Cascade Polyphase Channelizers Green Technology, Reduced Workload DSP (otherwise known as DSP Magic) Fredric J. Harris, PhD University of California San Diego Recently someone posted a question on a DSP blog I occasionally visit: “How does one design a very narrow bandwidth stopband filter?” As I recall there was a 10 kHz wide stopband, a 5 kHz wide transition band, and a 1 MHz sample rate. Stopband attenuation >60 dB, passband ripple <0.1 dB. A bad combination: low bandwidth, low transition bandwidth, high sample rate! Students post their homework problems on the blog, so I...