radio mic RF rssi comparator to avoid RF signal dropout

Discussion in 'The Projects Forum' started by benbiles, Jan 28, 2014.

  1. benbiles

    Thread Starter New Member

    Jan 27, 2014
    3
    0
    Hi, I am trying to design a circuit that can monitor the RSSI ( receive signal strength indicators ) of two audio RF boards.

    They output 0v - 3vdc to indicate signal strength.. higher vdc is better

    I am trying to get the board to quickly pan to ( use ) the audio output from the module with the highest RSSI output.

    This will hopefully create what they call 'true diversity' in the radio mic world hopefully avoiding some RF dropout because of the redundancy.. ( 2 antenna + 2 receivers ) Its not a new idea and now newer designs incorporate the diversity by switching packet data from RF receiver with higher rssi ( as far as I can tell )

    firstly the RSSI output goes to a comparitor and hopfully outputs high or low depending which board has the higher signal?

    then the idea is that the switch in high or low determins which LED's are lit and then triggers a PAN from one audio channel to the other.. untill the next switch.. and so on.. Hopefuly there will be some hysteresis comparator so the thing doesn't switch too quickly when the two RSSI voltage signals are too similar !!!

    The idea of the OPamps is to bias the audio swing from +-1v to be between 0v & +1v so that the audio wave can pass through the panning cicuit.

    I am sure most of the resistor values are wrong!! and I very much and i don't think the CMOS Pfet / Nfet pan section is correct at all since I nicked it from a anti clicking guitar effect pedal !!

    I would like the RC ( resistor capacitor ) to should slow down the switch state of the CMOS Pfet/Nfet so that the output is panned momentarily !! say 100ms

    So! I am definitely an electronics beginner and I'm far more at home playing about linux packages !! But any pointers in the right direction would be much welcome :)

    I am also working on an SDR ( software defined radio ) version of the 'true diversity' but want to use this board to test various RF audio receiver modules working together..

    Lastly there is a clock sync drawn on the schematic between modules.
    That's just the two modules sharing one crystal so they operate roughly in sync.. but maybe that's a bad thing!!! maybe they should be slightly out of sync for added receive diversity ??? !!!

    anyway, I'll keep updating the design if anyone is interested if and when I find improvements...;)

    ps.. These boards are uncompressed audio GSFK 2.4 ghz range but I will be also trying TV white space Channel 38 and other UHF frequencies as soon as I can get this board working :)

    Thanks

    BEN
     
  2. benbiles

    Thread Starter New Member

    Jan 27, 2014
    3
    0
    Maybe is makes more sense to use VCA's ( voltage controlled amps ) instead to pan the module audio outputs by controlling the Vcc on the VCA's from the RSSI comparator?
     
  3. benbiles

    Thread Starter New Member

    Jan 27, 2014
    3
    0
    update, VCA's changed to ones more suitable for audio.. AGC on audio inputs.. will probably add buffers..
     
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