Implications of Lorentz Reciprocity for Ultra-Wideband Antennas

Besides being directional filters, passive ultra-wideband antennas exhibit dispersive properties. To investigate these, spatio-temporal transmit and receive characteristics for an antenna and the corresponding far field impulse responses are defined. Then the relation of these characteristics is derived, starting at Maxwell´s curl equations and Lorentz´ reciprocity theorem. The constraints that Lorentz reciprocity imposes on the transmission and reception properties of ultra-wideband antennas are discussed based on this relation and focussing on the previously defined antenna impulse responses. Among other results, it is shown that, unlike the antenna pattern, these impulse responses are different for transmission and reception. As a side result, some classic antenna properties are obtained as well.