The previous chapters emphasize broadband linearly polarized MSAs. However,
there are many applications, where CP is required.
In a communication system that uses circularly polarized radiation the rotational orientations of the transmitter and the receiver antennas are unimportant in relation to the received signal strength.
With linearly polarized signals, on the other hand, there will be very weak reception if the transmitter and receiver antenna orientations are nearly orthogonal.
Also in CP, after reflection from metallic objects, the sense of polarization reverses from left-hand CP (LHCP) to righthandCP (RHCP) and vice versa to produce predominantly orthogonal polarization.
The system then tends to discriminate the reception of such reflected signals from other signals arising from direct paths.
Therefore, CP is useful for a number of applications, such as radar, communication, and navigational systems [1–3].