A DDC requires an output bandwidth of 80% of the output sample rate. A complex mixer generates I and Q signals from the real input, I and Q are decimated and filtered. To achieve the 80% complex bandwidth requirement are the individual I and Q the filter passbands at Fs-out * 0.8 or 0.4? Thanks!
Complex Filter bandwidth - newbie question
Started by ●September 23, 2008
Reply by ●September 23, 20082008-09-23
On Sep 23, 8:26 am, System Alchemist <dotter@nospam_btconnect.com> wrote:> To achieve the 80% complex bandwidth requirement are the individual I > and Q the filter passbands at Fs-out * 0.8 or 0.4?Each of I and Q has a passband from negative 0.4 to positive 0.4, it's a lowpass filter from zero to +/-0.4 FS. Having both I and Q lets you tell if a given signal is in the positive or negative half, but for I and Q taken individually as the seperate filters see them, there is no difference.