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The concept of sampling frequency can only be applied to Sampler s in which samples are taken periodically. Some samplers may sample at a non-periodic rate. The common notation for sampling frequency is which stands for frequency (subscript) sampled. SAMPLING THEOREM The (half the sample rate) exceeds the bandwidth of the signal being sampled. If lower sampling rates are used, the original signal's information may not be completely recoverable from the sampled signal. For example, if a signal has a bandwidth of 100 Hz, to avoid Aliasing the sampling frequency should be greater than 200 Hz. OVERSAMPLING In some cases, it is desirable to have a sampling frequency considerably more than twice the desired system bandwidth so that a Digital Filter can be used in exchange for a weaker analog Anti-aliasing Filter . This process is known as Oversampling .1 AUDIO In Digital Audio , common sampling rates are: VIDEO SYSTEMS In Digital Video , the temporal sampling rate is defined the frame/field rate, rather than the notional pixel clock. The image sampling frequency is the repetition rate of the sensor integration period. Since the integration period may be significantly shorter than the time between repetitions, the sampling frequency can be different from the inverse of the sample time. When analog video is converted to Digital Video , a different sampling process occurs, this time at the pixel frequency, corresponding to a spatial sampling rate along Scan Line s. Some common Pixel sampling rates are:
Spatial sampling in the other direction is determined by the spacing of scan lines in the Raster . The sampling rates and resolutions in both spatial directions can be measured in units of lines per picture height. Spatial Aliasing of high-frequency Luma or Chroma video components shows up as a Moiré Pattern . REFERENCES SEE ALSO
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