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Link Budget

Line-of-sight link budget for a CW carrier or a digitally modulated signal: received power, C/N₀, SNR, Eb/N₀, theoretical BER and link margin.

Inputs

Transmitter

Tx power Tx line loss dB Tx antenna · gain or dish diameter Tx dish efficiency %

Path

Frequency Distance Other losses (atmospheric, rain, pointing, polarization) dB

Receiver

Rx antenna · gain or dish diameter Rx dish efficiency % Rx line loss dB Noise figure dB

Signal

CW Modulated

Noise bandwidth Required SNR dB Modulation Symbol rate Roll-off factor (RRC α) α

Results

Tx antenna gain: – dBi
Rx antenna gain: – dBi
EIRP: – dBm
Free-space path loss: – dB
Received power: – dBm
C/N₀: – dB-Hz
Noise floor (noise bandwidth): – dBm
SNR: – dB
Bits per symbol: –
Channel bit rate (uncoded, R_s·k): –
Occupied bandwidth (approx.): –
Noise floor (occupied bandwidth): – dBm
C/N: – dB
Es/N₀: – dB
Eb/N₀ (per channel bit): – dB
Theoretical BER (uncoded): –
Sensitivity: – dBm
Link margin: – dB

FSPL = 20·log₁₀(4πd / λ) · Dish gain G = η · (πD / λ)² · N₀ = kT₀ + NF, T₀ = 290 K (≈ −174 dBm/Hz) · Es/N₀ = C/N₀ − 10·log₁₀(R_s) · Eb/N₀ = Es/N₀ − 10·log₁₀(k). BER values are theoretical channel-bit error rates before any FEC decoding (AWGN channel, Gray coding, ideal coherent or non-coherent detection). Occupied bandwidth: R_s(1 + α) for linear modulations, Carson's rule for FSK, 99% bandwidth for MSK/GMSK.