An Eifficient Method for Generating Coherent Digital Sweep Signals

Abstract

This paper presents an efficient method for generating coherent digital sweep signals. This proposed system is a hybrid of the digital sweep generator with the system using interpolation based direct digital frequency synthesis, where the start and end frequencies can be controlled by the initial content of the counter and the accumulator. The main idea of the new architecture is the use of the interpolator to generate the sine wave and it is summarized by using the predetermined interpolation coefficients to fit the sine wave from the calculated phase, instead of using a stored predetermined waveform in a big sized memory. This implies that a smaller look-up table for sine and cosine with minimum hardware overhead will be achieved. The computation of the sinusoidal values are performed by a piecewise parabolic interpolation structure and consequently the interpolation coefficients are stored only in the memory, because of that the size of the ROM is reduced by factor more than 128 with using 12 address lines and 15 bits word size.

High-Precision Digital Audio Waveform Synthesis Using a Multi-Frequency Interpolation Technique

“…In contrast, although interpolation techniques are steadily increasing in popularity, 10 their widespread adoption has been impeded by the diffi culties associated with synthesizing complex functions. Several authors report the use of algorithms which combine the look-up table approach with function approximation methods, [11][12][13] but the use of stored coeffi cients becomes problematic when real-time frequency manipulation is required. The method described here addresses these problems successfully by exploiting a bank of parallel interpolators in conjunction with phase, gain and fi nal summation stages.…”