Saw chirp filter technology for satellite on-board processing applications

Market growth in the area of thin route satellite communications services has led to consideration of non-traditional system architectures requiring sophisticated on-board processing functions. Surface acoustic wave (SAW) technology exists today which can provide implementation of key on-board processing subsystems by using multicarrier demodulators. This paper presents a review of this signal processing technology, along with a brief review of dispersive SAW device technology as applied to the implementation of multicarrier demodulators for on-board signal processing.     

Performance analysis and measurement of a saw-based group demodulator for on-board processing in communications satellites

Future satellites for ‘thin route’, mobile and portable services will require group demodulators on board the satellite to take advantage of the cost benefits offered with regenerative architectures. The demodulators will translate FDMA up-links into TDM down-links. This paper describes the measured performance of a 24-channel multi-carrier (64 kb/s QPSK for each carrier) group demodulator which uses SAW chirp Fourier transform (CFT) processing. The recovered data are combined into a single TDM bit stream at the standard T1 rate of 1.544 Mb/s. The 40 dB side-lobe suppression obtained in the CFT has resulted in less than 0.35 dB combined interference degradation achieved with all channels active. The added degradation over Olympus with a saturated up-link amplifier is less than 1 dB.     

表面波声电光效应耦合波方程

从参量互作用基本方程出发,导出表面波声光效应的耦合波方程,再将电光效应视作微扰,分别考虑晶体压电效应产生的交变电场和外加直流电场的影响,对此方程进行修正,得到表面波声电光效应耦合波方程。通过求解方程,得出衍射效率计算公式。由于表面波声电光器件多了一个信号输入端口,使用起来更加灵活,在实时信号处理中,如相关、卷积、匹配滤波、频谱分析、矩阵光计算等领域具有广阔应用前景。     

Investigations on groove design for modulating frequency response of SAW RAC chirp filter

Surface Acoustic Wave (SAW) Reflective Array Compressor (RAC) type chirp filters are used in radar compressive receivers as matched filters or compressors. The conventional way of designing the grooves in such filters is to make groove length constant throughout the length of the array. However, this does not give levelled frequency response and shows a rise toward the high frequency side. A new idea of tapering the groove length is suggested in this article. The suggested design shows that the frequency response of the chirp filter is flat in the frequency range of interest compared with a conventional one. Simulated results are shown for a chirp filter with centre frequency 450 MHz and bandwidth of 200 MHz.     

声表面波技术与电子战

本文介绍SAW器件在电子战(EW)系统中的应用。以声表面波滤波器组为核心的信道化接收机可以实现宽频的信道化接收和100%的截获概率(POI),可广泛应用于电子侦察(ELINT);以声表面波Chirp器件为核心的压缩接收机可有数百兆赫的带宽和2MHz—25kHz的频率分辨率,可以用于电子侦察和通信侦察,采用合适的结构亦可获得100%的POI。文章叙述了各种声表面波器件及声表面波声光(AO)器件在ESM、ECM、ECCM中的其它应用。文中还简单介绍了我所为EW研制的SAW器件。     

Real-time network analyser using dual analogue chirp transform

A dual implementation of analogue chirp transform is applied, for the first time, to the realisation of a network analyser capable of providing both amplitude and phase characteristics of the network transfer function. A chirp waveform excites the network and multiplies its response prior to processing in a surface-acoustic-wave chirp filter. This simple configuration ensures maximum energisation of the network and can allow bandwidths larger than the s.a.w. filter bandwidth to be analysed.     

