experimental data are in agreement with the detection mechanism based on the rectification of overdamped plasma waves excited by terahertz radiation in the transistor channel.      

Low-phase noise AlGaN/GaN FET-based voltage controlled oscillators(VCOs)

The first report of AlGaN/GaN HEMT-based voltage controlled oscillators (VCOs) is presented. Varactor-tuned oscillators implemented using distributed networks oscillate at 6 GHz with high output power (0.5 W), low-phase noise (-92 dBc/Hz SSB noise at 100 kHz offset), and high-tuning bandwidth (10%). The measured phase noise of AlGaN/GaN FETs is compared to the phase noise of GaAs FET and GaAs HBTs at 6 GHz, indicating the AlGaN/GaN FET exhibits equivalent SSB noise to GaAs FETs. These results indicate high power AlGaN/GaN-based VCOs may be used to simplify the line up in a communication radio, while improving the overall efficiency of the radio     

A 4-terminal wide-band monolithic amplifier

A bipolar monolithic amplifier is described which achieves 18 dB gain, 725 MHz-3 dB bandwidth and 4.4 dB noise figure. The circuit is housed in a 4-lead TO-46 package, consumes 180 mW of DC power and requires no external components. Input and output impedances are matched to 50 /spl Omega/ with VSWR less than 1.5 across the band. A high-power version of the circuit consumes 1 W of DC power and gives 152 mW output power at 200 MHz.     

哑铃形高功率全保偏大模场掺镱锁模光纤激光器

采用基于非线性光纤环形镜的哑铃形结构搭建了全光纤全保偏掺镱锁模激光器。通过使用全保偏大模场光纤、高功率光纤器件和优化的腔结构,实现了脉冲宽度在156 ps到8.1 ns范围内可调的高功率、大能量矩形耗散孤子共振脉冲输出,在最大泵浦功率22.7 W下激光器直接输出功率达到5.5 W,脉冲能量达到0.68μJ,峰值功率为84 W。得益于全保偏光纤结构,所设计的激光器具有出色的抗干扰性和稳定性。     

1 GHz low loss coupled resonator filter using surface skimming bulk waves and Bleustein-Gulyaev waves

A three-pole coupled resonator filter (CRF) based on the simultaneous excitation of surface skimming bulk waves (SSBW) and Bleustein-Gulyaev waves (BGW) with the same magnitude is described. This device operates at 1 GHz, has an insertion loss of 3-4 dB, a typical 1 dB bandwidth of 0.15% and can dissipate a power of more than 2 W on a quartz substrate area of 3 mm/sup 2/.<>     

2.5W低噪声CMOSD类音频功放设计

提出了一种基于0.5μm5VCMOS工艺的低噪声PWM调制D类音频功率放大器。该放大器在5V电源电压下以全桥方式可以驱动4Ω负载输出2.5W功率;转换效率等于87%,信噪比达94dB(负载8Ω,输出功率1W);THD+N仅0.05%(负载4Ω,输出功率1W);PSRR为68dB(频率1kHz)。分析了整体电路结构及其线性化模型,并着重介绍了高性能前置斩波稳定运算放大器(开环增益117dB,等效输入噪声16μV.Hz-1/2),线性三角波振荡电路(斜率偏差仅±0.2%)和功率器件、驱动电路的设计。最后给出了D类放大器的测试结果。     

Ultralow leakage In/sub 0.53/Ga/sub 0.47/As p-i-n photodetector grown on linearly graded metamorphic In/sub x/Ga/sub 1-x/P buffered GaAs substrate

A novel top-illuminated In/sub 0.53/Ga/sub 0.47/As p-i-n photodiodes (MM-PINPD) grown on GaAs substrate by using linearly graded metamorphic In/sub x/Ga/sub 1-x/P (x graded from 0.49 to 1) buffer layer is reported. The dark current, optical responsivities, noise equivalent power, and operational bandwidth of the MM-PINPD with aperture diameter of 60 /spl mu/m are 13 pA, 0.6 A/W, 3.4/spl times/10/sup -15/ W/Hz/sup 1/2/, and 7.5 GHz, respectively, at 1550 nm. The performances of the MM-PINPD on GaAs are demonstrated to be comparable to those of a similar device made on InGaAs-InP substrate.     

Coding of optical on-off keying signals impaired by phase noise

The benefits of coding for an optical communication system that employs binary on-off keying and heterodyne detection are quantified. The system is impaired by laser phase noise as well as by additive white Gaussian noise (AWGN). A receiver structure especially designed to mitigate the effects of phase noise in the presence of AWGN is assumed. This special receiver structure requires a wider-band front-end IF filter than would be required for a phase-noise-free signal. The results, computed for several different coding schemes, indicate that the benefits of coding are large and the costs are small. For a linewidth-to-bit-rate ratio (βT) of 0.64 (for example, 45 Mb/s and 29 MHz linewidth), a half-rate binary code that can correct 3 bit errors provides a 50% reduction in the required IF filter bandwidth (and, therefore, the required IF) and about 5 dB of reduction in required laser power. The benefits of coding are greatest under high-βT conditions, corresponding to low bit rates where coders and decoders are most practical to implement     

20GHz宽带GaAs PHEMT分布式前置放大器

采用0.5μm GaAs PHEMT工艺研制了一种光接收机分布式前置放大器.该放大器-3dB带宽接近20GHz,跨阻增益约46dBΩ;在50MHz~16GHz范围内,输入、输出电压驻波比(VSWR)均小于2;带内噪声系数在3.03~6.5dB之间,平均等效输入噪声电流密度约为14.6pA/ Hz ;在输入10Gb/s非归零(NRZ)伪随机二进制序列(PRBS)信号下,放大器输出眼图清晰,具有12ps的定时抖动和166mV峰峰电压.     

10Gb/s GaAs PHEMT电流模跨阻抗光接收机前置放大器

采用0.5μm GaAs PHEMT工艺研制了一种单电源共栅电流模跨阻抗前置放大器(TIA).测量得到放大器-3dB带宽为7.5GHz,跨阻增益为45dBΩ;输入输出电压驻波比(VSWR)均小于2;等效输入噪声电流谱密度在14.3～22pA/ Hz之间,平均值为17.2pA/ Hz.在输入10Gb/s非归零(NRZ)伪随机二进制序列(PRBS)信号下,放大器输出眼图清晰,具有14ps的定时抖动和138mV的峰峰电压.     

硅微陀螺仪接口位移噪声对检测性能的影响

研究了基于调制解调的硅微陀螺仪检测信号提取原理,推导了开环检测传递函数。根据调制解调的频谱转移特性,提出了有效位移噪声是高斯窄带噪声。推导了开环检测时位移噪声的等效角速度公式,分析表明,要提高噪声性能可以减小噪声功率密度、带宽和增加陀螺仪机械灵敏度。同时还推导了闭环检测时位移噪声的等效角速度公式。通过比较开环检测和闭环检测情况下由接口位移噪声导致的噪声等效角速度表明:闭环检测并不能减少由接口位移噪声导致的平均噪声等效角速度。据此设计实际电路,试验结果表明在100Hz频段内,闭环检测噪声谱密度基本等于开环检测噪声谱密度,验证了理论的正确性。