COST 286 – Joint technical action 1 (JTA1) Antenna/wire coupling in the near field simulation results Sinisa Antonijevic, Vesna Roje University of Split, Croatia

Problem description L  {1m, 5m, 10m} h  {5cm, 30cm, 80cm}  L=16cm x  [-32cm, L+32cm] antenna is a half-wave dipole powered by the 1V generator operating on 900 MHz with 50 Ohm internal resistance the cable is terminated by a 150 Ohm load the infinite perfectly conducting plane is placed in z=0

Results The cable is terminated by the Ohm load, where 50 Ohm represents the input resistance of the measurement equipment. The voltage drop on this resistor is calculated as a function of x (antenna position). The calculation is repeated for different cable heights h and lengths L. In this work, only a single wire length of 1m is considered as an illustration of the method. The results for current distribution along the wire are also presented if antenna is fixed in x=50 cm position. The problem of resistance connection In this work, NEC is used to calculate the currents for different cable-antenna setups. The termination resistance is realized by adding a single wire connecting cable and ground. This wire was set to 150 Ohm resistance (i.e. loaded) via LD NEC card. The basic principle of obtaining a voltage drop on a 50 Ohm part of termination resistance is to simply multiply the current through the termination resistance with the 50 Ohm value. Therefore, the problem of voltage calculation can be viewed as the problem of calculating a current through the termination load.

Fig. 2 - Segment count impact on the current distribution along a cable wire (antenna parallel to Y axis, h=30 cm, L=1m, X=0.5m)

Fig. 3 - Current distribution along a cable wire for L=1m, h=5cm, X= 0,5 m (comparison of results for different polarizations)

Fig. 4 - Voltage on a 50 Ohm resistor for L=1m, h=5cm (comparison of results for different polarizations)

Fig. 5 - Voltage on a 50 Ohm resistor for L=1m, h=30cm (comparison of results for different polarizations)

Literature [1] “Simulation of the coupling phenomena between a radiating antenna and a cable”; A.A. Kucharski, J.Skrzypczynski [2] “Antenna/wire coupling in the near field”; Heyno Garbe, Sven Battermann [3] “NEC-Win Pro – User’s Manual” – Nittany Scientific, Inc.

Concluding remarks NEC-Win Pro was used in a command line mode to generate results The results for a 3 different polarizations and two cable heights are presented The results differ significantly from those presented in [1], [2] probably due to the different termination load modeling