Unambiguous Direction Estimation and Localization of Two Unresolved Targets via Monopulse Radar

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors:

The authors presented a proposal of localization of two closely-spaced targets. Work on this problem is carried out in many research and industrial centers for many years. The authors proposed to supplement the known four-antenna system with an additional fifth antenna. The subject studied by the authors is very important and interesting, but very complex. Such networks may be needed for civilian and military applications such as electronic warfare, for example. Theory and results of simulations were presented. Experimental verification would be nice. The proposed solution will not replace other multi-antenna (multi-channel) systems (with more than five antennas), but this concept is worth exploring.

 

I. Following are the detail comments:

1. References are extensive enough.

2. I propose to supplement the Conclusions with an opinion on how the proposed algorithm reacts when there exist more than two targets in one resolution cell. In practice, we don’t know how many targets we are observing at the moment.

3. The authors tested a case where amplitude of one signal is twice as large as the other. It would be worth adding in Conclusions what will happen when the signals amplitudes from both targets are the same.

4. The statement that “… the algorithm has the best performance when SNR increased” and shape of the plot presented in Figure 9 are obvious.

5. Results of simulations presented in Figure 4 and 6 are very interesting and very promising for many applications. It is worth verifying them under real experimental conditions.

Author Response

Point 1. References are extensive enough.

Point 2. I propose to supplement the Conclusions with an opinion on how the proposed algorithm reacts when there exist more than two targets in one resolution cell. In practice, we don’t know how many targets we are observing at the moment.

Response 2: This study presents a closed-form solution to resolve the directions of arrival of two unresolved targets using a single snapshot of four independent channels in phase comparison monopulse radar, this method is especially suitable for estimating the angle of the target and the towed decoy. More antennas and more complex algorithms will be needed to detect the angle of three ambiguous targets. If there are three targets in one resolution cell, the estimated angles will be close to the angles of the targets with a larger amplitude and the proposed scheme cannot resolve them. We show the estimated angle of three targets by this method for the same amplitude and different amplitude targets in figure 1 and figure 2.

figure 1. Scatter plot of angle estimation of the real target (*) and decoy(Δ) for same amplitude three targets [decoy (O), target1 (x) and target2 (+)]

figure 2. Same as figure 1 only targets have different amplitude (the amplitude of target [+] is less than other targets [half of the other targets])

Point 3. The authors tested a case where amplitude of one signal is twice as large as the other. It would be worth adding in Conclusions what will happen when the signals amplitudes from both targets are the same.

Response 3: The same amplitude of the targets will not affect the proposed method for angle estimating of two targets. Figure 3, shows the simulation result of the estimated angle of two targets having same amplitude.

Figure 3. Two targets have the same amplitude

Point 4. The statement that “… the algorithm has the best performance when SNR increased” and shape of the plot presented in Figure 9 are obvious.

Response 3: We using this comment in our paper

Point 5. Results of simulations presented in Figure 4 and 6 are very interesting and very promising for many applications. It is worth verifying them under real experimental conditions

 

 

Author Response File: Author Response.pdf

Reviewer 2 Report

This is a good article, but I can't see where the algorithm in this article is more advanced than that in Ref 20? Please describe in detail. Everything else is great, but one disadvantage is that the innovation is relatively ordinary.

Author Response

In Ref 20, they propose a subarray-based four-channel monopulse method to achieve an efficient, four-channel monopulse unambiguous, and fast two-target resolution, which is applicable to a phased array radar with a regular shape, i.e., circular arrays, elliptical arrays, and regular-octagonal arrays, but Our method for ordinary phase comparison monopulse radar.

If your comment is Ref 19:

In this paper, the solution is mathematically similar to [19], but has less computational complexity and better performance, furthermore, our method can estimate the angles of two targets which are positioned at the same azimuth or elevation angle by using only one extra antenna, the Ref 19 technique is unable to resolve two targets when they have same azimuthal or elevation angles due to angular ambiguity. In addition the impact of SNR, targets direction, and phase difference of targets on the accuracy of angle estimation has also been described.