EE5410 Discrete-time filter : periodic with period 2*PI
1. For discrete-time filters, the frequency response H(e^jw) MUST be periodic with period 2*PI, with LOW frequencies near EVEN multiples of PI and HIGH frequencies near ODD multiples of PI.
2. Frequency-selective filtering is accomplished through the use of LTI systems described by linear constant-coefficient differential or difference equations.
3. Frequency-selective filters are a class of filters specially intended to accurately or approximately SELECT some bands of frequencies and REJECT others.
4. For ideal continuous-time highpass and bandpass filters, each of these filters is SYMMETRIC about w=0, and thus, there appear to be two passbands for the highpass and bandpass filters.
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