Synthesis of pulsed frequency modulated ultra wideband radar signals based on stepped phase shifting

Abstract

The current paper introduces a novel concept for low complexity and low power synthesis of pulsed frequency modulated ultra wideband (PFM UWB) signals. Instead of using a VCO-based synthesizer, we employ a simple digitally tuned phase modulator that varies the phase of a high order harmonic of a fixed frequency LO signal. The phase modulated harmonic is then injected into a switched injection locked pulse oscillator. Based on this concept, an arbitrary sequence of phase samples - i.e. UWB pulses where each pulse has a predefined carrier phase - can be generated. This sampled pulse sequence can be used for the generation of angle modulation schemes for communication signals and also for the generation of pulsed linear frequency modulated radar signals. The capability of the proposed concept is experimentally demonstrated for the synthesis of 6 to 8 GHz UWB pulsed frequency sweeps. Measurement results verify that this novel approach delivers a performance comparable to much more complex pulsed frequency modulation implementations.