A Linearity Improvement Front End with Subharmonic Current Commutating Passive Mixer for 2.4 GHz Direct Conversion Receiver in 0.13 μm CMOS Technology

Round 1

Reviewer 1 Report

Specific comments and remarks:

1) The abstract has to briefly describe the work of the authors and provide more facts about the proposed circuit. In this new form, the abstract is not of particular interest to potential readers - two sentences have been added to the abstract, which would only further distance the reader from the essence of the work;

2) The parameters listed in Table 1 do not reveal the advantages of the proposed circuit. The authors have to perform a detailed analysis of the advantages and disadvantages of the proposed circuit in comparison with similar circuits known in the literature - for example, what are the advantages in comparison with the electronic system given in [13];

3) In the conclusion of this work, the scientific contribution of the authors has to be defined – it’s still not defined. This type of contribution is not defined, but instead, the proposed circuit is briefly presented.

Author Response

Comment 1: The abstract has to briefly describe the work of the authors and provide more facts about the proposed circuit. In this new form, the abstract is not of particular interest to potential readers - two sentences have been added to the abstract, which would only further distance the reader from the essence of the work;

Answer: Thank you very much for your comment. This comment is very meaningful. The added some sentences in abstract for the purpose of the proposed circuit design:

 A novel complementary derivative superposition (DS) method is presented in LNA design to cancel both the third and the second order nonlinearity. As the authors known, this is the first time FBB technology is used in SHPM core to improve linearity. A Volterra series is introduced to provide analytical formula for FBB of SHPM core.

Comment 2: The parameters listed in Table 1 do not reveal the advantages of the proposed circuit. The authors have to perform a detailed analysis of the advantages and disadvantages of the proposed circuit in comparison with similar circuits known in the literature - for example, what are the advantages in comparison with the electronic system given in [13];

Answer: Thank you very much for your comment. The added some sentences in abstract for the purpose of the proposed circuit design:

• The proposed work has consumed more power and chip area compare to others which listed in the table 1, because the LNA has become the most power-hungry component when complementary DS method is introduced and occupied the most chip area. [8] has used single-to-differential transformer connecting to the tansconductance stage of the following mixer core that has saved chip area and power consumption. But complimentary DS method could not be used in single input LNA. Compare the proposed circuits to [27], voltage gain, NF and figure of merit are better than the latter, and the two have nearly same power dissipation if removing TIA’s. When bias body voltage is set to zero, figure of merit of the proposed circuit decreased to 67.3. It means that FBB technology dose work for the whole circuit performance enhancement.

2）topology row is added for clear comparison. Delete reference [5] of the table 1 and change reference [28] of the table 1 to a new reference [27] in the latest revision. 

Comment3: 3) In the conclusion of this work, the scientific contribution of the authors has to be defined – it’s still not defined. This type of contribution is not defined, but instead, the proposed circuit is briefly presented.

Thank you very much for your comment.

The scientific contribution of authors is highlight with red words. In this letter, a 2.4GHz front end with subharmonic mixer topology is proposed. The transconductance stage is an LNA with novel complementary DS method for linearity improvement. The mixer core is a passive SHM architecture because of the DC offset and flicker noise immunity is suitable for zero IF. The FBB technology is introduced for mixer core performance enhancement. As the authors known, this is the first time FBB technology is used to SHPM for performance enhancement, and a Volterra series is introduced to provide analytical formula for FBB of SHPM core. The measured result shows that it has good voltage gain and IIP3, with moderate NF and the highest figure of merit compare to the published state of arts.

Author Response File: Author Response.pdf

Reviewer 2 Report

1. The paper still needs to be revised and requires several English changes.

2. Please, revise your equations, some simplification (without losing precision) could be used in order to make the reading of the equations more tractable. For example, are there dominant terms in Equations 18 to 22?

3. The quality and presentation of Figures (both plots and schematics) could be improved to achieve better consistency and uniformity. 

Author Response

1.The paper still needs to be revised and requires several English changes.

Thank you very much for your comment. The grammaly software is used to improve the English expression.

2. Please, revise your equations, some simplification (without losing precision) could be used in order to make the reading of the equations more tractable. For example, are there dominant terms in Equations 18 to 22?

Thank you very much for your comment. A simplification is used. See the Equation 23 and 24.

3. The quality and presentation of Figures (both plots and schematics) could be improved to achieve better consistency and uniformity. 

Thank you very much for your comment. All figures and electrical circuits have been redrawn. But some circuits and figures are bigger, when insert into manuscript, they lessen much than the small circuits and figures. So the characteristics looks a little small, I have done my best to make them looks same.

Author Response File: Author Response.pdf

This manuscript is a resubmission of an earlier submission. The following is a list of the peer review reports and author responses from that submission.

Round 1

Reviewer 1 Report

Specific comments and remarks:

• The abstract has to briefly describe the work of the authors and provide more facts about the proposed circuit. In this form, the abstract is not of particular interest to potential readers;
• The authors have to explain the purpose of formulas (1), (2), and (3). Based on the analysis, the total harmonic distortion can be found. What is the value of the total harmonic distortion;
• The parameters listed in Table 1 do not reveal the advantages of the proposed circuit. The authors have to perform a detailed analysis of the advantages and disadvantages of the proposed circuit in comparison with similar circuits known in the literature;
• In Fig. 5, what does "conventional IDCS" mean - the relevant literature source has to be cited;
• Formula (8) has to be derived, if taken from the literature the relevant literature source has to be cited. What is the purpose of formula (8) further in the exposition of this work. Most formulas are well known in the literature; it is necessary to cite the literature sources from which they are taken;
• Section 2 has to be arranged. In this form, facts are given about the individual stages and parts with simulation results. The connection between them is missing. This section has to be rewritten and advance to carefully consider its contents;
• All figures are of different sizes and line thicknesses. In my opinion, all electrical circuits and characteristics have to be redrawn to have a unified graphical form.
• In the conclusion of this work, the scientific contribution of the authors has to be defined. A contribution is not defined, but instead, the proposed circuit is briefly presented. In addition, the title of the paper has to be changed so that it briefly reveals this work (instead of um to write μm and add CMOS technology). Of course, these additions in brackets is not sufficient, it is not clear what the scientific merit.

Reviewer 2 Report

Comments for the authors:

a. It is recommended that the article is revised in its use of the English language. It is poorly written in that respect. The manuscript is hard to follow many times due to that issue.

b. It is also recommended to give the manuscript a serious work on editing. Symbols for variables are sometimes inconsistent, and you should always use subscripts, not every once in a while.

c. Introduction is very short and does not clearly represents previous works, justification for the presented manuscript and technical contributions of the manuscript.

d. Figure 1 should include the balun and differential input.

e. What is Cpar in Equation (7)?

f. The title of the manuscript highlights the use of FBB as a main feature of the work, but this section is very short (approximately one page). No circuit theory nor analysis is used to justify the use of this technique. The presentation looks more like an heuristic-based approach (through simulations) to the solution.

g. Discussion should be given about technological-related issues of using body biasing, like the use of triple-well, for example. This is important because in normal CMOS processing the use of triple-well adds cost.

h. The comparison table does not show significant improvement with respect to the state of the art. Both power consumption and silicon area used are significantly greater than most of the previous works. In that respect, the merits of the presented work are hard to assess. The authors should use then some kind of figure of merit, that illustrates that the trade-offs show in balance an improvement of performance, and that the price paid in power consumption and silicon area are justified.