Hi,
one more issue to solve in one of my little project and that is a power level detector. What would be a good circuit approach to measure RF level in a signal path?
Current frequency range of interest: 100kHz to 30MHz, power levels of say up to 13dBm, measured range 20-30dB.
I think that using a single diode power detector, does not give very good and precise results. Therefore I am looking into some more interesting circuits.
I have tried to do a bit of research and come across this quite interesting circuit, from a Marconi 2018A/2019A RF generator.
I have attached the page from the service manual, where there is the output PA, some electronic attenuation stages, the power detector circuit, ALC loop and some signal conditioning circuitry for the ALC.
It seems that power detection is being done with D11 and D12, while IC1-b/4 is the amplifier for the detector. Wondering... what's the purpose of D13 in its feedback, and how does this detector topology work? I could not find any application note with anything similar to this.
I think that IC1-c/4 is the ALC servo, controlling the PIN diodes, based on the signal from the detector and the setpoint from the DAC chains below (interestingly enough, the reference signal also goes through an amp with a diode in its feedback - why?)
Thanks
Y.