Integration of digital-to-analog converter and sallen-key biquad for future transmitters

Abstract

Thesis presents the design of Digital-to-Analog (D/A) converter implemented in a standard 65nm CMOS technology with the active low-pass filter integrated at the output for future transmitters. The combination of binary weighted resistor ladder D/A converter and a 2nd order low-pass Sallen-Key filter with cut-off frequency 21MHz is chosen to support Long Term Evolution (LTE) communication systems. The sinusoidal dual tone signal (6MHz and 200MHz) is given as a digital input for the simulations. The filter architecture is differential based on the Sallen-Key biquad structures, where the miller-compensated differential amplifier is an active element and the resistors and capacitors are passive elements. The design work initializes with the study of various D/A converters and their applications. Next, the study of active filters is undertaken by comparing various architectures. Furthermore, the work is divided into several stages, starting with the implementation and simulation of ideal models followed by the transistor level simulations. Finally, the comparison between the ideal model simulations and schematic level simulations is presented for deeper insight.