Digital-To-Analog Converter for FSK

Abstract: This thesis is one part of a overall task of designing a module for frequency shift keying (FSK) to be used in an Ultra Wide Band (UWB) system. The FSK system has a Direct Digital Synthesizer (DDS) and Digital-to-Analog (DAC). The DACs differential current signals are directly fed to a RF (Radio Frequency) unit that generates the UWB RF signal. The focus of this thesis is on DAC while the DDS is developed in VHDL as another thesis work. This thesis demonstrates a low-power, ultra wide band 10 bit DAC with an update frequency of 24 MSPS(Mega Samples Per Second). The DAC uses a L-fold linear interpolation architecture. It includes a 16-tap voltage controlled delay line and a 10 bit binary-weighted DAC with a time interleaved structure. The linear interpolation technique improves the attenuation of mirror components and also reduces the glitch. This helps to relax the analog filter requirements and sometimes an off chip capacitor is enough as low pass filter. The attenuation of image components is doubled in decibels(dB) compared with that of conventional DAC. In this work various DAC architectures are studied. The current-steering DAC is chosen due to its high speed and high resolution. A binary weighted architecture is chosen to reduce the digital circuits. This helped in reducing the power consumption. The design and simulation is done with help of Cadence. The layout is done in Cadence Virtuoso and the DDS is integrated with the DAC. The chip is to be manufactured in 130 nm CMOS process.