A fully integrated Bulk-CMOS switch based tunable transformer for RF and antenna matching

A fully integrated tunable RF impedance matching network based on a transformer topology and on-chip RF switches is presented. Using the Infineon 130 nm Bulk-CMOS RF switch process with 2.4 μm alumina top metal, the chip integrates a 4-bit digitally tunable capacitor, a planar transformer with 4 independent windings and 12 taps, an on-chip charge pump and RF switches to control the operating mode of capacitor and the transformer. The circuit offers the possibility to cover the Smith Chart at either low and high impedance up to a VSWR of 10 on the GSM band 790-960 MHz. In by-pass mode the insertion loss is 0.8 dB at 850 MHz and features a harmonic generation of - 85 dBc (H2) and -75 dBc (H3) without the need of any external devices or extra controller. The current consumption at 1.5 V is 120 μA.