Magnetic-Free Nonreciprocal Multifunction Device Based on Switched Delay Lines
Round 1
Reviewer 1 Report
The paper is well written. On the other hand, the following revisions are needed in each section as follows:
Section "1. Introduction"
The introduction is clear and all the objectives well stated. At the same time, some recent technology developments are missing such as:
_ computing metamaterials [Inverse-designed metastructures that solve equations, Science 363 (6433), 1333-1338, 2019]
_ near-zero-index materials [Near-zero refractive index photonics, Nature Photonics, 11, 149–158, 2017]
_ plasmonics [Plasmonic Optical and Chiroptical Response of Self-Assembled Au Nanorod Equilateral Trimers, ACS nano, 2019]
_ metasurface [Curvilinear MetaSurfaces for Surface Wave Manipulation, Scientific reports 9 (1), 3107, 2019]
_ graphene [Graphene acoustic plasmon resonator for ultrasensitive infrared spectroscopy, Nature Nanotechnology 14, 313–319, 2019]
_ nanoparticles [Strategies in the design of nanoparticles for therapeutic applications, Nature Reviews Drug Discovery, volume9, 615–627, 2010]
It would be beneficial for the reader if authors include such technologies in the introduction section to have a complete picture of the state-of-art.
Section "2. Principle of the device"
1) The analytical model is very interesting, at the same time it is not reliable alone and appear insufficient.
To this regard you can refer to the following other mathematical approaches to explain in details the functionality of the different technologies: Multilayer model, Green's function, Polarizability and Scattering [All-metallic epsilon-near-zero graded-index converging lens at terahertz frequencies, IET Digital Library, 2018]
Explain in details what are the advantages/disadvantages and similarities/differences of the above-mentioned; and how they can be applied to the technologies you mentioned to your review.
Section "3. Simulation verification of the device"
1) A deeper study of the structures is needed.
Authors should write some lines in this paragraph to explain why they chose to use the proposed structure
What are the advantages/disadvantages?
2) To explore the device behavior, authors can consider the following interesting electromagnetic phenomena:
_ electric/magnetic currents, displaments currents, and surface waves [On the performance of an ENZ-based sensor using transmission line theory and effective medium approach, New Journal of Physics 21 (4), 043056, 2019]
Include such phenomena in your model and explain how they can affect the device properties in Fig. 11 and Fig. 13.
3) The paper lack in application examples of lenses. Take into consideration the following: sensing and diagnostics, biomedicine, telecommunications, absorbers, measurements, nanoelectronics, automotive.
I would suggest to create a small paragraph by considering such applications and explaining how you can use your device for them.
Please highlight what's new in yours.
Section "5. Conclusions"
1) No limitations of the proposed method have been highlighted.
2) No future improvements/works have been discussed.
Author Response
Please see the attachment.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
The concept is interesting. However the device size is very large and can not compete the ferrite passive devices. The device can not be implemented for pratical and industrial applications. The use of lines of 7-meter length is prohibitive. How to integrate this device in one ship ?
the performance is very low apart from the interference results, may be due to the switchs and wilkinson dividers. Could you evaluate their influence ? What tracks do you have to improve these performance?
the context about the frequency increase requires high operating frequency ranges higher than 2 GHz. What is the operating frequency limit of this device?
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
Authors answered properly to reviewer's questions.
New interesting applications and future works can be envisioned.
Reviewer 2 Report
Could you indicate the transition time of the swithes ?
Thank you
