why do i see vertical lines in SAR image?

Hello. I am using strip-map SAR example (https://www.mathworks.com/help/radar/ug/stripmap-synthetic-aperture-radar-sar-image-formation.html) for SAR imaging. when I change radar parameters according to my scenario, the raw data becomes like the below figure.

I attached my codes. I think the raw SAR data is not acquired correctly. what does the lines in figure mean? any ideas? Thanks so much for your time and consideration.