A Compact I/Q Network with Center-Tap Coupled Transformer-Based Quadrature Hybrids for Millimeter-Wave Applications

In this paper, a compact broadband in-phase/quadrature (I/Q) network is realized based on transformer-based quadrature hybrids. The coupling capacitors of the proposed hybrid locate at the center taps of the transformer. All output ports of the center-tap coupled quadrature hybrid locate at the same side of the transformer, which makes signal path and power routing much easier. Based on the center-tap coupled hybrid, the proposed I/Q network shows a good performance with less area. A lumped-element model of the center-tap coupled quadrature hybrid is also investigated. Based on the 40-nm CMOS process, an I/Q network with 2-stage transformer-based quadrature hybrids is implemented. Simulation results demonstrate that the proposed structure achieves an image rejection ratio (IRR) of more than 35 dB from 17 GHz to 31 GHz. Furthermore, the area of the proposed structure is 392*379 um
²
.