An Approach to 1-to- $2^{n}$ Way Microstrip Balanced Power Divider

In this paper, an approach to 1-to-2n (n = 2,3,4, ...) way microstrip balanced power divider is proposed for the first time. This approach is realized by one balanced-to-single-ended power divider, 2n-1 single-ended-to-balanced power dividers, and 2n-1 - 2 single-ended power dividers. The function of differential-mode power dividing and common-mode suppression can be ensured by the balanced-to-single-ended and single-ended-to-balanced power dividers. The advantage of this approach is that it can reduce the circuit size effectively when comparing with the approach using all the balanced-to-balanced power dividers. The analysis of the balanced-to-single-ended power divider and the single-ended-to-balanced power divider is realized by combining the standard S-parameters, the mixed-mode S-parameters, and the odd- and even-mode equivalent circuits. To verify the theoretical prediction, three prototypes (one balanced-to-single-ended power divider, one single-ended-to-balanced power divider, and one 1-to-4 way balanced power divider) are fabricated and measured. The fabricated 1-to-4 way balanced power divider with the size of 0.75λg × 2λg shows an insertion loss of 0.45 dB at 1.8 GHz, a fractional bandwidth for a 15-dB return loss of 29%, a 20-dB common-mode suppression of 74.6%, and a 20-dB differential-mode isolation (|Sdd32| and |Sdd42|) of 15.1% and 100%, respectively.