A Novel Miniaturized 100:1 Broadband Balun with a 4:1 Impedance Ratio

Design of a balun with tight amplitude and phase imbalance over several decades is challenging. In this paper, a simple structure balun was developed based on a T-junction divider where an inverting and a non-inverting sections were added to create an out of phase operation while keeping an adequate balance between the two output ports. The inverter is implemented in a double sided parallel strip line to use its balanced structure for phase inversion, while the non-inverting section is implemented on a coplanar stripline to reduce the inverter’s parasitic effects. A compact design has been developed with tight amplitude and phase imbalance from 10 MHz to 1 GHz (100:1) with impedance ratio of 4:1.