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nosnowtho OP t1_j5ff39a wrote

Reply to comment by Prestigious_Carpet29 in How do phased array antennas receive signals? by nosnowtho

I'm starting to see how and why this is done. The signal processing opens up many possibilities and capabilities. Thank you.

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Prestigious_Carpet29 t1_j5ftbtr wrote

(Digital) Signal-processing is a very broad field, but very powerful and important in modern communications systems.

As examples, you get audio signal-processing for lossy compression (bit-rate-reduction) and echo-cancellation and speech-recognition, and signal processing of radiofrequency signals in any "digital"-mode transmitter or receiver such as mobile phone or DAB radio or digital-TV (take a deep breath and look up OFDM :-) ).

It's amazing how Fourier transforms invented (or perhaps "discovered") by Joseph Fourier 200 years ago are at the heart of so much of modern technology.

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hatsune_aru t1_j5nwarb wrote

One more concept to realize is that since antennas are passive devices, they have to be reciprocal. In other words, radiation that goes through a reciprocal system has to work the same way forwards and backwards. In simpler words, if you imagine transmitting through the antenna and looking at the radiation pattern from far away--that antenna behaves exactly the same when the radiation shows up from far away receiving into the antenna--it behaves the same in transmission and reception.

Each phased array antenna element can be thought of as a radiator, and if its an active array, the radiating element can be thought of having a tuneable amplitude and phase. And the combined radiation pattern of the array is a superposition of all the individual elements.

When you have that kind of control, you can change the far-field radiation pattern by adding delays and changing the amplitude to tune the radiation pattern. It's quite ingenious actually.

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