RF chain
حاسبة ميزانية وصلة القمر الصناعي
Combine uplink, downlink and digital performance requirements.
المحتوى التفصيلي متاح بالإنجليزية، بينما الحسابات والوحدات والنتائج تعمل بنفس المحرك الهندسي.
أدخل قيم التصميم ثم شغّل الحساب لمراجعة النتائج.
Swipe the diagram sideways to see the full view. With a keyboard, focus the diagram and use the arrow keys.
Uplink C/N₀
Downlink C/N₀
Understand the system
Carrier ledger
At each receive plane, add transmit EIRP and receive gain, then subtract free-space and additional losses. Noise uses the equivalent system temperature at that same plane. Atmospheric absorption reduces carrier and thermal emission can contribute antenna noise; path loss and path noise are different mechanisms.
C: carrier power; L: positive dB losses.
Every term must belong to the same link direction and reference plane.
Source: week 3/reference.pdf · PDF page 263
Common mistakes
- Never add C/N values directly in dB.
- Do not subtract bandwidth twice.
- Use matching noise reference planes and common bandwidths for composite ratios.
Formula reference and symbol definitions
Carrier to noise
C,N: W
Common receive plane and bandwidth.
Example: For carrier 10⁻¹¹ W and integrated noise 10⁻¹³ W, C/N = 100 = 20 dB.
Open related tool →Carrier to noise density
EIRP: dBW; losses: dB; G/T: dB/K
SI Boltzmann reference; matching planes.
Example: With EIRP = 50 dBW, loss = 205 dB and G/T = 20 dB/K, C/N₀ ≈ 50 − 205 + 20 + 228.6 = 93.6 dB-Hz.
Open related tool →C/N from C/N0
B: Hz
Noise bandwidth, not symbol rate.
Example: For C/N₀ = 90 dB-Hz and B = 1 MHz, C/N = 90 − 60 = 30 dB.
Open related tool →Energy per bit
R_b: bit/s
State information/coded bit-rate convention.
Example: For C/N₀ = 90 dB-Hz and Rᵦ = 10 Mbit/s, Eᵦ/N₀ = 90 − 70 = 20 dB.
Open related tool →Composite C/N approximation
Q: linear dimensionless C/N
Independent noises; consistent common bandwidth.
Example: For uplink and downlink ratios of 10 each, Qc = 1/(1/10 + 1/10) = 5 ≈ 6.990 dB.
Open related tool →Course finite FT ratio
Q: dimensionless linear C/N
Course total-output-power normalization; not C/N₀.
Example: For Qu = Qd = 10, finite FT Qc = 100/(10 + 10 + 1) = 4.762 ≈ 6.778 dB.
Open related tool →Link margin
All terms: dB
Required BER/modulation/coding threshold and implementation loss.
Example: For available Eᵦ/N₀ = 12 dB, required threshold 9 dB and implementation loss 1 dB, margin = 12 − 9 − 1 = 2 dB.
Open related tool →