Accounting for Nonuniformity of the Electromagnetic Field when Calibrating Thin Dipole and Loop Antennas in Four-Wire Sources

The effect of nonuniformity of the electric and magnetic fields on the accuracy of calibration of dipole and loop antennas in field sources based on four-wire transmission lines is examined theoretically. It is proposed that the effect of nonuniformity of the electromagnetic field of a four-wire source be taken into account during calibration of antennas by using equivalence coefficients. The use of these coefficients, which take into account the distribution of the field in a source and of the current on the antenna conductors, makes it possible to greatly reduce the requirements for field uniformity when calibrating antennas. Formulas for the equivalence coefficients are derived in the approximation of a four-wire source for an infinite line for several widely distributed types of antennas. Simplified approximations are obtained for use in engineering calculations.