The comparison idea is good,& is commonly used.

I don't think the diode will be the limitation in a diode capacitor setup. I've seen them used at 200 or so MHz for this type of circuit.

As far as the power & dB stuff is concerned, it all depends on what impedance the voltage appears across.

For instance , with your quoted signal level of 2v p-p,the RMS voltage =0.7071volts.

If this is across 50ohms,from the standard formula:- P = V Squared/R the power will be:-0.01watts,or 10 milliwatts.

If you wanted to double the power to 20mw, you will need to increase the RMS voltage to 1 volt,corresponding to 1.4142

peak,or 2.8284 p-p.

Using the last voltage of 2.8284 p-p,or 1volt RMS,if this appears across 75 ohms, P= V squared/R

which in this case =1/75 =0.133 watts,or 13.3 milliwatts.

From this,you can see that the same voltage across different impedances represents different power levels, so that if you want to find the power gain or loss of a circuit,you must either calculate the power individually for both input & output,or ensure that both input & output are the same impedance.

**dB:-**

The human ear,& most physiological reactions are Logarithmic.

It was found,early in Radio & Telephony,that an increase in sound power of 2 times was just barely discernible.

This made it easier to design amplifiers,etc,as it made the specifications easier to achieve.

The original unit used was the Bel,but this was found to be too large for normal use,so the

"decibel" (1/10 Bel),or dB was established.

To express a power ratio in dB,the following formula is used:- dB = 10 log P1/P2.

If both PI & P2 appear in circuits of the same Impedance,you can use the voltage formula :- dB=20log V1/V2

**dBm**:- expressed in dB above & below 1.0milliwatt.This is used with systems of the same impedance,but the system impedance may differ in different fields

( RF may be 50 or 75 ohms ,audio 600ohms).

The advantage of dB use appears when you are using dBm; for instance if you have a signal of level +3 dBm & you put it through amplifier of 7 dB gain, the output is +10dBm.

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