双向行波式声光驻波调制器

提出了一种新型的声光驻波调制器，即双向行波式声光驻波调制器，建立了数学模型，进行了模拟计算，并从理论上证明了其衍射光的振幅和光强的表达式安全等效于反射式的声光驻波调制器，利用中心频率为５０ＭＨｚ的器件，测得其对衍射光强的调制频率两倍于声频，并随时间做周期的变化，其带宽Δω＝７ＭＨｚ，远远大于驻波器件；而且从对调制光的调制度的测试结果来看，较易获得对光强具有大的调制度的调制器件。     

HP5342A微汉频率计的故障检测

1 故障现象一台ＨＰ5342Ａ微波频率计 ,在 50 0ＭＨｚ～ 18ＧＨｚ量程上测量信号时 ,测出的结果与被测信号的频率值相差 2 30ＭＨｚ,改变信号源的输出频率时 ,发现仪器在50 0ＭＨｚ～ 18ＧＨｚ的量程中 ,只能在有限的不连续的频段内测出频率 ,读值偏差很大。　　 2 分析与检修ＨＰ5342Ａ微波频率计的测频范围为 10Ｈｚ～18ＧＨｚ,分为 10Ｈｚ～ 50 0ＭＨｚ(低频段 )、50 0ＭＨｚ～18ＧＨｚ(高频段 )两个量程。在这两个量程上 ,它采用了不同的测量方法 ,电路组成有较大的差异。在低频段 ,该频率计采用直接计数器、电源、10ＭＨｚ频标等电路…     

毫米波固态锁相系统的研究

毫米波的频率锁定源是激光频率测量的基础，本文报道了利用谐波混频技术以及耿氏振荡器的偏置电调特性，应用了以ＥＣＬ为基础的数字环路锁相技术，将８ｍｍ和４ｍｍ的毫米波的振荡频率，通过Ｘ波段固态微波锁相源，锁定在５ＭＨｚ高稳晶体振荡源上，获得了高稳定的微波信号，实现了从５ＭＨｚ至Ｗ波段频率稳定度的高精度传递。只要将５ＭＨｚ晶振锁定在铯束频标上，本系统可达到与铯频标相应的准确度。     

新型双向多功能声光器

介绍一种双向多功能声光调制器的设计原理、制作工艺及实验结果。两个方向均采用ｙ－３６°切割ＬｉＮｂＯ３单晶为换能器,双向声光器件的性能为：Ｘ方向的工作频率为４０±０．１ＭＨｚ,调制信号为１－１０ｋＨｚ;Ｙ方向的工作频率为１００±０．１ＭＨｚ,在激光测试装置中测得双向声光器件在驱动功率为８Ｗ时,Ｙ方向的衍射效率分别〉８０％,     

分频式计数型频率计的测频误差分析

本文主要分析以ＩＣＭ７２６１Ｄ计数模块为核心部件构成的１００ＭＨｚ数字频率计，因被测频率计十分频率产生夫落脉冲引起的误差，并总结了此种分频式计数频率计测频的总误差计算公式。     

偏远地区部队旅团有线电视系统设计,安装及升级,改造

本文主要介绍驻地偏远、部队相对集中的旅团营区有线电视系统，即３００ＭＨｚ宽带、通用型电视、广播复合系统的设计、安装及升级、改造。同时介绍由３００ＭＨｚ升级为５５０ＭＨｚ的改造。     

半导体激光器用铷D2线光电流谱稳频

本文报导了用铷原子７８００Ａ光电流谱来稳定半导体激光器的工作，在光电流谱线的中部发现了有利于稳频的凹陷，将半导体激光器频率锁定在凹陷的中央，估算的频率稳定度为１ＭＨｚ。     

Fe—47wt%Ni纳米晶粉芯磁谱及其压力效应

用蒸发冷凝法，制备成不同平均粒径的Ｆｅ－４７ｗｔ％／Ｎｉ纳米晶粉。将其压成小圆环，测其室温磁谱。结果表明，Ｆｅ４７ｗｔ％Ｎｉ纳主晶粉芯具有较好的高频特性。在（１－３００）ＭＨｚ频率范围内，其复数磁导率实部μ１〉１００，虚部μ２〈２０，损耗解正切ｔｇδ〈０．１，共振频率ｆｒ〉３００ＭＨｚ。当１ＭＨｚ〉ｆ〉４００ＭＨｚ时，μ２及ｔｇδ激剧上升。在（１－３００ＭＨｚ）范围，形成一个很宽的通频带。它有可能     

50MHz,1mW功率标准的研究

目前，国内外许多高性能电子仪器和测量系统都将５０ＭＨｚ，１ｍＷ功率作为基准电平，它是评价仪器准确度的一项重要指标。本文介绍５０ＭＨｚ，１ｍＷ功率标准的工作原理。     

如何正确选用VHF和UHF无线话筒?

