CAD CAD Antenna Designer Feed Networks and Impedance Matching 2

Question 1

On a Smith Chart, where is a perfect impedance match (Z = Z0) located?

Accepted Answer

At the center of the chart

Answer

A perfect impedance match corresponds to a normalized impedance of 1 + j0, which is located at the center of the Smith Chart.

Question 2

What is the input impedance of a lossless transmission line terminated in a short circuit (Z_L = 0) and exactly λ/4 long?

Accepted Answer

Infinite (open circuit)

Answer

A λ/4 shorted stub presents an open circuit (infinite impedance) at its input because Z_in = Z0²/Z_L → ∞ as Z_L → 0.

Question 3

What is the approximate return loss for a system with a VSWR of 2:1?

Accepted Answer

−9.5 dB

Answer

For VSWR = 2:1, Γ = (2−1)/(2+1) = 1/3, giving return loss = −20·log10(1/3) ≈ −9.5 dB.

Question 4

What is a Wilkinson power divider primarily designed to achieve?

Accepted Answer

Equal power splitting with high isolation between output ports

Answer

A Wilkinson power divider splits power equally between two output ports while providing high isolation between them, with all ports matched to the system impedance.

Question 5

What happens to the electrical length of a transmission line when the operating frequency is doubled?

Accepted Answer

The electrical length is doubled

Answer

Electrical length θ = βl = 2πfl/v_p is directly proportional to frequency, so doubling frequency doubles the electrical length of a fixed physical line.

(CAD) Certified Antenna Designer Practice Test

(CAD) Certified Antenna Designer Practice Test

CAD CAD Antenna Designer Feed Networks and Impedance Matching 2