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Oscillator based trigonometric function computation

IP.com Disclosure Number: IPCOM000241914D
Publication Date: 2015-Jun-08
Document File: 3 page(s) / 85K

Publishing Venue

The IP.com Prior Art Database

Abstract

Advances in semiconductor technologies and cost reductions have opened new markets for applications that are becoming increasingly complex. More computation power is expected from smaller footprint devices. Computation of trigonometric functions such as sine and cosine are found in a very wide array of embedded applications, including (but not limited to) controls engineering, motor control, signal processing, image processing, analysis and filtering, standard algorithms such as FFT, DCT, IIR, FIR, etc. This publication describes a cost effective module that can be added as IP or peripheral to any SoC directed to motor control, internet of things, signal processing, and industrial applications that require calculation of trigonometric functions such as sine and cosine.

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Document title:

Oscillator based trigonometric function computation

Abstract:

Advances in semiconductor technologies and cost reductions have opened new markets for applications that are becoming increasingly complex. More computation power is expected from smaller footprint devices. Computation of trigonometric functions such as sine and cosine are found in a very wide array of embedded applications, including (but not limited to) controls engineering, motor control, signal processing, image processing, analysis and filtering, standard algorithms such as FFT, DCT, IIR, FIR, etc.

This publication describes a cost effective module that can be added as IP or peripheral to any SoC directed to motor control, internet of things, signal processing, and industrial applications that require calculation of trigonometric functions such as sine and cosine.

Body:

At a high level the proposed trigonometric function computation module consists of the following parts:

  • A digital oscillator
  • Compare unit and capture registers.
  • Configuration registers.
  • DMA or peripheral interface.

A digital biquad oscillator is composed of two registers, two multipliers, and one adder (see Figure 1). Registers are placed instead of the typical a and b constants so that the oscillator can be configured at will to different frequencies.

A compare unit is used to detect when the oscillator has calculated the desired value. It consists of a counter that keeps track of the current oscillator angle, a comparator, a compare register and a result register. When the comparator detects that the compare register and the counter are the same, the result register latches the oscillator value.

Two modes of operation are identified:

  • Random angle mode: The application needs a certain angle computed, and so it needs to wait until the oscillator reaches the desired angle. Examples: filtering, signal processing.
  • Continuous mode: The application needs the continuous wave to be output. Examples: DC to AC converters, three phase generators,...