How to get rid of cats from the garden?

You can scatter citrus fruit skin in your garden. Orange/lemon peel should do the trick. They don't like the smell and will refrain from visiting your house as long as the smell is there. The downside is that you will have to replace the citrus skin when the smell goes.

Otherwise there are a few cat deterrent on the market but they may have chemicals in them

OR disguise as a dog. like Mr Bean.

get a dog...