EE5410 Discrete-time filter : periodic with period 2*PI

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.

http://techcrunch.com/2011/01/31/twitter-by-phone-egypt/

"It was only last week that Google acquired SayNow, a voice messaging startup, They’re already putting them to good use. I mean really good use.

As they’ve just announced on the Google Blog, the search giant has teamed up with the incoming SayNow team and Twitter to create a simple speak-to-tweet service for people currently engulfed in the turmoil in Egypt."