In practice an analog signal is subject to electronic noise and distortion introduced by communication channels and signal processing operations, which can progressively degrade the signal-to-noise ratio.

Therefore as analog signal processing systems become more complex, they may ultimately degrade signal resolution to such an extent that their performance is surpassed by digital systems.

* Analog signal processing

* Analog signal processing, processing electronic signals that represent continuous variables by use of analog circuitry

Audio signal processing, sometimes referred to as audio processing, is the intentional alteration of auditory signals, or sound, often through an audio effect or effects unit.

As audio signals may be electronically represented in either digital or analog format, signal processing may occur in either domain.

Analog signal processing ( ASP ) then involves physically altering the continuous signal by changing the voltage or current or charge via various electrical means.

Since that time, as computers and software became more advanced, digital signal processing has become the method of choice.

This permits signal processing using digital circuits such as microprocessors and computers.

Although such a conversion can be prone to loss, most modern audio systems use this approach as the techniques of digital signal processing are much more powerful and efficient than analog domain signal processing.

Here a musical signal is tuned to the correct pitch using digital signal processing techniques.

It is often used in signal processing for analyzing functions or series of values, such as time domain signals.

* In signal processing, autocorrelation can give information about repeating events like musical beats ( for example, to determine tempo ) or pulsar frequencies, though it cannot tell the position in time of the beat.

Signal processing would be applied to determine the direction of maximum illumination and so develop a signal to steer the antenna toward the target.

Bandwidth in hertz is a central concept in many fields, including electronics, information theory, digital communications, radio communications, signal processing, and spectroscopy.

In many signal processing contexts, bandwidth is a valuable and limited resource.

Other techniques, such as changing the phase of the base signal also work.

Analog ( or analogue ) television is the analog transmission that involves the broadcasting of encoded analog audio and analog video signal: one in which the information to be transmitted, the brightness and colors of the points in the image and the sound waves of the audio signal are represented by continuous variations of some aspect of the signal ; its amplitude, frequency or phase.

Higher clock rates in increasingly complex CPUs make it more difficult to keep the clock signal in phase ( synchronized ) throughout the entire unit.

In composite video signals, the U and V signals modulate a color subcarrier signal, and the result is referred to as the chrominance signal ; the phase and amplitude of this modulated chrominance signal correspond approximately to the hue and saturation of the color.

In NTSC and PAL, hue is represented by a phase shift of the chrominance signal relative to the color burst, while saturation is determined by the amplitude of the subcarrier.

Now, due to physical properties of interference, if two signals at a point are in phase, they add to give twice the amplitude of each signal, but if they are out of phase, they subtract and give a signal that is the difference of the amplitudes.

The Fourier transform converts the signal information to a magnitude and phase component of each frequency.

Each station transmitted a continuous wave signal that, by comparing the phase difference of the signals from the Master and one of the Slaves, resulted in a set of hyperbolic lines of position called a pattern.

Frequency modulation is known as phase modulation when the carrier phase modulation is the time integral of the FM signal.

In the 1970s, the ground-based Omega Navigation System, based on phase comparison of signal transmission from pairs of stations, became the first worldwide radio navigation system.

The light generated by stimulated emission is very similar to the input signal in terms of wavelength, phase, and polarization.

** Phase modulation ( PM ) ( here the phase shift of the carrier signal is varied in accordance to the instantaneous amplitude of the modulating signal )

In QAM, an inphase signal ( the I signal, for example a cosine waveform ) and a quadrature phase signal ( the Q signal, for example a sine wave ) are amplitude modulated with a finite number of amplitudes, and summed.

Converting an analog signal to digital form introduces a constant low-level noise called quantization noise into the signal which determines the noise floor, but once in digital form the signal can in general be processed or transmitted without introducing additional noise or distortion.

The effects of noise create signal loss and distortion.

This is impossible to recover, since amplifying the signal to recover attenuated parts of the signal amplifies the noise ( distortion / interference ) as well.

Ideally an amplifier increases the power of a signal without otherwise altering it ; practical amplifiers have finite distortion and noise which they invariably add to the signal.

When the signal drive to the amplifier is increased, the output also increases until a point is reached where some part of the amplifier becomes saturated and cannot produce any more output ; this is called clipping, and results in distortion.

Noise is not the same as signal distortion caused by a circuit.

* The point at which the device comes closest to being cut off is not close to zero signal, so the problem of crossover distortion associated with class-AB and-B designs is avoided.

Class AB is widely considered a good compromise for audio amplifiers, since much of the time the music is quiet enough that the signal stays in the " class A " region, where it is amplified with good fidelity, and by definition if passing out of this region, is large enough that the distortion products typical of class B are relatively small.

The exact choice of quiescent current, the standing current through both devices when there is no signal, makes a large difference to the level of distortion ( and to the risk of thermal runaway, that may damage the devices ); often the bias voltage applied to set this quiescent current has to be adjusted with the temperature of the output transistors ( for example in the circuit at the beginning of the article the diodes would be mounted physically close to the output transistors, and chosen to have a matched temperature coefficient ).

Class-C amplifiers conduct less than 50 % of the input signal and the distortion at the output is high, but high efficiencies ( up to 90 %) are possible.

This is called untuned operation, and the analysis of the waveforms shows the massive distortion that appears in the signal.

The residual distortion is dependent upon the bandwidth of the tuned load, with the center frequency seeing very little distortion, but greater attenuation the farther from the tuned frequency that the signal gets.

The digital control introduces additional distortion called quantization error caused by its conversion of the input signal to a digital value.

Often the signal is modified using effects such as reverb and distortion.

Typically the Quadravalve / PD-05 signal makes up the low end while a balance of the U5 and RBI make up the high end, with the RBI providing the " top end " distortion in Lee's sound.

Until 2000 the precision of the GPS signal available to non-U. S .- military users was deliberately severely limited by a timing pulse distortion process known as selective availability.

The equipment must also provide no noticeable distortion of the signal or emphasis or de-emphasis of any frequency in this frequency range.

This is called nonlinearity and results in distortion of the signal.