The design of a compact stubbed microstrip balun with very wide range higher order harmonic suppression, is presented based on multiple open stub units, for which advantages are twofold, compared to single and double open-stub based designs. First, the high degree of size and harmonic reduction is achieved within the realizable impedance values. Second, the achieved bandwidths are fairly large (close to those of conventional balun) for a given set of electrical lengths. Unlike other methods, here, predetermined bandwidth analysis is provided for various levels of size and harmonic reduction. A prototype balun, having 75% size reduction and simultaneous wide higher order harmonic suppression extended up to 12f0, while maintaining good input matching, amplitude and phase balance bandwidths, is fabricated for validation.
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