A new impedance transformer employing a transmission line and a coupled-line section is presented in this paper. It is physically a quarter-wavelength long, but can achieve three reflection zeros within the passband. Therefore, broad bandwidths can be obtained for a wide range of impedance ratios. The location of the reflection zeros can be synthesized through the transmission line and coupled-line parameters. Design curves for the transformer synthesis have been obtained by solving the design equations directly. Using these results, a stripline impedance transformer has been implemented. This 50-110-OMEGA impedance transformer achieved over 25-dB return loss from 0.6 to 1.6 GHz.
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