A 220 GHz to 325 GHz Grounded Coplanar Waveguide Based Periodic Leaky-Wave Beam-Steering Antenna in Indium Phosphide Process
, Marius Kretschmann 1, Joel Dittmer 2, Peng Lu 3, Andreas Stöhr 3 and Thomas Zwick 1
Round 1
Reviewer 1 Report
This paper presents a periodic GCPW leaky-wave beam steering antenna implemented in an InP process. The operating frequency range is 220 GHz-325 GHz, the absolute bandwidth is 105 GHz, and the relative bandwidth is 38.53%. The antenna is fabricated using a GCPW leaky-wave cell with two mirrored L slots. In this paper, Floquet theory is applied to analyze the leakage rate, phase constant and Bloch impedance of the leaky wave element, and the Bloch impedance of the mirrored L-shaped slot and the longitudinal symmetric L-shaped slot is compared. It is proved that the open stopband phenomenon is effectively reduced, which is a common problem in periodic leaky wave antennas.
On the other hand, the authors compared the EM simulation results of a periodic GCPW leaky-wave antenna with the results of an ideal model derived from a single leaky-wave element. It is worth noting that the results obtained by the two methods are very consistent. However, compared with the complete electromagnetic simulation model, the ideal model greatly reduces the number of hexahedral mesh elements required by nearly 20 times, thus providing a novel and efficient method for speeding up the development process of periodic leaky-wave antennas. To verify the simulation results, the authors also performed measurements with a secondary probe type antenna, which showed a good agreement in terms of reflection coefficient, peak antenna gain, beam steering Angle, and far field.
Overall, the paper is clear in logic and structure, the experimental design is able to test hypotheses, and the arguments are reliable and meaningful.
Some comments and suggestions for this paper are as follows:
1. On page 3, line124, The author states: "The antenna design begins with a GCPW having a characteristic impedance of 50 Ω." There is no further detail on the characteristic impedance of 50 Ω. As the measurement of the VNA excites the antenna with a probe, more discussion should be added to clear show how the probe contact the antenna port and the possible error of the contaction.
2. Pages 4 through 6 of the original paper discuss the performance of three different sizes of l2Ls, and finally conclude that: “Consequently, the optimum value of l2Ls is 135 µm, which provides a good trade-off between a sufficiently low leakage rate and a Bloch impedance that stays close to 50 Ω for most part of the target frequency range. "But for the selection of parameters during simulation, namely 120μm, 135μm and 150μm, the reasons for the selection of these three measurement parameters are not introduced in detail. And there is no further accurate measurement data to show that 135μm is indeed the best performance in this range. That is to say, there is no evidence or other reason to show that the performance of other l2Ls sizes around 135μm is worse than 135μm, which may be a less rigorous part of the paper.
3. The author states on page 10, line 320: "The measured and simulated curves in Figure 6b and Figure 6c exhibit a strong agreement." And in Figure 6b and 6c attached below, when the frequency is greater than or equal to 280GHz, the simulated data and the measured data are indeed in good agreement, but when the frequency is less than 280GHz, the corresponding measured data is less agreement, and the frequency range of the match should be precisely limited.
4. Here are the syntax errors in the paper:
Page 2, row 41, “Another critical requirement for future IMT systems is the ability to serve multiple users with pencil beams, which provide high spatial resolution and thus avoid mutual interference. "where" provide "and" avoid "should be changed to" provides "and" avoids "respectively.
This paper is well prepared. The overall quality of the English language is fine.
Author Response
Thank you for your feedback. Please find the answers to Reviewer 1 in the attached pdf file.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
The manuscript is well prepared with a quite comprehensive introduction to leaky-wave antenna design. The topic is interesting to the readers. The design is verified by a fabricated leaky-wave antenna with measured radiation patterns. Following is a list of questions or comments.
1. The unit cells are based on GCPW structures. What is the advantage of using a CPW-based antenna for leaky-wave antenna implementation?
2. One of the claimed novelty is implementation by using InP process. What is the advantage of using InP process?
3. Two L-slot patterned GCPW leaky-wave unit cells are analyzed. In Fig. 4(c), the antenna simulation results do not fully match with the derived results from leaky-wave unit cells. Those peaks on the plots are frequency offset to some extent. Please explain the possible reason.
4. Line 50, P. 2: The reference number is missing (after [5]).
Author Response
Thank you for your feedback. Please find the answers to Reviewer 2 in the attached pdf file.
Author Response File: Author Response.pdf
Reviewer 3 Report
Interesting and well-presented work. The research presents a theoretical analysis supported by practical outcomes. It's clear that the study has been executed skillfully and adds significant value to the field. Here are a few suggestions to further improve your work.
1) Regarding the text presented, there are a few typos and writing.
a. Line 50: reference
b. Line 94: frequency changed line
c. Line 292: 82%
2) Increase the font size of some figures. For example, Fig. 4b and e.
Regarding the text presented, there are a few typos and writing.
a. Line 50: reference
b. Line 94: frequency changed line
c. Line 292: 82%
Author Response
Thank you for your feedback. Please find the answers to Reviewer 2 in the attached pdf file.
Author Response File: Author Response.pdf
Reviewer 4 Report
The paper presents periodic leaky-wave beam steering antenna with GCPW structure for THz applications. I have some questions as follows:
1. The proposed structure consists of mirrored L-slot to mitigate the open stopband phenomenon, the authors should add the figures and analysis in terms of E- and H-fields of the proposed structure
2. In Figure 4(b), the parameters, which were used for simulation, should be added in the manuscript.
3. In Figures 6(b) and 6(c), the authors should add the measured results (from 220 GHz to 280 GHz) for beam steering angle.
Author Response
Thank you for your feedback. Please find the answers to Reviewer 2 in the attached pdf file.
Author Response File: Author Response.pdf
