高成品率砷化镓DPDT单片射频开关

采用砷化镓 76mm 0 .7μm离子注入 MESFET工艺技术研制出手机用砷化镓 DPDT单片射频开关(以下简称单片开关 )。该单片开关面积 1 3 1 0 μm× 1 2 5 0 μm,总栅宽 3 6mm,工作频率 DC～ 2 GHz,1 GHz下插入损耗 IL小于 0 .5 2 d B,隔离度 ISO大于 1 7d B,驻波 VSWR≤ 1 .3 ,2 GHz下 IL小于 0 .7d B,ISO大于 1 1 d B,驻波≤ 1 .3 ,反向三阶交调 PTOI优于 64 d Bm,1 W射频信号下的栅漏电小于 2 0 μA。连续五批共 60片的统计结果表明 ,该单片开关圆片上芯片的直流成品率最低 84 % ,最高 96% ;微波参数成品率在 75 %～ 86%之间 ,代表着国内 Ga As单片电路成品率的最高水平     

大功率短波宽带天线收发开关

为了实现天线收发共用,设计了一种大功率短波宽带收发开关,它主要用于高频雷达和大功率短波通信系统.从提高隔离度的角度提出了以对称式双PIN二极管为核心的开关电路,为了减少收发开关的转换时间、降低功耗和提高其稳定性,提出了单极性脉冲电路作为开关电路的控制脉冲电路,同时提出了接收机和发射机保护电路.在便携式高频地波雷达系统中,单极子/交叉环天线通过大功率短波收发开关实现了一发三收收发共用,简化了便携式高频地波雷达的天线系统,减少了天线的占地面积,同时降低了天线架设的难度,本系统硬件电路简洁,功耗低,工作稳定、可靠.     

Low-insertion-loss DP3T MMIC switch for dual-band cellular phones

We propose a new type of dual-pole triple-throw double heterojunction monolithic microwave integrated circuit (IC) switch for use in digital cellular phones. The IC we developed exhibits a low gate leakage current of 400 nA and an insertion loss as low as 0.4 dB, even at added power of 34 dBm at a frequency of 950 MHz. Measured P_{1 dB} was about 36 dBm, and a low distortion of 65 dBc was also obtained     

应用于大功率MMIC开关的AlGaN背势垒GaN HEMT

报道了应用于大功率开关的AlGaN背势垒0.25μm GaN HEMT。通过引入AlGaN背势垒,MOCVD淀积在3英寸SiC衬底上的AlGaN/GaN异质结材料缓冲层的击穿电压获得了大幅度的提升,相比于普通GaN缓冲层和掺Fe GaN缓冲层击穿电压提升幅度分别为4倍和2倍。采用具有AlGaN背势垒AlGaN/GaN 外延材料研制的GaN HEMT开关管在源漏间距为2μm、2.5μm、3μm、3.5μm和4μm时,估算得到的关态功率承受能力分别为25.0W、46.2W、64.0W、79.2W和88.4W。基于源漏间距为2.5μm的GaN HEMT开关管设计了DC-12GHz的单刀双掷MMIC开关。该开关采用了反射式串-并-并结构,整个带内插入损耗最大1.0dB、隔离度最小30dB,10GHz下连续波测试得到其功率承受能力达44.1dBm。     

Miniaturised microstrip antenna for MMIC applications

A novel miniaturised quarter wavelength, H-shaped antenna which will find applications in monolithic microwave integrated circuit (MMIC) design is presented. The antenna occupies approximately one tenth of the substrate area of a half wavelength patch antenna. The effect on the resonance frequency, bandwidth and gain of the antenna are reported     

High power gate-controlled switch

The ratings of GCS's have remained around 10 amperes and 600 volts since the early 1960's. The problem of increasing the device's capability is therefore reviewed. Experimental results show that turn-off is governed by the diversion of the anode current through the gate,the sequence of junction recovery, the optimum gate drive timing, and the condition of a low impedance drive voltage below the gate avalanche point. Furthermore, the scaling-up for high current assumes that the total current is shared by each elemental area at all times, Tests revealed that nonuiformity leads to shifting of load current during turn-off into on area which causes failure. With due consideration of these factors, a practical design and process for the high power GCS were developed. Data on developmental 50-ampere GCS's are presented.     

