2. MICROWAVE DEVICES
AND ENGINEERING Lecture No 3& 4
Review & Microstrip Transmission Line, Striplines, Coaxial Cables & Waveguides
Ref Material: Microwave Engineering by Pozar (2nd Ed)
Chapter 3, and Gonzalez Chapter 1.
Instructor: Irfan Ahmed
Avionics Engineering Department

3. This lecture will cover :
Block Diagram of Microwave System
Review of dB scale
Review of Transmission Line Concepts
Review of
Microstrip Transmission Lines
Waveguides / Coaxial cable / Stripline

4. deciBels Ratio of two Quantities Benefits : Nonlinear to Linear scale
Large numbers can be represented easily

5. Microwave Power, dB & dBm
0 dBm 1 mW
10 dBm 10 mW
30 dBm 1 W
-10 dBm .1 mW
-30 dBm .001 mW

7. Microwave Communication System

8. Microwave Communication System

9. Transmission Line Concepts
Diff b/w Circuit Theory and Transmission Line Theory is electrical size.
Transmission Line often represented as a two-wire line.

10. Two Wire Parallel Transmission Lines

11. Coaxial Cables

12. Coaxial Cables Wide bandwidth. No lower cutoff frequency. Low loss.
High isolation.
Supports TEM mode.
Cutoff frequency.

13. Coaxial Cables

14. Waveguides

15. Waveguides

16. Waveguides Metallic transmission lines used at microwave frequencies.
Negligible loss.
Excellent shielding.
Extremely high peak power.
High cost.
Large size, especially at lower frequencies.
Lower cutoff frequency. (Depends upon mode)
TE and TM modes will propagate
No propagation below cutoff frequency

17. Planar Transmission Lines

18. Microstrip Transmission Line

19. Microstrip Transmission Line

20. Microstrip Transmission Line
Developed by ITT laboratories as a competitor to stripline (1952).
All active components can be mounted on top of PCB.
Most popular microwave transmission line.

21. Microstrip Transmission Line

22. Microstrip Transmission Line

24. Stripline

25. Stripline Invented by R. Barrett in 1950s.
Conductor sandwiched by delectric between a pair of groundplanes.
TEM transmission line media.
Non-dispersive nature.
Much harder to fabricate.
Requires comparatively thicker boards and narrower strips.

26. Stripline t

28. Waveguides

29. Quarter Wave Transformer
Impedance match only at a particular frequency
Will see more interesting phenomena in an assignment or in lab

30. Quote of the day
Failures are often the results of timidity and fears; disappointments are the results of bashfulness; hours of leisure pass away like summer-clouds, therefore, do not waste opportunity of doing good.