无线话筒因没有传输电缆的束缚，使用方便、灵活，被音乐爱好者广泛采用。但是如果选用不当，使用中常常会发生信号时有时无、声音断断续续、噪声大、音质差和传输距离不远等令人烦恼的问题，产生这些问题的主要原因是没有根据现场环境和用途正确选择无线话筒的波段和不正确的安装方法。 现时的无线话筒广泛采用ＶＨＦ（甚高频）和ＵＨＦ（超高频）两个传输频段。ＶＨＦ波段的频率范围是３０ＭＨｚ－３００ＭＨｚ，波长为１０ｍ～１ｍ，通常称为“米波”； ＵＨＦ波段的频率范围是３００ＭＨｚ～３０００ＭＨｚ，波长为１ｍ～０.１ｍ，通常…     

基于声光偏频法的激光频率无调制锁定

为了进一步提高1.5 μm波段激光器的频率稳定性,利用声光调制器(AOM)的频移特性使激光发生频移,将乙炔(~(12)C_2H_2)v_1+v_3带的P9支吸收峰作为参考频率,通过两条频移的吸收谱线产生类色散鉴频曲线,实现对外腔半导体激光器的无调制频率锁定.实验中把以前直接对激光器的调制转移到声光调制器上,避免了直接调制所引入的额外噪声,通过闭环锁定,50 s内典型的频率起伏达到5.8 MHz以内,激光器的频率起伏较自由运转时明显得到抑制,实现了激光频率的稳定.     

Frequency Domain Analysis of Multiwavelength Photoacoustic Signals for Differentiating Tissue Components

The feasibility of differentiating tissue components by performing frequency domain analysis of photoacoustic images acquired at different wavelengths was studied in this paper. Firstly, according to the basic theory of photoacoustic imaging, a brief theoretical model for frequency domain analysis of multiwavelength photoacoustic signal was deduced. The experiment results proved that the performance of different targets in frequency domain is quite different. Especially, the acoustic spectrum characteristic peaks of different targets are unique, which are 2.93 MHz, 5.37 MHz, 6.83 MHz, and 8.78 MHz for PDMS phantom, while 13.20 MHz, 16.60 MHz, 26.86 MHz, and 29.30 MHz for pork fat. The results indicated that the acoustic spectrum of photoacoustic imaging signals is possible to be utilized for tissue composition characterization.     

小型化铷原子频标数字锁频环路设计与实现

设计并实现了一种用于铷原子频标的小型化锁频环路。采用数字锁相倍频技术,实现了10MHz信号的45.5645833次倍频。再经过一级15次倍频后获得频率为6834.6875MHz的铷原子频标微波探寻信号。通过数字电路技术实现了455.645833MHz信号的小调频。测量并分析了455.645833MHz信号的相位噪声,结果表明电路系统对铷频标频率稳定度的贡献为3.2×10^-12τ^-1/2。测量了利用该电路得到的铷频标的短期频率稳定度,结果为5×10^-12τ^-1/2（1s≤τ≤100s）,明显高于一般商品小型化铷原子频标。     

频率分裂在双频激光器和位移传感器中的两种新应用

主要介绍了激光频率分裂技术的两种新应用,包括用两种方法克服强模竞争以获得频差可覆盖1～40MHz的双频激光器,以及将一个双折射双频激光器本身用作一个位移传感器.这种双频激光器可以填补塞曼激光器和双折射激光器之间存在的3～40 MHz频差空白,可以用作激光干涉仪理想的光源.位移传感器结构简单,其分辨率为79 nm,测量范围达到了15 mm,并且可以自校准.     