An MMIC local oscillator for 16-QAM digital microwave radio systems

The first MMIC local oscillator for 16-QAM digital microwave systems is presented. The key advance is achieving the very low phase noise required by such systems. Low phase noise is realized with a low phase noise VCO (voltage-controlled oscillator) that is installed into a new PLL (phase-locked loop). Although the developed local oscillator is 90% smaller than the existing Dielectric Resonator-based local oscillators, it achieves comparable receiver performance     

Stochastic power control for cellular radio systems

For wireless communication systems, iterative power control algorithms have been proposed to minimize the transmitter power while maintaining reliable communication between mobiles and base stations. To derive deterministic convergence results, these algorithms require perfect measurements of one or more of the following parameters: (1) the mobile's signal-to-interference ratio (SIR) at the receiver; (2) the interference experienced by the mobile; and (3) the bit-error rate. However, these quantities are often difficult to measure and deterministic convergence results neglect the effect of stochastic measurements. We develop distributed iterative power control algorithms that use readily available measurements. Two classes of power control algorithms are proposed. Since the measurements are random, the proposed algorithms evolve stochastically and we define the convergence in terms of the mean-squared error (MSE) of the power vector from the optimal power vector that is the solution of a feasible deterministic power control problem. For the first class of power control algorithms using fixed step size sequences, we obtain finite lower and upper bounds for the MSE by appropriate selection of the step size. We also show that these bounds go to zero, implying convergence in the MSE sense, as the step size goes to zero. For the second class of power control algorithms, which are based on the stochastic approximations method and use time-varying step size sequences, we prove that the MSE goes to zero. Both classes of algorithms are distributed in the sense that each user needs only to know its own channel gain to its assigned base station and its own matched filter output at its assigned base station to update its power     

DC-110-GHz MMIC traveling-wave switch

This paper presents the broadest band monolithic-microwave integrated-circuit traveling-wave switch ever reported for millimeter-wave applications. The developed switch with the novel structure of a 400-μm-gate finger field-effect transistor (FET) indicated an insertion loss of less than 2.55 dB and an isolation of better than 22.2 dB from dc to 110 GHz. Also, the switch indicated no degradation of insertion loss and an ON/OFF ratio of more than 22.7 dB up to an input power of 26.5 dBm at 40 GHz. Circuit analytical results based on a lossy transmission-line model for small-signal performance and circuit simulation results using the two-terminal nonlinear FET model for large-signal operation successfully showed good agreement with the experimental results     

High performance antenna systems for new VOA stations

Advancements in curtain-type high-frequency (HF) broadcast antennas are reviewed. Novel high-performance antennas for the Voice of America (VOA) are described, including vertical and horizontal beam selections, performance measurements, effects of finite ground and hills, radiation hazard zones, and transmission lines. Specifications for antennas to be installed at four new VOA stations are examined. The designs provide substantial flexibility in radiation-beam characteristics with four vertical beam modes and seven horizontal beam angles. it is believed that the technique of selecting the optimum radiation beam for ionospheric propagation to VOA target areas will provide a substantial improvement in the performance     

Capacity of digital cellular TDMA systems

The capacity of digital TDMA (time-division multiple-access) systems is addressed. It is projected that capacity improvement will be of the order of 5-10 times that of analog FM without adding any cell sites. For example, the North American TIA (Telecommunication Industry Association) standard offers around 50 Erlang/km² with a 3-km site-to-site distance. In addition, the TDMA principle allows a faster handoff mechanism (mobile assisted handoff), which makes it easier to introduce microcells with a cell radius of about 200 m. This gives substantial additional capacity gain beyond the 5-10 factor given above. TDMA makes it possible to introduce adaptive channel allocation (ACA) methods. ACA is a mechanism that provides efficient microcellular capacity. ACA also eliminates the need to plan frequencies for cells. It is concluded that the air-interface of digital TDMA cellular may be used to build personal communication networks     

Small-signal switch model of GaN HEMTs for MMIC applications

Gallium nitride (GaN) high electron mobility transistor (HEMT) with symmetrical structure as a control device is discussed in this paper. The equivalent circuit model is proposed on the basis of physical and electrical properties of the GaN HEMT device. A transistor with 0.5 μm gate length and 6 × 125 μm gate width is fabricated to verify the model, which can be treated as a single pole single throw (SPST) switch due to the ON state and OFF state. The measurement results show a good agreement with the simulation results, which demonstrates the effectiveness of the proposed model.     

大功率ESP高频高压电源

针对静电除尘用工频电源存在缺陷,设计了一种静电除尘用高频开关电源,分析了各开关模态,采用基波近似法对LCC谐振变换器进行了分析,并用saber软件进行了仿真验证.仿真结果表明,控制频率与输出电压之间的关系具有非线性特点,越接近谐振频率,这种非线性越明显;电路开始谐振的阶段,谐振电路有明显的电流冲击,这可能会对主回路中的器件特别是IGBT产生较大电流应力.     

