Synthesis of codirectional couplers with ultralow sidelobes and minimum bandwidth.
A general variational optimization procedure is used to synthesize codirectional couplers with arbitrary sidelobe suppression down to -125 dB. Apodization shapes yielding sidelobe levels over the range of -40 dB to -75 dB are given by a single design formula. The limiting performance in terms of sidelobe suppression versus the bandwidth of passive evanescent-type couplers is found.
Little
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BE
Wu
C
C
Huang
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WP