Key Technologies for THz Wireless Link by Silicon CMOS Integrated Circuits
Round 1
Reviewer 1 Report
Most of the contents are borrowed from existing literature by the authors, which is understandable as it is a review paper in a special issue. However, the presented content is not much different from those published in electronics journals. If the purpose of this review paper is to introduce THz circuits to the readers mostly involved in photonics, it would be better to discuss the content in the frame of comparing photonic solution vs electronic solution for THz. For example, pros and cons of the presented electronic solution against photonic (or optical) solution can be further discussed.
Page 7 line 364: Provide a formula or reference to arrive at 70 dBi antenna gain with 1.2 m diameter antenna.
Page 7: When considering inter-planet or planet-satellite communication, the atmospheric attenuation or window needs to be considered for both bodies, not only for earth. The atmospheric attenuation may be small in moon or Mars compared to earth, but a brief discussion may be needed.
Author Response
Point 1: Most of the contents are borrowed from existing literature by the authors, which is understandable as it is a review paper in a special issue. However, the presented content is not much different from those published in electronics journals. If the purpose of this review paper is to introduce THz circuits to the readers mostly involved in photonics, it would be better to discuss the content in the frame of comparing photonic solution vs electronic solution for THz. For example, pros and cons of the presented electronic solution against photonic (or optical) solution can be further discussed.
Response 1:
Terahertz itself is considered to be one of the important fields of photonics. I added that point to page 2 line 37.
“Terahertz wireless communication is one of the important applications covered by the terahertz photonics field [3].”
In addition, a brief discussion on the photonics approach and the electronics approach in realizing the terahertz device was added to page 2 line 71.
“The realization of terahertz wireless communication has two approaches: all electronics and photonics-electronics hybrid. The latter covers a frequency band exceeding 500 GHz unachievable with all-electronics approach, which is desirable for downsizing and power reduction of the total communication system [6]. For this reason, photonics-electronics hybrid approach has been studied in advance to generate terahertz signals, but research using integrated circuits, which is based on all-electronics approach, has been active recently.”
Point 2: Page 5 line 147: It states that basic operation of the square mixer similar to the frequency doubler. Then what is the difference between a square mixer and a frequency doubler? A frequency doubler can be used in place of the square mixer in the circuit introduced?
Response 2:
The circuit of the doubler and the square mixer are the same, but the square mixer has a different function from the doubler. Therefore, the following description was added to page 5, line 148.
“A frequency doubler circuit is used for this mixer, called a square mixer since input signals are squared.”
Point 3: Page 7 line 364: Provide a formula or reference to arrive at 70 dBi antenna gain with 1.2 m diameter antenna.
Response 3:
This value was calculated using equation (5) with aperture efficiency of 70%. I added this point to page 13, line 369.
“In the 300 GHz band, the gain of a parabola antenna with a 1.2-m diameter will be 70 dBi from Eq. (5) if the aperture efficiency is 70%.”
Point 4: Page 7: When considering inter-planet or planet-satellite communication, the atmospheric attenuation or window needs to be considered for both bodies, not only for earth. The atmospheric attenuation may be small in moon or Mars compared to earth, but a brief discussion may be needed.
Response 4:
I added a brief discussion on the attenuation of terahertz by the moon and Mars atmosphere to page 143, line 14.
“It is noted that the moon's atmosphere is very low, almost vacuum. The atmospheric pressure of Mars is about 0.6% of the Earth, and most of the atmosphere is carbon dioxide. Carbon dioxide absorbs infrared to cause a greenhouse effect but does not absorb terahertz. Therefore, the terahertz absorption in the moon and Mars is negligible.”
Reviewer 2 Report
There is missing information or lack reference some paragraphs in the manuscript. For example in line 53:
" band of 252 GHz to 275 GHz has already been allocated to (what kind of ) communication". Strong paragraphs in my point of view are 2.2. and 2.3. It would be better in the conclusions to report results from these paragraphs instead of referring to issues of a historical nature.
Author Response
Point 1: There is missing information or lack reference some paragraphs in the manuscript. For example in line 53:
" band of 252 GHz to 275 GHz has already been allocated to (what kind of ) communication".
Response 1:
The above specific item was revised as shown on page 2 line 54.
“A band of 252 GHz to 275 GHz has already been allocated to mobile and fixed wireless communications [4].”
In addition, I added references [3-6,29]
Point 2: Strong paragraphs in my point of view are 2.2. and 2.3. It would be better in the conclusions to report results from these paragraphs instead of referring to issues of a historical nature.
Response 2:
The conclusion was revised according to your comments.
