Band-Pass Filter Design Example

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ELEC 412 RF Microwave Engineering
Fall 2004 Lecture 14
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Lumped Parameter Band-Pass Filter Design

• Design an N3 band-pass maximally flat
  (Butterworth) filter with a center frequency of
  900 MHz. The Bandwidth of the filter is 20
  That is, BW (0.20)(900 MHz) 1.8 MHz or ?0.9
  MHz.
• From the Maximally Flat Low Pass Prototype Table
  5-2,
• g0 g4 1, g1 g3 1, g2 2

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Low Pass Prototype Filter
Where the normalized center frequency is ?c
1, ?L 1.1(2?900 MHz), and ?U 0.9(2?900
MHz) So that ?U - ?L 1.13Grad/s and
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Finding the Filter Components
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Filter Simulation with Ansoft Designer
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Filter Simulation with Ansoft Designer
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Some Observations On The Results

• Values of components are unreasonable
• Some other method for implementing the filter
  design goals must be found
• Solution Use distributed filters using
  waveguides
• Richardson Transforms and Kurodas Identities

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Richards Transformation Lumped to Distributed
Circuit Design
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Kuroda Transforms