Joint Waveform and Receiver Design for Co-Channel Hybrid Active-Passive Sensing with Timing Uncertainty

TL;DR

This paper proposes joint waveform and receiver design strategies for hybrid active-passive radar systems operating in co-channel environments with timing uncertainty, enhancing spectral efficiency and mitigating interference.

Contribution

It introduces two novel optimization-based design methods for joint waveform and filter design under timing uncertainty in hybrid radar systems.

Findings

The proposed methods outperform conventional radar systems in simulations.

The designs effectively handle timing uncertainty, improving detection performance.

When timing uncertainty is zero, the methods simplify to a common solution.

Abstract

We consider a hybrid active-passive radar system that employs a wireless source as a passive illuminator of opportunity (IO) and a co-channel active radar transmitter operating in the same frequency band to seek spectral efficiency. The hybrid system can take advantage of the strengths of passive radar (e.g., energy efficiency, bi-/multi-static configuration, and spatial diversity) as well as those of active radar (dedicated transmitter, flexible transmit beam steering, waveform optimized for sensing, etc.). To mitigate the mutual interference and location-induced timing uncertainty between the radar and communication signals, we propose two designs for the joint optimization of the radar waveform and receive filters. The first is a max-min (MM) criterion that optimizes a worst-case performance metric over a timing uncertainty interval, and the other a weighted-sum (WS) criterion that forms a weighted sum of the performance metric at each delay within the delay uncertainty interval. Both design criteria result in nonconvex constrained optimization problems that are solved by sequential convex programming methods. When timing uncertainty vanishes, the two designs become identical and admit a simpler solution. Numerical results are presented to demonstrate the performance of the proposed hybrid schemes in comparison with conventional active-only and passive-only radar systems.