IWR6843AOPEVM: rx Gain

Morten Nissov

Part Number: IWR6843AOPEVM

Tool/software:

I noticed some inconsistencies in the default rxGain from the TI demo visualizer and from the ti_mmwave_rospkg. The demo visualizer seems to suggest 158 regardless of parameters, and the configs provided in the ti_mmwave_rospkg are all locked to 30.

From https://e2e.ti.com/support/sensors-group/sensors/f/sensors-forum/1349124/iwr6843-the-value-bounds-for-rxgain I see that 158 is 10011110 in binary. This post also says that the first 6 LSB bits are for the rxgain, and the remaining two for RF gain. This means 158 is also inputting 30 for the rx gain, right? What is the significance of the RF gain here, and in what circumstance should I consider changing it?

over 1 year ago

0 Pedrhom Nafisi over 1 year ago

TI__Mastermind 23177 points

Hello,

Can you elaborate with what you mean by locked to 30? For an out of box demo based binary/example, the cfg will have to have the rxGain notation as you pointed out, with 158 equaling 30. We have some threads explaining rf gain vs rx gain such as https://e2e.ti.com/support/sensors-group/sensors/f/sensors-forum/711285/awr1243-what-s-different-between-rx-gain-and-rf-gain-target , and increasing RX gain can potentially increase real detections but also reflection/ghost detections. Generally an RX gain of 30-36 is ample and playing around with TX Power and CFAR processing thresholds have been shown to be more beneficial with filtering out points to only what is desired to be detected.

Best Regards,

Pedrhom

0 Morten Nissov over 1 year ago in reply to Pedrhom Nafisi

Intellectual 380 points

I just meant to say that the demo visualizer returns 158 regardless of parameters, and all example configs in the ros driver have 30.

I was curious why these are different?

0 Pedrhom Nafisi over 1 year ago in reply to Morten Nissov

TI__Mastermind 23177 points

Hello,

158 = 10 011110

30 = 00 011110

They have the same RX Gain due to "011110", 158 chooses an RF Gain target of 36 dB due to "10", and 30 chooses an RF target of 30 dB due to "00".

This thread below has a bit more information than the one you linked

https://e2e.ti.com/support/rf-microwave-group/rf-microwave/f/rf-microwave-forum/1034827/about-rf-gain-and-rx-gain

Best Regards,

Pedrhom

0 Morten Nissov over 1 year ago in reply to Pedrhom Nafisi

Intellectual 380 points

What is the reason for this change in RF gain between two configs provided for the same sensor? Is there a generally-recommended value from TI, or is it dependent on the operating context?

0 Josh Dye over 1 year ago in reply to Morten Nissov

TI__Mastermind 20901 points

Hello,

Sorry for the delay. Pedrhom is currently out of office. He will respond when he returns next week. Thank you for your patience.

Best Regards,

Josh

0 Pedrhom Nafisi over 1 year ago in reply to Josh Dye

TI__Mastermind 23177 points

Hello,

We recommend RF Gain at 30-36. Higher values may show ADC saturation at short ranges due to near field antenna coupling. So it is definitely context based in the sense of what ranges you are expecting most targets to appear at.

Best Regards,

Pedrhom

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IWR6843AOPEVM: rx Gain