Efficiency of the surface-acoustic-wave diode convolver

The diode convolver performs signal processing, for example correlation, by mixing two input waveforms in an array of diodes, each diode being connected to a tap on a surface acoustic wave delay line. This paper gives the theory for the device efficiency, for a parallel circuit arrangement of taps and diodes. The effect of stray capacity is also analyzed. An experimental 31-tap device used hybrid circuitry in order to allow close spacing of the taps, giving a tap-to-tap propagation time of 90 ns. The efficiency agrees well with theory, showing that the bilinearity factor is maximized for an intermediate value of the bias current. The maximum bilinearity factor, relating external powers, was -34 dBm.     

An integrated piezoelectric-insulator DMOST surface-acoustic-wave convolver

A detailed investigation and analysis of a new device, the PI-DMOST convolver, is presented. The feasibility of this type of convolver has been previously demonstrated [1]. In this paper, we present the experimental results of another configuration of the device, fabricated with a new process. The theory is presented in detail for operation of the convolver using first-order Rayleigh-mode waves, and then extended to include other SAW modes.The convolver measures 100 μm by 1 cm, has a dynamic range of 70 dB, and is realized using ZnO piezoelectric films on a planar-processed silicon wafer.     

Correlation of long sequences by a surface-acoustic-wave convolver, with application to spread-spectrum communication

Segments of a long biphase coded waveform were correlated in a surface-acoustic-wave convolver, and the resulting correlation peaks were summed in a recirculation loop. With a 5 MHz chip rate, 250 ?s of the waveform was integrated, giving an experimental s.n.r. improvement of 36 dB. The application to fast synchronisation in spread-spectrum communication is discussed.     

Determination of capture cross section and surface-states concentration profile using the surface-acoustic-wave convolver

Energy distribution of surface states and majority-carriers capture cross section is determined using the surface-acoustic-wave (SAW) convolver. The semiconductor is placed a small distance above the SAW delay line, with a uniform air gap between the two media. A fast rise time dc pulse is applied across the semiconductor-delay line structure, and the resulting change in the SAW propagation loss is observed. The transient response of the SAW propagation loss represents the emission or trapping of majority carriers from surface states. From this transient response, the capture cross section and the concentration profile of the surface states are determined. The results obtained agree with the already known distribution of fast surface states; it is constant at the middle of the gap and increases towards the conduction band, whereas the capture cross section is constant in the middle of the gap and decreases toward the conduction band. This new SAW technique is simple, sensitive, and requires no contact to the semiconductor surface.     

Real-time Fourier transform with a surface-wave convolver

The generation of Fourier transforms of electronic signals in real time with an acoustic-surface-wave convolver is demonstrated. Two matched chirps propagating through each other behave as a narrowband filter in wavevector space, with the filter centre moving at a rate proportional to the acoustic velocity and the chirp rate.     

利用参考波形估计导航信号测距偏差

针对卫星导航信号存在的微小信号畸变,研究了因导航信号畸变而引起的测距偏差的估计问题。基于理想矩形脉冲波形和真实信号波形的上升沿零交叉点信息,给出参考波形定义,并以此为基础估计测距偏差。该方法可用于定量评估卫星导航信号波形畸变对测距偏差的影响及比较卫星之间的测距差异。以二阶模型为基础产生畸变波形,验证了该方法的有效性,并分析了估计精度与信噪比关系。通过大口径天线采集“北斗”卫星B1频点信号,利用该方法获得了B1频点I/Q支路信号的测距偏差,表明该方法可用于在轨卫星信号的测距性能评估。     

Fine tuning of surface-acoustic-wave resonator filters with metallisation thickness

Two-port surface-acoustic-wave resonator filters with Q factors in excess of 3000 and a sidelobe suppression of 30 dB have been fabricated from yz LiNbO3 with aluminium metallisation. The dispersion of the centre frequency with aluminium thickness has been found to be 70?10 kHz/?m at 35 MHz. The ability to fine tune with metal thickness has been used to compensate inherent substrate inhomogeneities and to fabricate a high-Q factor flat-top filter.     

Efficient SAW convolver with 30 ?s integration time

A SAW convolver is described with input bandwidth 20 MHz and integration time in excess of 30 ?s. It displays a high convolution efficiency (? ?63 dBm) and self convolution suppression exceeding 40 dB.     

Frequency-hopped-waveform synthesis with a surface-acoustic-wave tapped delay line

A coherent frequency-hopped-waveform synthesiser, based on the detection of contradirected chirp signals within a surface-acoustic-wave tapped delay line, is reported. Attractive features are programmable bandwidth and hop duration through control of external chirps, plus the capability to synthesise many simultaneous coherent outputs.     

Asynchronous operation of an analog convolver

A surface-acoustic-wave convolver can correlate a signal waveform by using an appropriate reference only if the signal arrives within a small time range related to the propagation delay in the device. It is shown here that the complete correlation function can be obtained for arbitrary signal timing if the reference waveform is made repetitive.     

