A Flash Frequency Tuning Technique for SC-Based mm Wave VCOs

Round 1

Reviewer 1 Report

1. Kindly add the varactor diode response against controlled voltage to see the variation in capacitance that can help to derive numerical mode for the readers.  
2. How will you  provide the stabilize controlled voltage to VCO, is there any tolerances in supply?
3.  What is the reference source?  what about its performance?  

Author Response

1. Kindly add the varactor diode response against controlled voltage to see the variation in capacitance that can help to derive numerical mode for the readers. 

The varactor diode response has been included (new Fig. 4 in the revised manuscript) .

2. How will you provide the stabilize controlled voltage to VCO, is there any tolerances in supply?

In the final application, the power supply comes from a voltage regulator, which uses a band-gap voltage reference. A small variation could arise from process tolerances . However, this variation does not affect the performance of the VCO.

3. What is the reference source? what about its performance?

Agilent 81160A signal generator was used to generate the PLL input reference signal. It provides -115 dBc/Hz phase noise performance at 10-kHz offset frequency.

Reviewer 2 Report

A remarkable work on MMIC design well supported by measurements.

Figure 5. Could you add a photograph of the set up to the diagram shown in fig. 5?

Figure 9: Could you please explain/describe the set up to obtain figure 9?

Line 122: BEOL. I assume you mean Back End of Line, but maybe you should explain.

Line 127: ... an off-chip second-order loop filter (LPF) Usually LPF stands for Low Pass Filter, but it is not clear here if you mean Loop Filter or Loop filter, which is additionally a Low Pass Filter

Author Response

1. Figure 5. Could you add a photograph of the set up to the diagram shown in fig. 5?

The requested photograph has been added (new Fig. 6(b) in the revised manuscript).

2. Figure 9: Could you please explain/describe the set up to obtain figure 9?

As already stated in the paper (lines 173, 174 of the revised manuscript), a reference signal with a triangular-shape frequency modulation was provided to the PLL input.

3. Line 122: BEOL. I assume you mean Back End of Line, but maybe you should explain.

You are right. The acronym has been explained for better clarity.

4. Line 127: ... an off-chip second-order loop filter (LPF) Usually LPF stands for Low Pass Filter, but it is not clear here if you mean Loop Filter or Loop filter, which is additionally a Low Pass Filter

You are right. LPF stands for Low Pass Filter. The manuscript has been modified accordingly.

Reviewer 3 Report

Authors have an actual integrated circuit built, and tested in a lab environment. Overall, the paper is quite interesting and important for mmWave system design. Adding more simulation related details may improve the overall quality of the paper.

Author Response

Authors have an actual integrated circuit built, and tested in a lab environment. Overall, the paper is quite interesting and important for mmWave system design. Adding more simulation related details may improve the overall quality of the paper.

Thanks for your comment. A further simulation of the varactor response has been included (new Fig. 4 in the revised manuscript).