Rapid Detection of Spectral Line Components in Wideband Noise Using a Swept Second-Order Phase-Locked Loop Preceded by a Digital Time Compressor

摘要

In some information processing systems, it is desirable to be able to detect the presence of 'weak' spectral line components in wideband noise. In low-power and/or low-cost systems, such spectral line detection is presently most economically accomplished through the use of a swept phase-locked loop. When employed in this manner, the loop can be considered as a kind of variable center frequency bandpass filter that passes signals and rejects noise. When the bandwidth of this 'filter' is narrow relative to the total frequency band to be searched, the time required to sweep through the band may be excessive. This report discusses the manner in which time-compression techniques can be employed to reduce the required detection time. This is done by using a digital time compressor at the input to the phase-locked loop. The resulting system is called a 'fast phase-locked loop.' (Author)