Design and implementation of a 16-bit flexible ROM-less direct digital synthesizer

A ROM-less direct digital synthesizer architecture is presented in this paper. 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. This design was simulated in Xilinx system generator (Sysgen) and mapped on to Virtex-6 FPGA. The analysis results of the Sysgen and FPGA data show that the proposed design is an effective alternative.