光纤光栅Sagnac环级联特性

为了解决单个均匀光纤光栅Sagnac环信道隔离度差的缺点,提出了级联Sagnac环组成梳状滤波器的方案。采用Jones矩阵理论分别对单个光纤光栅Sagnac环和二阶、三阶级联时的频谱特性进行了理论分析和数值仿真。对于三阶Sagnac环级联时的情形,实现了通道间隔为0.8 nm、FWHM为0.1 nm的梳状滤波器,在相同信道间隔下使得FWHM降低为单个光纤光栅Sagnac环的1/4,从而有效提高了系统信道隔离度。得到了具有均匀通带间隔、信道隔离度高、光谱半高宽度FWHM窄等特性的梳状滤波器,使其性能能够更好地满足WDM的使用要求。     

SAW Vestigial Sideband Filter for TV Broadcasting Transmitter

This paper reports the application of an SAW vestigial sideband (VSB) filter to a TV broadcasting transmitter. The filter requires steep cutoff characteristics and large fractional bandwidth. The X-112° Y · LiTaO/sub 3/ is one of the most suitable substrates for this filter, because it is possible to satisfy specifications without any compensation for typical temperature variations. The first application of LiTaO/sub 3/ substrates to a VSB filter is discussed in this paper. The filter is designed by a new optimization method using nonlinear programming. Because of the lack of a microstrip coupler and due to a large number of fingers, various second-order effects had to be compensated for. Experimental results are presented, when the filter is installed in a 10-kW TV transmitter.     

Ultra low bulk orientations of lithium niobate for SAW TV filters

A range of orientations of lithium niobate substrates is shown both theoretically and experimentally to give very good rejection of spurious bulk wave signals in the stopband of a SAW TV filter and other SAW filters of similar bandwidth.     

SAW电视中频滤波器三次行程的分析方法

随着立体声电视和高清晰度电视等的发展,对声表面波电视中频滤波器的性能提出了更严格的要求,首先介绍了声表面波电视中频滤波器三次行程反射问题形成的主要原因,由于它与主信号的幅度只差12dB,将会使滤波器的通带波动达到不可容许的地步,因此必须加以抑制,本文讨论了分别采用同相位法;声表面波单相单向换能器（Single Phase Unidirectional Transducer,SPUDT）来消除三次行程信号的影响。     

Design of New SAW DQPSK Matched Filter

A new surface acoustic Wave differential quadraphase shift key（SAW DQPSK） spread spectrum （SS） signal matched filter based on the fusion of SS and differential modulation is reported. The design of multi-phase coded SAW matched filter is proposed rather than another design of SAW DQPSK filter, which can cut in a half of the delay time of SAW DQPSK matched filter and SAW fixed delay line（FDL） used for differential demodulation. This breakthrough is made the system largely reduce a size and process much easily. This method can also be feasible in other SAW MPSK matched filter design especially when the modulation phase number is larger than 4. The design example and its experimental results are given.     

基于一种改进型DMS结构的极窄带SAW滤波器

该文采用一种改进型双模声表面波(DMS)结构来设计1.5 GHz的极窄带声表面波(SAW)滤波器。DMS结构两端的反射器采用分布式多周期加权结构能够消除在声通道上传播的多种声反射模式。为灵活设计滤波器阻带抑制及带宽指标,在DMS结构的两个叉指换能器(IDT)之间加入反射器。结果表明,研制的极窄带SAW滤波器中心频率为1.5 GHz,实测带宽为878.75 kHz,插入损耗为5.8 dB,阻带抑制达到45 dB。     

Miniaturized SAW devices for radio communication transceivers

Various applications of surface-acoustic-wave (SAW) technologies are investigated in which the use of SAW devices would result in reduced volume and weight for VHF/UHF radio communication transceivers. Attention is given to improved insertion loss and power requirements reported for SAW filters. In particular, by analyzing the loss mechanisms of a previously developed high-performance SAW filter for mobile telephones, a new extremely low-loss SAW filter (loss of as low as 1.2-2.0 dB at 600 MHz) has been developed. The results of fundamental experiments for a SAW antenna duplexer using this new SAW filter as the transmitter filter with a semicoaxial filter as the receiver filter at 800 MHz are presented     

