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Original question:

AWR1243: BPM Configuration for the entire frame

IWR1642: BPM configuration chirp selection

Dongye Zhang
Prodigy 110 points
Part Number: IWR1642

I understand that for BPM, on 

TX1, we send S1 S1 S1 S1

TX2, we send S2 -S2 S2 -S2

where S1 and S2 represent chirps from the two transmitters.

I'm wonder how should we design S1 and S2 to have better result? Can S1 and S2 be the same chirp configuration? 

I'm thinking is S1 and S2 are the same. When mixing at receiver, we mixing Rx with (Tx1+Tx2), then (Tx1+Tx2) would be S1-S2=0 on even number of chirps. 

  • 0
    TI__Mastermind 37500 points

    Hello,

    There is an example in the 01020005 version of the mmWave SDK User Guide it refers to profile_2d_bpm.cfg.  I suggest you use the IWr1642, 4Rx 2Tx 15 deg best range resolution, add the Noise display, then save that configuration.   Then use the BPM example, and create a best range resolution version.    There is a discussion of the BPM MIMO in the swra554 application note.  

    I have included the default TDM MIMO, 2Tx 4Tx 15 deg - tdmmimo.JPG, and the profile_2d_bpm.cfg bpmmimo.jpg example.

    Regards,

    Joe Quintal

  • 0 in reply to Radio-Joe
    Prodigy 110 points
    Thanks for the reply. From the BPM configuration, Tx1 and Tx2 are using same chirp design (that is S1 and S2 are the same). What I don't understand is how mixing is done at receiver side. If we mix Rx with (Tx1+Tx2), then (Tx1+Tx2) would be S1-S2=0 on even number of chirps. So after mixing, on chirp number 2, 4, 6,...we have nothing. Is this expected?
  • 0 in reply to Dongye Zhang
    TI__Mastermind 37500 points
    Hello,
    in the swra544a MIMO app note, there is a discussion of the processing in section 4.2. In the mmwave SDK the bpmCfg function is used to setup this feature. I would trace through the DSP code to see what is being performed.
    I think that the terms S1 and S2 are at the Transmitter boundary. When they reflect from objects depending on the angle to the object, the radial distance would be different. In that case if there is a difference in radial distance Tx1 to target to Rx1,2,3,4 and Tx2 to target to Ex1,2,3,4

    Since the BPM phase reversal is done after the reference signal to the Downconversion mixer. The Tx2 on the odd chirps would be 180 degrees out of phase. When we process two chirps of data, the odd chirps have a negated Tx2. Note in the recombination, hadamard coding provides Tx1 -> Rx extraction during 0 or even chirps, and Tx2 -> Rx extraction during odd chirps.. This is explained in the paragraph below Figure 10.

    I think the key
    0 or even# chirp, Tx1 inphase, Tx2 inphase -> R0x1, R0x2, R0x3, R0x4
    odd# chirp, Tx1 inphase, Tx2 invertphase -> R1x1, R1x2, R1x3, R1x4

    R0x1 + R1x1 -> results in Rx1 signal related to Tx1 (Rx1 antenna)
    R0x1 - R1x1 -> results in Rx1 signal related to Tx2 (pseudo Rx5 antenna)

    You can use TDM MIMO to simplify this processing, but its a lower Tx power level.

    Regards,
    Joe QUintal
  • 0 in reply to Radio-Joe
    Prodigy 110 points
    I've read through the MIMO application note a few times. In addition to your reply, now I have a better understanding. Thank you.