Hello Achal,

     I understand your concern and I am here to help you regarding your query !!

So, basically CAD ( Computer aided design) is needed for Mechanical engineering students and there is no wronh in learning that being a Electronics and communication engineering student. But, hopefully it is not ghat necessary in ECE because you will have a lot about purely circuits and devices followed by their design and working. 

Hope this helps you !!

All the very best !!