Ka 波段应用的捷变频高频率分辨率频率合成器

传统基于锁相环(PLL)实现带宽信号输出的频率合成方案,常常为了获得高输出频率而降低频率分辨率和缩短跳频时间。相较而言,基于直接数字频率合成器(DDS)实现带宽信号输出的频率合成方案,其频率分辨率更高,跳频时间更快。然而,DDS 输出频率低,须经多次混频或倍频操作以提升输出频率,对频率源中的滤波器设计造成极大压力,并且这种压力随着频率源输出频率的升高而不断上升。对此,基于高性能、小型化无源滤波器的设计能力,实现了基于DDS 变频的34-35GHz 捷变频、高频率分辨率频率源。实验结果表明,其工作相位噪声优于-85dBc/Hz@1kHz,杂散和谐波抑制优于45 dBc,频率分辨率达到1.86Hz,跳频时间最快4ns。     

基于InP HBT工艺的高功率高谐波抑制W波段宽带八倍频器MMIC

基于0.7μm InP HBT工艺,设计实现了一种高功率高谐波抑制比的W波段倍频器MMIC。电路二倍频单元采用有源推推结构,通过3个二倍频器单元级联形成八倍频链,并在链路的输出端加入输出缓冲放大器,进一步提高倍频输出功率。常温25℃状态下,当输入信号功率为0 dBm时,倍频器MMIC在78.4~96.0 GHz输出频率范围内,输出功率大于10 dBm,谐波抑制度大于50 dBc。芯片面积仅为2.22 mm²,采用单电源+5 V供电。     

A direct digital synthesizer with a tunable error feedbackstructure

A basic premise for a direct digital synthesizer (DDS) with error feedback (EF) is that the output frequency being generated is low with respect to the clock frequency used. This is necessary because the transfer function of the EF has zero(s) at DC. In the proposed architecture the clock frequency need only be much greater than the bandwidth of the output signal, whereas the output frequency could be any frequency up to somewhat below the Nyquist frequency. In this novel method, the coefficients of the EF filter are tuned according to the output frequency     

Fully integrated SiGe VCOs with powerful output buffer for 77-GHz automotive Radar systems and applications around 100 GHz

It is demonstrated that SiGe bipolar technologies are well suited for voltage-controlled oscillators (VCOs) in 77-GHz automotive radar systems. For this, the design of a VCO with powerful output buffer (with good decoupling capability and high output power), comparatively wide tuning range, and reasonably low phase noise is described. To achieve the required high output power, the potential operating range of the output transistors, limited by high-current effects and avalanche breakdown, respectively, had to be exploited using adequate transistor models. The VCOs need a single supply voltage only and have been fully integrated (including resonant circuit and output buffer) on a single small (1 mm/sup 2/) chip, demonstrating their low-cost potential. Experimental results showed, at a center frequency of around 77 GHz, a usable tuning range of 6.7 GHz and a phase noise of -97 dBc/Hz at 1-MHz offset frequency averaged over this range. In addition, the center oscillation frequency can be coarsely adjusted within a wide range by cutting links in the upper metallization layer. The total signal power delivered by both buffer outputs together is as high as 18.5 dBm at a power consumption of 1.2 W. Simulations let us expect a potential doubling of the output power (for two or four outputs) by extension of the output buffer. To get an impression of the maximum frequency achievable with the circuit concept and technology used, a second VCO (again with buffered output) has been developed. To the best of the authors' knowledge, the measured maximum oscillation frequency of about 100 GHz, at 12.4-dBm total output power (14.3 dBm at 99 GHz), is a record value for SiGe VCOs with buffered output operating at their fundamental frequency. The usable tuning range is still 6.2 GHz.     

A MEMS-based piezoelectric power generator array for vibration energy harvesting

Piezoelectric power generator made by microelectromechanical system (MEMS) technology can scavenge power from low-level ambient vibration sources. The developed MEMS power generators are featured with fixed/narrow operation frequency and power output in microwatt level, whereas, the frequency of ambient vibration is floating in some range, and power output is insufficient. In this paper, a power generator array based on thick-film piezoelectric cantilevers is investigated to improve frequency flexibility and power output. Piezoelectric cantilevers array has been designed and fabricated. The cantilevers array can be tuned to the frequency and expanded the excited frequency bandwidth in ambient low frequency vibration. Serial connection among cantilevers of the array is investigated. The prototype generator has a measured performance of 3.98 μW effective electrical power and 3.93 DC output voltage to resistance load. This device is promising to support networks of ultra-low-power, peer-to-peer, wireless nodes.     

