Multitone Waveform Design Toward Enhancing Conversion Efficiency for RF Electronics Detection

Nonlinear radar has attracted considerable attention in recent years due to its unique advantage in detecting nonlinear targets, such as radio frequency (RF) electronics, under strong clutter conditions. However, the low nonlinear RF-to-RF conversion efficiency (RRCE) severely limits its operational range and application scenarios. So far, the research community has mainly focused on improving the RRCE from the hardware aspects while ignoring the signal design. In this article, we study the waveform design problem that maximizes RRCE for detecting nonlinear targets. Assuming known channel state information and target characteristics, we develop a tractable block-oriented nonlinear model and formulate the waveform design as a constrained optimization problem. Then, two iterative algorithms based on successive relaxation are proposed to solve the nonconvex problem for different cases. Besides, the simulations and laboratory experiments demonstrate the effectiveness of the system model and the superiority of the proposed waveform design method over various baselines. More than 4-dB improvement in RRCE is observed for the given configurations in the experiment. The study provides a promising alternative for extending the maximum distance of nonlinear radar.