IWR6843AOPEVM: TDM-MMIO vs BPM-MIMO, and examples for 6843AOP

Morten Nissov

Part Number: IWR6843AOPEVM
Other Parts Discussed in Thread: IWR6843AOP

I'm curious on the advantages/disadvantages of using BPM-MIMO on something like the IWR6843AOPEVM.

The application report on MIMO radar states that BPM-MIMO should see some (10 log10(N_TX)) SNR benefit, but doesn't mention any disadvantages. Transmitting on two TX simultaneously costs more power, but also shortens the overall transmission time. Does this mean that the max velocity also decreases? What other disadvantages can one expect? Given that BPM isn't included in any of the default configs from the Demo Visualize I assume there must be some reasons to still consider using TDM-MIMO.

Also, I haven't seen any but is there an example CFG for the IWR6843AOP using BPM-MIMO with the OOB demo.

over 2 years ago

0 Nathan Block over 2 years ago

TI__Mastermind 37805 points

Hi,

Thank you for your patience over the holiday. We will be able to give a response on Tuesday when work resumes. Thank you!

Best,

Nate

0 Morten Nissov over 2 years ago in reply to Nathan Block

Intellectual 380 points

Hey,

I was curious if you had a chance to look at this?

0 Nathan Block over 2 years ago in reply to Morten Nissov

TI__Mastermind 37805 points

Hi,

The equation for the maximum velocity stays the same regardless of BPM or TDM.

Best,

Nate

0 Morten Nissov over 2 years ago in reply to Nathan Block

Intellectual 380 points

I'm curious to hear your thoughts on

What other disadvantages can one expect?
...

Also, I haven't seen any but is there an example CFG for the IWR6843AOP using BPM-MIMO with the OOB demo.

0 Nathan Block over 2 years ago in reply to Morten Nissov

TI__Mastermind 37805 points

Morten Nissov said:
What other disadvantages can one expect?

BPM will draw more power during transmission and also relies on objects staying relatively stationary over the time of the transmissions more than the TDM method requires.

See the vital signs example for a BPM configuration.

0 Morten Nissov over 2 years ago in reply to Nathan Block

Intellectual 380 points

relies on objects staying relatively stationary over the time of the transmissions

Relatively stationary meaning what exactly? Is there some rule of thumb for max tolerable velocity in the BPM config? I figure BPM means 2 periods of Tx (1 set of simul antennas and 1 single antenna in 6843AOP), the total time depends on the chirp but likely in the range of microseconds.

I'm not sure what the margin is, but I figured the max resolvable velocity (defined by the chirp parameters) puts some pretty hard constraints on how much anything can really move in such a short time frame right?

0 Nathan Block over 2 years ago in reply to Morten Nissov

TI__Mastermind 37805 points

This is the same principle as TDM, where we chirp with each antenna sequentially, but assume that all chirps happen at once for successful angle processing. There isn't a rule of thumb, but microseconds are quite short, so I would calculate the maximum velocity you might measure and work your way backwards to make sure that the difference in the object positions isn't terribly large in between BPM chirps.

Best,

Nate

0 Morten Nissov over 2 years ago in reply to Nathan Block

Intellectual 380 points

BPM should be less sensitive than TDM then, right? Since the time from first chirp begins to last chirp ends per measuring cycle is shorter (since 2 of the three will chirp simultaneously)?

0 Nathan Block over 2 years ago in reply to Morten Nissov

TI__Mastermind 37805 points

If you design it to only use BPM on two chirps and TDM with three chirps, then yes, two chirps will take less time than three.

Best,

Nate

0 Morten Nissov over 2 years ago in reply to Nathan Block

Intellectual 380 points

... relies on objects staying relatively stationary over the time of the transmissions more than the TDM method requires.

Okay so this isn't true then right? Sorry I'm just a little confused.

only use BPM on two chirps and TDM with three chirps

As far as I could understand this is just how TDM and BPM works on the 6843AOP given the current SDK (3.6). Right?

0 Morten Nissov over 2 years ago in reply to Morten Nissov

Intellectual 380 points

Sorry to bother, I was curious if you had seen the previous message.

0 Nathan Block over 2 years ago in reply to Morten Nissov

TI__Mastermind 37805 points

Morten Nissov said:
As far as I could understand this is just how TDM and BPM works on the 6843AOP given the current SDK (3.6). Right?

You could design it to work like this or not depending on your configuration file. You could design a BPM encoding/decoding scheme with three chirps.

Morten Nissov said:
Okay so this isn't true then right? Sorry I'm just a little confused.

Both TDM and BPM require the object stay relatively stationary in between successive chirps. If you design a TDM scheme that chirps for less time, then the object needs to stay less stationary because the chirping time will be shorter.

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IWR6843AOPEVM: TDM-MMIO vs BPM-MIMO, and examples for 6843AOP