Time slot assignment techniques for TDMA digital cellular systems

In TDMA system each channel may have more than one time slot to serve more than one user. Techniques for the assignment of time slots to users while minimizing co-channel interference are important. The paper presents six time slot assignment techniques. A discrete event stochastic simulation study was performed on 120° and 60° sectored systems. The simulation employs the “blocked calls cleared” traffic model and a log-linear path loss propagation model. Only the down link is considered. The results compare the performance of the six techniques and investigates the effect of the number of time slots per frame and the maximum acceptable interference level     

Downlink power control algorithms for cellular radio systems

Power control is an effective technique to reduce cochannel interference and increase capacity for cellular radio systems. Optimum centralized power control can minimize the outage probability, but requires the information of all link gains in real time, which is very difficult to successfully implement for a large system; besides, the computational complexity of an optimum power control algorithm makes it impractical for real implementations. We propose some centralized power control algorithms with reasonable computational complexity. One of the algorithms, called the SMIRA algorithm, has an outage probability that is very close to the minimum. We also study a class of distributed power control algorithms that can achieve a balanced carrier-to-interference ratio with probability one. Among the class of algorithms, we found that the one proposed by Grandhi, Vijayan, and Goodman (1992), gives the minimum outage probability     

Efficient distributed power control for cellular mobile systems

Various distributed carrier-to-interference (C/I) balancing procedures have been developed to cope with implementational drawbacks of centralized power-control schemes. However, it would be inevitable for these distributed schemes to lose some system performance compared to a centralized one since they control their power level based on only the local C/I measurements. An efficient distributed power-control (DPC) scheme is proposed to maximize the system performance. A distributed C/I balancing algorithm is suggested, which converges fast and is robust to C/I estimation errors. A simple instability detection rule is also suggested to accelerate the balancing phase of DPC schemes. Numerical results indicate that our algorithm achieves improvements in terms of the outage probability as well as the algorithm speed. Robustness to the C/I measurement errors is also explored     

Grey-based power control for DS-CDMA cellular mobile systems

The propagation channel of a mobile radio system exhibits severe signal shadowing and multipath fading, which results in wide variation of signal-to-interference ratio (SIR) at the receiver. To tackle this problem, power control is used to maintain the desired link quality and thus achieve higher capacity. In order to mitigate the channel variation effect precisely, a new application of grey theory to the power control strategy in the direct-sequence code-division multiple-access cellular mobile systems is introduced. This scheme aims to predict the SIR affected by the channel variation at the receiver and issue an appropriate control signal to the transmitter. The simulation results indicate that the grey-based scheme can offer less outage probability than the previous mechanisms     

Decentralized dynamic power control for cellular CDMA systems

The control of transmit power has been recognized as an essential requirement in the design of cellular code-division multiple-access (CDMA) systems. Indeed, power control allows for mobile users to share radio resources equitably and efficiently in a multicell environment. Much of the work on power control for CDMA systems found in the literature assumes a quasi-static channel model, i.e., the channel gains of the users are assumed to be constant over a sufficiently long period of time for the control algorithm to converge. In this paper, the design of dynamic power control algorithms for CDMA systems is considered without the quasi-static channel restriction. The design problem is posed as a tradeoff between the desire for users to maximize their individual quality of service and the need to minimize interference to other users. The dynamic nature of the wireless channel for mobile users is incorporated in the problem definition. Based on a cost minimization framework, an optimal multiuser solution is derived. The multiuser solution is shown to decouple, and effectively converge, to a single-user solution in the large system asymptote, where the number of users and the spreading factor both go to infinity with their ratio kept constant. In a numerical study, the performance of a simple threshold policy is shown to be near that of the optimal single-user policy. This offers support to the threshold decision rules that are employed in current cellular CDMA systems.     

基于DSP的大功率数字开关电源设计

结合电力电子技术和嵌入式技术,设计了以全桥隔离式PWM变换器为核心,基于DSP处理器TMS320F2812的高精度大功率数字开关电源.完成了系统硬件电路设计及软件数字PID算法,实现数字化采样、运算、控制输出、系统监控和人机接口等功能.     

Novel power combining technique for MMIC oscillators

A novel method of coherently power-combining four identical monolithic microwave oscillators is presented. This central injection locking scheme achieved a 4.4 dB oscillator output power gain with low noise characteristics. The processing repeatability of the monolithic oscillator minimises the phase adjustments required in power combining.<>