This paper discusses the problems arising in the realization of practical, wide-band signal correlation systems and presents some possible solutions to these difficulties. Function generators and shift-register encoders in particular solve the problem of long, stable delays, by providing wide-band signals that can be reproduced accurately with any desired time delay or Doppler compensation. The use of clipped signals permits operation over a wide range of input-signal amplitudes, while sacrificing absolute amplitude information and some processing gain. High search rates and processing real time are achieved with multichannel correlators, compressed-time correlators, and matched filters. Several ways of instrumenting digital delay-line time compressors, digital-scanned-storage time compressors, and digital matched filters are discussed, including their integration into real-time processing systems. The relative advantages of the different approaches are discussed.
The cryogenic system for the Large Hadron Collider (LHC) under construction at CERN will include twelve new local helium transfer lines distributed among five LHC points in underground caverns. These lines, being manufactured and installed by industry, will connect the cold boxes of the 4.5-K refrigerators and the 1.8-K refrigeration units to the cryogenic interconnection boxes. The lines have a maximum of 30-m length and may possess either small or large re-distribution units to allow connection to the interface ports. Due to space restrictions the lines may have complex routings and require several elbowed sections. The lines consist of a vacuum jacket, a thermal shield and either three or four helium process pipes. Specific internal and external supporting and compensation systems were designed for each line to allow for thermal contraction of the process pipes (or vacuum jacket, in case of a break in the insulation vacuum) and to minimise the forces applied to the interface equipment. Whenever possible, flexible hoses were used instead of bellows to allow for thermal compensation of the process pipes. If necessary, compensation units were integrated in the vacuum jacket. The thermal design was performed to fulfil the specified heat-load budget. This paper presents the main technical design choices for the lines together with their expected performance. ABSTRACTThe cryogenic system for the Large Hadron Collider (LHC) under construction at CERN will include twelve new local helium transfer lines distributed among five LHC points in underground caverns. These lines, being manufactured and installed by industry, will connect the cold boxes of the 4.5-K refrigerators and the 1.8-K refrigeration units to the cryogenic interconnection boxes. The lines have a maximum of 30-m length and may possess either small or large re-distribution units to allow connection to the interface ports. Due to space restrictions the lines may have complex routings and require several elbowed sections.The lines consist of a vacuum jacket, a thermal shield and either three or four helium process pipes. Specific internal and external supporting and compensation systems were designed for each line to allow for thermal contraction of the process pipes (or vacuum jacket, in case of a break in the insulation vacuum) and to minimise the forces applied to the interface equipment. Whenever possible, flexible hoses were used instead of bellows to allow for thermal compensation of the process pipes. If necessary, compensation units were integrated in the vacuum jacket. The thermal design was performed to fulfil the specified heat-load budget.This paper presents the main technical design choices for the lines together with their expected performance.
New methods of underwater acoustic-propagation research have been developed in which noiselike or pseudorandom signals, generated by shift-register encoders, are detected by correlation techniques. The principles and problems of three classes of experiments are discussed: (1) the signal received is crosscorrelated with a time-delayed and time-compressed replica of the transmitted signal; (2) two received signals are crosscorrelated and studied as a function of hydrophone separation; (3) the received signal is correlated with that received from a later repetition of the transmitted signal. It is shown theoretically that the results of the first class of experiments are different from and unpredictable from those obtained by employing the usual filtering and detection of impulsive or single-frequency signals. The severe problem arising from multipath interference in the second class of experiments, which is different for the multipath problem in the first class of experiments, is discussed and some solutions proposed. The essential identity of the second and third classes of experiments is discussed. A companion paper discusses the instrumentation for and execution of the experiments and presents some preliminary observations.
A real-time electronic spectrograph that produces a time-versus-frequency display on a cathode-ray storage tube is described. A DELTIC (DElay Line TIme Compressor) is used to obtain high-frequency multiplication ratios aad thereby essentially real-time analysis with a swept-filter heterodyne analyzer. The device examines the time-frequency structure of a stored sample. The resulting output displays the complele content of the store in one recirculation per bandwidth. The entire sample is thus analyzed in a fraction of a second. Pulses, tones, and noise transients were used to text the capabilities of the analyzer with respect to time resolution, frequency resolution, response to noise, and processing gain. Results of these tests aad other illustrative examples of the analyzer output are presented, which show that (1) frequencies separated by one bandwidth or more can be resolved, (2) pulses shorter than the filter buildup time are lengthened whereas pulses longer than the buildup time retain their original length, and (3) the device does not respond to level changes of white noise at the input.
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