Evaluation and Impact Reduction of Common Mode Currents on Antenna Feeders in Radiation Measurements

Abstract

Common mode currents on antenna feeders usually occur when feeding a symmetric radiator through an asymmetric line, or when the ground plane is electrically small. Such currents may have magnitudes comparable to the feed currents and therefore have a major impact on the total radiated field. For antenna radiation measurements, both assessment and reduction of the common mode currents on antenna feeders are crucial. Techniques to discriminate antenna and feeder radiation are mainly needed for design and optimization purposes. Antenna gain measurements in a multipath site can be performed by using the distance averaging method. In this paper, we show that the distance averaging technique can be applied to reduce the effect of common mode currents for measuring the field radiated by symmetrical antennas. Two measuring configurations are proposed depending on the number of symmetry degrees of the antenna under test, and a differential approach for extracting the field created by the common mode currents was also developed. The experimental validation was performed by measuring a simple wire dipole and a log-periodic dipole array (LPDA) with a small square loop as a probe, both on the feeder side and on the feeder free side.

A Compact Monopole Antenna for Underwater Acoustic Monitoring Beacons

“…In a previous paper [ 35 ], we focused on developing a method to reduce the effect of common currents but also on proposing a differential approach to extract the radiation generated by these currents from the total radiated field. The method that allows for a reduction of the effect of common mode currents, i.e., the distance averaging method, provides very good results; this is due to the fact that these currents have a distance variant distribution.…”

“…The most important analytical relations [ 35 ] for applying our method express the average figures for the transfer functions (10), the contribution of the common mode current to the output current (11) and the magnetic field generated by the common mode currents (12): …”

“…In order to investigate the effect of the common mode currents, we used a distance averaging approach [ 35 ].…”

Antennas and Propagation: A Sensor Approach

“…In Ref. [ 19 ], the authors show that the distance averaging technique can be applied to reduce the effect of the common mode currents for measuring the field radiated by symmetrical antennas. Two measuring configurations are proposed, depending on the number of symmetry degrees of the antenna under test.…”

The Application of Electromagnetic Sensors for Determination of Cherenkov Cone Inside and in the Vicinity of the Detector Volume in Any Environment Known

“…These inductors will be wound on a toroid with an outer diameter of 6 mm and an inner diameter of 4 mm. For (L1 ÷ L4) 4 coilers were wound in parallel on one of the halves of the torus and on the other two coils (L5, L6) were wound in parallel [34]. The adapters "in Π" are used to cancel the imaginary (reactive) part of element impedance.…”