Design and Simulation of Digitally Assisted High Frequency Transmitter I

Abstract

Due to the rapid growth of information technology, wireless communication is inevitable in nowadays IT society. One of the major recent technology trends in wireless communication system is the employment of digital techniques in analog transmitting and receiving systems. This project focuses on the design of an RF transmitter that employs the digitally-assisted analogue technique. The new RF Transmitter, namely Delta-Sigma (or Sigma-Delta) Digitized Polar RF Transmitter, comprises several blocks from both digital and analogue domain and work closely. This project aims to study and simulate the operation of some of the blocks in the analogue domain of the transmitter. The DS -Digitized Polar RF Transmitter is built using Polar Modulation, DS -Modulation which can be implemented using the low-cost CMOS process. Polar Modulation uses the envelope modulated power to control the power supply of a Power Amplifier (PA), it also solves the non-linearity problem introduced into the PA by converting the time-varying envelope signal to a constant envelope signal that turns the PA in either on or off state. The DS -Digitized RF Transmitter consists of a high performance Digital Signal Processing (DSP) Engine, two Digital-to-Analogue Converters (DAC), DC-to-DC Converters and Inverters (Pulse Amplifier), a Frequency Synthesizer, a Variable Gain Amplifier (VGA) and a Switched-Mode Power Amplifier. However, due to the complexity of the system, only DAC, DC-to-DC Converter, Frequency Synthesizer, VGA and Switched-Mode Power Amplifier are designed in this work. These building blocks have been designed based on CMOS technology and the simulation results have demonstrated that these building blocks are functioning well.