What do you really want to capture ? Resulting, decoded images and sound and subtitle or the raw flow of digital data?
If this is the decoded data, you could look at the products from Eyetv Geniatech or less integrated
(Old) Create a Customer Service Case · Support Portal or chips such as DVB-T Silicon Tuner IC | NXP Semiconductors and similar such as Broadcom’s BCM7563 and the likes supporting diversity
If not and if you have funding, you could ask specializedcompanies on a custom work that their hardware handles to receive a channel before decoding...
If you want to do it yourself - you probably have quite a steep learning curve ahead of you