基于窗函数的Chirp-UWB信号研究

与目前普遍研究的超宽带通信系统中所使用的高斯脉冲波形不同,线性Chirp信号具有良好的自相关性和高处理增益,能够更好地抵抗窄带干扰和多普勒频移。由于目前研究的线性Chirp信号普遍采用的方波包络,经过匹配滤波之后输出的sinc波形中,部分能量泄露到旁瓣中去,从而影响判决的精确度。选取了四种窗函数,经过窗函数处理之后的线性调频信号能有效地降低旁瓣的幅度,从而提高信号传输的能量利用率。通过仿真发现这种经过加窗处理之后的线性Chirp信号和方波包络的线性Chirp信号相比,在高斯噪声信道下具有更好的抗噪声性能。     

Extension of time-bandwidth product in SAW spectrum analysers

Surface-acoustic-wave (SAW) spectrum analysers use the chirp transform algorithm for real time analysis over wide (MHz) signal bandwidths. This letter reports a new technique for the generation of the long-duration wideband linear frequency modulated (chirp) waveforms used in these analysers. It now permits the overall time bandwidth product of these spectrum analysers to exceed that of the constituent SAW filters, and has consequent application in analysis of communication signals. An externally programmable weighting technique, for optimising time sidelobe suppression is also demonstrated.     

Frequency synthesis via the discrete chirp and prime sequence ROM's

Surface-acoustic-wave (SAW) sampled-data filters can be utilized as serial access READ-ONLY memories to directly implement at carrier frequencies a coherent fast-frequency-hop synthesizer in the VHF and UHF ranges. An example of frequency synthesis using surface acoustic wave discrete chirp filters is shown. A frequency synthesis scheme using a SAW prime-sequence filter is described.     

声电荷输运延迟线

声电荷输运技术是80年代初出现的一种新型高频高速信号处理技术，是模拟信号处理领域的重要发展方向。文内报道了声电荷输运延迟线的设计考虑、器件结构和制作，讨论了所采用的一些关键工艺，给出了器件性能。声电荷输运延迟线样品具有1μs的延迟时间，声表面波频率为358MHz。     

A novel Sigma–Delta based parallel analogue-to-residue converter

An important step in the residue number system (RNS) based signal processing is the conversion of signal into residue domain. Many implementations of this conversion have been proposed for various goals, and one of the implementations is by a direct conversion from an analogue input. A novel approach for analogue-to-residue conversion is proposed in this research using the most popular Sigma–Delta analogue-to-digital converter (SD-ADC). In this approach, the front end is the same as in traditional SD-ADC that uses Sigma–Delta (ΣΔ) modulator with appropriate dynamic range, but the filtering is done by a filter implemented using RNS arithmetic. Hence, the natural output of the filter is an RNS representation of the input signal. The resolution, conversion speed, hardware complexity and cost of implementation of the proposed ΣΔ based analogue-to-residue converter are compared with the existing analogue-to-residue converters based on Nyquist rate ADCs.     

High-speed DQPSK chirp spread spectrum system for indoor wirelessapplications

A chirp spread spectrum communication link for high-speed indoor wireless systems using a broadband SAW chirp filter is proposed. This system combines the multipath resolving ability of spread spectrum with the diversity of a RAKE-type receiver. Computer simulations and experimental results show nearly ideal performance in multipath fading conditions     

一种SAW RFID阅读器的信号处理电路设计

为适应复杂环境中RFID系统的使用,基于SAW标签的RFID系统弥补了传统基于IC标签的RFID系统易受环境干扰等缺点。介绍了识别SAW标签的RFID阅读器的系统设计方案,详细说明阅读器信号处理电路的设计过程,通过软件仿真与电路调试,验证了基于C8051F的SAW RFID阅读器设计可行性。信号处理电路具有结构简单,成本低廉等特点,有较好的应用价值。     

SAW chirp Fourier transform for MB-OFDM UWB receiver

1 Introduction Multiband orthogonal frequency division multiplexing (MB- OFDM) ultra wideband (UWB) is a novel multicarrier UWB system that has been proposed as a physical layer for reliable high bit rate and short-range communication network. It uses OFD…     

Range Resampling in the Polar Format Algorithm for Spotlight SAR Image Formation Using the Chirp z -Transform

