Constant envelope OFDM signals for radar applications

Abstract

Orthogonal frequency division multiplexing (OFDM) radar signals, because of their prominent properties have been recently of interest of many researchers. But the large amplitude fluctuations of the OFDM signals makes it susceptible to system nonlinearities. This paper proposes a new concept of radar coding using OFDM signals which combines orthogonal frequency division multiplexing and phase modulation (OFDM-PM) or frequency modulation (OFDM-FM). The PM or FM creates a constant envelope signal which allows high power amplifiers to operate near saturation levels thus maximizing power efficiency and OFDM increases the robustness to multi-path fading and also range resolution capability. The feasibility of this signalling as a radar pulse compression technique is also studied, and some codes for constant envelope OFDM signals (CE-OFDM) with favourable autocorrelation functions are introduced.