1. 2-Port Networks & S-Parameters
AE-323 MICROWAVE DEVICES
AND ENGINEERING Lecture No 05 &6
2-Port Networks & S-Parameters
Instructor: Irfan Ahmed
Class: BATCH 2 Avionics 6
Number of Slides: 20
Avionics Engineering Department

2. Learning Objectives 2-port networks
Network characterization techniques
S-parameters
How to Measure S-Parameters?
S-parameters for N-port networks
Z, Y, H and ABCD parameters

3. (a) 1 port network, (b) 2 port network
1-Port & 2-Port Networks
(a) 1 port network, (b) 2 port network

4. Basic Definitions Insertion Loss:
“Reduction of Microwave signal as it passes trough a component”
Gain:
“Increase of Microwave signal as it passes trough an Amplifier”

5. Basic Definitions
Return Loss “Whenever a microwave transmission line is connected , The (EM field does not match). So some of the power is reflected back”

6. Insertion Loss & Return Loss
Microwave power is sent through a transmission line from the left and it reaches the Component.
This power is Incident power. When It reaches the component some portion is reflected back to the transmission line where it came from
Incident power
Component
Transmitted Power
Reflected Power

7. Insertion Loss & Return Loss

8. Insertion Loss in Cascade
14dbm
Filter 3dB
Attenuator 10dB
Incident Power
Filter 3dB
0.5 Watt
0.25 Watt
1 Watt
0.025 Watt
25mW
27dbm
24dbm
30dbm
Total Insertion Loss
Of Chain
3dB+3dB+10dB=16dB
14 dBm
30 dBm

9. Gain
If the component is an amplifier, then the transmitted power is greater than that of the incident power
Gain=10log 𝑂𝑢𝑡𝑝𝑢𝑡 𝑝𝑜𝑤𝑒𝑟(𝑡𝑟𝑎𝑛𝑠𝑚𝑖𝑡𝑡𝑒𝑑 𝑝𝑜𝑤𝑒𝑟) 𝐼𝑛𝑝𝑢𝑡 𝑝𝑜𝑤𝑒𝑟(𝑖𝑛𝑐𝑖𝑑𝑒𝑛𝑡 𝑃𝑜𝑤𝑒𝑟)

10. Cascaded insertion loss & Gain

11. Network Characterization
Characterizing a network requires measurement of transfer and impedance functions.
At low frequencies, short and open circuit tests are used for characterization.
Network functions are represented by z, y, h and ABCD parameters.

12. S-Parameters
S parameters are another way of specifying return loss and insertion loss
Ratio of reflected electric field to incident electric field is reflection coefficient
Ration of transmitted electric field to incident electric field is transmission coefficient

13. S-Parameters

14. S-Parameters

15. 2-port Network S-Parameters Output port Input port S12 a2 a1 S21 S11b1 b2
Port 1
Port 2
a1=electric field entering at component input
b1=electric field leaving at component input
a2=electric field entering at component output
b2=electric field leaving at component output

16. S-Parameters Input reflection coefficient
Gain/Loss(Forward transmission coefficient )
Isolation
Output reflection coefficient

17. S-Parameters

18. S Return Loss

19. S21 Insertion Loss or Gain

20. S12 Reverse Gain or isolation

21. S-Parameters
Input reflection coefficient with output properly terminated
(a2=0).
Forward transmission coefficient with output properly terminated.
S-parameters
Output reflection coefficient with input properly terminated
(a1=0).
In matrix form
Reverse transmission coefficient with input properly terminated.

22. S-Parameters

23. S-Parameters for Larger Networks

24. S-Parameters

25. How to Measure S-Parameters?

26. On What S-Parameters depend Upon?

27. Z, Y, H & ABCD Parameters Y-parameters H-parameters Z-parameters
In matrix form
ABCD-parameters

28. Conversion Between 2-port Network Parameters

29. Summary

30. Questions