# Microwave Engineering Questions and Answers – Wilkinson Power Dividers

This set of Microwave Engineering Multiple Choice Questions & Answers (MCQs) focuses on “Wilkinson Power Dividers”.

1. A major disadvantage of the lossless T-junction power divider is:
a) Not matched at all the ports
b) Low power output
c) Complex construction
d) None of the mentioned

Explanation: A T-junction hybrid cannot be matched at all the ports if the power divider is lossless. It can be matched only at 2 ports. This is one of the major disadvantages when they are to be used along with other microwave devices.

2. The Wilkinson power divider is a:
a) 2 port network
b) 3 port network
c) 4 port network
d) None of the mentioned

Explanation: Wilkinson power divider is a 3 port network; if it is used as a divider it has one input port and 2 output ports. If it is used as coupler, it has two input port and one output port.

3. Wilkinson power divider is an equal split power divider.
a) True
b) False

Explanation: Wilkinson power divider can be used to divide power in any ratio, but the most commonly used configuration is the equal split power divider.

4. If 10 watt is applied to the input port of a standard Wilkinson divider, then the sum of the power measured at the two output ports of the Wilkinson coupler is
a) 5 watt
b) 10 watt
c) 7.07 watt
d) 8 watt

Explanation: For a standard Wilkinson coupler, the output power is 3 dB less than the total input power in decibels. That is, 70.7% of the total input power is delivered to the output port.

5. The analysis of Wilkinson coupler is done using:
a) Even-odd mode analysis
b) Symmetry
c) S matrix approach
d) None of the mentioned

Explanation: Even-odd mode analysis is one of the simplest methods of analysis for Wilkinson coupler. This involves normalizing all impedances with the characteristic impedance of the transmission line used and carrying out some analysis.
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6. A Wilkinson coupler designed can be operated at any frequency.
a) True
b) False

Explanation: The length of the branches of a Wilkinson coupler is all wavelengths dependent and hence Wilkinson coupler designed to operate at one frequency cannot be used to operate at another frequency.

7. For an equal-split Wilkinson power divider of 50Ω system impedance, the characteristic impedance of quarter wave transmission line used is:
a) 70.7 Ω
b) 50 Ω
c) 100 Ω
d) None of the mentioned

Explanation: The characteristic impedance of a Z Ω system is given by √2*Z. hence, the characteristic impedance of 50Ω system is 70.7 Ω.

8. The plot of frequency v/s S11 parameter of a Wilkinson coupler has a dip at the frequency at which it is designed to operate.
a) True
b) False

Explanation: S11 parameter signifies the fraction of the power reflected back to port 1 when power is applied to port 1 of the coupler. Since the ports are matched at the frequency of design S11 is minimum and the curve has a dip.

9. The plot of S23 v/s frequency has the same curve as that of S11 v/s frequency.
a) True
b) False

Explanation: When input is applied to port 1, output is measured at port 2 and port 3. S23 signifies the output at port 3 due to port 2 when input is applied at port 1. This parameter is minimum at the designed frequency.

10. S12 curve of a Wilkinson coupler when plotted versus frequency is a line passing through origin.
a) True
b) False