Frequency domain reflectometry of plasma chambers

Frequency domain reflectometry (FDR) is used to compare the electrical characteristics of five industrial plasma chambers, without the plasma present, used in the manufacture of semiconductors devices at Intel-Ireland. A scalar network analyzer (SNA), consisting of a tracking generator/spectrum analyzer and a radio frequency bridge was used to sweep the chambers from 1 MHz to 1 GHz. The non-invasive nature of the measurement interrogates the matching network, the wafer platen electrode fringing capacitance to ground, and radio frequency resistive loss. The resulting frequency response gives a unique fingerprint of the chamber, and is completely transferable between chambers for post-maintenance qualification and chamber comparison. The results from three electron cyclotron resonance (ECR) chambers are compared with the two single-frequency capacitively coupled plasma chambers and one dual-frequency inductively coupled plasma chamber. A comparative chamber survey of the three ECR chambers reveals a strong wafer electrode reflection in the 500 MHz frequency region. Whereas, for slab-like plasma chamber designs (such as the LRC Rainbow 4400 chamber) the wafer electrode response is at 14-15 MHz. It is found that the chamber design and individual components have a unique frequency response. A linear analogue circuit simulator was used to verify and characterize the measurements.     

H型亚微米梁的混频特性测量

本文简述了H型亚微米梁的工艺实现过程,从实验上详细研究H型梁的两种混频方式:向下混频和向上混频.考察的H型梁长度分别为8μm、10μm、12μm和15μm,小激励下谐振频率分别为13.30 MHz、8.77 MHz、6.12 MHz和3.65 MHz.通过在梁上施加两路不同频率的静电激励信号,调整两信号频率差值及和值在梁的本振频率附近变化,经过梁的自适应过程实现信号混频,最后由多普勒测振仪检测梁的混频特性.实验结果表明梁在向下混频时的振幅随两路信号频率的平移而改变,出现所谓的窗口效应;对于这两种混频方式,混频分量越接近梁的本征频率,梁的振幅越大,反之梁振幅下降越多;在输入信号功率均设置为14 dBm时,对比向上混频,向下混频使得梁的振幅更大,诸如12μm长的梁向下混频时梁振幅为4.082 nm,而向上混频时混频处振幅仅为1.826 nm.     

A Synchronous Sweep Frequency Oscillator

This paper describes a linear frequency sweep oscillator which is accurately controlled by a master clock. The voltage controlled oscillator which generates the frequency sweep is first phase-locked to the master clock. Then, a ramp generator drives the voltage controlled oscillator over the required frequency range, while a phase-sampling loop controls the instantaneous frequency to the desired ramp accuracy. The phase-sampling control loop is synchronized to the master oscillator by the sampling rate, which is derived directly from the master clock frequency. A laboratory system constructed on these principles sweeps from 2.095 MHz to 2.320 MHz in approximately 1.709 seconds, with a deviation from linearity of less than ±75 Hz.     

电视信号中标准时间频率的应用

本文介绍了电视信号中标准时间、频率的应用 ,其中包括彩色副载波标准频率综合器、电视行同步标准频率综合器、采样保持鉴相器、电视标准时间数字钟等设备的研制。藉助这些设备 ,只要直接接收中央电视台 1、2或 4套节目的全电视信号 ,便可输出常用的标准频率和时间 ,可用于精密时间测量、计量和校频 ,也可作为标准频率信号源使用 ,其校频精度达 5× 10 - 12 / 30min ,时间同步精度在 1μs以下。     

A High-Stability Low-Offset Phase-Locked-Loop Frequency Synthesizer

Small offsets in frequency from a given reference can be generated in a single sideband mixer employing a PLL. It is shown that the output frequency stability depends linearly on the fractional shift of the offset frequency generated, and on the coherence of the VCO. For the typical digital phase-locked loop synthesizer techniques, employing a crystal-stabilized VCO at 5 MHz, a 500-Hz offset can be realized with a 1-s frequency stability no better than a few parts in 107. An improved design is described which employs a pair of analog multipliers as an instantaneous phase detector together with feedback in quadrature. In laboratory tests this design demonstrated one second frequency stability of better than 1 part in 1010 when synthesizing the frequency 4.9995776 MHz from a 5.0-MHz cesium reference.     

An Active Frequency Technique for Precise Measurements on Dynamic Microwave Cavity Perturbations

A new method for the dynamic measurement of the passive parameters of a microwave cavity is described. Both the resonant frequency (f0s) and the loaded Q factor (QLs,) are measured simultaneously from active frequency signals generated by a closedloop circuit containing the test cavity. Resonant frequency deviations of up to 20 MHz are measured with an accuracy of better than ±0.25 percent, and loaded Q-factor variations (from 500 to 7000) are measured with an accuracy of better than ±1.2 percent. The unperturbed cavity resonance was at 2452.0249 MHz, and the time of measurement of each cavity parameter was < 1 s.