TIDEP-01012: IF amplitude varying over the chirp

Jonathan Jones2

Part Number: TIDEP-01012

Dear Support,

I have run the mmWave Studio 03_00_00_13 4chip_cascade_MIMO_example example on the TIDEP-01012 and get the follow result. Can you let me know why the ampitude of the beat signal in the plot on the right decreases from 1400pk-pk to ~ 200pk-pk over the duration of the chirp? It seems to do this irrespective of target range which leads me to think that it is not caused by a fading issue. Well please let me know if you know what may be causing this issue and how it can be rectified?

I appreciate your help with this.

Best regards

Jonathan

over 4 years ago

0 Jonathan Jones2 over 4 years ago

Intellectual 680 points

Uploaded plot below

0 Cesar over 4 years ago in reply to Jonathan Jones2

TI__Guru*** 148684 points

Please give us a couple of days to review this with our team and get back to you

thank you

Cesar

0 Vivek Dham over 4 years ago in reply to Jonathan Jones2

TI__Guru 58035 points

Hello Jonathan,

The RF gains ( both Tx, Rx) would change across the RF frequency. Also the antenna gain will reduce at higher frequencies. That could cause the reduction in signal amplitude. What is the chirp BW you are using?

regards,
Vivek

0 Jonathan Jones2 over 4 years ago in reply to Vivek Dham

Intellectual 680 points

Hello Vivek,

Thanks for getting back to me on this. We are using 3.16GHz BW chirp starting from 77GHz as per the default setting for the MIMO example in the mmWave Studio. Do you have any simulation results for the antennas that show how the gain and antenna pattern varies over frequency from 77 to 80/81GHz. I can see that there is a result for the TX1/TX2 over frequency on SWRU553A (Fig 24) but I can find any information for the RX antennas over frequency. So if you can provide more information on the performance (gain and antenna pattern) of the TX/RX antennas over frequency from 77-80GHz that would be really helpful.

Best regards

Jonathan

0 Vivek Dham over 4 years ago in reply to Jonathan Jones2

TI__Guru 58035 points

Hello Jonathan,

The Rx antenna gain variation will be similar to the Tx since the antenna design is the same. You can see > 3dB gain variation from 785Ghz to 81Ghz.

The device Rx gain would have additional ~1.5dB variation from 76 to 81Ghz.

The Tx o/p would have ~0.5 - 0.75 dB variation from 76-81Ghz.

Regards,

Vivek

0 Jonathan Jones2 over 4 years ago in reply to Vivek Dham

Intellectual 680 points

Thank you Vivek for your support with this issue.

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TIDEP-01012: IF amplitude varying over the chirp