Multimillisecond timse delays with wrap-around surface-acoustic-wave delay lines

Time delays of up to 3 ms in passive systems, and up to 20 ms with the addition of loss compensation by means of internal surface-wave amplifiers, have been observed in wrap-around surface-wave delay lines constructed of Bi12GeO20 and operating in a recirculating mode at 52 MHz.     

Laser probing of a surface-acoustic-wave resonator

An acoustic surface-wave resonator was studied using a heterodyning laser probe. The resonator consists in two periodic gratings ion-implanted in an ST cut-quartz substrate and an interdigital transducer deposited between gratings. The positioning of the transducer with respect to the standing wave pattern was investigated, the frequency being about 125 MHz. The variation of the transducer impedance around the resonance frequency is a function of this positioning and it was established that the greatest impedance change is obtained when the transducer fingers are in coincidence with the standing wave antinodes of the displacement perpendicular to the surface.     

High-frequency operation of surface-acoustic-wave muiltielectrode transducers

The operation of transducers with more than two electrodes per electrical period is disussed. When two different structures are used for input and output transducers, the frequency responses can be made to overlap at one desired band of frequencies, while reducing other surface-and bulk-wave responses.     

Theoretical and experimental study of transverse-horizontal convolver

The letter presents the results of theoretical and experimental studies for the transverse-horizontal convolver (THC) fabricated on LiNbO3. First, the definition of the figure of merit for the THC is proposed and, secondly, the existence of the crystal orientation and the direction of propagation with high efficiency and large electromechanical coupling coefficient for an LiNbO3 SAW THC is shown.     

Analysis of the surface-acoustic-wave crossbar coupler

An analysis of the scattering of surface acoustic waves at a region of periodic surface mass loading is presented. Experimental measurements of the scattered-wave amplitudes show close agreement with theoretical calculations.     

Modified bit-level systolic inner product/convolver architecture with increased throughput

We show how the architecture of a recently proposed bit-level systolic convolver/inner product array can be modified to provide a significantly improved word throughput rate. The approach is particularly beneficial to applications involving large numbers of low-resoultion products, and in some cases a 100% improvement in throughput can be achieved.     

基于LabVIEW的DSO存储波形处理与分析

为了对DSO存储波形进行进一步的分析和处理,利用LabVIEW在工程应用和信号处理上的优势,编写了具有DSO存储波形显示、频谱分析、滤波处理、单频信息分析的多功能软件.结合实例对滤波处理和提取单频信息方法的处理结果进行了对比分析,根据两种方法的原理和优缺点,指出了各自的应用条件,可为工程中DSO存储波形的分析和处理提供指导.     

Properties of the MZOS surface wave convolver configuration

The MZOS (metal-zinc oxide-silicon dioxide-silicon) structure is investigated in order to provide a phenomenological understanding of the charge transfer and trapping properties of the zinc oxide layer. Results of fast-ramp measurements of capacitance versus voltage are presented, and on the basis of these results, some biasing and operating procedures are suggested to make effective use of the memory capabilities of this configuration or to avoid unwanted memory effects. A technique for optical imaging is described which offers several advantages over other surface wave imaging techniques. Finally, some potential applications are mentioned.     

Unidirectional surface-acoustic-wave transducers with a ZnO film on glass substrate

A unidirectional surface-acoustic-wave transducer with a sputtered ZnO film on a glass substrate is presented, consisting of interdigital electrodes and a plate electrode on both sides of the film. Experiments are in good agreement with the equivalent-network approach, which is similar to Smith's networks for the normal interdigital transducer.     

Array signal Processing in the known waveform and steering vector case

The amplitude estimation of a signal that is known only up to an unknown scaling factor, with interference and noise present, is of interest in several applications, including using the emerging quadrupole resonance (QR) technology for explosive detection. In such applications, a sensor array is often deployed for interference suppression. This paper considers the complex amplitude estimation of a known waveform signal whose array response is also known a priori. Two approaches, viz., the Capon and the maximum likelihood (ML) methods, are considered for the signal amplitude estimation in the presence of temporally white but spatially colored interference and noise. We derive closed-form expressions for the expected values and mean-squared errors (MSEs) of the two estimators. A comparative study shows that the ML estimate is unbiased, whereas the Capon estimate is biased downwards for finite data sample lengths. We show that both methods are asymptotically statistically efficient when the number of data samples is large but not when the signal-to-noise ratio (SNR) is high. Furthermore, we consider a more general scenario where the interference and noise are both spatially and temporally correlated. We model the interference and noise vector as a multichannel autoregressive (AR) random process. An alternating least squares (ALS) method for parameter estimation is presented. We show that in most cases, the ALS method is superior to the model-mismatched ML (M/sup 3/L) method, which ignores the temporal correlation of the interference and noise.