Measured Performance of a Delay Lock Tracking Loop when Noise Power Exceeds Signal Power

摘要

In the communications area there is a general interest in recovering signals below the noise level. In the military this interest translates to low-probability-intercept (LPI) and anti-jam (AJ) communications systems. The receiver improves the signal-to-noise ratio so data can be reliably recovered. This improvement is usually accomplished by matched filtering or by correlation. In this report correlation is used as a post-detection processing technique to derive a synchronous reference. The system considered in this experiment can operate noncoherently by means of a delay lock tracking loop at signal-to-noise ratios as small as -5.0 to -7.1 dB. Furthermore, synchronization is achieved while the received signal is being modulated by data. No preamble or other type of synchronization is required.