WCDMA系统中基于多普勒频移估计的信道估计方法

Rake接收机是CDMA系统抗多径的有效手段，信道估计对其性能有很大的影响。传统方法是利用连续多个时隙的导频段估计出的信道参数，再对估计值进行平均。这种固定平均的方法不适合3G系统信道变化范围大的环境。本文提出了直接利用每个导频段的信道参数的包络来估计最大多普勒频移，再运用指数平滑法来调整各被估计时隙的权值的信道估计方法。仿真结果表明，该方法能准确有效地估计出信道参数，改善系统性能。     

基于晶振倍频鉴相的C波段低相噪频率源设计

针对数字锁相技术相位噪声的构成和特性进行了探讨与研究,并在对比传统单环锁相方案的基础上,介绍了一种基于晶振倍频信号作为参考进行鉴相的低相噪频率合成器。经测试,传统锁相方案在输出6 480 MHz时,相位噪声为?109.1d B/Hz@10 k Hz。而本文设计的低相噪频率源在使用同样的参考晶振、锁相环芯片以及压控振荡器的情况下,输出相同频率时,相位噪声相比传统方案改善了约8 d B。     

A ring oscillator based frequency synthesizer without using frequency divider

A novel indirect frequency synthesizer (FS) circuit comprising a multiplexer (MUX) controlled ring oscillator (RO) and a Hogge phase detector has been proposed. The circuit will synthesize signals having better spectral purity and will consume less power compared to conventional indirect FS circuits. The MUX controlled RO will provide higher flexibility in frequency control and the voltage controlled oscillator (VCO) sensitivity can be varied easily to keep loop gain fixed for different values of synthesized signal frequencies. Hardware experimental results have been given to establish theoretical anticipations.     

一种基于倍频的微波频率源设计

利用阶跃恢复二极管的非线性特性,设计并制作了一个基于倍频的微波频率源。结合ADS软件的仿真结果,对频率源的各单元电路进行了原理分析,为其设计了一个平行耦合结构的窄带滤波器,对实际制作的频率源成品进行了测试。结果表明,该频率源的输出频率为1.5 GHz,输出功率为0 dBm,输出频谱纯净,并已成功应用于某光发射系统中。     

基于光学频率乘法器的THz通信载波研究

为解决THz波无线通信系统载波存在的频率稳定性及精度问题,提出基于光学频率乘法器的THz载波产生方法.该乘法器由光梳信号生成器、光学可调滤波器和UTC-PD光学混频器组成.光梳信号和可调光纤进行光学频率相乘产生双模相干光信号,通过UTC-PD进行光外差混频产生高频率和高饱和输出功率的THz载波,并对载波的线宽、单边带相...     

基于频差倍增法的频率标准装置建模与分析

在航天测控及广电电力领域,为了保证时间和频率统一,需要对时统的铷钟及髙稳晶振等设备进行高精度频率测量。采用了一种以铯原子频率标准为参考,基于频差倍增法构建的频率标准装置,根据频差倍增法测量原理,推导了测量铷钟及髙稳晶振过程中数据影响因素的数学模型,在此基础上,通过对测量影响因素的分析及实测数据计算,对装置的测量不确定度进行了分析和评定。评定结果表明,标准装置符合铷钟及髙稳晶振的检定规程要求,能够确保测量结果准确可靠。     

W波段二次谐波回旋振荡器

针对谐波回旋管互作用效率低的问题, 以自洽非线性理论为基本工具, 系统地分析了三个关键因素, 即互作用腔体长度(Q值)、电子注的横纵速度比和工作电压对二次谐波互作用系统性能的影响.研究发现当工作磁场选择在硬激发区时, 通过综合调节电子注的横纵速度比和工作电压能够获得较高的互作用效率.基于自洽非线性理论优化设计了一个W波段二次谐波回旋振荡器, 粒子模拟(PIC)结果显示当电子注速度离散３％, 工作电压37 kV, 电流4 A时, 输出效率达到了39.5%.     

同频段内雷达站与IMT-2000 WCDMA的干扰分析

概述雷达的英文名称为RADAR(Radio Detection and Ranging),其含义是指用无线电方法对目标进行探测和测距。雷达的基本任务有两个,一是发现目标的存在,二是测量目标的参数。雷达的用途十分广泛,使用的频率遍布全部无线电频段。如果按工作频段为雷达分类,则有短波雷达、米波雷达、分米波雷达、微波雷达和毫米波雷达等。如果按雷达作用分类的话,主要分为军用雷达与民用雷达两大类。根据频率划分表,2700-2900MHz以主要业务划分给航空无线电导航业务,以次要业务划分给无线电定位业务,另外在本频段中气象雷达业务也与航空无线电导航业务处于…     

Short-term frequency stability of an L band oscillator with a superconducting cavity

An L band oscillator with a superconducting cavity is described, and the measurement of the oscillator's short-term frequency stability is presented. The sideband power density is ?120 dB/Hz relative to the carrier at modulation frequencies greater than 1 kHz from the carrier.     

A digital phase-locked loop for generating frequency discriminating codes and frequency multiplication

A new digital phase-locked loop system realizale by a few off-the shelf digital ICs is described. The system is locked by tracking the input square wave and produces an output binary code whose value is proportional to the input frequency. It is characterized by wide locking range and fast capture time down to very low frequencies (<1 Hz) and suited to low frequency multiplication. Asymmetry in capture time, however, limits its use as an FM demodulator to only slowly varying signals.     

