Low-power CMOS integrated circuits for radio frequency applications

This paper presents results for a mixer, two voltage-controlled oscillators (VCOs) and a frequency doubler (FD) suitable for low-power CMOS radio frequency (RF) systems. Results are first described for a mixer which uses the body terminal of the transistor as one of the inputs to down-convert a 1.9 GHz RF signal to a 250 MHz intermediate-frequency signal. Next, two VCOs are described. The first VCO is an ultra-low-power oscillator designed to operate in the 2.4 GHz industrial scientific medical band with a supply of 0.4 V. The second VCO described is a fully integrated LC-tank VCO with automatic amplitude control operating at 4 GHz. Frequency tuning for this VCO is performed by accessing the body of cross-coupled transistors of the VCO core. Finally, a wideband, low-power implementation of a frequency doubler is presented. The frequency doubler consists of two identical unbalanced source-coupled pairs with different W/L ratios, whose inputs are connected in parallel and its output taken single-ended. The FD is based on the MOS transistor in saturation. All circuits were designed in a deep n-well 0.18 μm technology, allowing application of different potentials to the body of different NMOS transistors.