**Yongsheng Zhao, Dexiu Hu \*, Yongjun Zhao, Zhixin Liu and Chuang Zhao**

PLA Strategic Support Force Information Engineering University, Zhengzhou 450001, China **\*** Correspondence: paper\_hdx@126.com

Received: 30 May 2019; Accepted: 24 July 2019; Published: 31 July 2019

**Abstract:** Transmitter and receiver position errors have been known to significantly deteriorate target localization accuracy in a multi-static passive radar (MPR) system. This paper explores the use of calibration targets, whose positions are known to the MPR system, to counter the loss in target localization accuracy arising from transmitter/receiver position errors. This paper firstly evaluates the Cramér–Rao lower bound (CRLB) for bistatic range (BR)-based target localization with calibration targets, which analytically indicates the potential of calibration targets in enhancing localization accuracy. After that, this paper proposes a novel closed-form solution, which includes two steps: calibration step and localization step. Firstly, the calibration step is devoted to refine the inaccurate transmitter and receiver locations using the BR measurements from the calibration targets, and then in the calibration step, the target localization can be accurately achieved by using the refined transmitter/receiver positions and the BR measurements from the unknown target. Theoretical analysis and simulation results indicate that the proposed method can attain the CRLB at moderate measurement noise level, and exhibits the superiority of localization accuracy over existing algorithms.

**Keywords:** multi-static passive radar; target localization; calibration target; bistatic range; transmitter and receiver position error; Cramér–Rao lower bound