TM310高次模圆柱形谐振腔耦合矩形波导输出回路研究

设计了适用于多注速调管,工作在TM310高次模圆柱形谐振腔耦合矩形波导输出回路,其工作中心频率为7 585.3 MHz,计算了腔体内各漂移管间隙阻抗的频率特性,并分析了输出回路的输出带宽.研究结果表明: 在相同频率条件下,采用圆柱形TM310工作模式的谐振腔体积将是采用圆柱形TM010工作模式谐振腔体积的7倍;TM310高次模圆柱形谐振腔耦合矩形波导后,各漂移管特性阻抗与耦合前相比有稍微变化,但耦合后各间隙特性阻抗非常接近;反射系数相位法及等效电路法计算输出腔外观品质因数分别为为154和160,输出中心频率7 585.263 MHz,比耦合前腔体谐振频率降低26.525 MHz,输出带宽约为3%,因此,该类型输出回路比较适合用作高射频段的窄带多注速调管.     

260 GHz GaN高功率三倍频器设计

基于GaN太赫兹二极管芯片,采用非平衡式电路结构,设计了一款260 GHz三倍频器。采用GaN肖特基二极管芯片提高电路的耐受功率和输出功率;采用“减高+减宽”的输出波导结构抑制二次谐波;采用高低阻抗带线结构设计了倍频器的输入滤波器和输出滤波器。测试结果显示,该三倍频器在261 GHz峰值频率下,实现最大输出功率为69.1 mW,转换效率为3.3%,同时具有较好的谐波抑制特性。     

多倍直流偏置电压对碳纳米管薄膜声源的影响

针对碳纳米管薄膜声源系统的输出声信号频率失真问题,提出在交流信号上施加多倍直流偏置电压的方法。从热致发声原理入手,利用碳纳米管薄膜声压理论,分析出增加多倍直流偏置电压后,输出信号中的一倍频与二倍频声压幅值,并探究两者幅值比变化规律。实验结果表明,随着输入频率和直流偏置电压增加,输出声信号中两者幅值之比亦增加,当直流偏置电压是交流电压的两倍后,输出声信号波形与输入电信号近似一致,较好地解决了频率失真问题;同时,输出声压级也有较大幅度提升。     

基于FPGA和DDS的声光调制器驱动电路的实现

以La~(3+)和Nb~(5+)分别为A、B位不等价取代离子,研究了A、B位不等价离子掺杂引起的空位比对[(Pb_(0.93)La_(0.07))1-αα][(Zr1-y-zTiyNbz)1-ββ]O3(PLZTN)陶瓷性能的影响,并找出了A、B位同时掺杂取代时影响锆钛酸铅(PZT)陶瓷性能的关键因素。在该文的y、z、α、β取值范围内制备出的压电陶瓷均具有较纯净的钙钛矿结构,表现出弛豫铁电体特性。当摩尔比r(Ti)/r(Zr)=39/61,Nb在B位的摩尔分数z=0.02,空位比α/β=2/1时,陶瓷样品具有最佳的压电性能:压电应变常数d33=800pC/N,平面机电耦合系数kp=71.85%。该陶瓷样品具有较大的电致伸缩系数。以其制作的0.22mm×7.8mm×45mm压电片的横向机电耦合系数k31达0.46。该陶瓷片组装的双晶片在180V电压驱动下,其悬臂梁结构的自由端推力为32g,空载位移量为0.8mm。该材料是纺织经编机压电贾卡制造的较理想材料。     

Millimeter Wavelength Frequency Multipliers

Mechanically tuneable millimeter wavelength frequency doublers typically exhibiting 10-percent conversion efficiency at any output frequency in the range 100-260 GHz have been fabricated. Output power varies from 10 mW at 100 GHz to 6 mW at 260 GHz, with a fixed tuned instantaneous 1-dB bandwidth typically 5 percent of the center frequency. A frequency tripler to 215-GHz output frequency is also described. For this device, a mechanically tuneable 3-dB bandwidth of 210 to 240 GHz was obtained, with a peak conversion efficiency of 6 percent at 4.8-mW output power.     

Buried-channel GaAs MESFET's with frequency-independent output conductance

The output conductance of GaAs MESFET's is shown to be a function of frequency and to have a well-defined temperature dependence. This behavior is in agreement with other reports of the behavior of GaAs ion-implanted MESFET's. The output conductance of buried-channel GaAs MESFET's is shown to be independent of frequency and temperature. This is an important improvement in the output characteristics with many implications for GaAs analog and digital circuits.     

FDA最优频率增量选取必要性分析

在干扰背景下,深入研究了频率分集阵列（FDA）雷达选取最优频率增量的必要性。在采用最优波束形成算法进行抗干扰的前提下,推导出目标与干扰的位置关系对FDA雷达输出信干噪比（SINR）的影响,进而分析输出SINR与频率增量的关系,并得出结论：在只有副瓣干扰的情况下,可不进行最优频率增量的选取,采用常规固定的频率增量也能输出高SINR;而当存在主瓣干扰时,不当的频率增量会使得输出SINR急剧下降并形成凹陷,且这种凹陷会随着频率增量的选取呈现周期性变化,极大地影响了FDA雷达的目标检测性能。计算机仿真也验证了这种周期性的凹陷变化,这表明了FDA雷达在抗主瓣干扰时必须进行最优频率增量选取。     

