[Doubt]I have some doubts regarding the design of a RF Power Detector

Hello all.

I'm designing a Radio-Frequency Power Detector. This circuit will detect any signals ranging from 50MHz to 8GHz

I found some IC's that say they do the job:

- 50 MHz to 4 GHz 40 dB Logarithmic Power Detector for CDMA and WCDMA (LMH2100);
- 50 MHz to 8 GHz Logarithmic RMS Power Detector with 45 dB dynamic range (LMH2110).

This IC's basic implementations is described on the image below:
https://imgur.com/Js3xLjo

So, my doubt is:
- Which one of this should i choose?
- Do i need some bandpass filter before my RFinput? Will i need an Amplifier?

The datasheets don't explain this things...
And i couldn't find application notes from Ti, or Linear...

Sorry for my English.

Thank You. I finally had the "balls" to write for some guidance. I already read many topics here.

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Edit:

All the applications that i Find are made for measurements on the Transmitting side.
I would like ti know if i could the the "reverse" and apply it to the Receiving side:
- (Signal Received by the antenna, the signal is amplified with a Low-Noise Amplifier and then, the result is the Input of my Power detector.)

Have a look also at ANALOG.COM site, they have some good IC.

I have used some ic to make a signal strenght indication, sniffing the signal from the 1st IF of the receiver.
this allows to expand the dynamic range of the detector.
To use a filter before the detector is useless, because you will not decrease the noise floor.
the filter is needed if you have some strong signals out of band.
Using an amplifier at the input, will help, but remember that that you increase the noise of the system.

Mandi

yes I too recommend the analog devices chips, have used them in a few projects. However, the analog voltage out is small, so you will want a voltage gain stage after the log amp.



Looks to me that you should be able to see signals in the -93 to -2 dBm range if you are willing to switch in/out a 40 dB gain stage. I assumed 2 dB noise figure.

Note, if this is a true receiver hooked to an antenna, ANY broadcasted signal in the area will also be received--limiting how low in power the received signal can be for the circuit to work. If you have a narrowband system, a bandpass filter in front would help that.

Due to the noise floor of the world, anything less than -93 dbm will need a superhetrodyne receiver to detect accurately.

If the RF Power Detector circuit is used only for conducted measurements, and if the circuit is designed properly in terms of the PCB design and using shield cans to give isolation to external electromagnetic field, everything would work fine and able to measure the power of low signal levels.

There are more RF Power Detectors options from Analog Devices, which personal I prefer more than others:

https://www.analog.com/en/technical...ources/rfif-components/detectors/listing.html

Thank you all for the great help.

Yes, the Power Detector will only be used to detect if for example GSM cellphone is near.

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Edit: Let me refrain... The doubt that i have is "How would i know that the GSM frequency is being transmitted?" Because the Power detector detects that range of frequencies...