Investigation of polarization structure of ultrawideband radiation pulses

Summary form only given. Applications of high-power sources of ultrawideband (UWB) radiation require knowing the polarization structure (PS) of the field of radiated pulses. The paper presents the design of a vector receiving antenna and technique of measuring the polarization structure of UWB pulses radiated and scattered on objects. The receiving antenna consists of mutually perpendicular identical dipoles, the signals from them being recorded simultaneously and independently by a two-channel oscilloscope. The dipole length is approximately 1/4 of the UWB pulse space length and the ratio of the transverse dimension to the longitudinal one is 1/4. To spread the receiving antenna passband, the dipoles were loaded to the screened symmetric feeders with the wave impedance of 150 Ohm via impedance transformers 4:1. An algorithm has been developed allowing determination of the electric field vector E orientation in a Cartesian coordinate system related to two mutually perpendicular dipoles placed at the plane of the incident wave front by the registered current values at the loads. The suggested vector antenna was used to investigate the PS the field of a combined radiator excited by a 2-ns long bipolar voltage pulse. It was shown that in the direction of radiation maximum, vector E didn´t change its position during a pulse, i.e., it was linearly polarized. At the essential angle deviation from the direction of radiation maximum, vector E is rotating during a pulse making 1.5 circles. The velocity of vector E rotation during a pulse isn´t constant. In the pulse reflected from the objects, vector E rotates in the transverse direction. The error of determination of vector E angular position is 2-4 degrees.