Math Problem Statement

A coaxial TL with a Z0 of 50-Ω is connected to the 50-Ω output of a signal generator, and also to a 20-Ω load impedance. Calculate the mismatch loss.

Solution

To calculate the mismatch loss for the given transmission line (TL) system, we need to determine the amount of power lost due to the impedance mismatch between the load and the characteristic impedance of the transmission line.

Step-by-step solution:

  1. Reflection Coefficient (Γ):

    The reflection coefficient Γ\Gamma is calculated using the formula: Γ=ZLZ0ZL+Z0\Gamma = \frac{Z_L - Z_0}{Z_L + Z_0} where:

    • ZLZ_L is the load impedance (20 Ω)
    • Z0Z_0 is the characteristic impedance of the transmission line (50 Ω)

    Substituting the values: Γ=205020+50=3070=370.4286\Gamma = \frac{20 - 50}{20 + 50} = \frac{-30}{70} = -\frac{3}{7} \approx -0.4286

  2. Mismatch Loss:

    Mismatch loss (in dB) is given by the formula: Mismatch Loss (dB)=10log10(1Γ2)\text{Mismatch Loss (dB)} = -10 \log_{10}(1 - |\Gamma|^2) First, calculate Γ2|\Gamma|^2: Γ2=(0.4286)2=0.1837|\Gamma|^2 = (-0.4286)^2 = 0.1837

    Now, substitute into the mismatch loss formula: Mismatch Loss (dB)=10log10(10.1837)=10log10(0.8163)\text{Mismatch Loss (dB)} = -10 \log_{10}(1 - 0.1837) = -10 \log_{10}(0.8163) Mismatch Loss (dB)=10×(0.0886)=0.886dB\text{Mismatch Loss (dB)} = -10 \times (-0.0886) = 0.886 \, \text{dB}

Result:

The mismatch loss is approximately 0.886 dB.

Would you like further clarification or additional details on any step?

Here are five related questions you might find helpful:

  1. What is the physical significance of the reflection coefficient in transmission lines?
  2. How would the mismatch loss change if the load impedance increased?
  3. What are some practical methods to minimize mismatch loss in transmission lines?
  4. How does the reflection coefficient affect power delivery to the load?
  5. What is VSWR (Voltage Standing Wave Ratio), and how does it relate to mismatch?

Tip: Minimizing mismatch loss can be achieved by using impedance-matching techniques, such as matching transformers or tuning stubs, to ensure maximum power transfer.

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Math Problem Analysis

Mathematical Concepts

Transmission Lines
Reflection Coefficient
Mismatch Loss
Logarithmic Functions

Formulas

Reflection Coefficient: Γ = (Z_L - Z_0) / (Z_L + Z_0)
Mismatch Loss (dB): Mismatch Loss = -10 log10(1 - |Γ|^2)

Theorems

Reflection Coefficient Theorem
Power Transfer Theorem

Suitable Grade Level

Undergraduate (Electrical Engineering)