Transcript COST 286 – Joint technical action 1 (JTA1)

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
z
z
10 cm
L
T
T (x, y, z)
x
10 c
y
m
R
L
y
h
T
z
b)
a)
x
10 c
m
d)
T
y
x
10 cm
10 cm
z
x
10 c
m
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
•
•
•
•
•
c)
y
Results
The cable is terminated by the 100+50 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.
0,85
0,8
0,75
0,7
0,65
0,6
I [A] x 1E-3
0,55
0,5
0,45
0,4
0,35
0,3
0,25
0,2
0,15
0,1
0,05
0
0,1
0,2
0,3
0,4
I(X) - 100 segments
0,5
X [m]
0,6
0,7
0,8
0,9
1
I(X) - 500 segments
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)
0,8
0,7
0,6
0,5
0,4
0,3
0,2
0,1
0
0,1
0,2
0,3
antenna parallel to X axis
0,4
0,5
X [m]
0,6
antenna parallel to Y axis
0,7
0,8
0,9
antenna parallel to Z axis
Fig. 3 - Current distribution along a cable wire for L=1m, h=5cm, X=
0,5 m (comparison of results for different polarizations)
0,045
0,04
0,035
U [V]
0,03
0,025
0,02
0,015
0,01
0,005
-30
-20
-10
0
10
antenna parallel to X axis
20
30
40
50 60
X [cm]
antenna parallel to Y axis
70
80
90
100 110 120 130
antenna parallel to Z axis
Fig. 4 - Voltage on a 50 Ohm resistor for L=1m, h=5cm (comparison of
results for different polarizations)
0,045
0,04
0,035
U [V]
0,03
0,025
0,02
0,015
0,01
0,005
0
-40 -30 -20 -10
0
10
antenna paralell to X axis
20
30
40
50 60
X [cm]
antenna paralell to Y axis
70
80
90 100 110 120 130 140
antenna paralell to Z axis
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