A 186 to 212?GHz Downconverter in 90?nm CMOS

The design and measurements of a 200?GHz downconverter in 90?nm standard CMOS are presented. A positive conversion gain of +6.6?dB, a noise figure of 29.9?dB and an output bandwidth of 3?GHz are measured for an LO power of ?14.9?dBm. The conversion gain remains within 3?dB for an RF frequency between 186 and 212?GHz. Downconversion of BPSK and QPSK signals is demonstrated with eye diagrams and constellation plots with data rates over 4?Gbit/s. A mathematical analysis is made of the MOSFETs in the triode region and a new small-signal parameter κ is introduced, which enables the design of the mixing transistors for minimum conversion loss.     

Small signal analysis of THz optical-frequency conversion in aninjection-locked semiconductor laser

A theory of terahertz optical-frequency conversion using highly nondegenerate four-wave mixing (FWM) in an injection-locked semiconductor laser is presented, using small-signal analysis. The optical frequency conversion can be realized through the use of cavity-enhanced highly nondegenerate FWM in an injection-locked semiconductor laser in a range of 1-THz detuning frequency between the pump and the probe waves, when the probe frequency is tuned close to one of the resonance modes. The frequency conversion is mainly attributed to the nonlinear gain effect. The maximum bandwidth of the converted signal is increased by shortening the laser cavity length. The frequency conversion efficiency is asymmetrical with respect to both the zero detuning frequency and the resonance mode where the converted signal appears. The theoretical results agree with experiments     

InAlAs/InGaAs/InP基PHEMTs小信号建模及低噪声应用

利用改进的小信号模型对采用100nmInAlAs/InGaAs/InP工艺设计实现的PHEMTs器件进行建模, 并设计实现了一款W波段单片低噪声放大器进行信号模型的验证。为了进一步改善信号模型低频S参数拟合差的精度, 该小信号模型考虑了栅源和栅漏二极管微分电阻, 在等效电路拓扑中分别用Rfs和Rfd表示.为了验证模型的可行性, 基于该信号模型研制了W波段低噪声放大器单片.在片测试结果表明:最大小信号增益为14.4dB@92.5GHz, 3dB带宽为25GHz@85-110GHz.而且, 该放大器也表现出了良好的噪声特性, 在88GHz处噪声系数为4.1dB, 相关增益为13.8dB.与同频段其他芯片相比, 该放大器单片具有宽3dB带宽和高的单级增益.     

Novel high-gain, improved-bandwidth, finned-ladder V-bandtraveling-wave tube slow-wave circuit design

In this paper, the three-dimensional electrodynamic simulation code MAFIA (Solution of MAxwell's Equations by the Finite-Integration-Algorithm) is used to investigate methods of increasing the bandwidth and lowering the operating voltage of the ring-plane circuit. Calculations of frequency-phase dispersion, beam on-axis interaction impedance, attenuation, and small-signal gain per wavelength were performed for various geometric variations and loading distributions of the ring-plane TWT slow-wave circuit. Based on the results of the variations, a circuit termed the finned-ladder TWT slow-wave circuit was designed and is compared here to the scaled prototype ring-plane and a conventional ferruled coupled-cavity TWT circuit over the V-band frequency range. The simulation results indicate that this circuit has a much higher gain, significantly wider bandwidth, and a much lower voltage requirement than the scaled ring-plane prototype circuit, while retaining its excellent thermal dissipation properties. The finned-ladder circuit has a much larger small-signal gain per wavelength than the ferruled coupled-cavity circuit, but with a moderate sacrifice in bandwidth     

（英）D波段InP基高增益、低噪声放大芯片的设计与实现

利用90-nm InAlAs/InGaAs/InP HEMT工艺设计实现了两款D波段（110~170 GHz）单片微波集成电路放大器。两款放大器均采用共源结构,布线选取微带线。基于器件A设计的三级放大器A在片测试结果表明：最大小信号增益为11.2 dB@140 GHz,3 dB带宽为16 GHz,芯片面积2.6×1.2 mm2。基于器件B设计的两级放大器B在片测试结果表明：最大小信号增益为15.8 dB@139 GHz,3dB带宽12 GHz,在130~150 GHz频带范围内增益大于10 dB,芯片面积1.7×0.8 mm2,带内最小噪声为4.4 dB、相关增益15 dB@141 GHz,平均噪声系数约为5.2 dB。放大器B具有高的单级增益、相对高的增益面积比以及较好的噪声系数。该放大器芯片的设计实现对于构建D波段接收前端具有借鉴意义。     

Two-stage dielectric-loading for broadbanding a gyro-TWT

A scheme of dielectric-loading for a gyro-traveling wave tube (gyro-TWT) is proposed for a wider bandwidth at a higher gain. The method uses two-section dielectric-loaded cylindrical waveguide as the interaction structure, with the first section overloaded to exhibit a valley between the two peaks in the gain-frequency response, while the other suitably loaded to exhibit a single peak centered at the valley so as to yield an overall wideband response. A bandwidth ~8.8% at a relatively high small-signal gain ~30 dB is predicted     

Theoretical power output and bandwidth of traveling-wave amplifiers

Expressions are developed to calculate the theoretical power output of traveling-wave amplifiers using any type of RF structure. Calculations are made for helix-type tubes and it is shown how to calculate the power output of tubes using more dispersive structures in terms of calculations made for helix tubes. The principal factors accounting for higher power output of dispersive structures are presented and discussed. The gain and bandwidth of forward-wave helix amplifiers are derived from the small-signal theory as functions of frequency and it is shown that the gain in db times the frequency bandwidth is a constant as a function of helix length for highgamma_{0}a'and the gain times the bandwidth squared is a constant for lowgamma_{0}a'.     

