AWR2243: the noise figures read from the two AWR2243 chips are different

Hello Miles,

differences of 1-2 dB between chips is very normal and nothing to be concerned about.

Regards,

James

ok，thank you！

But now I'm encountering a phenomenon: when a person approaches the radar from a distance of 150 meters, some frames will have 7 to 8 point clouds,

while others may only have 1 to 2 point clouds, or even no point clouds at all; this situation persists until the person is approximately 65 meters away from the

radar before it stabilizes.

And it appears that this phenomenon recurs in a cyclical manner according to this period.

Hello Miles,

a human does not have a very large radar cross section compared to e.g. a car, so at 150 meters you may need to do additional engineering of the profile to detect the person.  you can reference this app note

mmWave Radar Sensors: Object Versus Range (Rev. A) (ti.com)

and also this app note for some basic understanding of how to increase maximum range:

ti.com/lit/an/swra553a/swra553a.pdf?ts=1663338455889

And this lab, which has some pointers/ideas on how to increase range:

Range Tuning Guide (ti.com)

Regards,

James

Hi, when RX Gain is 48,the NF will be 11, according this pictute;

Now, devID0 and devID1 ,RX Gain is 48,

but the NF:

  devID0 is 13dB.

  devID1 is 15dB.

then, Compared to the standard diagram provided by TI, Chip 0 has a difference of 2dB, while Chip 1 has a difference of nearly 4dB. What are the reasons for this?

Hi Miles,

There are a few things to consider here:

1. It's very typical for there to be several dB of variation from part to part.  You need to measure a very large number of parts to get an accurate understanding.  It appears that you have two devices which are a bit over the average for NF, but statistically this can happen.

2. If you are using the on-chip monitor to measure NF, its also important to note that the NF is measured by loopback of the TX into the RX.  Therefore, slight variations in matching at the TX can impact the accuracy of the monitor by a few dB, since the chip uses an estimate of the power coupled back into the RX to estimate the noise figure.  

Regards,

James

Hi James,

Thank you for your response!

I'm currently looking to optimize the noise figure and try to get it as close as possible to what's shown in TI's official documentation, for example, achieving a

noise figure of 11dB when the RX GAIN is set to 48dB. Could you please let me know if there are any methods to achieve this, as this metric will significantly

impact my detection capability?

Best Regards!

Miles

Hi Miles,

Also, I need to let you know that the NF monitor is very susceptible to interference, so we don't usually recommend its use. 

Generally, the noise figure will improve with higher gain, as shown in the plot (however, be careful since higher gain also reduces linearity, so can result in more spurs).  Also, the noise figure improves as you reduce loss into the device, so its important to keep the trace loss to the antenna and the antenna efficiency as high as possible.

Regards,

James

Hi James,

Thank you for your reply!

During my testing, the radar antenna surface was tightly attached to a large piece of microwave absorbing material, so there should not be much interference.

Regards,

Miles

Hi James,

Therefore, I don't think there should be too much interference. So, I'm wondering why there is such a large difference between the NF I measured and the one in TI's official testing, and how I can improve or avoid this issue. Thank you.

Regards,

Miles

Hi Miles, 

the monitor itself is not recommended for use, so it's difficult to conclude based on using it that the NF is too high.  Additionally the variation you are seeing should not be problematic.  

Regards,

James

Hi James,

Thank you very much for your reply! While I acknowledge that NF (Noise Figure) may not provide absolute conclusions, I believe it can offer some relative insights. Please consider these sets of NF data I have tested. The radar was tested in close proximity to the wave-absorbing material, with no other factors influencing the results. Each set of data was collected for approximately 5 minutes, with only the gain configuration varying between sets. I have conducted a statistical analysis by taking the maximum, minimum, and average values of the data for reference. I believe that the average values over this period hold some significance. From the data, we can observe the following phenomena:

1. For most of the data, the fluctuations between the maximum and minimum values are relatively large. Even in the file named "78G_EM_ABSORB_44", the maximum NF measured by RF2 ranges from 37 to 42, and the maximum NF measured by RF3 exceeds 50. What could be the reason for such large fluctuations?

2. If you look at the average values for each RF in each file, you'll notice that Chip 1 generally has a higher NF than Chip 0. Based on my analysis, this could be due to differences in the gain of the two chips. However, what factors contribute to these differences in gain?

3. Additionally, as observed from the data, the NF values of RF1 appear to be more normal compared to RF2 and RF3. May I ask why the performance of RF2 and RF3 is relatively poorer?

2627.noise figure data.docx

Regards,

Miles

Hi James,

Thanks for your reply！

Yes, I would like to proceed with collecting and analyzing raw ADC data next.

Regards,

Miles

Hi Miles,

Makes sense, good luck!

Regards,

James