Re: antenna array's..?
In conventional antenna arrays, there are three main kinds of arrays, end-fire, broadside, and phase-scanning based. It could be further classificed into: linear and non-linear, and uniform and non-uniform.
The main drawback of endfire arrays or broadside is that they're fixed to specific tranmission/reception angle of 0 or 90. There're, however, sometimes applications where we need an arbitrary angle, say 30. Here comes the role of phase scanning array.
However, what I do need to comment about is that there's a big misconception when we talk about Smart Antennas.
In Smart Antennas, the main objective is not that easy of that of the phase scanning, it rather monitors (stastically) the wanted signal and the infereing signal(s), so that the array can reject the interefering and keep the wanted signals with enhanced power (higher SNR). Thus, we could achieve higher capacities and extended coverage, with enhanced QoS. Smart Antennas have gained much attention in military applications since mid 80's in radar systems. However, for mobile communications applications, THEY'RE USED IN THE 3G which already adopted in Korea, Japan and throughout Europe. FOR 4G MOBILE COMM., Multiple-Input Multiple-Output (MIMO) is used which increases capacity and coverage more than that of "conventional" Smart Antennas. MIMO can be thought of as smart antenna in both the transmit and receive sides.
For any Q's about MIMO, you know where to find me. Hope I could help.
Regards