Design and Implementation of a 16-Bit Flexible ROM-Less Direct Digital Synthesizer in FPGA and CMOS 90nm Technology
Sunny Raj Dommaraju · Journal of Bioresource Management · 2013
A ROM-less direct digital synthesizer architecture is presented in this thesis. This architecture eliminates the ROM-based phase to sine wave amplitude converter, which is a bottleneck for pushing clock frequencies into the gigahertz range. The design consists of a 16-bit phase accumulator, a set of 18 band pass finite impulse response filters, a 12-bit digital to analog converter and a low pass filter to produce a sine wave with output frequencies ranging from 36 MHz to 72 MHz with a resolution of 3.05 kHz and a 55 dB spur free dynamic range. The same hardware can be used to achieve output frequency ranging from hertz to gigahertz and a 191 Hz resolution by changing the clock frequency. A resolution of 0.05 Hz can be achieved by using a 32-bit phase accumulator. The average phase noise obtained was -87 dBc/Hz at 100 kHz offset, -118 dBc/Hz at 1 MHz offset and -151 dBc/Hz at 5 MHz offset. This design was implemented on Virtex-6 FPGA. The analysis results of FPGA data show that the proposed design is an effective alternative. An ASIC design was also implemented in CMOS 90nm technology to reach higher frequency ranges.