There are many solutions that you can try if you want to keep your yard free of the neighborhood cats. To start, you can set up an odor barrier by using a repellent cat spray, or you can plant Coleus canina, mint, or lavender on your property as felines hate the smell of these plants.
Another alternative that you can use is a physical barrier. For example, you can use spiked mats, chicken wire, or stone mulch to deter them from entering your property. Most of the products of this kind that you can find online are safe and will not cause harm to the animals.
A less drastic solution is to use your sprinkler system to your advantage. As you probably know by now, water is like kryptonite for felines. So, next time you see some unwanted visitors in your garden, squirt some water to scare them away. Very practical electric devices that emit ultrasonic sounds are also available.