# Microwave Engineering Questions and Answers – Power Dividers( T Junction)

This set of Microwave Engineering Interview Questions and Answers for Experienced people focuses on “Power Dividers( T Junction)”.

1. A T junction power divider can be used only for division of power.
a) True
b) False

Explanation: A T junction power divider is a 3 port network that can be used either for power dividing or power combining. For power division, one of the ports is excited with the source and the other two ports are used to receive power. For power combining, 2 ports are excited with the source and output is taken at the third port.

2. The lossless T junction dividers can be can all be modeled as a junction of three transmission lines.
a) True
b) False

Explanation: A T junction consists of three ports; hence they can be modeled with 3 transmission lines. However, they cannot be both lossless and matched simultaneously.

3. For the realization of lossless T-junction power divider using transmission lines, the characteristic impedance of the transmission line has to be real.
a) True
b) False

Explanation: From various analyses, it is found that for a transmission line must have real characteristic impedance. If they are not real, they capacitive and inductive passive elements result in retaining some energy in the junction making them lossy.

4. The output power measured at the 2 ports of the T junction:
a) Is a constant
b) Variable
c) Is not real power
d) None of the mentioned

Explanation: The output line impedance determines the power delivered to the 2 output ports in a T junction coupler. Depending on the value of the power desired, the impedance can be changed and the corresponding power is obtained.

5. Hybrid couplers are also a type of directional couplers.
a) True
b) False

Explanation: Hybrid couplers are also a type of directional couplers that give a coupling factor of 3db) A coupling factor of 3dB means that 70.7% of the total input power is received at the output port.
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6. If the input power is divided in the ratio of 2:1 in a T- junction coupler and the characteristic impedance of the 2 output lines is 150Ω and 75Ω, then the impedance of the input line is:
a) 100Ω
b) 50Ω
c) 150Ω
d) None of the mentioned

Explanation: The input impedance of the T junction is the equivalent of the 2 output impedances in parallel. That is 150││75. Solving this, (150*75/(150+75)), the input impedance is 50 Ω.

7. A lossy T junction can be matched at all the three ports.
a) True
b) False

Explanation: If a T junction is constructed using resistors, the T junction becomes lossy, but it can be simultaneously matched at all the three ports.

8. The diagonal elements of the s matrix of a resistive T junction are:
a) 0
b) 1
c) 0.5
d) 1.5

Explanation: A resistive junction can be matched at all the three ports of the junction. Hence no power is reflected back. As a result, the diagonal elements are all 0 for a resistive T junction.

9. The power delivered to the input port of a resistive power divider is equal to the source voltage applied.
a) True
b) False

Explanation: Since power is applied to a resistive power divider, there is loss and hence not all the supply power is delivered to the input port of the power divider.

10. The power input at the port 1 of resistive T junction is equally divided among the 2 output ports of the T junction.
a) True
b) False

Explanation: The power division ratio of a resistive T junction depends on the resistance of the resistors used in forming those junctions. Depending on the resistors used, the power gets divided accordingly.

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