Advances in and Applications of Microwave Photonics in Radar Systems: A Review

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

Article overview: The article addresses an extremely timely and important topic in recent times, namely radar systems. Undoubtedly, as the Authors point out, such systems face various limitations, particularly in terms of bandwidth, transmission speed, and resolution. Therefore, there is a clear need for research in this area. The article concisely presents how microwave photonics (MWP) is utilized to improve radar performance. The described technical solutions enable the achievement of wider bandwidth, reduced noise, and increased resistance to electromagnetic interference, which adds value by contributing to improved radar accuracy.
Detailed opinion: The article is substantively correct. It is written in a technically accurate and comprehensible manner. The scope of the references is also appropriate (the sources are up-to-date and relevant to the article's subject matter and purpose). In the Reviewer’s opinion, the manuscript may benefit from the addition of a section on "Open Problems" (which could be placed before the "Conclusions"), to synthesize the information presented in the article through comparative analysis -but this is merely a suggestion. In practice, the decision to include such a section is left to the Authors, as the necessary information has already been sufficiently addressed in the main text.
Comments: The Reviewer has identified minor editorial issues (a Proofreader’s task), which do not diminish the Reviewer’s positive opinion of the manuscript. The initial letters of subsection titles should be capitalized; additionally, more spacing should be added between the figures and the subsequent text. On the first page (at the very top), it is recommended to use Review instead of Article, as this is a review paper. But all mentioned minor editorial issues may be addressed during the proofreading stage by Proofreader. Apart from these points, there are no other comments.
Final conclusion and decision: Acceptance of the article in its current form.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

This paper comprehensively expounds on the applications of microwave photonics in radar systems. However, there are still some issues, and it can be further improved in terms of research content, analysis depth, and writing norms. The specific review comments are as follows. 

1. While optoelectronic oscillators (OEO) achieve low phase noise, their frequency limits (mentioned as 100 GHz) are not contextualized with practical challenges like optical delay line stability and temperature sensitivity at high frequencies.

2. Photonic DACs for radar waveform generation (referencing works [69-72]) mention "limited time duration" but fail to evaluate its impact on long-range radar applicability.

1. Phase drift due to temperature fluctuations in fiber transmission (Section 2.1) briefly mentions compensation methods but omits evaluations of their maturity, cost, and complexity.
2. Optical beamforming networks (Section 2.7) relying on long fiber delays do not address added system bulk or mechanical stability issues, raising doubts about airborne radar feasibility.
3. Optical real-time Fourier transform (Section 2.8) focuses on dispersion-based methods but overlooks integrated photonic chip solutions (e.g., silicon delay lines).
4. Overlapping content between radar waveform generation (Section 2.3) and mixing techniques (Section 2.4)—e.g., photonic DACs serving both roles—blurs technical boundaries.
5. Key equations (e.g., spatial resolution Δr = c/2B) lack context (e.g., idealized propagation assumptions), risking misinterpretation of atmospheric attenuation effects in high-frequency radar.
6. "optical-microwave synchronization" (Section 2.2) vs. "optical injection locking" (Section 2.3) lacks differentiation, causing conceptual confusion.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

1. The authors have comprehensively summarized the application of microwave photonic technology to radar systems, which can overcome the limitations of conventional electronic-based radar systems by enabling ultra-wide bandwidth, low phase noise, and highly reconfigurable signal processing. My comment is as follows:

   The authors have summarized the technical literature of microwave photonic radar, but radar systems must operate in real environments. Therefore, it is recommended to additionally summarize the field experimental results that demonstrate the practical feasibility of applying microwave photonic technology to radar systems.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf