Modeling and Fabrication of a Reconfigurable RF Output Stage for Nanosatellite Communication Subsystems

Round 1

Reviewer 1 Report

General: A reconfigurable RF output stage design with the component AD9364 is presented, commissioned, and somewhat tested. It seems to me that this is a typical RF design which is controlled digitally. Nothing special is mentioned w.r.t. the application, which is in space. It reads more like an application note than a paper. I do not see a characterization of the design.

Major:
Title: If I understand it correct you are proposing a reconfigurable RF transmitter. I propose to do this change in the title "... RF output stage ..."
63: The RF transmitter design may follow the receiver design as the AD9364 does with the included ADC. Please elaborate on that.
Table 1: What is a working frequency? What are important properties such as: digital input BW, output frequency range and BW, power, noise power ratio, SNR, output power, ... Do you mean CLK instead of CK? In the units column I would use V instead of volts. In the abstract 10 cm^2 are mentioned here it looks more like ~ 100 cm^2.
Figure 4: Caption needs a reference as well since this is straight out of the data sheet.
223: You claim that device transmits from 0.070 to 6,000 GHz without testing it? This is not sufficient. Additionally you should state how other parameters change over the frequency range.
227: You do not mention anything that makes the space environment so special: TID, SEE, vibration, thermal, vacuum, ...

Minor:
Table 1 (caption) and 172: What is ABE-R?
Figure 6: Looks like you have a lot of room left on the PCB. What else could you put on there, e.g. power amplifier, ...?
Figure 8 (caption): This is not a block diagram.
(1): Where is the bps coming from? The unit is already in the BW.
Figure 9: The caption does not make sense. The plot is not in English! What is the spike at 2.5994?
211 and 214: There is no Table 4.
218: Fig.
227: You might want to think how you can combine it with flexible digital processing [1] and the use of adaptable analog components [2].

[1] A. Hofmann, R. Glein, L. Frank, R. Wansch and A. Heuberger, "Reconfigurable on-board processing for flexible satellite communication systems using FPGAs," 2017 Topical Workshop on Internet of Space (TWIOS), 2017, pp. 1-4, doi: 10.1109/TWIOS.2017.7869767.
[2] A. Jaschke, M. Tessema, M. Schühler and R. Wansch, "Digitally tunable bandpass filter for cognitive radio applications," 2012 IEEE 17th International Workshop on Computer Aided Modeling and Design of Communication Links and Networks (CAMAD), 2012, pp. 338-342, doi: 10.1109/CAMAD.2012.6335363.

Author Response

Major:
Title: If I understand it correct you are proposing a reconfigurable RF transmitter. I propose to do this change in the title "... RF output stage ..."

title change : Design and fabrication of a reconfigurable RF output stage for nanosatellite communication subsystems

63: The RF transmitter design may follow the receiver design as the AD9364 does with the included ADC. Please elaborate on that.

the present work is only for a transmitter prototype and all its components, the receiver stage and the ADC components are in separated stages.

Table 1: What is a working frequency? working frequency or frequency range  allowed by Mexican authorities for research in space communications

What are important properties such as: digital input BW, output frequency range and BW, power, noise power ratio, SNR, output power, ...

Do you mean CLK instead of CK? corrected

In the units column I would use V instead of volts. corrected

In the abstract 10 cm^2 are mentioned here it looks more like ~ 100 cm^2. corrected 

Figure 4: Caption needs a reference as well since this is straight out of the data sheet. reference included 

223: You claim that device transmits from 0.070 to 6,000 GHz without testing it? some tests was made but main frequency range  allowed by Mexican authorities for research in space communications is 2.3 GHz

This is not sufficient. Additionally you should state how other parameters change over the frequency range.

227: You do not mention anything that makes the space environment so special: TID, SEE, vibration, thermal, vacuum, ...thermal vacuum and EMI was mentioned, but TID, SEE and vibration will be taken into account

Minor:
Table 1 (caption) and 172: What is ABE-R? ABE-R = RABE , ... corrected

Figure 6: Looks like you have a lot of room left on the PCB. What else could you put on there, e.g. power amplifier, ...?

The space left on the PCB was intended to be used to place RF switches and select different devices (antennas, amplifiers , filters ) with the ability to tune the required bands. In addition to this, the work prepared by Hofmann et al and Jashke et al can be integrated.

Figure 8 (caption): This is not a block diagram. corrected

(1): Where is the bps coming from? The unit is already in the BW.
Figure 9: The caption does not make sense. The plot is not in English! What is the spike at 2.5994? corrected. 

211 and 214: There is no Table 4. included 
218: Fig. Corrected

227: You might want to think how you can combine it with flexible digital processing [1] and the use of adaptable analog components [2]. included

[1] A. Hofmann, R. Glein, L. Frank, R. Wansch and A. Heuberger, "Reconfigurable on-board processing for flexible satellite communication systems using FPGAs," 2017 Topical Workshop on Internet of Space (TWIOS), 2017, pp. 1-4, doi: 10.1109/TWIOS.2017.7869767.
[2] A. Jaschke, M. Tessema, M. Schühler and R. Wansch, "Digitally tunable bandpass filter for cognitive radio applications," 2012 IEEE 17th International Workshop on Computer Aided Modeling and Design of Communication Links and Networks (CAMAD), 2012, pp. 338-342, doi: 10.1109/CAMAD.2012.6335363.

Reviewer 2 Report

This paper presents a reconfigurable RF stage for nanosatellite communications. The novelty is crucially limited, as the paper does not introduce some optimizations on the architecture. It merely implemented the system by combining the existing techniques, and then enumerates the techniques adopted. Moreover, the performance and the hardware complexity of the proposed system is not compared with those of the state-of-the-art works in detail. Miscellaneously, the first letters in the expansions of acronyms are unnecessarily capitalized.

Author Response

This paper presents a reconfigurable RF stage for nanosatellite communications. The novelty is crucially limited, as the paper does not introduce some optimizations on the architecture. 

It merely implemented the system by combining the existing techniques, and then enumerates the techniques adopted.

RABE's proposal is focused on the reconfiguration of the system in terms of transmission variables such as frequency, power, bandwidth, among others.

Moreover, the performance and the hardware complexity of the proposed system is not compared with those of the state-of-the-art works in detail.

The complexity for the work team was to develop the PCB and to be able to control the transmission by means of an FPGA, the works mentioned in the state of the art mainly speak of implementing on a commercial card without the development of any prototype, that is why a certain value was given to our work.

Miscellaneously, the first letters in the expansions of acronyms are unnecessarily capitalized. corrected

Round 2

Reviewer 1 Report

Thank you for the improvement. Here are just a couple more comments. 

Table 1: Dimensions of 9.5 cm * 9.5 cm = 90.25 cm^2 which is different from the stated 10 cm^2. Please state if you only use a fraction of the PCB. 
227: You do not mention anything that makes the space environment so special: TID, SEE, vibration, thermal, vacuum, ...thermal vacuum and EMI was mentioned, but TID, SEE and vibration will be taken into account --> Please state your answer in the paper.

Author Response

Table 1: Dimensions of 9.5 cm * 9.5 cm = 90.25 cm^2 which is different from the stated 10 cm^2. Please state if you only use a fraction of the PCB. 

Corrected

227: You do not mention anything that makes the space environment so special: TID, SEE, vibration, thermal, vacuum, ...thermal vacuum and EMI was mentioned, but TID, SEE and vibration will be taken into account --> Please state your answer in the paper.

Please review abstract, introduction, table 1, fig 3, 241-259, fig 13 and 14, and conclusions. 

thanks

Reviewer 2 Report

The paper does not seem to be improved much from the revision. The novelty still seems marginal. Due to the lack of comparison, in addition, it is hard to say that the proposed scheme is advantageous.

Author Response

Please review abstract, introduction, table 1, fig 3, 241-259, fig 13 and 14, and conclusions. 

thanks

Round 3

Reviewer 2 Report

The authors’ replies seem to be for another reviewer. As mentioned in the previous comments, the reviewer would like to see the comparison of the presented one with the existing ones. Anyway, as the authors have included some analyses in the previous rounds of revision, the paper can be marginally accepted by the editorial decision.