A simple formulation to compute the envelope correlation of an antenna diversity system is derived. It is shown how to compute the envelope correlation from the S-parameter description of the antenna system. This approach has the advantage that it does not require the computation nor the measurement of the radiation pattern of the antenna system. It also offers the advantage of providing a clear understanding of the effects of mutual coupling and input match on the diversity performance of the antenna system.

Fractal objects have some unique geometrical properties. One of them is the possibility to enclose in a finite area an infinitely long curve. The resulting curve is highly convoluted being nowhere differentiable. One such curve is the Koch curve. In this paper, the behavior the Koch monopole is numerically and experimentally analyzed. The results show that as the number of iterations on the small fractal Koch monopole are increased, the Q of the antenna approaches the fundamental limit for small antennas.

Experimental and computed results show a multiband behaviour over five bands for the new fractal Sierpinski antenna. Such a behaviour is based on the self-similarity properties of the antenna's fractal shape, which might open an alternative way for designing new multiband and frequency independent antennas.

A small but long wire fractal antenna based on the Koch curve is presented. Experimental and numerical results show that the antenna improves the features of a common linear monopole. The radiation resistance is increased and the Q is reduced at each fractal iteration, approaching the fundamental limit on small antennas.