Relatively Moving Target Return Emulation for high Coherently Processed Time-Bandwidth Products

The accurate modelling of relative target motion is essential for coherent radar processing and suitable emulation approaches for radar testing. Special consideration will be required if an instantaneously wide signal spectrum is processed over a long timespan and a non-stationary target return migrates in relative range. Thereby, a fast moving isotropic point scatterer will span concurrently a set of distinct Doppler frequencies and range cells. The often used, processing inherent, short-term narrowband motion approximation becomes then too inaccurate. This publication describes the Doppler effect modelling for relative fast target motion with a conceptual modelling principle, which is independent of the spectral content in the processed radar bandwidth. It is founded on the intentional sampling clock difference between two clock domains. Based on this principle, conceptual approaches have been tested to verify its real-time capability for moving target response emulation and modelling. In addition, the sampling rate transfer requirement in DSP based bistatic radar architectures is highlighted. Further, experimental moving and effectively accelerated target returns are related to emulated and simulated return shapes by the use of a coherently received multi-carrier OFDM waveform with digital reference.

I. Introduction

A widely used application since the early days of radio de-tection and ranging (RADAR) is moving target detection and tracking. Modern radars, which aim to detect moving targets coherently, require an accurate target return modelling as a fundamental and essential step in their processing. In particular for large coherently processed timespans and bandwidths, it becomes important to consider the relatively effective motion of the target during the coherent processing interval (CPI). This is essential to evaluate the overall radar performance, to conduct the respective radar testing and to develop suitable mitigation strategies to compensate effects that are caused by the movement of the target with respect to the radar geometry.