I need help with hairpin filter design. Can anyone help me with the design steps and equations?
Coupled line
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Hairpin
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  -----|  
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Bend each line in half to make a hairpin from each straight line prototype
Arrange the hairpins facing each other so that each end is still next to the middle of the next one
Expect to tweak the design slightly to cope with the coupled length being a slightly different proportional length of the resonators, and the different non-adjacent coupling.