On-chip transformer modeling, characterization, and applications in power and low noise amplifiers

A fully integrated radio-frequency (RF) front-end transceiver having no board-level components is highly desirable in order to lower costs. Typical RF front-end circuits are differential to minimize the effect of ground noise on a low noise amplifier (LNA) and to double the output power of a power amplifier (PA) under the same supply voltage. Baluns are thus needed to interface the differential RF circuits with the single-ended antenna. Low insertion loss is desired for on-chip transformer baluns because it directly affects the noise figure of LNA and the output power of PA.; In this work, a compact model for various on-chip spiral transformers was first developed and verified by simulation and experiment. A new layout technique was introduced to achieve high magnetic coupling coefficient and low insertion loss by segmenting and interleaving wide primary and secondary traces. Using the model and layout technique, a fully integrated front-end with on-chip transformers individually optimized for the LNA and PA, and targeted for medium power applications (e.g., WLAN) was designed and fabricated in a 0.18mum 1P5M 1.8V/3.3V standard digital CMOS technology. The receive path achieves S21 of 17dB, NF of 4.1dB and IIP3 of 0dBm at 2.45GHz. The PA achieves Psat of 21dBm, P1dB of 17dBm, and max PAE of 21%.