RF Sensing - Controlling a Relay

[5wp]

I have an RF signal at 2 Ghz that I want to use to turn on a relay and keep
the relay on as long as the Rf is present.
Any suggestions on circuit design to accomplish this?
Thanks,

 

[VEBill]

If the RF is extremely high amplitude, e.g. *inside* a microwave oven (~2.4 GHz), then the RF could easily power the relay more-or-less directly (as the relay slowly melts).

If the RF is relatively weak, e.g. detecting a signal from a distant transmitter, then you'll need a suitable 2 GHz receiver that provides a signal *amplitude* output, and interface circuitry to connect the receiver to the relay.

You don't really want a "circuit design" until you've sourced a suitable receiver. Once you have a suitable receiver bought and delivered, then you might reasonably ask for assistance with the circuit design for the interface to the relay.

 

[Overvoltage]

What frequency? Is it a licensed frequency or unlicensed? If it's licensed, then you'll know the transmitter and receiver specs you need. If it's unlicensed, how are you going to handle interference at the same frequency (which could cause unwanted triggering of the relay)?

Lots of questions you need to consider. However, once you know the receiver, then triggering a relay from it may be trivial (if it has a open/close contact output), or non-trivial (if you need to process the incoming signal at baseband, decode if it is your signal, and then drive an contact output).

Ultimately, you may want to get an Electrical Engineer involved just to make sure you're not getting into trouble you don't know you're in (such as with the FCC if you're in the US) or similar organizations.

 

[DRWeig]

At 2 GHz, I immediately pictured a worried parent who wants to know when his or her errant child is having a cell phone conversation in the middle of the night, or powering up wi-fi for illicit late-night internet business.

There are some commercially available devices that do this. Google up the following:

cell phone detector

You may be able to purchase one and observe how others have done it in the past.

Sneaky, you are.

Best to you,

Goober Dave

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[OperaHouse]

I got a small wifi detector, about the suze of a memory stick, with multiple LED for about $5 shipped on ebay. This might be a start to mod up.

 

[5wp]

Thanks for all the info. Will do some thinking on it.