IWR6843: What causes the non-linearity at the start of the chirp?

Johanwww

Part Number: IWR6843

In related post, (e2e.ti.com/.../730050)

there mentions that the non-linear behavior in the beginning of the chirp is due to "various settling time".

What are these settling times due to?

I ask because I want to find a good value for adcStartTime, I will use MMWAVE-STUDIO to compute the ADC Start time parameter based on the inputs provided for Ramp Slope, sampling mode, sampling rate,number of samples etc. as recommended.

over 5 years ago

0 Kyle Cousino over 5 years ago

TI__Mastermind 24955 points

Johan,

Please refer to section 5.1 "Idle Time" of this whitepaper: http://www.ti.com/lit/an/swra553/swra553.pdf

This will explain the reasons for the various settling times based on the chirp bandwidth along with other factors.

Regards,
Kyle

0 Johanwww over 5 years ago in reply to Kyle Cousino

Intellectual 500 points

I have now read the article. It was useful to understand the need to an idleTime and how big it should be.

And it explains what causes the non-linear behavior at then end of a chirp, or beginning of the next if idleTime is picked too small.

But the question is then, if idleTime is used to wait for the synthesizer ramp down settling time, what is TxStartTime used for? I want to know what causes the non-linear behavior at the beginning of a chirp if idleTime is taken big enough for the synthesizer ramp down to settle. I am referring to the non-linear ramp up shown in the image in mmwave sdk user guide 3.4, figure 2 (chirp diagram).