मुफ्त लिंक बजट कैलकुलेटर
RF लिंक बजट विश्लेषण करें। ट्रांसमीटर शक्ति, गेन और हानि दर्ज करें।
Cascaded Noise Figure
1.80 dB
Cascaded Noise Figure vs Stage 1 Noise Figure
सूत्र
## Friis Noise Figure Formula ### Formula **F_total = F1 + (F2 - 1)/G1 + (F3 - 1)/(G1 x G2) + ...** All values in linear (not dB). The first stage dominates overall noise figure. Use a low-noise amplifier (LNA) first for best sensitivity.
हल किया गया उदाहरण
LNA (1.5 dB NF, 20 dB gain) followed by mixer (10 dB NF, 15 dB gain) and IF amp (15 dB NF).
- 01F1 = 10^(1.5/10) = 1.413
- 02F2 = 10^(10/10) = 10, G1 = 10^(20/10) = 100
- 03F3 = 10^(15/10) = 31.62, G2 = 10^(15/10) = 31.62
- 04F_total = 1.413 + (10-1)/100 + (31.62-1)/(100x31.62) = 1.413 + 0.09 + 0.0097 = 1.513
- 05NF = 10 x log10(1.513) = 1.80 dB
अक्सर पूछे जाने वाले प्रश्न
Why is the first stage so important?
Noise from later stages is divided by the gain of preceding stages. High first-stage gain makes subsequent noise negligible.
What is a good LNA noise figure?
Below 1 dB for satellite receivers. 1-3 dB for typical RF systems. Above 3 dB is considered noisy.
Loss before the LNA?
Any loss (cable, filter) before the LNA adds directly to the noise figure. A 3 dB cable loss adds 3 dB to system NF.
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