Lowest power/size RF carrier detector?

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?

You won't do any better then some thing like these RF Transmitter, Receiver and Transceiver Modules :- ../imgqa/eboard/Antenna/rf-zq4tq0k224d.jpg
Frank

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.

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。

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).