I've gotten interested in beam-forming via a phased antenna array. I read a few articles/tutorials and they have very nice diagrams of antenna arrays and how the antennas interact to behind each antenna is the key piece: A phase shifter. And yet when searching for it it seems like more of a theoretical device rather than a physical one-yet really phased antenna arrays exist. What is it exactly? Is it something so simple it's just assumed I know what it is?

What, physically, is a phase shifter?

  • \$\begingroup\$ The parts needed to shift phase depend on the base frequency. \$\endgroup\$ – Ignacio Vazquez-Abrams Oct 29 '15 at 7:13
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    \$\begingroup\$ Different lengths of coax work nicely as delay lines and, of course, a delay line can also be regarded as a phase shifter. So, pick the length of cable you need to produce a delay that corresponds to the correct phase shift at the frequency in question. \$\endgroup\$ – Andy aka Oct 29 '15 at 8:17

It depends heavily on the frequency at which you want to use your phase array antenna how you would implement the phase shifting. Possible solutions are:

  • separate receivers/transmitters per antenna or set of antennas, this phase shift can be implemented in baseband or at the LO signal
  • a shorter or longer transmission line to the antennas
  • RC filters and/or polyphase filters
  • some form of delay line

Note that usually a phase array antenna is used for a certain narrow band so the phase shift only has to be predictable at that particular frequency band. So in practice the phase shift is simply a time delay of the signal.

There might be more that I can't think of now.


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