Low-Profile Proximity-Coupled Cavity-Less Magneto-Electric Dipole Antenna
Round 1
Reviewer 1 Report
Comments and Suggestions for AuthorsThis work presents a wideband ME-dipole antenna without the cavity structure. It’s interesting work, and the results, including the simulation and measurement, are provided and validated the effectiveness of the proposed design. They also agree well with each other. Here are some suggestions for consideration. In Fig. 4, which software is used for the analysis? The horizontal line should be very critical for the excitation of M-dipole. If so, a comparison with and without it would be help for the demonstration of the working principle.
Author Response
Thank you for your valuable feedback and insightful suggestions.
1- In response to your question about Figure 4, it presents the E-field distributions of the ME-dipole antenna at different time periods using CST software. This figure demonstrates that the proposed ME-dipole mode operates as intended.
2- Regarding the horizontal suspended transmission line, we agree that it plays a critical role in the excitation of the M-dipole mode. The operating principle of the magneto-electric (ME) dipole relies on the simultaneous excitation of the electric and magnetic dipoles with equal magnitude and phase. This design results in two distinct resonances: the first, at a lower frequency band, is associated with the E-dipole, while the second, at a higher frequency, corresponds to the M-dipole. Due to the fringing fields between the ends of the E-dipole and the ground reflector, the E-dipole effectively exhibits a longer equivalent electrical length compared to the M-dipole. To illustrate this, a detailed parametric study is provided in Section 4.6, where the length of the suspended coupling line (L_arm) is analyzed. As shown in Figure 12, the results confirm that the E-dipole and M-dipole modes are excited at specific lengths of L_arm. For effective excitation of both modes, the transmission line length must fall within the range of 18 mm (0.15λ₀) to 27 mm (0.23λ₀). Furthermore, the S11 and Z11 figures indicate that when Larm<18 mm, only the M-dipole mode is excited.
We sincerely appreciate your comments and hope the additional details clarify the points you raised.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
Comments and Suggestions for AuthorsThis work demonstrates that the design has smaller size and is cavity-less. I think the authors missed many important references on ME antennas because this topic is very hot in recent years, and many miniaturized ME antennas have been reported. Moreover, the technique behind the proposed design is not very clear. Why the proposed one can have smaller size but better performance? If this design is just an optimized one, it does not make sense.
Author Response
Thank you for your thoughtful feedback.
Regarding the references, we acknowledge that magneto-electric (ME) antennas have gained significant attention in recent years, and numerous advancements have been reported. We carefully reviewed recent literature, particularly on ME dipole antennas with various feeding methods, and ensured that they are properly cited and discussed in the revised version of the paper, specifically in Section 1 of the introduction, with a summary provided in Table 4.
The proposed antenna achieves a smaller size and improved performance due to several factors, including the novel horizontal suspended transmission line feeding method and the careful excitation of both the electric dipole and magnetic dipole modes. The design utilizes a suspended transmission line to excite these modes through proximity coupling, which enhances the impedance bandwidth compared to the direct coaxial feeding method reported in the literature. Notably, the proposed ME dipole antenna achieves a wide impedance bandwidth of 53% in simulation and 45% in measurement. The discrepancy arises from fabrication tolerances, particularly in maintaining the 1 mm spacing between the horizontal suspended line and the antenna patches, which was a challenging aspect of fabrication.
The feeding structure consists of a vertical semi-rigid coaxial cable and a horizontal flat transmission line, enabling the excitation of the M-dipole mode without the need for quarter-wavelength cavity walls. As a result, the antenna achieves a low profile of approximately 0.17 times the free-space wavelength. Furthermore, due to the reduced profile, the fringing field of the E-dipole mode is less pronounced. This innovative feeding method allows the size of the ground reflector to be reduced to 0.78 (lambda) while maintaining a wide impedance bandwidth and stable high gain. To validate its uniqueness, we provided a comparison with state-of-the-art designs in terms of size, bandwidth, and realized gain in Table 4.
Thank you again for your valuable input. We hope the additional details and revisions address your concerns.
Reviewer 3 Report
Comments and Suggestions for AuthorsThe paper is written well but the authors need to clarify the new materials added in this manuscript compared to their conference paper [10]. The only new materials that I noticed are parametric study of few more parameters and measurement results (however the measurement results are not complete). Therefore, if this manuscript meets the publication requirements of this journal, major revision is recommended.
1. Instead of Fig. 4, show the E-field at a frequency where E-dipole radiation is dominant and H field at a frequency where M-dipole radiation is dominant.
2. Page 7, line 175, add the figure number instead of “??”.
3. Add simulated cross pol to Fig. 16(a), (c), and (e).
4. In Fig. 16, add radiation patterns at the maximum frequency of operation which is larger than 3 GHz.
4. The text from the beginning of section 4 to the beginning of 4.1 can be written more concisely.
Comments on the Quality of English LanguageNo comment.
