A load of 3 + j4Ω is connected to a 1Ω lossless line. The magnitude of reflection coefficient at the load will be :

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  1. 0.058 
  2. 0.79
  3. 0
  4. 1

Answer (Detailed Solution Below)

Option 2 : 0.79
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Explanation:

To find the magnitude of the reflection coefficient (Γ) at the load, we need to use the formula:

|Γ| = |(ZL - Z0) / (ZL + Z0)|

Where ZL is the load impedance and Z0 is the characteristic impedance of the lossless transmission line. Given:

  • ZL = 3 + j4Ω
  • Z0 = 1Ω

Step-by-Step Solution:

1. Calculate the numerator (ZL - Z0):

ZL - Z0 = (3 + j4) - 1 = 2 + j4

2. Calculate the denominator (ZL + Z0):

ZL + Z0 = (3 + j4) + 1 = 4 + j4

3. Find the magnitude of the numerator and the denominator:

|ZL - Z0| = |2 + j4| = √(22 + 42) = √(4 + 16) = √20 = 2√5

|ZL + Z0| = |4 + j4| = √(42 + 42) = √(16 + 16) = √32 = 4√2

4. Calculate the magnitude of the reflection coefficient:

|Γ| = |(ZL - Z0) / (ZL + Z0)| = |(2 + j4) / (4 + j4)| = (2√5) / (4√2) = (2√5) / (2√2 * 2) = √5 / (2√2) = (√5 / √2) / 2 = √(5/2) / 2

By simplifying √(5/2):

√(5/2) ≈ 1.58

Therefore:

|Γ| ≈ 1.58 / 2 ≈ 0.79

Hence, the magnitude of the reflection coefficient at the load is approximately 0.79. Therefore, the correct answer is Option 2.

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