High output power from an efficient praseodymium-doped fluoridefiber amplifier

A praseodymium doped fluoride fiber amplifier (PDFFA) exhibiting efficient operation in both the large- and the small-signal regimes is described. The amplifier, based on a high NA fluoride fiber, exhibited a maximum small-signal gain of 29 dB and a low-pump small-signal. efficiency of 0.13 dB/mW. In the saturated regime a maximum output power of 212 mW was achieved. In this format, the signal-out versus pump-in characteristic, exhibited a slope efficiency of 30%, representing the most efficient conversion from pump to signal yet reported. Detailed spectral characterization reveals small-signal gain in excess of 20 dB over a wavelength range of almost 50 nm and in excess of 100 mW of saturated output available over a 30-nm wavelength range     

Influence of gain saturation, gain asymmetry, and pump/probedepletion on wavelength conversion efficiency of FWM in semiconductoroptical amplifiers

The effects of gain saturation, gain asymmetry, and pump/probe depletion on the conversion efficiency of four-wave mixing (FWM) in semiconductor optical amplifiers are studied analytically and numerically. The power dependence of FWM coupling coefficients and ultrafast relaxation-related gain mechanisms are included in the model. By studying the FWM efficiency in the transition from unsaturated to strongly saturated regions, it is seen that gain asymmetry results in deviation from small-signal models when the pump-probe detuning and pump powers are small. At high pump injection or gain conditions, it is also shown that the small-signal model breaks down even for relatively large detuning frequencies. Probe depletion is also seen to be critical under saturated conditions and an upper bound is derived for ranges of input pump power, pump-probe detuning, and gain for a given amplifier under which the small-signal model is valid     

Effect of linear gain saturation on small-signal dynamics of MQWDFB lasers

The linear gain saturation effect is shown to be important in determining the dynamics of multiple-quantum-well (MQW) distributed-feedback (DFB) lasers. A more realistic logarithmic dependence of material gain on carrier density is assumed in a comprehensive MQW DFB laser model. It is found through simulation that because of the linear gain saturation, the interplay between modal gain and differential gain leads to an optimal κL for maximum small-signal modulation bandwidth in λ/4-shifted MQW DFB lasers     

Gain-Bandwidth Properties of a Class of Matched Feedback Amplifiers

This paper considers the analysis and synthesis of small-signal feedback amplifiers which use shunt feedback around a generic gain block. The analysis presented leads to estimates of all network element values and predicts the closed-loop broad-band gain, bandwidth and quality of match at both ports. The tradeoff of gain for quality of match is made evident by a graphical technique. The paper also describes, a synthesis method and two illustrative design examples.     

Analysis of helical waveguide

The dispersion characteristics of the large-diameter helical waveguide are calculated using Pierce's small-signal theory. The backward wave oscillation poses a serious problem for the development of this circuit as a broad-band high-gain amplifier. The gain of the backward waves is in general higher than the gain of the forward waves. For the first space harmonic (m = 1) mode, the forward and the backward wave gains are, respectively, 2.17 and 2.24 dB/cm. The bandwidth is 40 percent for a total gain of 30 dB if the backward waves are ignored. The onset of the backward wave oscillation limits the bandwidth to 5 percent for such high gain. The threshold interaction length for the onset of oscillation is also calculated. If the oscillations are not suppressed, the total gain of the circuit is limited to about 12 dB. At this low gain, the bandwidth can be as high as 57 percent. The device performs better with the low-order space-harmonic modes. Not only are the gain and the bandwidth larger for the low-order modes, but the ratio of the backward to forward wave gains and the number of backward waves excited are also smaller.     

High-gain broad spectral bandwidth erbium-doped fibre amplifier pumped near 1.5 mu m

A small-signal gain exceeding 25 dB, and a 3 dB spectral bandwidth of 35 nm around 1.545 mu m are obtained for an erbium-doped silica fibre amplifier pumped in the short wavelength wing of the 1.5 mu m absorption band.<>     

