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Automatic gain control on CC254x

1960865
Intellectual 775 points
Other Parts Discussed in Thread: CC2541, CC2540

Hello

I stumbled on AGC in the user's guide and would like to know what it is in details. Has anyone modified its value and what were the results of such modifications.  Is the AGC same on either cc2540 or cc2541?  I can appreciate TI's answer to clarify or point me to the right place where I can read more about this topic.

thanks in advance

~LD

  • 0
    Genius 4125 points

    It is there to keep the received RF signal at a level which gives good dynamic range for demodulation as the signal level at the RF input can vary over many orders of magnitude based on rss (a fundamental part of most radio receivers). It is presumably controlled by the BLE stack link layer. What would you hope to achieve by modifying it?

  • 0
    TI__Genius 10955 points

    There is no AGC on CC2540. On the CC2541, there is an option to use a simple AGC in proprietary mode, but there is no AGC when running BLE. This AGC is recommended only for 2 Mbps.

    The reason for not running AGC on these chips is that the front-end is capable of receiving strong signals. It will be clipping, but since the modulation format is FSK (GFSK or MSK), there is no information i the amplitude anyway. On the 2 Mbps mode, the receiver runs zero-IF, and in this case strong signals will give problems for the receiver. This is why an AGC is needed for 2 Mbps.

    The AGC running in proprietary mode on CC2541 is described in Section 25.9.2.1. If you are using CC2541 for BLE only, this chapter is not relevant.

  • 0 in reply to hec
    Intellectual 775 points

    Hec

    we conducted a chamber testing and we observed a gain of about -12dBm when distance is 60cm. I will be sending the report to other TI Engineers and would like to include you since you have provided the above answer.

    thanks
    ~LD