In flat-top sampling, or square-wave sampling, the peak of the samples remains constant and is equal to the instantaneous value of the baseband signal x(t) at the beginning of the sample. The duration or width of each sample is τ and the sample rate is equal to fs = 1 / Ts.
Flat Top Sampling
During transmission, noise is introduced at the top of the transmit pulse, which can be easily removed if the pulse is in a flat top shape. Here the top of the samples is flat, i. H. they have a constant amplitude. Hence it is called flat-top sampling or practical sampling.
Natural sampling is mathematically equivalent to multiplying the original signal by a sequence of unit amplitude rectangular sampling pulses. Therefore, the spectrum of a naturally sampled signal can be determined by convolving the spectrum of the original signal with the spectrum of the sequence of sampling pulses.
The difference between natural sampling and flat-top sampling is this: With natural sampling, the analog input is multiplied by a train of evenly spaced, rectangular pulses. While with flat-top sampling, the tops of the samples are flat, which means they have constant amplitude.
In flat-top sampling the peaks of the samples are constant and correspond to the instantaneous value of the signal, while a more practical method of sampling is natural sampling, where the pulse width is finite.p>
The Nyquist theorem is also known as the sampling theorem. It is the principle of accurately reproducing a pure sine wave measurement or sample rate, which must be at least twice that. The Nyquist theorem underpins any analog-to-digital conversion and is used in digital audio and video to reduce aliasing.
The Nyquist rate, or frequency, is the minimum rate at which a finite-bandwidth signal must be sampled to obtain all of the information. For a bandwidth of span B, the Nyquist frequency is only 2 B. If a time series is sampled at regular time intervals dt, then the Nyquist rate is only 1/(2 dt ).
Hence, with flat-top sampling, the sampled signal consists of attenuated high-frequency components and this effect is known as the aperture effect. The aperture effect can be improved by making the value of the pulse width τ very small and using an equalizer circuit.
(i) Immediate sampling. (ii) Natural Sampling. (iii) Flat Top Sampling. Of these three, immediate sampling is referred to as ideal sampling, while natural sampling and shallow sampling are referred to as practical sampling methods.
INSTANTANEOUS AND SCAN SAMPLING Instantaneous sampling is a technique in which the observer records a person’s current activity at preselected times (e.g. every minute to the minute throughout the day).< /p>
The sampling theorem states that “a signal can be reproduced exactly if it is sampled at a rate fs greater than or equal to twice the maximum frequency of the given signal W.”
The sampling theorem specifies the minimum sampling rate at which a time-continuous signal must be uniformly sampled so that the original signal can be fully recovered or reconstructed from these samples alone. This is commonly referred to in the literature as Shannon’s sampling theorem.
The flat-top PAM signal is shown in the figure below. Flat-top sampling is the process by which the sampled signal can be represented in impulses for which the amplitude of the signal cannot be changed with respect to the analog signal being sampled. The amplitude peaks remain flat.
A PAM is created from a pure sine wave modulation signal and a square wave generator that produces the carrier pulse and a PAM modulator circuit. A sine wave generator based on the circuit of the Wien bridge oscillator is used. This can produce a distortion-free sine wave at the output.
Of all three pulse amplitude modulation methods, flat-top PAM is the most popular and widespread. The reason for using flat-top PAM is that during transmission, noise interferes with the peak of transmitted pulses and this noise can be easily removed if the PAM pulse has a flat top .