Time-domain simulation and characterisation of TEM horns using a normalised impulse response

A common way of describing antennas in the time domain is by means of their impulse response. When the time-domain antenna equations are expressed in terms of the normalised impulse response (normalised IR), they become very simple to use, because all frequency-dependent antenna characteristics are included in the normalised IF:. This paper describes a method for measuring the normalised IR experimentally, using a vector network analyser. The nor malised IRs of different air and dielectric-filled TEM horn antennas are co mpared and discussed. The normalised IR is found to be a powerful tool for simulating antenna behaviour directly in the time domain. Thanks to the int roduction of the virtual source, (i.e. an apparent point in the antenna fro m which the radiated field degrades by a factor 1/r), the time-domain anten na equations can also be used near the TEM horns, although still in the far field of the antenna. Some examples of time-domain simulations and system modelling using the normalised IR are presented. In each example, the simul ations are compared with measured data.