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CC2400 with CC2591

Other Parts Discussed in Thread: CC2591, CC2430, CC2400, CC2530-CC2591EM

I'm using the CC2400 with the CC2591 chip.  I used the CC2430 CC2591 reference design since both the CC2400 and CC2430 have the same load matching.  My problem is that I have to lower the output power to establish a link.  If the power is set to the maximum (~17dBm) the devices won't talk. 

Thanks

  • Might, be a compression issue. Try increasing distance between the two devices to see if communication resumes.

    Tor-Inge

  • In my current set-up, I'm using coax and some attenuators between the two devices so I'm not overloading the receiver.  It doesn't matter how much loss I add between the devices, if the cc2400 is set to max output power, the devices won't talk.

    Thanks

  • Brandon,

    Remove the coax connection between the two boards and run the test. See if the receiver picks up the transmitted signal and what the corresponding RSSI is. Sometimes, boards in close proximity, can receive signals even with a poor antenna or no antenna.

    I'm not sure if this is the reason, but it is worth finding out.

  • Still no luck.  Is 17dBm output expected at the output or is it a little low?  I think the cc2591 tuning might need tweeked but not sure.

  • 17dBm is not the ideal output power from the CC2591 at max setting, you will need a little bit of tweaking to eek out a couple more dB of output power

  • Hi Brandon

    If you could provide a couple of spectrum analyzer screen dumps it might give us a better idea of where to focus our attention. I am thinking of a narrow span plot showing the modulation spectrum and a full span plot showing behavior of harmonics and spurious.

    Tor-Inge  

     

  • So looking at the signal, the distortion is worst at 2.4GHz than at 2.48GHz.  It seems to work fine at 2.48GHz but not at 2.4GHz.  I think this is because the cc2591 isn't tuned properly.  I already have a board built so how can I tune the inductive bias traces for the PA?  I'll try and get a spectrum plot.

    Thanks

  • Hi Brandon

    Tuning the CC2591 circuitry is often a cumbersome task that requires a network analyzer and numerous iterations. Your observation that the performance is better at high channels indicates a response shift to higher frequencies. To compensate for this on the bias feeds the Tlines should be lengthened. This impossible for an existing PCB design and you are left with trying to tune on the RF/match/filter. I would start increasing L111(CC2530-CC2591EM reference design) and monitor the performance changes. Widening the experiments to include C112 opens another tuning dimension allowing a wider set of impedances to be presented on CC2591 ANT pin.

    http://e2e.ti.com/support/low_power_rf/f/155/t/153328.aspx#556494 Discuss CC2591 circuit tuning/design in a bit more detail.

    Tor-Inge