RF and Microwave Engineering: Fundamentals of Wireless Communications

7.7 Modern Antenna Concepts

As seen before a group of antennas can be used to shape the radiation pattern or steer the direction of the main lobe. Further developments are possible when multi-antenna systems are combined with signal processing algorithms. These algorithms are beyond the scope of this introductory book. However, we will briefly mention some interesting concepts to encourage the reader to study this interesting topic elsewhere in the literature.

• A smart antenna uses a group of antennas to dynamically adapt the radiation pattern in order to optimize a communication link. The radiation pattern can be formed by adjusting the amplitude and phase of each individual antenna element. A smart antenna can steer the direction of the main lobe towards a certain wireless transmitter to increase the signal-to-noise ratio. Furthermore, by producing nulls in the radiation pattern, interfering sources can be suppressed. The smartness of a smart antenna comes from its adaptive algorithms rather than from the antenna hardware [21].
• Diversity is another method to use more than one antenna at the receiver or transmitter site to improve a wireless communication link. There are different types of diversity: using antennas with different polarizations (e.g. vertical and horizontal polarization) is called polarization diversity. Using different antennas at different points in space is called space diversity. As we will discuss in Section 8.3.1, radio wave propagation in multipath environments ...