Table of Contents
Insertion loss is a key parameter in evaluating the performance of filters within signal chains. It measures how much signal power is reduced when passing through a filter. This guide provides a clear, step-by-step process to calculate the insertion loss of filters.
Understanding Insertion Loss
Insertion loss is expressed in decibels (dB) and indicates the difference in signal power before and after the filter. A lower insertion loss means the filter allows more signal to pass through with minimal attenuation.
Required Measurements
To calculate insertion loss, you need to measure the signal power at two points:
- Input power (before the filter)
- Output power (after the filter)
Calculation Steps
Follow these steps to determine the insertion loss:
- Measure the input power (Pin) in milliwatts (mW) or watts (W).
- Measure the output power (Pout) after the filter in the same units.
- Calculate the power ratio: Power Ratio = Pin / Pout.
- Convert the power ratio to decibels using the formula: Insertion Loss (dB) = 10 × log10(Pin / Pout).
Example Calculation
If the input power is 1 mW and the output power is 0.8 mW, the calculation is as follows:
Power Ratio = 1 / 0.8 = 1.25
Insertion Loss = 10 × log10(1.25) ≈ 10 × 0.0969 ≈ 0.97 dB