同频段内雷达站与IMT-2000 WCDMA的干扰分析(续)

干扰计算(一)IMT-2000 WCDMA对雷达的干扰1.移动台对雷达的干扰本文中我们以移动台的典型发射功率即20dBm进行分析计算。由于移动台可能距离雷达站很近,可采用自由空间传播模型,也可采用ITU-P.452建议的模型。应用公式(3),可得同频工作时,IMT-2000WCDMA移动台与雷达的隔离距离如表5。当IMT-2000 WCDMA移动台与雷达的工作频率相差5MHz、10MHz时,可根据表2移动台的频谱MASK进行计算,也可采用表4的数据进行计算,这时公式(3)中的PTX应使用带外发射功率,其值为PTX-ACLR。由于雷达工作在市区或郊区,其四周将存在大量的手机用户…     

Efficient difference frequency oscillator based on a Ti:sapphirelaser

The problem of expanding the Ti:sapphire laser wavelength range by generating difference (sum) frequencies is discussed. The authors present a high-efficiency coherent radiation source, based on a Ti:sapphire laser and a nonlinear LiIO₃ crystal, operating in the spectral range from 0.34 to 2.3 μm. For this purpose a Ti:sapphire dual-wavelength laser has been developed where the process of self-synchronization of both channels has been realized. A difference frequency oscillator with 2w_s-2w_l and 2w_l-w _s, including the spectral range from 0.503 to 0.79 and from 0.83 to 2.3 μm, has been realized. A detailed study of the temporal characteristics of Ti:sapphire lasing is given, the development of methods for mixed pulse overlapping is discussed, and other subjects, such as configuration of widely tunable coherent radiation sources, are addressed     

基于级联光纤环微波光子滤波器的微波倍频技术

为了得到高倍频的微波信号,实现获得了一种基于 外调制技术与级联光纤环微波光 子滤波器(FRMPF,fiber ring microwave photonic filters)的新型倍频微波信号光学产生 技术。利用外调制的方法,采用大功率信号驱动马赫曾德尔 调制器(MZM)得到了高阶谐波信号,再利用级联的FRMPF进行选频。理论计算与实验测试了FR MPF的滤波特性。通过调节每个FRMPF的环长,利用第1个FRMPF将基频信号与三阶谐波滤除 ,再通过第2个FRMPF将二阶谐波滤除,最终得到四倍频信号。 研究结果表明,利用频率为2.018GHz 的信号驱动MZM, 得到了 频率为8.073GHz的四倍频信号,信噪比(SNR)大于13dB。     

A fractional-N frequency synthesizer for WCDMA/Bluetooth/ZigBee applications

esented.     

A multiply-by-3 coupled-ring oscillator for low-power frequency synthesis

A frequency-synthesis technique which extracts the Nth harmonic from an N-stage oscillator is presented. This technique enables significant power savings in the prescaler of a frequency synthesizer. The maximum achievable voltage swing from such an oscillator is estimated. To study this technique, a multiply-by-3 circuit with two 180/spl deg/-coupled single-ended three-stage ring oscillators has been fabricated in 0.24-/spl mu/m CMOS, designed to work in the 902-928-MHz ISM band (U.S. and Canada). It provides two outputs: one at the normal operating frequency of the oscillator and the other at three times that frequency. The circuit can work at voltages as low as 1.3 V, while consuming 210 /spl mu/A of current.     

基于433频段无线传输的试验研究

针对实际生产环境中对无线传输质量产生影响的因素,结合固态酿醋控制系统对433 MHz的无线传输模块进行试验研究。针对机械设备中存在的电磁波干扰、不同材质障碍物对无线信号的衰减损耗、不同房间不同楼层间传输的特性及特定环境下不同传输距离的误码率进行试验,重点衡量误码率、传输损耗、信号强度、传输距离等指标,试验结果可以为无线传输系统的设计提供参考。     

基于偏振调制器的微波光子倍频系统实验研究

为了证明微波光子倍频系统可以构成光载无线通信系统的一部分,采用不受光纤色散影响的基于偏振调制器的倍频系数可调的微波光子系统,理论论证和分析了基于偏振调制器的二倍频、四倍频和六倍频的系统原理和特性。针对于不同的倍频系数,构建了相应的实验方案,进行了实验验证、数据分析和实验结果讨论,在不断进行实验系统优化的基础上实现了良好的倍频输出结果。结果表明,倍频输出的微波/毫米波信号在仪器测量允许的范围内最大可达到42GHz,且此系统具有受光纤色散影响小的优点。     

基于ADF4106的低相噪本振设计

为了实现低相噪的本振信号输出,本文设计出一种基于锁相环芯片ADF4106的低相噪本振源.通过实际调试,测试结果满足设计要求,并作为第二点频本振应用于一款通信测试仪器的中.     

A ring oscillator based on HIFETs

A hygroscopic insulator field-effect transistor (HIFET) ring oscillator with three inverters was built and tested under ambient laboratory conditions. An operating voltage of −2 V was used, yielding a peak-to-peak output voltage of 1.1 V and an oscillation frequency of 28 mHz. For Spice (simulation program with integrated circuit emphasis) simulation of the HIFET circuits the measured HIFET output characteristics were fitted to a DC (direct current) model and additional measurements were made to find the magnitude of the capacitive and resistive elements in the HIFET gate structure. The results indicated that HIFETs have a good potential for use in amplifier and sensor circuit applications where high operation speed is not crucial.