RF Electronics Chapter4: Transmission Line Transformers and Hybrids Page 68
2022, C. J. Kikkert, James Cook University, ISBN 978-0-6486803-9-0.
OC SC
I
V
Distance from Load
Figure 4.6. Standing wave along TL2.
Figure 4.7. Circuit for analysis purposes.
Since the input power is the same as the output power, the voltage V
c
at port 1 and the
voltage V
a
at port 2 relate as V
a
= 2 V
c
.
The maximum current and maximum voltage on a transmission line relate as:
max 0 max
I Z V
Eqn. 4.9
In figure 4.4, the current at the port 3 side of TL2 will thus be:
0
0 0
max
2
2 2 2
Z
V
Z
V
Z
V
I
a a c
Eqn. 4.10
Since this current must come through the load resistor R then
0
max
2Z
V
R
V
I
a a
Eqn. 4.11
So that R = 2Z
0
for best isolation.
The circuit can be realised using a Microstrip PCB layout. A Rogers 4003 laminate with
1 oz. copper and 0.8128mm thickness are to be used. To calculate the required track
widths and lengths, the properties of the PCB to be used are to be selected first. The
TLIN
ID=TL1
Z0=70.7 Ohm
EL=90 Deg
F0=1000 MHz
TLIN
ID=TL2
Z0=70.7 Ohm
EL=90 Deg
F0=1000 MHz
RES
ID=R1
R=100 Ohm
PORT
P=1
Z=50 Ohm
PORT
P=2
Z=50 Ohm
PORT
P=3
Z=50 Ohm
Vc
Va
RF Electronics: Design and Simulation
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