AWR2243: RX Monitoring in cascading usecase

Taro Shibata

Expert 8260 points

Part Number: AWR2243

Hi,

This is regarding RX Monitoring feature in cascading usecase.

I’m referring below document.

Application Report: Self-Calibration in TI’s mmWave Radar Devices (spracf4.pdf)

Figure 3. On-Chip TX-RX Test Signal Loopback Architecture

In this block diagram, it look like internal LO (I/Q) is used for RX Monitoring.

In cascading usecase also, internal LO is used for RX Monitoring, or external LO received from FM_CW_SYNCIN1/ FM_CW_SYNCIN2 are used for slave devices?

My concern is that the gain/phase condition with internal LO is not the same with the external LO (actually used for chirp).

Best regards,

-Shibata

over 4 years ago

0 Vivek Dham over 4 years ago

TI__Guru 58035 points

Hello Shibata San,

We use internal LO for the slave device monitoring. The LO does not impact the Rx gain unless the external LO input level goes below the speced level in the datasheet. If its higher than that it should not impact the Rx gain.

regards,

vivek

0 Taro Shibata over 4 years ago in reply to Vivek Dham

TI__Expert 8260 points

Hi Vivek,

My concern is that there are any gap between the other slaves by using internal LO.

Please let me know your thought.

Best regards,

-Shibata

0 Vivek Dham over 4 years ago in reply to Taro Shibata

TI__Guru 58035 points

Hello Shibata San,

None that we are aware of.

Regards,

Vivek

0 Taro Shibata over 4 years ago in reply to Vivek Dham

TI__Expert 8260 points

Hi Vivek,

I’m not fully understand why there are no concern.

After RX calibration is done by internal LO, RX channels in each slaves will receive the chirps generated from external LO.

In that case RX gain and phase imbalances caused by external LO might be not taken care of by the calibration.

Pease let me know if I am wrong.

Thanks,

-Shibata

0 Vivek Dham over 4 years ago in reply to Taro Shibata

TI__Guru 58035 points

Hello Shibata San,

The LO is routed internally using a bunch of LO buffers. The same set of buffers are used in both internal LO mode and external LO mode. The gain primiraly depends on the swing at the buffer output, hence it does not change with internal LO or external LO mode. Incase the external LO level falls to a very low level then it starts impacting the gain.

Regards,

Vivek

0 Taro Shibata over 4 years ago in reply to Vivek Dham

TI__Expert 8260 points

Hi Vivek,

Thanks for your explanation.

I understand there are no concern using internal LO for RX monitoring for RX channels in a device.

I’m still curious to know about RX phase calibration between master/slaves in cascading usecase.

Are there any consideration about it?

Best regards,

-Shibata

0 Vivek Dham over 4 years ago in reply to Taro Shibata

TI__Guru 58035 points

Hello Shibata San,

There is no phase calibration done within the device, its only gain calibration. The phase mismatch between the channels comes due to antenna mismatch on the board and silicon process mismatch. This is typically calibrated by the user at sensor level calibrations at their production.

Regards,
Vivek

0 Taro Shibata over 4 years ago in reply to Vivek Dham

TI__Expert 8260 points

Hi Vivek,

Understood.

Thanks for the clarification.

Best regards,

-Shibata

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AWR2243: RX Monitoring in cascading usecase