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.