[信息与通信]Filters_package.pdf

3/1/2005 Filters 1/2 5. Filters Recall that the electromagnetic spectrum is generally full of signals at all different frequencies. Q: Yikes! How can we possibly do that? A: Each signal has its own “IP address”—its carrier frequency ω ! We can build devices that select or reject 0 signals based on this carrier frequency. . HO: Filters HO: The Filter Phase Function Q: Why do we give a darn about phase function ∠S ω ? 21 ( ) After all, phase doesn’t matter. A: HO: Filter Dispersion HO: The Linear Phase Filter Jim Stiles The Univ. of Kansas Dept. of EECS 3/1/2005 Filters 2/2 Q: So how do we specify a microwave filter? How close to an ideal filter can we build? A: HO: Microwave Filter Design Q: A: HO: The Filter Design Worksheet HO: The Microwave Filter Spec Sheet Jim Stiles The Univ. of Kansas Dept. of EECS 3/1/2005 Filters.doc 1/8 Filters A RF/microwave filter is (typically) a passive, reciprocal, 2- port linear device. P P out inc Filter If port 2 of this device is terminated in a matched load, then we can relate the incident and output power as: 2 P S P out 21 inc We define this power transmission through a filter in terms of the power transmission coefficient T: