Daffodil International University

1. Welcome to our presentation
• Coaxial line
• microstrip line
• Quarter Wave Transformer
Topic:
Presented by
 Md Abu Bakar Siddik
ID:141-19-1536
 Al-Amin Prince
ID:141-19-1539
 Mst. Tamanna Yeasmin
ID:141-19-1548
 Samia Nur Tisah
D:141-19-1535

6. Microstrip Line
Microstrip transmission lines consist of a conductive strip of width "W" and thickness
"t" and a wider ground plane, separated by a dielectric layer (a.k.a. the "substrate") of
thickness "H" as shown in the figure below.
Microstrip is by far the most popular microwave transmission line, especially for
microwave integrated circuits and MMICs

7. Properties
Practical Microstrip Lines has the following Properties,
 Height is of milimetre
 Have width-to-height ratio (u=w/h)
0.1<u<10
 Propagating in Z-direction

8. Losses in Microstrip line
 Dielectric loss
 Related to loss tangent of the substrate
 Small for most substrate except silicon
 Conductor loss
 Dominate at microwave frequency
 Radiation loss
 Due to discontinuities on the microstrip line
 Small for substrate thickness h/λ<<0.01
 Surface wave propagation also causes loss

9. Advantage and Disadvantage
 The major advantage of microstrip over stripline is that all active
components can be mounted on top of the board.
 The disadvantages are that when high isolation is required such as
in a filter or switch, some external shielding may have to be
considered.

10. Quarter-wave Transformer
A quarter-wave transformer is a simple impedance transformer which is
commonly used in impedance matching in order to minimize the energy
which is reflected when a transmission line is connected to a load.

11. Quarter wave transformer

12. Use of Quarter wave transformer
A quarter-wave impedance transformer, often written as λ/4 impedance
transformer, is a component used in electrical engineering consisting of a length of
transmission line or waveguide exactly one-quarter of a wavelength (λ) long and
terminated in some known impedance.
The quarter-wave transformer uses a transmission line with different characteristic
impedance and with a length of one-quarter of the guided-wavelength to match a
line to a load.

13. Some notes for quarter wave :
o The characteristics impedance of the Quarter wavelength section
should be equal to √ZoRL if a quarter wavelength transformer is
used to match RL to Zo.
o The matching is good only for a narrow frequency range .
o Multiple section can be used for broadband matching.
o For complex load ZL=RL+jXL, one can add a single stub tuner to
tune out the reactive part, then use the quarter wavelength
transformer

14. Thank You ALL