An Injection-Locked Power Up-Converter in 65-nm CMOS for Cellular Applications

This paper presents an injection-locked 65-nm CMOS circuit that upconverts and power amplifies baseband signals to RF. The circuit delivers an RF output power of 28.7 dBm, with a power gain and maximum power added efficiency (PAE) of 20.6 dB and 68.1%, respectively. Both AM–AM-conversion and AM–PM-conversion are low, less than 1 dB and 1°, respectively, resulting in an EVM of 4.7% for Long Term Evolution (LTE) and 4.1% for WCDMA signals. The circuit provides an average output power of 20.3 dBm for LTE, with a PAE of 44.1%, and for WCDMA, the average output power is 23.8 dBm with a PAE of 55.6%. Supply modulation improves power back-off efficiency and the voltage range is from 540 mV to 3 V. The spectral mask for LTE signals has a worst case ACLR of 33.2 dBc using predistortion. For WCDMA signals, ACLR₁ is 39.9 dBc and ACLR₂ is 47.2 dBc, both values worst case and using baseband predistortion. This performance is achieved by introducing a cross-coupled cascode topology, and supporting theory and simulations are presented. The startup loop-gain and small-signal equivalents are derived, a power dissipation analysis is performed, and the injection circuit is analyzed to investigate the AM–PM behavior. Analysis and simulations show that, compared to conventional cascode amplifiers, PAE is improved by 24% (15% points). The circuit is implemented in an STM 65-nm CMOS process and occupies an area of <inline-formula> <tex-math notation="LaTeX">$1.0 \times 0.53$ </tex-math></inline-formula> mm².