科技进展

我国一台He-Ne激光器可同时辐射出6条不同波长的光束。这一结果冲击着现行大学教科书上的有关论点,引起了国内外同行的兴趣。据介绍这6条光束的波长分别为612、629、633、635、640和650nm。这台激光器是副研究员、中国计量院院长赵克功及其小组研制的。其输出性能很稳定。这种碘稳频612He-Ne激光器被认定为国家测定米长度的波长标准用激光器,被国际上推荐为执行     

简单的稳频He－Ne激光器

稳频He-Ne激光器一般用作精密检测光源。本文介绍一种整体结构小型He-Ne激光器,尺寸小,能用于恶劣环境,寿命长,频率稳定,结构上增加了阴极面积,防止污染,选用了适当的材料和工艺。     

弹性加力中频差He-Ne塞曼-双折射双频激光器及稳频

为了提高激光干涉仪的测量速度,研制了一种新型塞曼一双折射双频激光器(Z-B激光器),该激光器对增益管加横向磁场和对其"透射反射镜"加外力.采用了弹性加力方案,使其频差比刚性加力He-Ne激光器具有更高的赋值精度,达到±0.2 MHz.同时,还报道了对该激光器进行的稳频研究.利用调谐腔中平行光和垂直光的等光强点作稳频点,以光强平衡为依据设计热伺服控制电路,考虑了成本的最小化和系统的集约化,采用纯模拟元件实现了中频差He-Ne Z-B激光器频率的稳定.对频差5.4 MHz的Z-B激光器的稳频结果为:3 h稳频精度优于2.1xlO-8.     

新型1.292μm窄线宽单频He-Ne激光器及1.292μm稳频He-Ne激光器技术鉴定会在南京召开

1993年8月26日在南京市东南大学,由国家自然科学基金委员会及江苏省科委联合主持召开“新型1.292μm窄线宽单频He-Ne激光器及1.292μm稳频可调谐He-Ne激光器”     

基于声光调制器的光学锁相环He-Ne激光稳频方法研究

报道了一种基于声光调制器与光学锁相环相结合的高稳定度激光稳频方法,用于提高热稳频He-Ne激光器的频率稳定度和准确度。为了克服全内腔热稳频He-Ne激光精密调谐困难的缺点,发展了基于声光调制器两次移频的频率调谐光路,有效地消除声光调制器移频光束路径对衍射角θ的依赖。自行研制了具有高灵敏度与捕获带宽的光学锁相环系统,利用声光调制器的高频率响应特性实现热稳频He-Ne激光高速、准确的锁定。成功实现了热稳频He-Ne激光器偏频锁定至碘稳频HeNe激光器。实验结果表明,环路锁定后拍频频率波动在±0.2 Hz范围内,频率抖动的标准差为0.04。偏置频率为30 MHz时,系统在1 s和1 000 s积分时间的相对阿伦方差分别为3.3×10^-9和1.4×10^-12。系统锁定后,压缩后的拍频线宽小于2 kHz。该研究表明,采用基于声光调制器与光学锁相环相结合的激光稳频方法可以实现亚赫兹级的激光频差控制,通过将热稳频He-Ne激光器偏频锁定至高稳定度的参考激光源可以显著提升其频率稳定度和准确度。     

双频双模He-Ne激光器稳频稳幅的一种新方法

本文提出了一种新的实现双频双模He-Ne激光器稳频稳幅的干涉方法.     

“偏频锁定”无调制的稳定激光器

本文介绍了一种无调制激光输出的“偏频锁定”稳频方法.文中对“偏频锁定”型激光器的工作原理、系统的主要部件及设计的考虑进行了较详细的描述.最后还给出了一台已用于碘稳定He-Ne激光器的“偏频锁定”稳频的实际电路.     

He-Ne双折射塞曼双频激光器的等光强稳频研究

在精密测量领域,He-Ne 激光器是制造激光干涉仪的首选光源,因波长作为测量的尺子,激光器的频率稳定性至关重要。介绍了双频激光器的稳频技术原理,利用调谐腔中平行光和垂直光的等光强点作为稳频点,以光强平衡为依据设计热伺服控制电路,采用数字和模拟电路共同控制,实现了He-Ne双折射塞曼双频激光器的频率稳定。对大频差(7.95 MHz)的双频激光器进行拍频测试,单次频率稳定度达10-9量级,重复多次多日测量,频率不确定度达1.07410-8(k=2)。同时对频差稳定度进行测试,频差波动范围在8 kHz以内,相对偏差度为0.001,完全达到商用双频干涉仪的标准。     

一种光学时标的研制

首次描述了一个用稳频的He-Νe激光器的光学振荡周期做为时标的时间标准。我们获得了超高频波段的具有极高频率稳定度的振荡，超高频振荡被锁定于由甲烷吸收共振稳定的He-Ne激光上，后者的振荡频率为3.39微米。直接比较了铷频标和He-Ne/CH4激光器的频率稳定度。对Ηe-Ne/CH4激光频率进行绝对测量得到一个新的频率值。     

一种自稳频大功率单频He-Ne激光器的功率估算

介绍了一种大功率单频、自稳频、高输出功率He-Ne激光器功率估算方法的改进。用这种方法的估算值与实际输出功率值符合得较好。     

Wideband frequency modulation of frequency synthesisers

Two-point frequency modulation gives a flat frequency response irrespective of the loop cutoff frequency of a p.l.l. digital frequency synthesiser. The spurious modulation components otherwise generated are also then suppressed. The modulation index is typically limited to N? where N is the divider ratio.     

