Plume – LNA

Good evening.

Since Sunday, we are choosing, with Guénolé, the components that we will use in the receiver and the emitter.
For the receiver, our biggest challenge is the noise. And I realize that designing our own circuit isn’t the better solution. It’s better to use a LNA (Low Noise Amplifier) with the following design.

Sans titre 3


3 comments to Plume – LNA

  • Would you explain a tiny bit more your architecture?
    For example, why do you need an LN amplifier and a variable gain amplifier?
    What’s the multiplexer role, switch from one antenna to another sequentially?
    If yes, can’t you avoid redundancy with only one amplification stage?

    PS: the coil schema is really cool.

  • Don’t understand neither. You told us not to buy LT6200 samples because you wanted to use an LNA. But the LT6200 *IS* a LNA (ultra-low-noise in fact) !
    As Drix said, some explaination would be great 🙂

  • oliviert

    Yes sure.

    Since we have a big coil, we can easily design a pass band filter with a RLC serie. This narrow our noise band.

    After, we have to amplify the signal. I wanted to use a AO amp low noise until I realize I could use a LNA chip specially designed for our purpose, with lower noise, lower consumption that we could design in one week. For instance, AD8331 or AD8338 but we haven’t chosen yet. This afternoon we will see the teacher specialist of amplifier at Télécom. We will ask him if we can use a multiplexer between the different coils before the LNA without adding to much noise.

    Then our signal decrease following a 1/r^3 law. The ratio between the tension at 0,2 cm and 5 m is (5/0.2)^3 = 15625.
    I doubt we will have enough precision to detect the variation of 1 cm with a single gain.
    We need at least 2 gain channels.
    The first solution is to multiplex different gain channels,
    the other is to control the gain with a tension, we are more flexible but our gain is less accurate.