Figure 4: A two-dimensional beam-steering architecture of (a) Butler
Matrix [34] and (b) Nolen Matrix [38].
Although such matrices are easy to design and implement, and then can
provide a good degree of freedom in terms of customized EM beams for
designated applications, they need a large form factor and hence
increase the overall size and cost of manufacturing the antenna system.
Phased array antennas have seen significant development over the past
few decades and are now being used extensively for different
applications. They can provide a wide beam-steering with small
form-factor; however, they are costly to manufacture and high-power
consumption requirements which may not be ideal for mass deployment of
the system.