A frequency multiplier for reference frequency in frequency synthesizer systems

A low jitter frequency multiplier, which requires less power, area, and design complexity than reference multiplying PLL or DLL circuits can be used to generate the reference frequency for a low phase noise frequency synthesizer. This paper proposes a mixed signal solution based on the fact that the average DC value of a signal is proportional to its duty cycle. The solution uses a feedback loop with coarse and fine delay resolution to generate a \(90^{\circ }\) phase shifted clock that is used to produce a doubled frequency signal with 50% duty cycle. This method can be used to multiply the input frequency of 40 MHz by multiples of 2, up to 16. The design is implemented in 65 nm UMC CMOS process. Operating from 1.2-V supply, it dissipates 0.46 to 1.2 mA at output frequencies 80–640 MHz, achieving ? 162.3 and ? 139 dBc/Hz phase noise at 1 MHz offset, respectively.     

C波段宽带捷变频率综合器设计

本文介绍了一种C波段宽带捷变频率综合器的设计方法,采用直接数字频率合成器(DDS)实现频率捷变,采用倍频链路扩展输出带宽,通过与锁相环(PLL)合成产生的本振信号混频将输出频率搬移到C波段。论述了DDS时钟电路、倍频链路以及混频部分的设计方法,并给出了达到的主要技术指标和测试结果。     

Improvement of natural frequency extraction in frequency domain

Natural frequency extraction in the frequency domain using measured frequency responses is an ill-conditioned problem. A method is proposed to improve the accuracy of the previously extracted natural frequencies. It is shown from results that the method can improve the accuracy of the natural frequencies extracted from synthetic and measured frequency response samples     

频率估计的时频分析方法研究

时间和频率是信号处理与分析中最重要的两个变量,时频分析技术力求在计算复杂性和时频分辨率之间找到最佳平衡点,利用时频分析研究瞬时频率估计及各种方法的性能具有重要意义。本文阐述了瞬时频率时频分析理论研究和应用发展概况,并给出了几种典型的瞬时频率估计算法及其性能评价。     

抽样频率转换在数字下变频中的应用

数字下变频技术是软件无线电中的关键技术之一。从信号中去除高频信息，降低抽样频率而不导致频谱混叠的过程称之为抽取。若信号不进行滤波就抽取，信号将出现混叠，那么其关键问题就是抽取前的滤波。现以软件无线电的基本知识为基础，分析了单级和多级抽样频率转换，并进行了比较。     

GHz band frequency hopping PLL-based frequency synthesizers

In this paper we describe a full-integrated circuit containing all building blocks of a completed PLL-based synthesizer except for low pass filter（LPF）. The frequency synthesizer is designed for a frequency hopping （FH） transceiver operating up to 1.5 GHz as a local oscillator. The architecture of Voltage Controlled Oscillator （VCO） is optimized to get better performance, and a phase noise of -111.85-dBc/Hz @ 1 MHz and a tuning range of 250 MHz are gained at a centre frequency of 1.35 GHz. A novel Dual-Modulus Prescaler（DMP） is designed to achieve a very low jitter and a lower power. The settling time of PLL is 80 μs while the reference frequency is 400 KHz. This monolithic frequency synthesizer is to integrate all main building blocks of PLL except for the low pass filter, with a maximum VCO output frequency of 1.5 GHz, and is fabricated with a 0.18 μm mixed signal CMOS process. Low power dissipation, low phase noise, large tuning range and fast settling time are gained in this design.     

Dual-polarization frequency reuse with frequency band shiftingallocation

Spectrum is a limited and precious resource in wireless communications. Effective spectrum utilization becomes more and more important because of the expeditious increase of demand for wireless communications. In principle, the dual-polarization frequency reuse system, which employs two orthogonally polarized electromagnetic waves to carry information, can double the system capacity. However, the system performance degrades seriously and sometimes becomes unacceptable due to cross polarization and fading. In this paper, a new linear-polarized dual-polarization frequency reuse system that utilizes the concept of orthogonal frequency allocation to increase spectrum utilization is proposed. We analyze the performance of the dual-polarization system modulated by the quadrature phase-shift keying in the multipath fading channel with cross-polarization interference and Doppler effect. Because of the orthogonality of the polarized carriers and frequency spacing, the effect of cross polarization, which defeats the performance of the dual-polarization system severely, can be ignored. The proposed system has a bit error rate around 10^-7 at the bit energy-to-noise ratio of 14 dB, while the bit error rates of the dual-polarization cancellation with bootstrap system and the conventional orthogonal frequency-division multiplexing system are about 10^-4     

单光束脉冲激光引信扫描频率和脉冲频率研究

为确保反鱼雷鱼雷（ATT）与来袭鱼雷交会过程中激光近炸引信能够探测到目标,推导能够满足要求的扫描频率和脉冲频率计算公式。研究激光近炸引信工作原理,得到激光近炸引信恰能探测到目标所需的激光束最低扫描频率和脉冲激光最低脉冲频率的临界条件。采用三种坐标系描述ATT 与目标间的交会关系,基于交会关系和临界条件,建立最低扫描频率和最低脉冲频率计算模型,获得最低扫描频率和最低脉冲频率的变化规律,并通过模拟试验验证所建理论模型的正确性,试验结果与理论计算结果吻合。计算拦截不同典型目标鱼雷时所需最低扫描频率和最低脉冲频率取值。所得计算模型和结果可为激光近炸引信应用中扫描频率和脉冲频率设计提供理论依据。     

一种双频双模射频电路的设计

给出了一种基于802．11b／g下的双模电路设计，该电路能很好地应用于2．4GHz和5.8GHz两个工作频段，并能实现全向和定向两种工作模式的转换。仿真结果表明，该电路有良好的回波损耗和传输特性，可以较好地满足无线局域网中的应用。