| The practical implementation of an analog cubing function in 0.18mum CMOS technology is presented. Analog cubing circuits have analog signal processing applications, such as Radio-over-Fiber predistortion. A literature review of the state-of-the-art revealed a need for CMOS cubing circuits with high gain and bandwidth. The theory and design of the CMOS circuits, which exploit the non-linear and high-frequency characteristics of deep submicron transistors, is presented. Three measures of cubicity, the degree to which a circuit can produce a purely cubic response, were proposed in order to compare the simulated and measured results.;The implemented circuits have measured voltage gains in the range of 1.01 to 31.3V-2, where the units V-2 arise from the cubing nature of the circuit. The direct current draw of the circuits ranged from 4.4mA to 7.2mA. The off-chip test environment prevented high-frequency operation due to capacitive loading and transformer performance issues, but results were observed in the 7 to 100MHz range. |
