produced by a nonlinear amplification resulting in nonlinear distortion there

# Produced by a nonlinear amplification resulting in

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produced by a nonlinear amplification resulting in nonlinear distortion. there are two types of nonlinear distortion that create unwanted frequencies that interfere with the signal and degrade the performance : 1. Harmonic distortion occurs when unwanted harmonics of a signal are produced through nonlinear amplification. harmonics are integer multiples of the original signal. The original signal is the first harmonic (fundamental harmonic), a frequency two times the fundamental frequency is the second harmonic , three times is the third harmonic and so on. Distortion measurements : 22 Correlated noise 1. Harmonic distortion distortion measurements : - Nth harmonic distortion = ratio of the rms amplitude of Nth harmonic to the rms amplitude of the fundamental. - Total Harmonic Distortion (THD) (6.4) where all in rms value. 23 100 % l fundamenta higher v v THD 2 4 4 3 3 2 2 .... n higher v v v v v Correlated noise 2. Intermodulation distortion intermodulation distortion is the generation of unwanted sum and difference frequencies produced when two or more signals mix in a nonlinear device (cross products). unwanted ! 24 Other type of noise 1. Impulse noise characterized by high amplitude peaks of short duration (sudden burst of irregularly shaped pulses) in the total noise spectrum. common source of impulse noise : transient produced from electromechanical switches (relays and solenoids), electric motors, appliances, electric lights, power lines, poor-quality solder joints and lightning. 2. Interference electrical interference occurs when information signals from one source produces frequencies that fall outside their allocated bandwidth and interfere with information signal from another source. most occurs in the radio frequency spectrum. 25 Noise Parameters Signal-to-noise Power Ratio signal-to-noise power ratio (S/N) is the ratio of the signal power level to the noise power level and can be expressed as (1.1) in logarithmic function (1.2) in terms of voltages and resistance (1.2) (6.7) can be reduced to (1.3) 26 n s P P N S n s P P dB N S log 10 ) ( 2 2 / ( ) 10log / s n S V R dB N V R n s V V dB N S log 20 ) ( Noise Factor and Noise Figure Noise factor is the ratio of input signal-to-noise ratio to output signal-to-noise ratio (1.4) Noise figure is the noise factor stated in dB and is a parameter to indicate the quality of a receiver (1.5) Noise Figure in Ideal and Non-ideal Amplifiers - an electronic circuit amplifies signal and noise within its passband equally well - in the case of ideal/noiseless amplifier, the input signal and the noise are amplified equally. - meaning that, signal-to-noise ratio at input = signal-to-noise ratio at output 27 out in N S N S F ) / ( ) / ( out in N S N S F NF ) / ( ) / ( log 10 log 10 Noise Factor and Noise Figure Noise Figure in Ideal and Non-ideal Amplifiers (continue)  #### You've reached the end of your free preview.

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