Showing papers on "High dynamic range published in 1985"

Small-Aperture Focusing Chirp Transducers vs. Diffraction-Compensated Beam Compressors in Elastic SAW Convolvers

Abstract: Abstmct-High performance has been achieved in SAW convolvers using diffraction-corrected multistrip beam compressors. However, two different levels of metalization are required for optimum performance. A significant simplification of device fabrication was achieved with the design of convolvers using small-aperture chirp transducers, which require only one metalization layer. A design procedure is described that makes the transducers focusing to minimize diffraction loss. Experimental results are presented, which show that performance of this new design surpasses conventional designs in several respects. I. INTRODUCTION M ONOLITHIC acoustic surface wave convolvers on YZ-LiNb03 combine high-speed signal processing capability with ruggedness, small size, and relatively low cost of the device-thanks to the simplicity of its construction. However, the intrinsic nonlinearity of the substrate material polarization, which is used to generate the mixing product of the two input signals, is low and limits the efficiency of the device. High efficiency is crucial to achieve high dynamic range and economize input power. Since the introduction of beamwidth compression [l] to boost device efficiency, the elastic convolver has been developed to high performance in several laboratories [2], [3], [4] by optimization of its various components. The aim of such optimization was to increase the device efficiency by eliminating sources of loss in the acoustic path and providing good match at all electrical ports, while tailoring the device characteristics to minimize signal distortion and suppress spurious signals [5]. This means that the convolution efficiency vs. frequency should be reasonably flat and smooth in magnitude and linear in phase over the desired bandwidth. Notably reflections of acoustic waves in the device have to be suppressed to avoid selfconvolution of one input signal. The distributed output signal has to be collected from the integrating electrode in such a way as to avoid electromagnetic propagation loss or destructive interference of various signal components due to long-line effects. By these considerations one arrives at a standard design scheme as shown in Fig. 1. Interdigital transducers, which convert the input signals, typically are unapodized to avoid

High Dynamic Range Acousto-Optic Receiver

Abstract: basic architectures are discussed: the direct detection approach and the interferometric(heterodyne) detection approach. The interferometric spectra analyzer was implemented usinga cascade -cell configuration. The system demonstrated a two -tone spurious -free dynamicrange of 50 dB above tangential sensitivity.IntroductionIn recent years there has been considerable interest in the development of electronicwarfare (EW) receivers utilizing acousto -optic (AO) techniques. The AO receiver offers theadvantages of large instantaneous bandwidth, moderate frequency resolution, high probabilityof intercept and the ability of handling simultaneous pulsed signals. High performancepotential of the AO approach was demonstrated, for instance, in an RF spectrum analyzer thatachieved 1 GHz bandwidth, 20 MHz frequency resolution and 40 dB instantaneous dynamic rangeabove tangential sensitivity.' For operational EW receiver applications the demonstrateddynamic range is not sufficient. There is, therefore, a need to significantly increase theinstantaneous dynamic range of AO receivers.Two basic architectures have been used in the implementation of AO receivers. Theseinclude the power spectrum analyzer (PSA) and interferometric spectrum analyzer (ISA).

A Novel High-Dynamic-Range PLL System for Synchronous Detection in AM Receivers

Abstract: This paper presents a novel nested phase-lock loop system for synchronous detection in AM radio receivers with frequency-synthesizer tuning. The VCXO of the phase-lock loop simultaneously acts as the reference frequency for the synthesizer. A unique compensation technique that ties the poles of the PLL transfer function down in fixed positions effectuates an extremely high dynamic range, thereby alleviating the i. f. filter requirements drastically. With a loop bandwidth of 3.5Hz, an interfering carrier with a 50dB higher level and at a distance of 9kHz from the desired carrier is adequately rejected.

Performance of a Picosecond Streak Camera Used in Conjunction with a Photodiode Array Measuring System

Abstract: Publisher Summary This chapter discusses the performance of a picosecond streak camera used in conjunction with a photodiode array measuring system. Complete diagnostic in laser-matter-interaction experiments requires characterization of the laser pulse incident on the target and some experimental plasma parameters. The ultrafast streak camera is an important comprehensive diagnostic tool for the measurements of these parameters. The use of streak cameras is still often limited by the long procedure required for film processing before delivering useful information. This chapter presents some works undertaken to achieve automatic readout, processing, and display of streak images. It shows the construction of an image sensor using an RL 1024 S Reticon linear photodiode array, which presents interesting properties such as good linearity, high dynamic range, and insignificant lag. This last feature allows the measurement of the trace that is produced by the streak camera used in a single shot, which is extremely difficult with TV cameras, which are valuable for their high sensitivity and dynamic range in low-light level permanent trace measurements. After a brief look at the theory of operation of photodiode arrays and an examination of their characteristics, the chapter describes the acquisition device and provides results obtained with this system coupled to an S·1 picosecond streak camera.