Lowest power/size RF carrier detector?

[doragasu]

I want to build a RF transsmitter and receiver. The transmitter only have to tx a carrier signal of a known frequency, and the receiver has only to detect the carrier signal at that frequency. There is no data transmission/signal modulation. Only carrier tx/rx.

I want to embed the receiver inside a key ring, so it must be really small (including the antenna) and power consumption must be really low. I want to power the receiver with 2~3 button cells. Due to the small size, I suppose frequency must be high (hundreds of MHz or higher) to be able to use a small aerial.

At first I thought about using a CC430 for the receiver, because I have a eZ430 Chronos I can use to transmit, but I think this is overkill, and also power consumption is high (15 mA for receiving).

I suppose there must be a better solution maybe using discrete components. Any help about this?

 

[chuckey]

You won't do any better then some thing like these RF Transmitter, Receiver and Transceiver Modules :- **broken link removed**
Frank

 

[doragasu]

But I don't need a full RX/TX module, only something that can detect carrier in a predefined RF frequency. There must be a even simpler and smaller solution. Something similar to LTC5505, but more selective in frequency, or maybe with discrete components.

If I do not find a better solution, I think I will go for the CC430, but I'd like to avoid it mainly because of the power consumption.

 

[jiripolivka]

The problem is that you do not indicate at what frequency your system works. To detect a carrier, an antenna is important. Sensitive detectors are abundant but your keychain should be able to get > -40 dBm from the antenna to achieve a reliable signal detection.
There are many RF sources around, from FM, UHF TV, door openers, radars, cell phones... You should also use a good filter to detect "your" signal among many interferers.
Logarithmic detectors like LTC5505 can detect RF signals from >-60 dBm, but many interference sources will trigger it rather than "your" signal.

 

[fenglau]

The problem is that you do not indicate at what frequency your system works. To detect a carrier, an antenna is important. Sensitive detectors are abundant but your keychain should be able to get > -40 dBm from the antenna to achieve a reliable signal detection.
There are many RF sources around, from FM, UHF TV, door openers, radars, cell phones... You should also use a good filter to detect "your" signal among many interferers.
Logarithmic detectors like LTC5505 can detect RF signals from >-60 dBm, but many interference sources will trigger it rather than "your" signal.

I agree with this ideal。

 

[doragasu]

I only want to activate a buzzer when I send a RF signal, so I thought the easiest solution (and maybe the smallest and lowest power) was to detect only a carrier. No demodulation, no fancy signal processing. As you have pointed, it looks like this approach has many disadvantages, so I think I'll go with my initial plan (CC430).