Author Response
Thank you for your valuable feedback and insightful suggestions. Please find a few comments about the notes:
The conference paper [10] presents a conceptual design but does not include a detailed design procedure or a parametric study of the various design parameters that affect the performance of the ME dipole. Furthermore, the journal paper validates the design concept by comparing the simulated and measured results of the prototype. To demonstrate its uniqueness, the journal also includes a comparison with state-of-the-art designs in terms of size, bandwidth, and realized gain, as summarized in Table 4.
Note1:
1. Instead of Fig. 4, show the E-field at a frequency where E-dipole radiation is dominant and H field at a frequency where M-dipole radiation is dominant.
The E-field presented in the journal paper illustrates the ME dipole modes at different intervals. Due to the structure of the antenna, I believe the current view of the E-field effectively represents both the electric (E) and magnetic (M) dipole modes. The required field patterns for the E-field and H-field are attached for your reference to clarify that the current view provides a better representation.
Note2:
2. Page 7, line 175, add the figure number instead of “??”.
Corrected, Thank you
Note3:
3. Add simulated cross pol to Fig. 16(a), (c), and (e).
Since the simulation assumes a perfectly symmetrical structure and does not account for fabrication errors, particularly the small 1 mm gap between the feed line and the radiation patches, the simulated cross-polarization level in the E-plane is below -80 dB. However, the measured cross-polarization level is approximately -18 dB. We did not plot the simulated cross-polarization in the E-plane because the Y-axis range would need to span from -100 dB to 10 dB, which would make it difficult to effectively compare the radiation patterns with those in the H-plane. Due to the magneto-electric dipole's operating principle, where the electric dipole and magnetic dipole are oriented orthogonally, this discrepancy does not affect the overall performance of the antenna.
Note4:
4. In Fig. 16, add radiation patterns at the maximum frequency of operation which is larger than 3 GHz.
The radiation patterns are presented at three different frequencies representing the lower, middle, and higher ends of the impedance bandwidth to demonstrate the antenna's performance. A summary of these radiation patterns is provided in Table 3. The front-to-back ratio is approximately 20 dB across the operational bandwidth.
The variation in the 3-dB beamwidth across the operational bandwidth (Δ₁) is 5 degrees in the H-plane and 7.8 degrees in the E-plane. The 3-dB beamwidth difference between the two planes (Δ₂) is 12.6 degrees, 13.2 degrees, and 22.75 degrees at the lower, middle, and higher frequencies, respectively.
The required radiation pattern at 3.2 GHz is attached for your reference.
We sincerely appreciate your comments and hope the additional details clarify the points you raised.
Author Response File: Author Response.pdf
Round 2
Reviewer 2 Report
Comments and Suggestions for AuthorsUnfortunately, the authors did not add many recently reported ME antennas for comparison. There are many designs that can have a lower profile. Besides, the design just achieves two poles to expand the bandwidth, which is not novel from my angle.
Author Response
We appreciate the reviewer's valuable feedback and would like to clarify the novelty and contributions of the proposed design:
The novelty of the proposed ME dipole antenna lies in the innovative feeding method using proximity coupling. Unlike conventional designs, the antenna is fed using a combination of a suspended transmission line and a vertical semi-rigid coaxial cable. This unique feeding mechanism enables the excitation of two orthogonal dipoles—electric (E-dipole) and magnetic (M-dipole)—each with distinct resonance and impedance properties. The E-dipole operates in the lower frequency band, while the M-dipole operates in the higher band, allowing the antenna to achieve a wide impedance bandwidth and stable high realized gain.
Additionally, this novel approach eliminates the need for quarter-wavelength cavity walls, resulting in a cavity-less design and a low profile of approximately 0.17 λ₀. This design also allows for a reduced ground reflector size (0.78 λ₀) while maintaining a wide impedance bandwidth of 53.3% in simulation and 45.3% in measurement, along with an average in-band gain of 9 dBi and a stable ±1 dBi variation.
We acknowledge the reviewer’s comment regarding the comparison with recently reported ME antennas. In response, a recently published journal paper on ME dipole antennas has been added to the comparison table. While certain designs may achieve a lower profile, our proposed design offers a contribution by introducing an innovative feeding method that enables size reduction without compromising bandwidth or gain.
We hope this clarification highlights the key contributions and the novelty of our work. Thank you for your valuable feedback.
Reviewer 3 Report
Comments and Suggestions for AuthorsThe authors did not revise the paper based on my previous comments:
1. Please add both simulated and measured patterns at the maximum frequency (3.2 GHz) to the paper otherwise it cannot be claimed that the antenna is working up to 3.2 GHz.
2. You still need to add the measured cross pol response at different frequencies 2, 2.5, and 3.2 GHz. You may not show the simulated cross pol and instead mention that it is very small.
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