Analysis of phase-controlled resonant DC-AC inverters with class Eamplifier and frequency multipliers

This paper presents a minute analysis and experimental results of phase-controlled resonant DC-AC inverters with class E amplifiers and frequency multipliers. The circuit is composed of two identical class E amplifiers or frequency multipliers, which are used as DC-AC inverters and connected in parallel. The two inverters are driven at the same switching frequency, and the overall output power of the circuit can be controlled by varying the phase shift between the drive voltages of the two inverters. The circuit can regulate the output voltage at a constant switching frequency. The measured efficiency was over 93% at an output power of 0.98 W and a switching frequency of 0.5 MHz for both of the inverters with amplifier and frequency doubler     

C波段宽带下变频型锁相高速跳频合成器

介绍了一种C波段宽带下变频型锁相高速跳频合成器,主要用于雷达及通信领域。该频率合成器采用锁相环(PLL)与外插电路组合的方式,将较高的输出频率迁移到较低频率后送至鉴相器,大大降低N分频器的工作频率,提高了频率合成器的最高输出频率,且输出频率间隔不变,解决了提高合成器输出频率和不降低频率分辨率的矛盾,实现低相位噪声输出。测试结果表明,输出频率4 460 MHz时,在频偏10 kHz处相位噪声为-123 dBc/Hz。采用可控输出的稳压芯片给HMC704LP4供电,通过控制电源的通断,保证HMC704LP4进入正确的工作模式,有效解决了HMC704LP4上电模式选择错误造成的失锁问题。     

L波段多注速调管同轴线滤波器宽带输出回路的研究和设计

该文设计了一个相对工作带宽超过14％、可用于L波段多注速调管的宽带输出回路四耦合槽模强耦合双间隙腔加载同轴线滤波器,并对其进行详细地分析和计算。研究结果表明,在较低频率波段宽带速调管中,采用同轴线滤波器的宽带输出回路是完全可行的,并且具有更大的输出带宽潜力和较小的体积,特别有利于整管的小型化。     

Very-high-rank avalanche diode frequency multiplier

Recent experimental observations on silicon avalanche diode multipliers operated at about 35-GHz output frequency are presented. High-rank (up to 35) frequency multiplication is achieved with output power over 250 mW and conversion loss of 13 dB. The possibility of frequency multiplication by any integer n ranging from 8 to 35 with the same diode and without any idler circuit is pointed out. It is concluded that any output frequency can be selected between 28 and 39 GHz by varying the input frequency and the circuit tuning.     

Improved frequency tripler with integrated single-barrier varactor

A monolithically integrated frequency tripler on semi-insulating GaAs substrate with a 210 GHz output frequency is presented. The measured conversion efficiency using a GaAs-GaAlAs single-barrier varactor is 13.5%, with an output power of >10 mW     

多阳极220 GHz倍频器单片设计

介绍了一款基于GaAs肖特基二极管单片工艺的220 GHz倍频器的设计过程以及测试结果。为提高输出功率,倍频器采用多阳极结构,8个二极管在波导呈镜像对称排列,形成平衡式倍频器结构。采用差异式结电容设计解决了多阳极结构端口散射参数不一致问题,提高了倍频器的转换效率和工作带宽。对设计的倍频器进行流片、装配和测试,测试结果显示：倍频器在204~234 GHz频率范围内,转化效率大于15%;226 GHz峰值频率下实现最大输出功率为90.5 mW,转换效率为22.6%。设计的220 GHz倍频器输出功率高,转化效率高,工作带宽大。     

Bandpass sampling criteria for nonlinear systems

Sampling criteria for nonlinear systems with a band-pass input are developed in this paper. It is well known that nonlinear systems may produce an output signal with a larger bandwidth than that of their input signal. According to the Nyquist sampling theorem, the sampling rate needs to be at least twice the maximum frequency of the output signal; otherwise, the sampled output would be aliased. However, if the input is a bandpass signal, the spectrum of the output signal often occupies multiple frequency bands. In this case, it is possible, by using the bandpass sampling concept, to sample the output signal at a rate much lower than the Nyquist sampling frequency. In this paper, all conditions in which bandpass sampling can be achieved are derived for nonlinear systems up to the third order. Furthermore, for nonlinear systems higher than the third order, some conditions in which bandpass sampling can be guaranteed are derived. The result can be used to choose an appropriate sampling frequency for nonlinear systems of an arbitrary order     

A 125-260-GHz Gyrotron

The second gyrotron constructed at the University of Sydney has produced continuous microwave output at more than 60 frequencies in the range 125-260 GHz at power levels approaching 10 W. A gyrotron Iike this, with broad frequency coverage and moderate power output, has a wide range of possible applications, from spectroscopy to scattering from waves and fluctuations in plasmas. In this paper, the results of detailed measurements of frequency, magnetic field, frequency pulling, and starting current are compared with theory. Agreement is excellent. We find that mode conversion at the output end of the cavity determines the level of output power.