Contents
What is oversampling and undersampling in ADC?
Oversampling increases the cost of the ADC. The cost of 200 MSPS ADC is at least twice the cost of the 56 MSPS ADC which is an additional cost for the system designers. By effectively using the undersampling technique and designing the proper filter, the cost of the ADC can be reduced.
How can aliasing be reduced or eliminated?
One solution to the aliasing problem is to sample the signal at a very high rate and then filter out the high frequencies with digital techniques. o Any frequency components above half the sampling rate (also called the Nyquist frequency) must be eliminated by an anti-alias filter before sampling.
What should be the bandwidth of an anti aliasing filter?
For the audio signal application example in the previous section, it may be decided that, signal levels below 40 dB will cause insignificant aliasing. The anti-aliasing filter used may have a bandwidth of 20 kHz but the response is 40 dB down starting from 24 kHz.
What should be the sampling frequency of an aliased signal?
Frequency spectrum of an aliased signal. According to Shannon’s sampling theorem, the sampling frequency should be a minimum of twice the signal frequency, as shown in Equation 1.12.3: (1.12.3)Fsignal
What kind of signal is corrupt by aliasing?
Recalling that aliasing can corrupt the signal of interest, consider a special class of band-limited signals known as bandpass signals. A bandpass signal is characterized by a bandwidth not bounded by zero at its lower end.
Can a bandpass signal permit a lower sampling frequency?
Consider a baseband and a bandpass signal, each with the same value of maximum frequency. The bandpass signal permits a lower sampling frequency only if the recovery method includes a bandpass filter that isolates the original signal spectrum (the white rectangles in Figure 5).