What Is the Friis Cascaded RF Noise Figure & Noise Temperature Calculator?
Noise Figure (NF) specifies the degradation in signal-to-noise ratio caused by components in an RF signal chain.
How Does the Friis Cascaded RF Noise Figure & Noise Temperature Calculator Work?
Converts dB noise figures and gains to linear ratios and divides downstream noise additions by cumulative preceding gains.
Friis Cascaded RF Noise Figure & Noise Temperature Calculator Formula & Variables
The core mathematical equation utilized by this calculator is expressed as:
F_{ ext{casc}} = F_1 + rac{F_2 - 1}{G_1} + rac{F_3 - 1}{G_1 G_2}, quad T_e = T_0 (F_{ ext{casc}} - 1)
Friis formula for noise factor of cascaded linear two-port networks with T0 = 290 K.
How to Use the Friis Cascaded RF Noise Figure & Noise Temperature Calculator
- Input noise figure and gain for each successive stage in the RF receiver chain.
Step-by-Step Example Calculation
Satellite Ground Station Front-End
Input Values:
stage1NoiseFigureDb:1.2
stage1GainDb:18
stage2NoiseFigureDb:7
stage2GainDb:10
Worked Steps: Total cascaded NF = 1.34 dB; equivalent noise temperature T_e = 104.9 K with 97% first-stage dominance.
Understanding Your Result
Demonstrates that high first-stage gain effectively suppresses the noise contributions of all downstream components.
Factors That Affect the Result
- Losses ahead of the LNA (cables, duplexers) add directly dB-for-dB to the total system noise figure.
When Should You Use This Calculator?
- Radar receiver design, satellite downconverter LNB engineering, and wireless transceiver front-ends.
Assumptions & Limitations
- Assumes impedance-matched stages (typically 50 Ohms) operating at reference temperature T0 = 290 K.
Frequently Asked Questions
Calculation Accuracy & Reference Note
Standard IEEE Friis noise factor formulation.