A transmission line has a phase constant β = 29.8 rad/m. At a frequency of 1000 MHz, what will be the wavelength of the signal?
Electronics and Communication Engineering
Microwave Communication
Difficulty: Medium
Choose an option
-
A29.8 m
-
B2.98 m
-
C2.1 m
-
D0.21 m
-
E0.0298 m
Answer
Correct Answer: 0.21 m
Explanation
Introduction / Context:The phase constant β in a transmission line is related to the propagation constant and wavelength. Calculating wavelength from β is a common problem in RF and microwave engineering.
Given Data / Assumptions:
- β = 29.8 rad/m.
- Frequency f = 1000 MHz = 1 GHz.
- Formula: β = 2π / λ.
Concept / Approach:
By definition, wavelength λ = 2π / β. Once β is known, λ can be calculated directly.
Step-by-Step Solution:
λ = 2π / β.= 6.283 / 29.8 ≈ 0.211 m.Thus wavelength = 0.21 m approximately.Verification / Alternative check:
For 1 GHz in free space, λ ≈ 0.3 m. A phase constant of 29.8 rad/m corresponds to a slightly shorter wavelength due to dielectric or guide effects, consistent with 0.21 m.
Why Other Options Are Wrong:
- 29.8 m, 2.98 m, 2.1 m: too large, do not satisfy β formula.
- 0.0298 m: too small, not matching calculation.
Common Pitfalls:
Using frequency-speed formula instead of β relation; ignoring 2π factor.
Final Answer:
0.21 m