Avoid looking directly at animals and you'll be surprised how little you intimate them. Some say avoid eye contact but I believe it's less about them seeing your eyes, than it is seeing both eyes. Prey animals know what a predator is and predators have eyes in the front of their heads. I think this is what the angling 30 degrees does, keeps only one eye visible to the antelope. The crouching is a great point too, you're not less intimidating when you crouch, you're more. There's a great video from a couple summers ago of a woman in South Dakota getting charged by a bison, the bison didn't care one bit until she crouched, then it was on.Another possible helpful hint- in my experience the thing that will make antelope skittish is a stopping vehicle. They know.
And I've walked up to within 250 yards of a buck by just angling 30 degrees off and using a normal pace (no crouching like a lion, no running like I'm hell bent on getting to them). All why wearing dull grey shorts and a BRCC t-shirt. And when you use that tactic- try to stay visible the whole time- because if you disappear for a minute, it will make them nervous and bolt. Doesn't always work- but in flat country your options are limited.