Sharif Digital Repository

A compact low power circuit for implementation of a direct conversion OQPSK modulator is proposed. The circuit consists of a digital to analog converter, a low pass filter and an up-converter mixer. By embedding these three blocks, the circuit performance is enhanced and the total power consumption is reduced. The mixer is designed base on a Gilbert cell with on chip inductor loads. Instead of transconductance transistors of Gilbert cell, a fully deferential current mode DAC is used and proficiently a low pass filter is embedded between them and therefore the linearity of total system is improved. All of circuits are designed based on 0.18 μm CMOS technology with a single 1.8 volt power... 

Design of a novel RF front - end structure for 2450-MHz Band IEEE 802.15.4 ZigBee standard in a 0.18-μm CMOS process is presented. Utilizing a common-gate structure instead of conventional inductive degenerated common source amplifier, Low noise figure is achieved with LNA bias current as low as 1mA. An analytical method is presented to minimize the Noise figure of proposed common-gate LNA structure. Together with the LNA, an active Gilbert Cell mixer is adopted to convert the RF signal to 2MHz IF signal. Employing an enhanced current re-use structure, simulation results show a conversion gain of 37.7dB, a Noise figure of 5.9dB and an IIP3 of -4dBm for the front -end. The RF front - end...