Ateneo de Naga UniversityCollege of Engineering

Electronics and Computer Engineering DepartmentFirst Semester

S / Y 2015 – 2016

Transmission Media and Antenna Systems Lab Engr. Anacleto CasimiroECEM516 lab INSTRUCTORName: Date Performed: June 22, 2015Section: GE51Laboratory Activity No.: 2OBJECTIVES

To measure the characteristic impedance / resistance of transmission lines using frequency domain method and to differentiate between the matched and unmatched lines.MATERIALS/EQUIPMENT

Transmission line trainer/analyser Transmission line 10 Mhz CRO with X-Y facilityEQUIPMENT SET-UP

Ateneo de Naga UniversityCollege of Engineering

Electronics and Computer Engineering DepartmentFirst Semester

S / Y 2015 – 2016

PROCEDURES1. Set up the equipment as before.2. Connect a transmission line at the Load Out terminal.3. The scope shall display standing wave pattern if the line is open circuited or shorted.4. This is due to reflections from the other end of the line due to impedance mismatch.5. A coaxial lead shat suffice a real transmission line.6. Connect the other end of the transmission line to the load.7. The load input terminal provides a purely resistive termination.8. Adjust the impedance measure control on TLA so that the standing waves on the CRO are minimized.9. The characteristic impedance of the line is displayed on the LCD in Ohms.10.The underlying principle is that when a transmission line is terminated into its characteristic impedance power is reflected from the end of the line and hence there are no standing waves being formed in the line.

DATA

Ateneo de Naga UniversityCollege of Engineering

Electronics and Computer Engineering DepartmentFirst Semester

S / Y 2015 – 2016

Description Figure

Other Transmission wire (RG174 Cable)

Ateneo de Naga UniversityCollege of Engineering

Electronics and Computer Engineering DepartmentFirst Semester

S / Y 2015 – 2016

Other Transmission wire (RG58 Cable)

ANALYSISThe term “impedance matching” is rather straightforward. It’s simply defined as the process of making one impedance look like another. Frequently, it becomes necessary to match a load impedance to the source or internal impedance of a driving source. A key factor of this theorem is that when the load matches the source, the amount of power delivered to the load is the same as the power dissipated in the source. Therefore, transfer of maximum power is only 50% efficient. If the line impedance and load are matched, line length doesn’t matter. However, if the line

Ateneo de Naga UniversityCollege of Engineering

Electronics and Computer Engineering DepartmentFirst Semester

S / Y 2015 – 2016

impedance and load don’t match, the generator will see a complex impedance that’s a function of the line length.With matched impedance, no reflected wave occurs, the probe will indicate the same voltage amplitude at every point. When it is terminated by an open and short circuit, the total voltage in the line is standing wave.