1. What is Cascaded Noise Figure?

The cascaded noise figure represents the overall noise performance of a multi-stage system. It accounts for the noise added by each stage and the gain of preceding stages. This is important in RF systems where multiple amplifiers and components are connected in series.

2. How Does the Calculator Work?

The calculator uses the Friis formula for cascaded noise figure:

Where:

• \( F_i \) — Noise figure of stage i (linear scale)
• \( G_i \) — Gain of stage i (linear scale)
• The formula assumes all values are in linear scale (not dB)

Explanation: The noise contribution of each subsequent stage is reduced by the gain of all preceding stages.

3. Importance of Noise Figure Calculation

Details: Calculating the total noise figure is crucial for designing RF systems, communication receivers, and any system where signal-to-noise ratio is important. It helps determine the overall system sensitivity.

4. Using the Calculator

Tips:

• Enter noise figures and gains in dB
• The calculator automatically converts between dB and linear scale
• Noise figure must be ≥ 0 dB (linear ≥ 1)
• Gain must be > 0 dB (linear > 1)

5. Frequently Asked Questions (FAQ)

Q1: Why is the first stage most important?
A: The noise figure of the first stage contributes directly to the total noise figure, while subsequent stages' contributions are reduced by preceding gains.

Q2: What's the difference between noise figure and noise factor?
A: Noise factor is the linear ratio (F), while noise figure is 10*log10(F) in dB. This calculator works with both.

Q3: How does gain affect the total noise figure?
A: Higher gain in early stages reduces the noise contribution of later stages.

Q4: What's a typical good noise figure?
A: For RF systems, 1-3 dB is excellent, 3-6 dB is good, and above 6 dB may be problematic for sensitive applications.

Q5: Can I use this for lossy components?
A: Yes, for passive components (like cables), noise figure equals the loss (in dB), and gain is the reciprocal of the loss (in linear).