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DIRECT DIGITAL SYNTHESIS USING ANALOG EEPROM

IP.com Disclosure Number: IPCOM000006557D
Original Publication Date: 1992-Aug-01
Included in the Prior Art Database: 2002-Jan-15

Publishing Venue

Motorola

Related People

Authors:
Wayne P. Shepherd Bob Stengel

Abstract

Analog memory storage can replace the computa- storage for a phase accumulator resolution of 32 bits. tion of the output function and the digital to analog @AC) Amplitude quantization occurs as a result of the X bit blocks in a Direct Digital Synthesizer (DDS). The com- resolution of the DAC and the DAC non-linearities. putation of the sine function from the phase argument Replacing the computation and DAC blocks with ana- 6(n) is dilticult to pipeline and becomes a bottleneck in log memory significantly reduces the calculation inten- the maximum achievable system clock rate. To improve sity throughput limit and provides the flexibility for this the sine function is approximated (truncated) with additional output signal functions that do not have a corn- storage compression algorithms applied and a look up putation algorithm. In addition the phase and amplitude table is used over a fraction of a cycle. This results in quantization errors are a function of the analog memory phase quantization errors and creates spurious output read and write value resolution only. Figure 1, is an exam- noise. A straight forward implementation of the sine tic- ple of a direct digital synthesizer using phase computa- tion look-up table requires more than 4 Gsamples of tion and a DAC convertor.