Modeling and State Representation of Ultrawideband Antennas

A method is proposed to represent the states of ultrawideband (UWB) antennas. In UWB systems, the classical design parameters of antennas become strongly frequency dependent as compared to those in traditional narrowband systems. Therefore, both the transmit (TX) and receive (RX) antennas in UWB systems play a very important role in the performance evaluation of UWB systems. Moreover, as the transmitter design must comply with the spectral masks and the receiver design must collect efficiently the emitted energy, UWB antennas have to act as pulse shaping filters and therefore can be modeled as linear time invariant (LTI) systems. The associated transfer function and impulse response can be determined from classical method of measurement in frequency domain (i.e., S₂₁ parameter). Analytical and compressed expressions of characteristics are obtained using parametric model approaches. A state representation, that characterizes UWB antenna as LTI system, is achieved. The results are illustrated using a specific UWB antenna.