Is it possible?

Hi Everyone,
I have an idea about a basic led indicated circuit that detects a phone being on standby mode in someones pocket and is not being used. Yes it should also be able to detect active calls, receiving or sending text messages and gprs 3g data usage but my priority is for it to be very sensitive to detect a standby mode signal of a phone. Is it possible?

This could be better if it detects only an opened standby mode phone and will have it indicated in the led but right now it detects an active usage of any type and beeps sound at the same time.

Pls help me... Thanks for the reply.

A phone that is active - is listening for incoming calls - will connect to the cell tower whenever it loses and then reacquires the cell tower. This is how the cell system knows where to direct the incoming call. But if the phone is simply sitting there and has already acquired the tower it will not transmit again (for awhile anyway).

However, it will emit a weak LO (Local Oscillator signal). But this could be too weak to reliably detect or the LO signal from another nearby phone could cover up the LO of another phone. And, different phones may have different LO frequencies.

So, can it be done? Yes, but I don't know that it can be done such that every phone will be detected.

Thank you for reply dear friend
So firstly i have to learn lowest LO ferequency then find a wwy to build that circuit pieces and circuit plan etc hope somebody helps thank again and again

This is a job for a spectrum analyzer.

Im not proffesional on these task i only want to ask people if they know a way and pieces to build this circuit thanks for your kind understanding i ll wait for a reply have a nice day