fractional bandwidth of 73% is presented in this letter. Wide bandwidth and high odd-
harmonic suppression is achieved by adopting a new technique for the transformer balun
design, resulting in a very low magnitude imbalance of 0.13 dB and a phase imbalance of
0.4° over 7-15 GHz. The balun performance is improved by offsetting the radius of the
primary and secondary coils, which reduces the parasitic coupling capacitance. The input …