in these days I have been studying communication systems.
and I want to know the role of wideband phase shifter in the picture above.
Electronic – what is wideband phase shifter in modulator
amModulationphase shiftradioRF
Related Solutions
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.
If you are happy with feeding a signal into a "block" and getting two signals out that are 90 degrees apart may I recommend this: -
Select R = R1 = R2 = \$\sqrt{\frac{L}{C}}\$. This ensures that OUT1 and OUT2 have a phase differential of 90 degrees across all frequencies. The phase relationship between OUT1 and OUT2 is always 90 degrees but amplitudes do change with frequency as with any high-pass or low-pass fliter.
Best Answer
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.