Working Principle and Functions of Smart Antennas in Software Defined Radio
A smart antenna, also known as an adaptive antenna, consists of multiple antenna elements. Each element is connected to a complex weight multiplier, and the outputs are combined by a summing device for final output. This structure allows the smart antenna to perform spatial domain processing.
A smart antenna capable of both spatial and temporal processing has a more complex structure. In this case, each antenna element is followed by a delay-tap weighting network (structurally identical to a time-domain FIR equalizer). The terms"adaptive" or"smart" primarily refer to the ability of these weight coefficients to be adaptively updated and adjusted according to specific adaptive algorithms.
Assuming the antenna meets the narrowband transmission condition – meaning the response outputs of the incident signal across the antenna elements differ only in phase, and the incident signal is a plane wave (i.e., arriving from a single direction) – these phase differences are uniquely determined by the carrier wavelength, angle of incidence, and the spatial distribution of the antenna elements. Given a set of weight values and a certain incident signal strength, signals from different angles of incidence will produce different output signal strengths after the combiner, due to their distinct phase differences across the antenna array. Ideally, it's possible to configure the antenna pattern so that the main lobe aligns with the desired signal, while sidelobes or nulls align with interfering signals.
However, real-world wireless communication environments are complex. Factors such as numerous interfering signals, multipath effects, limited degrees of freedom (determined by the number of antenna elements), and scenarios where the desired and interfering signals have very small angular separation often prevent the achievement of ideal performance. Nevertheless, maximizing the Signal-to-Noise Ratio (SNR) remains the ultimate goal.
Working Principle and Functions of Smart Antennas in Software Defined Radio
by sdruav.com | Sep 28, 2025 | Articles
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