Besides an inverse two-dimensional (2-D) Fourier transform, the polar format algorithm (PFA) for the spotlight synthetic aperture radar (SAR) image formation can be normally divided into two cascaded processing stages, which are called the range and azimuth resampling, respectively. This paper focuses on a new implementation of the first stage, i.e., the range resampling, using the chirp z-transform (CZT). The presented algorithm requires no interpolation. It works for the SAR system directly digitizing the echo signal, as well as that employing the dechirp-on-receive approach. The parameters of the CZT, including the frequency spacing and the start frequency, are derived to accommodate the PFA in both cases. Related filtering and compensation procedures are developed for the chirp z-transformed range signal with and without dechirp, respectively, in order to achieve a signal format entirely suitable for the azimuth resampling. Furthermore, incorporating the new algorithm with the existing CZT-based azimuth resampling and focusing algorithm, we can achieve a PFA totally free of interpolation. The presented approach has been validated by point target simulation, and the test is carried out with a very critical relative bandwidth of 30%     

声表面波器件在雷达对抗技术中的应用

介绍了声表面波器件在雷达对抗技术中的应用。以声表面波滤波器组为核心的信道化接收机,可以实现对雷达信号的宽频的信道化接收和１００％的截获概率。以声表面波延迟线为核心的距离欺骗、多重回答欺骗、噪声欺骗技术是对雷达信号的综合干扰手段之一。在对雷达的低空突防技术中,以ＳＡＷ色散线为核心构成的脉压高度表解决了地形跟踪的难题。     

SAW chirp filter performance above 1 GHz

The performance of a practical compact SAW dispersive filter with a bandwidth in excess of 500 MHz and centered at 1.3 GHz is described. The linear FM chirp filter was fabricated and serially reproduced by electron-beam microfabrication. The effect of an externally implemented weighting function on the time domain performance is discussed. The filter has been found suitable for pulse compression in a high-resolution monopulse radar. Replication of filter sets with identical characteristics is discussed.     

Behavior of the partial correlation coefficients of a least squareslattice filter in the presence of a nonstationary chirp input

This paper studies the performance of the a posteriori recursive least squares lattice filter in the presence of a nonstationary chirp signal. The forward and backward partial correlation (PARCOR) coefficients for a Wiener-Hopf optimal filter are shown to be complex conjugates for the general case of a nonstationary input with constant power. Such an optimal filter is compared to a minimum mean square error based least squares lattice adaptive filter. Expressions are found for the behavior of the first stage of the adaptive filter based on the least squares algorithm. For the general nth stage, the PARCOR coefficients of the previous stages are assumed to have attained Wiener-Hopf optimal steady state. The PARCOR coefficients of such a least squares adaptive filter are compared with the optimal coefficients for such a nonstationary input. The optimal lattice fitter is seen to track a chirp input without any error, and the tracking lag in such an adaptive filter is due to the least squares update procedure. The expression for the least squares based PARCOR coefficients are found to contain two terms: a decaying convergence term due to the weighted estimation procedure and a tracking component that asymptotically approaches the optimal coefficient value. The rate of convergence is seen to depend inversely on the forgetting factor. The tracking lag of the filter is derived as a function of the rate of nonstationarity and the forgetting factor. It is shown that for a given chirp rate there is a threshold adaptation constant below which the total tracking error is negligible. For forgetting factors above this threshold, the error increases nonlinearly. Further, this threshold forgetting factor decreases with increasing chirp rate. Simulations are presented to validate the analysis     

基于声表面波技术的变压器无线温度传感器信号处理方法

目前配电变压器的状态监测迫切需要一种无线无源的传感监测方式,而声表面波(SAW)传感器是满足此需求的重要技术手段之一。该文以用于变压器出线端测温的SAW传感器为研究对象,提出了一种SAW传感器回波信号处理流程,设计了信号去噪、频谱分析等信号处理环节。为解决同频信号对传感器测量带来的干扰问题,研究了基于奇异谱分析和独立分量分析的单通道盲源分离算法对SAW传感器的抗干扰作用,利用搭建的信号采集平台验证了该算法在信号分离和干扰抑制上的有效性。     

一种性能良好的线性调频信号的产生方法

介绍一种产生窄脉冲调制激励信号，并通过它激励声表面波器件产生所需线性调频信号的方法。该方法的电路结构简单，性能优良，载频分量抑制达７０ｄＢ以上，对其它电路干扰小，产生的线性调频信号频率高，频带宽，时宽大。