“Think of an antenna on top of a tower pointing at individual cars”
But the antenna points to lots of cars.
I’m thinking that radar can’t tell the elevation of a plane and its signal is bounced off of distant objects.
A long time ago, there was this thing called side-lobe, which was an intractable problem and which sent a lot of the power in directions that were more than merely wasteful, but also insecure. Engineers noticed that sidelobe isn’t merely a spreading of EM, but an interaction of the energies, creating multiple lobes at specific proportions to the main signal, and at specific natural angles. This applied to both telecommunications, and radar.
https://en.wikipedia.org/wiki/Side_lobe
Then engineers learned how to cancel out sidelobe, and now line of sight was both more efficient, and less simple to eavesdrop on.
One of the things you may notice is that cellular antennae would come in groups of three - at 120-degree facings from one another. Now they come in groups of three, with several subcomponents, such as a electromagnetic wave refractor, which allows enhanced directionality.
Later, engineers learned how to use a similar cancellation effect to split beams, and make the main bursts of power extend in odd directions.
https://en.wikipedia.org/wiki/MIMO
These MIMO (Multiple input, multiple output) antennae were in use with 4G, and represent a large improvement in channel capacity over 3G. 5G takes that to an order of magnitude better, with a host of other improvements.
Think of the bumps on a ferro-fluid, then imagine tens of thousands of bumps, each electronically tunable by strengthening and cancelling lobes via resonance. The physical antenna points in an arc. Electronically, the signal is broken into tens of thousands of beams capable of each being aimed anywhere in that 120-degree arc, plus a little, as well as to a lesser extent, up and down.
oh, and radar is looking at tens to hundreds of miles, with atmospheric bending often out of its control. 5G nodes are designed to be every few hundred yards, and making use of ricocheting off buildings.