This letter presents the synthesis of a broadband rat-race consisting of a miniaturized broadband rat-race hybrid and transmission line cascades. This broadband technique involves connecting a cascade of transmission lines with lengths equal to a quarter of the wavelength at the design frequency to each port of a previously proposed rat-race hybrid. Butterworth and Chebyshev performances of the broadband rat-race hybrid are also reported. The broadband rat-race hybrid was implemented on an FR4 substrate using spiral inductors and chip capacitors. For the frequency range of 420-800 MHz, which corresponds to a relative bandwidth of more than 62%, the broadband rat-race hybrid exhibited power splits of -3.8 ± 1.0 dB, return losses of greater than 19 dB, and isolation between output ports of greater than 20 dB. The phase difference between S21 and S41 was 180° ± 3°.
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