SNRout

SNRout is the signal-to-noise ratio at the output of a system, indicating how well the output preserves the input signal relative to the noise after amplification, filtering, and processing. It is a key metric in communications, RF design, and audio electronics for assessing end-to-end signal integrity.

In many cases SNRout can be related to the input SNR and the system’s noise figure. If the cascade is linear and the gain is included, SNRout in decibels is approximately SNRin_dB minus NF_dB, where NF is the noise figure of the device or chain (NF_dB = 10 log10(F)). More generally, SNRout = P_signal_out / P_noise_out, with P_signal_out = G^2 P_signal_in and P_noise_out = G^2 P_noise_in + P_noise_added_out; bandwidth and noise sources thus influence the exact value.

Measurement of SNRout involves applying a known test signal at the input, measuring the output signal power and the integrated noise within the output bandwidth, and computing the ratio. Accurate assessment requires accounting for gain, bandwidth, impedance, and filtering. Calibration with a noise source and spectrum analyzer is common.

Applications include characterizing RF amplifiers and receivers, ADC/DAC front-ends, and any signal chain where noise performance limits fidelity.

See also SNR; noise figure; ENOB.