基于滤波方法的OFDM信道估计研究

维纳滤波和卡尔曼滤波都是基于最小均方误差准则的滤波方法,本文主要研究这两种滤波方法在OFDM信道估计中的应用。为了跟踪频率选择性信道的变化,采用在OFDM系统中易于实现的梳状导频进行研究。传统的MMSE在统计意义上是最好的线性估计器,但是需要对矩阵求逆,是一种计算量较大,算法较复杂的方法。LMMSE是频域维纳滤波方法,其减小了MMSE的复杂度,但只适用于慢衰落信道,针对时变信道,本文提出卡尔曼滤波的信道估计方法,仿真结果表明,卡尔曼滤波的信道估计方法在时变信道中具有良好的性能。     

声表面波可程序选通滤波组件

通信的现代化使得空间电磁环境日益密集和复杂强劲,在码分多址（CDMA）扩频跳频通信系统中,必须解决系统的抗干扰问题。文章给出了一种新技术,即：采用声表面波（SAW）技术,直接在接收机前端或发射端的宽带信道上,自适应地选能不同的SAW信道滤波器抑制空间以及系统内部的杂波信号,提高抗干扰能力。介绍了一个16信道声表面波可程序选通滤波组件。本组件产品已用于接收机前端宽带接收信道的自适应抗干扰,证明该产品对于改善宽善CDMA信道的接收灵敏度和加强抑制干扰能力均有好的效果。属于新技术新产品,有很好的应用前景。     

小型多通道声表面波滤波组件的抗干扰设计

滤波组件作为当代通信系统中不可或缺的重要部分,高性能、高集成、低损耗是未来的发展方向.该文针对在小体积多通道声表滤波组件设计中如何减少系统受到电磁干扰的核心问题,采用了抗干扰设计,并重点研究了射频(RF)电路中多层电路板的布局和布线.通过实验验证了其各通道性能指标均能有效地正常工作,且各通道间无相互串扰的现象,解决了电...     

任意波长间隔的光纤光栅梳状滤波器设计与实现

采样啁啾光纤光栅理论是实现超高信道数梳状滤波器的理想方案,但是一个啁啾模板只能实现特定波长间隔的光梳状滤波器。提出一种利用光纤布拉格光栅(FBG)直流相移实现任意波长间隔梳状滤波器方法。该方法只需一个啁啾模板与亚微米精度的位移台,在灵活性、简单性和制作成本方面有明显优势。仿真和实验表明FBG直流折射率调制可以引入任意的相位偏移。利用该方法实现了波长间隔为100,50,40GHz的梳状滤波器。最后分析了直流相移光栅长度与相位误差对滤波器边带抑制度的影响。     

Surface-acoustic-wave multiplexing techniques

Two approaches to frequency division multiplexing using SAW devices are described. The first one uses a 9-channel filter array, where the signal combining and splitting is performed using wide-band power splitters. Two of these filter arrays were used in a data link, with data rates up to 7.5 Mbit/s for a total data rate of 67.5 Mbit/s. The second approach uses offset multistrip couplers to channel a wide-band signal into various narrow-band outputs according to frequency. Consequently, this approach exhibits lower insertion loss and is especially suitable for a large number of channels. An 8-channel MSC multiplexer has been constructed with less than 10-dB insertion loss.     

