Generalized characteristics of the spatio-temporal signal resolution for radar sounding with a small pulse period-to-duration ratio and angular-coordinate scanning

摘要

The results of the theory of spatio-temporal signal processing are widely used for increasing the resolution and interference immunity of radars. The spatial (in particular, adaptive) processing of signals is conventionally used to suppress jamming, which is possible due to the difference between directions toward the detected target and jammers [1, 2]. The temporal (Doppler) selection of moving targets is conventionally considered an aid against passive interference. The well-known way of improving the selection of moving targets is by decreasing the period-to-duration ratio of sounding radar pulses [3, 4]. In this case, either the repetition rate of sounding pulses is increased, so that their repetition period becomes a few times smaller than the time of signal delay from the most remote target, i.e., the round-trip time of electromagnetic-wave propagation between the target and the radar, or the pulse duration is increased up to a value comparable with the above-mentioned delay time. Improving the selection of moving targets in this case is related to increasing the quality of the temporal (Doppler) resolution of signals [4, 5]. However, in the case of a small pulse period-to-duration ratio, weak useful signals from remote targets are received simultaneously with powerful passive-interference signals from objects located at small and medium distances. In [6-10], a method of spatial target selection with accelerated angular-coordinate scanning was proposed for such conditions. At present, however, there is no theory which allows one to reveal the capabilities of spatial resolution using the differences between object distances and to justify the method proposed in [6-10] from this viewpoint. Therefore, in what follows we develop the results of [5], generalizing them to the scanning regime for one-position radars, and analyze the accelerated scanning. The analysis proves, in particular, that an increase in the speed of angular-coordinate scanning results in transformation of the differences between object distances to the spatial differences between reemitted signals, thereby ensuring the spatial distance resolution and the possibility of spatial selection of a weak useful signal from a remote target against the background of powerful passive-interference signals from nearby objects. As was already noted, the signal resolution and selection based on the differences between Doppler frequency shifts rather than those based on the delay time are here called the temporal resolution and the temporal selection, respectively. Such a nomenclature is explained by the fact that the above-mentioned Doppler resolution is realized using the methods of temporal processing, i.e., processing of signal readouts separated in time with the help of, e.g., delay lines [5].