IWR6843: IWR6843 Chirp Frequency Deviation.

Jesse Wang

Part Number: IWR6843
Other Parts Discussed in Thread: AWR1843BOOST, ,

Hi,

We tested the IWR6843ISK with the lab0015 people counting. While measuring the chirp frequency by spectrum, we see the frequency will have a spike which causes the frequency deviation about 110k~120kHz (in RMS). Please see below picture of the measurement.

Is this correct? How can I eliminate this spike?

PS: we also checked the AWR1843BOOST without seeing the same behavior. This only happens on IWR6843.

We also modified the chirp with different start frequency and slope, but still see the same behavior. Please see below 2nd picture.

over 6 years ago

0 Jesse Wang over 6 years ago

TI__Intellectual 2285 points

Sorry to see the attach pictures here.

0 CHETHAN KUMAR Y.B. over 6 years ago in reply to Jesse Wang

TI__Mastermind 25835 points

Hello,

Could you please share the chirp start frequency, stop frequency used for the operation. Is the slope is 10.2Mhz/us.
Also could you please share the chirp configuration used for above measurement?

Thanks and regards,
CHETHAN KUMAR Y.B.

0 Jesse Wang over 6 years ago in reply to CHETHAN KUMAR Y.B.

TI__Intellectual 2285 points

Hi,

For the first picture of measurement, it is based on TI's labs\lab0015_pplcount_68xx, and it cfg is

profileCfg 0 60.6 30 10 62 0 0 53 1 128 2500 0 0 30

For the 2nd picture of measurement, its chirp configuration is as below:

Start frequency: 61.29 GHz

Center frequency: 62 GHz

Stop frequency: 62.7 GHz

Ramp slope: 10.28 MHz/us

Chirp ramp up time=	137 us
Chirp down time=	1 us
Chirp idle time=	6 us
Chirp cycle time=	144 us
one frame time=	4.608 ms

0 CHETHAN KUMAR Y.B. over 6 years ago in reply to Jesse Wang

TI__Mastermind 25835 points

Hello,

Which board you are using for the measurement? Is it IWR6843ISK or IWR6843ISK-ODS board?

For the 2nd case, could you please try to avoid 62.1 GHz frequency and use other frequency band and see if this goes away?

For the 1st case also you could try avoiding 62.1 GHz by reducing the bandwidth of the Chirp, of-course this would impact the range resolution.
However frequency deviation of 120 KHz over 2.8 GHz bandwidth would be % wise smaller quantity and it should have negligible impact on the system performance.

Thanks and regards,
CHETHAN KUMAR Y.B.

0 Jesse Wang over 6 years ago in reply to CHETHAN KUMAR Y.B.

TI__Intellectual 2285 points

Hi,

We tested on IWR6843ISK board. We will try to set start freq to be higher than 62.1GHz and test again.

Sorry that your post doesn't show how much % it will impact on the system performance. Could you elaborate a little?

0 CHETHAN KUMAR Y.B. over 6 years ago in reply to Jesse Wang

TI__Mastermind 25835 points

Jesse Wang,

For narrow bandwidth application (1.41GHz), as long as if you keep the same RF bandwidth within 60-64GHz bandwidth avoiding 62.1 GHz there is no impact on the Range resolution. However we need to ensure Antennas would support this bandwidth (i.e. Start and stop frequencies should be within Antenna bandwidth). If you cannot avoid this frequency, then you could reduce the Bandwidth then range resolution would be impacted to the extent bandwidth is reduced.

For wider bandwidth 3GHz and above frequency deviation error is negligible as compared to RF bandwidth hence impact on the system performance is very minimal.

Thanks and regards,
CHETHAN KUMAR Y.B.

0 CHETHAN KUMAR Y.B. over 6 years ago in reply to CHETHAN KUMAR Y.B.

TI__Mastermind 25835 points

Jesse Wang,

Were you able to overcome the glitch problem by avoiding the 62.1 GHz frequency?

Thanks and regards,
CHETHAN KUMAR Y.B.

0 Jesse Wang over 6 years ago in reply to CHETHAN KUMAR Y.B.

TI__Intellectual 2285 points

Yes, we can. Thanks.

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IWR6843: IWR6843 Chirp Frequency Deviation.