![]() This is a digital system representation of signal to noise ratio. The carrier to noise ratio required for a certain BER is a function of the Eb/No of the signal. Eb/No is the ratio of the Energy per bit (Eb) to the noise spectral density (No - the noise power present in 1 Hz). Noise Figure added to thermal noise (kTB).īit Error Rate (BER) is the sensitivity benchmark for digital modulation systems.This represents a carrier to noise ratio 4 dB. For an analog FM land mobile radio system using 25 kHz channels, the receiver must have approximately 4 dB more signal power than noise power. The required ratio of signal power to noise floor is known for certain types of modulation. ![]() In order to achieve the desired quality of demodulated signal, the signal power must be higher than the noise floor. This raises the noise floor at the demodulator. The noise figure of circuits in the receiver such as amplifiers and mixers, adds additional noise to the receive channel. This noise is present in the receive channel and cannot be removed. The thermal noise at the input to the receiver passes through to the demodulator. The Noise figure is the amount of noise power added by the electronic circuitry in the receiver to the thermal noise power from the input of the receiver. This is the amount of noise power in a 1 Hz bandwidth. Next, to convert from dBWatts to dBmilliwatts (dBm) increase this value by 30 dB: If we look at the normalized (B = 1 Hz bandwidth) noise floor equation, we have:
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