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IWR1443: multiple simultaneous TX beam forming with TX phase shift

Gunter Schmer
Genius 14212 points
Part Number: IWR1443
Other Parts Discussed in Thread: IWR1642

Hi,

in the data sheet of the IWR1443 it says:

“The three transmit channels can be operated up to a maximum of two at a time (simultaneously) for transmit beamforming purpose as required; whereas the four receive channels can all be operated simultaneously.”

My understanding is that typically with say 2x TX, the IWR1443 is transmitting chirps alternately on TX1, TX2, TX1 etc, which allows to have 2x virtual RX antennas.

Additionally is it possible to transmit on 2x TX simultaneously  and thereby steer the beam? There is a note in one of the presentations for a mode that is called, BPM-coded simultaneous TX, multiple TX being used for TX beamforming (simultaneous TX with phase shift).

Is this supported?

Thanks,

--Gunter

  • 0
    TI__Mastermind 37500 points

    Hello,

    Tx use of BPM is supported.  How electronically steered BPM0 and BPM180 are decoded, has not been tried.  We typically use BPM 0 (no BPM active).

    The Tx can have two simultaneous (of three) transmitters enabled.   The BPM was initially considered to shift the phase by 180 degrees for interference mitigation, it is controlled on a per chirp basis.  Normally to perform electronic steering, the antennas have a specific delay in phase.   On the EVM we have Tx1, Tx3 at the same  elevation, and Tx2 at a a different elevation.  So you could have 3 electronically steered combinations:

    MultiTx, Tx1, Tx2, Tx3

    #1,  BPM0, -, BPM0

    #2, BPM180, -, BPM0

    #3, BPM0, - BPM180

    In the use of BPM as a MIMO - we need to load a matched filter into the Hardware Accelerator 1443, DSP 1642 to decode the Received signal from just the BPM180 channel.

    Future devices, will have Tx phase shifting, while the IWR1443, IWR1642 do not, only the BPM contol by chirp.

    Future devices with 3 Tx, may use a different PMIC power rail to bypass the internal 1.3 to 1.0 v LDO, allowing 3 simultaneous Tx operation.

    Regards,

    Joe Quintal

  • 0 in reply to Radio-Joe
    TI__Genius 14212 points
    Hi Joe,

    thanks for the explanation. So I think what I am understanding from this is, that the BPM-coded transmits in your example with TX1 and TX3 would fundamentally create the following beams, assuming that TX1 and TX3 are separated from each other by 2x lamda.

    #1 BPM0, -, BPM0 --- here the main lobe beam is at 0 degrees
    #2 BPM180, -, BPM0 --- here the main lobe beam is at approx. 15 degrees
    #3 BPM0, -, BPM180 --- here the main lobe beam is at approx. -15 degrees

    Am I understanding this correctly?

    Which future devices can steer the TX beam with higher granularity?


    Thanks,
    --Gunter
  • 0 in reply to Gunter Schmer
    TI__Mastermind 37500 points
    Hello Gunter,
    There is an automotive AWR1243P, next year there is another device.
    Regards,
    Joe Quintal
  • 0 in reply to Radio-Joe
    TI__Genius 14212 points

    Hi Joe,

    based on your comment above it looks like beam steering is only enabled in the azimuth direction.

    one more question on the same topic.

    If TX1 and TX2 are used while TX2 has a different elevation, can we do beam steering in the elevation direction??

    Thanks,

    --Gunter