Trigonometric wave generation circuit using series expansion

• US 20050262175A1
• Filed: 05/18/2005
• Published: 11/24/2005
• Est. Priority Date: 05/18/2004
• Status: Abandoned Application

• Current Assignee: ROHM Co., Ltd.
• Original Assignee: ROHM Co., Ltd.
• Inventors: Iino, Yukinobu, Kurihara, Naoki
• Application Number:
  US11/132,066
• Publication Number:
  US 20050262175A1
• Time in Patent Office: Days
• US Class Current: 708/276
• CPC Class Codes: G06F 1/022 Waveform generators, i.e. devices for generating periodical functions of time, e.g. direct digital synthesizers G06F1/025, G06F1/03 take precedence
• CPC Class Codes: H04L 27/30 wherein each code element is represented by a combination of frequencies

Abstract

A DTMF signal generating circuit is provided with a frequency designating unit which designates frequencies to form a DTMF signal, a sinusoidal wave computing unit which computes sinusoidal waves by referring to frequencies designated by the frequency designating unit, and a sinusoidal wave synthesizing unit which synthesizes two sinusoidal waves computed by the sinusoidal wave computing unit. The sinusoidal wave computing unit is provided with operators such as an adder-subtracter and a multiplier and generates a sinusoidal wave by determining terms of a Taylor expansion of a sinusoidal function by arithmetic operation.

Claims

1. A trigonometric wave generating circuit comprising an operator which determines terms of a series expansion of a trigonometric function by direct arithmetic operation, so as to generate a trigonometric wave.

2. The trigonometric wave generating circuit according to claim 1, further comprising a memory which holds coefficients of the terms of the series expansion of the trigonometric function.

3. The trigonometric wave generating circuit according to claim 1, wherein the operator performs the operation after bounding the phase of the trigonometric function to fall within a range from −

½

π

to ½

π

by a shift operation.

4. The trigonometric wave generating circuit according to claim 2, wherein the operator performs the operation after bounding the phase of the trigonometric function to fall within a range from −

½

π

to ½

π

by a shift operation.

6. The dual tone multi-frequency signal generating circuit according to claim 5, wherein the first frequency sinusoidal wave generating unit and the second frequency sinusoidal wave generating unit are formed to share a single trigonometric wave generating circuit according to claim 1.

7. The dual tone multi-frequency signal generating circuit according to claim 6, further comprising a frequency designating unit which designates the first frequency and the second frequency to the single trigonometric wave generating circuit.

9. A sound signal generating circuit comprising:

the dual tone multi-frequency signal generating circuit according to claim 6;

an acoustic signal generating unit which generates a digital acoustic signal; and

a mixing unit which mixes the digital dual tone multi-frequency signal generated by the dual tone multi-frequency signal generating unit with the digital acoustic signal generated by the acoustic signal generating unit.

10. A sound signal generating circuit comprising:

the dual tone multi-frequency signal generating circuit according to claim 7;

an acoustic signal generating unit which generates a digital acoustic signal; and

a mixing unit which mixes the digital dual tone multi-frequency signal generated by the dual tone multi-frequency signal generating unit with the digital acoustic signal generated by the acoustic signal generating unit.

12. The sound signal generating circuit according to claim 9, further comprising:

an interpolator which interpolates between values of the sound signal mixed by the mixing unit;

a Δ

Σ

D/A converter which subjects an output signal from the interpolator to digital-to-analog conversion; and

a filter provided in a stage subsequent to the Δ

Σ

D/A converter.

13. The sound signal generating circuit according to claim 10, further comprising:

an interpolator which interpolates between values of the sound signal mixed by the mixing unit;

a Δ

Σ

D/A converter which subjects an output signal from the interpolator to digital-to-analog conversion; and

a filter provided in a stage subsequent to the Δ

Σ

D/A converter.

5. A dual tone multi-frequency signal generating circuit comprising:

a first frequency sinusoidal wave generating unit which computes a sinusoidal wave of a first frequency using a series expansion;

a second frequency sinusoidal wave generating unit which computes a sinusoidal wave of a second frequency using a series expansion; and

a sinusoidal wave synthesizing unit which synthesizes the sinusoidal wave computed by the first frequency sinusoidal wave generating unit and the sinusoidal wave computed by the second frequency sinusoidal wave generating unit.

8. A sound signal generating circuit comprising:

the dual tone multi-frequency signal generating circuit according to claim 5;

an acoustic signal generating unit which generates a digital acoustic signal; and

a mixing unit which mixes the digital dual tone multi-frequency signal generated by the dual tone multi-frequency signal generating unit with the digital acoustic signal generated by the acoustic signal generating unit.

11. The sound signal generating circuit according to claim 8, further comprising:

an interpolator which interpolates between values of the sound signal mixed by the mixing unit;

a Δ

Σ

D/A converter which subjects an output signal from the interpolator to digital-to-analog conversion; and

a filter provided in a stage subsequent to the Δ

Σ

D/A converter.

14. A communication apparatus comprising the audio signal generating circuit according to claim 8.

15. A communication apparatus comprising the audio signal generating circuit according to claim 11.