Dynamics and Temperature-Dependence of 1.3-μm GaInNAs Double Quantum-Well Lasers

We have measured the small-signal modulation response of 1.3-mum ridge waveguide GaInNAs double quantum-well lasers over a wide range of temperatures (25 degC-110 degC) and analyzed the temperature dependence of the modulation bandwidth and the various bandwidth limiting effects. The lasers have low threshold currents and high differential efficiencies with small temperature dependencies. A short-cavity (350 mum) laser has a modulation bandwidth as high as 17 GHz at room temperature, reducing to 4 GHz at 110 degC, while a laser with a longer cavity (580 mum) maintains a bandwidth of 8.6 GHz at 110 degC. We find that at all ambient temperatures the maximum bandwidth is limited by thermal effects as the temperature increases with current due to self-heating. The reduction and subsequent saturation of the resonance frequency with increasing current is due to a reduction of the differential gain and an increase of the threshold current with increasing temperature. We find large values for the differential gain and the gain compression factor. The differential gain decreases linearly with temperature while there is only a weak temperature dependence of the gain compression. At the highest temperature we also find evidence for transport effects that increase the damping rate and reduce the intrinsic bandwidth     

Demonstration of enhanced performance of an InP/InGaAsheterojunction phototransistor with a base terminal

The optical gain and the small-signal frequency response of an InP/InGaAs heterojunction phototransistor (HPT) with a base terminal are investigated in detail for the first time. When operated under an optimally chosen external base current, the optical gain is enhanced more than five times over that of the same device operated as a two-terminal device, over a 17-dB range of input optical power. The small-signal 3-dB bandwidth of the three-terminal device is enhanced 15 times over that of the two-terminal device over the same range of input optical power. For a pseudorandom NRZ bit stream at 100 Mb/s, a clear eye opening is observed at an incident optical power of -33 dBm (500 nW)     

A high-gain 50-GHz-band monolithic balanced gate mixer with anexternal IF balun

This paper presents a 90-GHz-band high-gain monolithic balanced gate mixer. IF impedance of the balanced gate mixer is approximated from a small-signal equivalent circuit, and conversion gain of the mixer is improved by using an external IF balun with high impedance-transforming ratio. The maximum conversion gain of 8.2 dB is achieved at LO power of 0 dBm. Effectiveness of the described mixer is confirmed experimentally     

Small-signal response of 1.3-/spl mu/m InAsP-InGaAsP quantum-well laser diodes obtained with a terahertz-bandwidth frequency comb

We describe an optical method to carry out small-signal frequency response measurements in laser diodes. This method uses a midinfrared tunable femtosecond optical parametric oscillator (OPO), whose frequency spectrum consists of a comb composed by the multiple harmonics of the 81-MHz repetition rate of the same intensity and extending over 2 THz. Tuning of the OPO allows selective generation of carriers in the different regions of the test laser active area without compromising the frequency bandwidth. The small-signal frequency response of the test laser is retrieved from the intensity changes in the frequency comb spectrum. We apply this method to investigate the small-signal frequency response of 1.3-/spl mu/m InAsP quantum-well (QW) lasers. The results of these experiments show that the intrinsic frequency bandwidth of these lasers is limited to less than 10 GHz as a result of state filling and related carrier escape out of the well. An analysis of the frequency response traces through a solution of a system of rate equations allows us to estimate the magnitude of the gain compression associated with this process.     

An analytic and experimental comparison of direct and externalmodulation in analog fiber-optic links

Analytic lumped-element small-signal models of directly and externally modulated analog fiber-optic links are derived. Incremental modulation efficiency is defined and used to compare the performances of these modulation techniques. In experiments to optimize link RF-to-RF gain and noise figure, the measurements obtained agreed with calculations to within ≈1 dB. The externally modulated link was operated with two different impedance matching circuits. With a low-pass match the bandwidth was 150 MHz, and the link transducer gain was 1 dB; with a bandpass match the bandwidth was 22 MHz, the link transducer gain was 11 dB, and the noise figure was 6 dB. The directly modulated link was operated with a low-pass match. In this case, the bandwidth was 1 GHz, the link transducer gain was -14 dB, and the noise figure was 33 dB. These experimental results were achieved with no amplification,     

多单元压电陶瓷类变形镜高压驱动电源

针对变形镜压电陶瓷类驱动器单元数多的特点,设计一种高带宽适合扩展成多通道输出的压电陶瓷驱动电源,它利用光耦分相隔离从源极驱动功率NMOS管,简化了电路结构并保证了功率带宽。该驱动电源驱动100 nF容性负载时,可实现单端到地-300~＋300 V双极性高压输出,电压增益35.5 dB,信号不失真情况下,小信号响应频率达10 kHz,大信号响应频率2 kHz,瞬时充放电电流可达400 mA。实验表明该驱动电源的性能能够满足变形镜驱动的要求且电路结构简单。     

Effect of gain and index nonlinearities on single-mode dynamics insemiconductor lasers

The finite intraband relaxation time in semiconductor lasers leads to gain saturation at high laser powers. The nonperturbative solution of the single-mode density-matrix equations shows that both the optical gain and the refractive index become intensity dependent as a result of intraband relaxation dynamics. Gain and index nonlinearities are included in the rate equations, and how the modulation response and noise characteristics of semiconductor lasers are affected by such nonlinearities is studied. The intensity dependence of the frequency and the damping rate of relaxation oscillations leads to a fundamental limit imposed on the small-signal modulation bandwidth; the analysis provides an expression for the ultimate modulation bandwidth in terms of the material parameters