Comparison of Frequency Domain and Time Domain Measurement Procedures for Ultra Wideband Antennas

Spectrum is presently one of the most valuable goods worldwide as the demand is permanently increasing and it can be traded only locally. The United States FCC has opened a portion of the spectrum from 3.1 GHz to 10.6 GHz, i.e. a bandwidth of 7.5 GHz, for unlicensed use with up to –41.25 dBm/MHz EIRP [1]. Numerous applications in communications and sensor areas are showing up now. Like all wireless devices, these devices have an antenna as an integral part of the air interface. The antennas are modeled as linear time invariant (LTI) systems with a transfer function. The measurement of the antenna’s frequency dependent directional transfer function is described. Furthermore, the measured transfer function is transformed into time domain, where it is used to characterize pulse-shaping properties of the antennas. Additionally, measurements in time domain, which were performed with a picosecond pulse generator and a 50 GHz sampling oscilloscope, are presented and compared to the transformed frequency domain measurements. These measurements enable the realistic characterization of ultra wideband antennas for UWB link level simulations.