20-07-2013, 02:53 PM
3 dB POWER DIVISION AND ISOLATION CHARACTERISTICS
Aim:
Measurement of power division and isolation characteristics of a microstrip
3dB power divider.
Components Required:-
Power Supply
VCO
50 ohm Transmission line
Branch line coupler
Parallel line in coupler
50 ohm terminations
Cables with SMA connector
Oscilloscope / VSWR meter / Power Meter
Theory:
Power divider is a 3 port device in which one input port and two ouput ports.When
the power is fed at input port 1,power will emerge from the other two ports 2 and 3.it
os impossible to match all the ports of power divider.
Inorder to match all the three ports, an isolation resistance of 2Z0 is added between
ports 2 and 3.With this the proper isolation is provided between ports 2 and 3.
Procedure:-
1. Set up the system
2. Keeping the voltage at minimum, switch on the power supply.
3. Insert a 50 ohm transmission line and check for the output at the end of the
system using a CRO/VSWR meter/ RF power meter.
4. Vary the power supply voltage and check the output for different VCO
frequencies.
5. Keep the VCO frequency constant,note down the output.This value can b taken
as the input to the power divider.
6. Replace the 50 ohm transmission line with the Wilkinson power divider.
7. Tabulate the output at Ports 2 and 3.
8. Calculate Insertion loss and coupling factor in each coupled arm.
9. Calculate the isolation between ports 2 and 3 by feeding the input to port 2 and
measure output at port 3 by terminating port 1.
10.Repeat the experiment for different VCO frequencies.
Conclusion :
Measurement of power division and isolation characteristics of a
microstrip 3dB power divider is achieved successfully.