Quint-band branch-line coupler with open- and short-circuited stubs

A branch-line coupler with five operating frequencies is presented. A conventional branch-line coupler and four shunted reactances are adopted for the proposed quint-band branch-line coupler. Detailed formulas are analytically derived and experimentally tested for the proposed quint-band branch-line coupler. Moreover, both simulated and measured results are included to validate the proposed coupler.