phase shiftphysical-design
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?
Yes of course it's possible - any analogue filter can be taken into the Z domain and a digital equivalent constructed. This happens all the time. So if you have an analogue circuit that does what your need there are several methodologies that produce an equivalent digital "circuit" that can be implemented in MCUs, FPGAs etc..
Try looking up: -
As to whether your original analogue circuit is a pure delay, that is another matter. Anyway, I forgot that I wrote a paper on it and the front sheet should help you understand: -
It begins with a simple RC and converts it to an op-amp equivalent in position (2). Position (3) re-shapes it slightly and position (4) arrives at the finished digital filter.
See Wikipedia for the mathematical formulation of Single Sideband: it is a special case of quadrature modulation, in which the quadrature signal is derived directly from the in-phase signal by a 90-degree phase shift. The Wideband Phase Shifter in your diagram produces the Q signal from the I signal (taken as the input).
Your diagram was traditionally known as the Phasing Method of SSB generation (in contrast to the Filter Method). It is difficult to accomplish an accurate 90-degree phase shift over a wide band (even a typical audio bandwidth) with passive components, which is why the Filter Method has dominated SSB generation until recently. Modern DSPs implement a Hilbert transform to accomplish the phase shift, dramatically reducing the cost, size, weight and power consumption of an SSB generator.
Best Answer
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:
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.