Electronics Engineering Tools
110+ engineering calculators spanning RF, power, optics, IC test, and more.
Cascaded Noise Figure Calculator
/en/cascaded-noise-figure
NF_total = NF₁ + (NF₂-1)/G₁ + (NF₃-1)/(G₁×G₂) + ...
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dBm ↔ mW ↔ Volts Converter
/en/dbm-volts-converter
P(mW) = 10^(P(dBm)/10)
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Free-Space Path Loss (FSPL) Calculator
/en/fspl-calculator
FSPL(dB) = 32.44 + 20×log₁₀(d_km) + 20×log₁₀(f_MHz)
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Microstrip Impedance Calculator
/en/microstrip-impedance
ε_eff = (ε_r + 1)/2 + (ε_r - 1)/(2×√(1 + 12h/W))
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Pi Attenuator Design
/en/pi-attenuator-design
K = 10^(Att(dB)/20)
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Radar Range Equation Calculator
/en/radar-range-equation
P_r = (P_t × G_t × G_r × σ × λ²) / ((4π)³ × R⁴)
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Reflection Coefficient Calculator
/en/reflection-coefficient
Γ = (Z_L - Z₀)/(Z_L + Z₀)
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T Attenuator Design
/en/t-attenuator-design
K = 10^(Att(dB)/20)
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Transmission Line Parameters Calculator
/en/transmission-line-calc
Z₀ = √((R + jωL)/(G + jωC)) ≈ 60/√ε_eff × ln(8h/W + 0.25W/h)
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VSWR ↔ Return Loss Converter
/en/vswr-return-loss
RL(dB) = -20×log₁₀((VSWR-1)/(VSWR+1))
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cascaded-noise-figure
级联噪声系数计算器
计算多级放大器系统的总噪声系数
Overview
Friis公式揭示：链路的总噪声几乎完全由第一级的噪声系数和增益决定，后级的贡献会被前级增益迅速衰减。通过逐级输入NF与Gain，可直观看到哪个环节拖累系统灵敏度。
Key Parameters
- 噪声系数 NFᵢ(dB)
每级器件在290K参考温度下的噪声表现
- 增益 Gᵢ(dB)
功率增益（可以为负，代表衰减/滤波）
- 级数 N(级)
串接的级数，本工具允许最多50级以覆盖复杂前端
Influencing Factors
- 第一级指标：NF₁与G₁直接决定总噪声，先优化LNA比修改后级更有效
- 级间损耗：滤波器与互连若放在LNA之前，会当作负增益显著恶化总NF
- 工作温度与带宽：Friis公式默认290K、1Hz带宽，温度升高或带宽变宽都会按 kTB 增加噪声功率
Formulas
第一级对总噪声系数的影响最大，后续级的影响随着增益递减
Example: Stage1: NF=3dB(G=10dB), Stage2: NF=6dB(G=20dB) → NF_total ≈ 3.04dB
从dB转换为线性值
Example: 3 dB → 1.995 linear
Calculation Steps
- 1
1. 输入级数（最多5级）
- 2
2. 为每级输入噪声系数(dB)和增益(dB)
- 3
3. 将dB值转换为线性值
- 4
4. 使用Friis公式计算总噪声系数
- 5
5. 显示各级的贡献和总值
Use the calculator above to validate numeric results.