I generally understand how radar antennas work (specifically dipoles) from a bunch of videos I dug out. I also learnt that at large distances and using radio waves, an antenna needs to be impractically huge to provide good resolution. Hence idea of SAR was conceived.
However I need some help to visualise how a moving sensor can act as a “large antenna”…
In: Physics
So resolution in imaging is limited by the size of your aperture (and the wavelength of the light), right? You need a really big aperture to get a very find resolution. Let’s say you want to take some radar images of Earth from space for whatever reason. It turns out you’d need to have an absolutely massive antenna on the spacecraft to get any useful images from it. So you need to do something creative.
Well, let’s think about what a really big radar antenna even is. It’s just a bunch of smaller radar antennas smushed together and then linked up so they can generate radio waves in a specific direction. So this is what SAR mimics. Instead of a bunch of smaller radio antennas transmitting and receiving at one time over a very large area, you have a single small radio antenna transmitting and receiving at *different times* over a large area (since the platform is moving). Then when you get all the data back, you can just say do some math to workout the configuration of an antenna that follows the path of the platform’s movement, and use that to combine it into a nice, pretty image.
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