Do you have pets or a deer problem? It looks something like pee damage. It could be a fungus, are these patches have a red tinge, or brown tinge? or possibly white tinge? Are they in spirals or circles? Can't tell from your photo.

What happens when you rake out the dead grass, does it come back indicating top growth problem but crown of the grass plant is ok?

Good questions from boogey. Can you take another picture close up showing some blades of brown, green, and anything that looks like it might be halfway brown and green?

Looks like you have a mix of grasses. Do you know what the predominate grasses or mix is? I'm guessing fescue but is there any Kentucky bluegrass?