anchor tag download is not working on live laravel project

I am using this code to download the pdf files which are placed in main directory “public/download/ca/”
CODE:

      <a download="" class="download" target="_blank" href="{{ asset('download/ca/'.$doc>
              file_name) }}">
      </a>

It is working perfectly on my local server project also downloads the files but it is not working on my live server project, its showing “failed – Server Problem”.