Bridged-T Coil for Miniature Dual-Band Branch-Line Coupler and Power Divider Designs

In this paper, a new design method for bridged-T coil (BTC) is proposed such that it can be made equivalent to two different transmission line sections at two different frequencies. In this way, on-chip dual-band branch-line coupler and dualband power divider designs with very compact circuit sizes can be made possible through the use of BTCs. Specifically, the proposed 2.45/5.8-GHz dual-band branch-line coupler realized using the integrated passive device (IPD) process features a compact circuit size of only 2.8 mm × 1.4 mm while the proposed 2.4/5.5-GHz dual-band power divider in IPD exhibits a very small circuit size of only 1.8 mm × 1.7 mm. To the best of our knowledge, the proposed dual-band branch-line coupler is the smallest one ever reported while the circuit size of the proposed dual-band power divider is comparable to the smallest in the literature.