频率合成邻频电视调制器原理分析

分析了一种频率合成邻频电视调制器的稳频原理及设定振荡频率的方法。阐述了采用射频声表面波滤波器实现邻频传输所采取的一些技术措施。     

采用SAW和PLL技术的扩频通信信道模块

通过采用锁相环(PLL)技术实现了射频载波的跳频扩频(FHSS)，跳变载波相噪小于-98dBc／Hz@1kHz，杂散抑制大于70dB，收发端隔离度大于105dB；声表面波(sAw)匹配滤波器保证了20Mbps的直接序列扩频(DSSS)信号的实时解扩，SAW固定延迟线实现了延迟差分解调与解码。导出采用2阶有源比例积分器作为PLL频率合成器的低通滤波器的中相位边界与环路衰减系数之间的数学关系式。     

GSM用低损耗声表面波滤波器的设计

报道了双模声表面波滤波器（ＳＡＷＦ）的研究结果和设计的ＧＳＭ用９０２．５ＨＭｚ的ＳＡＷＦ,对双膜ＳＡＷＦ的基本原理和分析方法进行了描述,并给出理论模拟结果,对几个关键参数进行了比较计算,研究表明,双模ＳＡＷＦ具有低损耗,宽带的特性,较好地满足了ＧＳＭ用９０２．５ＭＨｚ的ＳＡＷＦ电性能要求。     

A multipurpose CCD comb filter with combing and delaying functions

Describes the organization and performance of a multipurpose CCD comb filter to separate luminance and chrominance from the composite color video signal. The filter consists of a main (long) and two sub- (short) channels terminated at two comb outputs (add and subtract) and a simple delayed output. It is operated at 4/spl times/f/SUB SC/(f/SUB SC/: color subcarrier frequency). The comb filter transfer functions are usually shifted toward the lower frequency and the rejection ratios are degraded, due to the incomplete charge transfer. However, the small notch frequency shifts (<25 Hz) and high rejection ratios (>40 dB) were experimentally obtained. Moreover, low differential gain (<1 percent) and low differential phase (<1.5/spl deg/) were obtained for the separated chrominance signal, regardless of APL variation. The second-order comb filter was constructed using three identical devices and used in a TV receiver. The reproduced image was much superior to that obtained by the conventional separation circuit. Some other application schemes in video signal processing systems were proposed.     

符号成形及SAW技术实现优化研究

本又提出利用声表面波（SWA）滤波器在载波上直接实现符号成形与调制。用切尾余弦系列作为基函数在连续相位，恒包络及附加谱分布字条件下对成形符号函数进行设计，并提出一种新的采样重构法优化设计此SAW调制滤波器，最后给出模拟结果并得出结论。     

一种基于采样布拉格光栅的梳状滤波器解决方案

基于采样布拉格光纤光栅,设计出一种多通道数梳状滤波器,所设计的梳状滤波器可应用于光纤通信中的波分复用（WDM）系统。在光栅中引入一种非连续线性啁啾阶梯式结构,并且在采样内,使折射率调制深度符合汉明分布,设计出一个具有26个通道、通道间隔25GHz的梳状滤波器,它能够产生具有平顶、陡峭边沿以及高透射率的多个相同的通带,可用作多通道光分插复用器,广泛应用于WDM系统。     

激光扫描探测声表面波特性

介绍一种新型的探测声表面波传输特性的测量技术.实现了各向异性晶体声表面波衍射场分布的一维扫描显示;二维扫描在电视屏上可对声表面波阵面直接成象,在此基础上求出了声表面波相速以及探测声表面波器件表面缺陷.     

数字电视网络前端监视系统的开发

针对目前数字电视监控系统的匮乏及其自动化管理的需要，按照MPEG-2及欧洲DVB（Digital Video Broadcasting）的标准，采用模块化和复用的方法，设计并实现了一套视频监控系统。在该系统开发过程中，提出一种解析描述子的相对优化的算法；提出将输入接口、通道、可复用的过滤器和高效队列缓存区结合起来，开发了一种能有效地接收和分发数字业务平台传输流的接收器，该系统不仅能实现MPEG-2流的分析、DVBSI的分析、PES流的播放等功能，而且还能对数字电视各节目的码流量和相关记录值进行统计，有助于数字电视实现自动化管理。