[Paper Review] Leakage Mitigation and Internal Delay Compensation in FMCW Radar for Small Drone Detection

Junhyeong Park, Seungwoon Park+1 more|arXiv (Cornell University)|Jul 17, 2018

Radar Systems and Signal Processing14 references4 citations

TL;DR

This paper proposes a novel down-conversion technique for FMCW radar that mitigates transmitter-receiver leakage and compensates for internal signal delay. By combining frequency planning and digital signal processing, the method reduces the noise floor by 7.0 dB in the near-distance region and recovers the maximum detectable range, significantly improving dynamic range and detection performance for small drone detection.

ABSTRACT

One of the notorious problems of frequency modulated continuous-wave (FMCW) radar is leakage between the transmitter and the receiver. The phase noise of the leakage is expressed as a skirt around the leakage signal on power spectrum. It causes the deterioration of the dynamic range, especially, in the near-distance region. Therefore, although FMCW radar has an advantage over pulse radar in terms of near-distance target detection due to its way of operation, the advantage of FMCW radar can be lost because of the leakage. Another problem of FMCW radar is internal delay in the radar system. It leads to the decrease of the maximum detectable range. In this paper, a novel down-conversion technique which resolves these problems is proposed. Detailed theory and procedures to implement the proposed technique are explained. Then, performances of it are verified with the experiment results. The proposed technique can be implemented through frequency planning and digital signal processing without additional parts. The results show that the proposed technique lowers the noise floor about 7.0 dB in the near-distance region and 2.1 dB even in the far-distance region. Also, the results demonstrate the proposed technique recover the reduced maximum detectable range by compensating the internal delay.

Motivation & Objective

• To address the critical issue of transmitter-receiver leakage in FMCW radar, which degrades dynamic range, especially in the near-distance region.
• To resolve the problem of internal signal delay that limits the maximum detectable range in FMCW radar systems.
• To develop a solution that enhances radar performance without requiring additional hardware components.
• To verify the effectiveness of the proposed technique through experimental validation in real-world conditions.
• To enable reliable detection of small, low-RCS drones by improving sensitivity and dynamic range in challenging near-field scenarios.

Proposed method

• A novel down-conversion technique is proposed that separates the leakage signal from the desired echo signal in the baseband domain.
• The method employs precise frequency planning to shift the leakage spectrum away from the baseband signal of interest.
• Digital signal processing algorithms are applied to estimate and cancel the phase noise components of the leakage signal, which appear as spectral skirts.
• Internal delay in the radar chain is modeled and compensated using a calibration-based digital correction technique.
• The approach leverages existing signal processing blocks, avoiding the need for additional hardware components.
• The technique is implemented using standard FMCW signal processing chains, ensuring compatibility with existing radar systems.

Experimental results

Research questions

• RQ1 How can transmitter-receiver leakage in FMCW radar be effectively mitigated to improve dynamic range in the near-distance region?
• RQ2 To what extent can internal signal delay degrade the maximum detectable range in FMCW radar systems?
• RQ3 Can leakage and internal delay be compensated using only frequency planning and digital signal processing without additional hardware?
• RQ4 What is the achievable improvement in noise floor and detection range after applying the proposed compensation techniques?
• RQ5 How does the proposed method perform in real-world conditions for detecting small, low-RCS drones?

Key findings

• The proposed technique reduces the noise floor by approximately 7.0 dB in the near-distance region, significantly improving sensitivity for close-range targets.
• Even in the far-distance region, the noise floor is lowered by 2.1 dB, enhancing overall dynamic range.
• The internal delay in the radar system is successfully compensated, restoring the maximum detectable range that was previously reduced.
• The method achieves these improvements using only frequency planning and digital signal processing, without requiring additional hardware components.
• Experimental results confirm the effectiveness of the technique in practical FMCW radar systems for small drone detection.
• An upgraded version of the work was published in IEEE Transactions on Microwave Theory and Techniques, validating its technical contribution and performance.