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BLE vs ANT and their coexistence with classical BT

Filosofi
Intellectual 925 points

Other Parts Discussed in Thread: CC2567

Our product is a portable device. It has to have two different radio modules, each with its own antenna:

2. 8-channel ANT module
1. Class-1 Bluetooth module (Max Tx power: +20dBm)

The ANT module should collect broadcast messages from a number of local sensors, while the BT module
should transmit data to a remote peer (long-distance).
Unfortunately from preliminary tests it results the BT transmitter interferes with ANT receiver.
When the BT transmission starts, 20% of ANT packets are lost.

Also instructing the BT module to disable those channels near the ANT frequency (2457MHz) the interference still remains.

I know that there exist multi-com chips like the TI CC2567 (BT+ANT) where the solution is a scheduler to allow operation
of the different protocols at different time slot without user noticeable interferences.
However, AFAIK none of the multi-com modules currently available neither give more than 10dBm BT, nor more than 1 channel ANT.

We are wondering if you know some other effective way to obtain coexistence and simultaneous operation for those two radio modules.
For us the Bluetooth module is very important.
It may be the only viable solution would be to give up ANT in favor of BLE.

Does a BLE link coexist better than ANT near a BT transmitter ?

Regards,
Gabriele

  • 0
    Intellectual 870 points

    Hello Gabriele,

    How many channels near 2457 did you disable?

    As for the CC2567, I do not believe it can do 20dB without some gain circuitry, however it DOES support 8 ANT channels. You could configure the CC2567 to guarantee ANT reception, however it would impact BT.

    I can't comment on BLE for this scenario.

    Best Regards,

    Kassandra

  • 0 in reply to Kassandra Rizopoulos
    Intellectual 925 points

    Kassandra,

    Just as an example, using the command (AT-like)

    HCI 7007000a00ff00ff00ff00ff00ff00ff0000000000ff007f

    I program the BT module to skip channels 48 to 63 (i.e. 2450 to 2465 MHz).
    In this case I obtained the following results

    ---------------------------------------------------------
    ANT Tx pwr: -20dm
    BT channel: all                           -> ANT msg failure rate: 622/2880 = 21.5%
    BT channel: 0..47 and 64..79  -> ANT msg failure rate: 605/2880 = 21%     (no improvement)

    ANT Tx pwr: 0dm
    BT channel: all                           -> ANT msg failure rate: 140/1920 = 7.3%
    BT channel: 0..47 and 64..79  -> ANT msg failure rate: 84/1920 = 4.4%      (light improvement)

     

    As you can see the failure rate is about 20% if the ANT signal is weak (-20dBm), and the HCI command does not improve much.
    Can you confirm this order of magnitude basing on your experience ? I suspect it would be unacceptable for our application.
    FYI, tomorrow I will be able to repeat the measurement with a Spectrum Analyzer, because I need to be sure the HCI command is really working.

    Generally speaking I'm not very optimistic the WT41 could coexist with the ANT module
    So, basing on your expertise

    1. what do you think about the developement of a custom CC2567 based module, similar to PAN1317 but with the desired 20dBm Tx power ?
    2. In which way the use of 8 ANT channels on CC2567 could impact the BT performance ? (distance and/or bit-rate ?)


    Regards,
    Gabriele