JP2005045674A - Device and method for generating trigonometric function wave, and device and method for outputting color signal - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a DDS (direct digital synthesizer) circuit as a trigonometric function wave generating device whose cost can be suppressed. <P>SOLUTION: This trigonometric function wave generating device is configured as the following. A phase incremental value θ is calculated, and a sawtooth wave SW is outputted on the basis of a phase integrated value θ<SB>1</SB>obtained by calculating the phase incremental value θ. A parabolic signal P is outputted on the basis of the sawtooth wave SW. An error between the parabolic signal P and a sinusoidal signal is corrected for each phase X and the sinusoidal signal is outputted as a sinusoidal signal W1. In comparison with when data are read from a ROM in each phase to generate a sinusoidal signal or when Taylor series expansion is used to generate a sinusoidal signal, it is possible to easily output the sinusoidal signal W1 obtained by suppressing an error of a sinusoidal signal with a relatively small circuit scale to be able to suppress cost. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a trigonometric function wave generation device that outputs a trigonometric function wave signal having a predetermined frequency, a color signal output device including the same, a trigonometric function wave generation method, and a color signal output method.

Conventionally, this type of trigonometric wave generator includes a ROM that stores sine wave data of a plurality of frequencies, and has a configuration in which sine wave data of a desired frequency is read from the ROM for each phase and output. (For example, refer to Patent Document 1).
JP 2002-305413 A (page 3-6, FIGS. 1 to 5)

  However, in the above-described trigonometric function wave generation device, the use of a ROM in which data for each phase is recorded makes the ROM capacity relatively large and the circuit scale relatively large, thereby reducing the overall cost. There is a problem that it is not easy to do.

  The present invention has been made in view of these points, and provides a trigonometric function wave generation device capable of suppressing costs, a color signal output device including the same, a trigonometric function wave generation method, and a color signal output method. Objective.

  The trigonometric function wave generation device according to claim 1 is a trigonometric function wave generation device that outputs a trigonometric function wave signal of a predetermined frequency, calculates a phase increment value, and integrates the phase increment value. An integration circuit unit that outputs a predetermined periodic signal based on the above, a multiplication circuit unit that outputs a predetermined trigonometric wave approximate signal based on the predetermined periodic signal output by the integration circuit unit, and this multiplication circuit An error correction unit that corrects an error between the predetermined trigonometric wave approximate signal output from the unit and the trigonometric wave signal for each phase based on the phase integration value, and outputs the corrected signal. Is.

  Then, a predetermined periodic signal is output by the integrating circuit unit based on the phase integrated value obtained by integrating the phase increment value, and a predetermined trigonometric wave approximate signal is output based on the predetermined periodic signal output by the integrating circuit unit. Is output from the multiplication circuit unit, and the error between the predetermined trigonometric wave approximate signal and the trigonometric wave signal output from the multiplication circuit unit is corrected for each phase based on the phase integration value, and the corrected signal is converted into an error. Output by the correction unit, for example, when reading data from the ROM for each phase to generate a trigonometric function wave, or when generating a trigonometric function wave using Taylor series expansion or the like, it is relatively small Since it becomes possible to easily output a signal in which an error is suppressed with respect to the trigonometric wave signal with a circuit scale, the cost is suppressed.

  The trigonometric function wave generating device according to claim 2 is the trigonometric function wave generating device according to claim 1, wherein the multiplication circuit unit is x (0 ≦ 0) proportional to the phase of the predetermined periodic signal output from the integration circuit unit. For x ≦ 1/2), the half wave y of the trigonometric function wave approximate signal is output at y = 8x (1-2x).

  Then, by outputting a half wave y of the trigonometric function wave approximate signal at y = 8x (1-2x) with respect to x proportional to the phase of the predetermined periodic signal output from the integrating circuit unit, the trigonometric function It is possible to easily output a trigonometric wave approximate signal approximated to a wave signal.

  4. The color signal output apparatus according to claim 3, wherein a first input unit to which a first color difference signal of a predetermined image signal is input, and a second color difference different from the first color difference signal of the predetermined image signal. A second input unit to which a signal is input, and either one of a sine wave signal and a cosine wave signal is output to and integrated with the first color difference signal, and one of the sine wave signal and the cosine wave signal 3. The trigonometric function wave generation device according to claim 1 or 2, wherein the other is output to the second color difference signal and integrated, and the first color difference obtained by integrating one of the sine wave signal and the cosine wave signal. And an output unit that adds the signal and the second color difference signal obtained by integrating the other one of the sine wave signal and the cosine wave signal and outputs the resultant signal as a color signal.

  The cost is reduced by providing the trigonometric function wave generating device according to claim 1 or 2, and either the sine wave signal or the cosine wave signal is added to the first color difference signal of the predetermined image signal. And adding the other one of the sine wave signal and the cosine wave signal to the second color difference signal different from the first color difference signal of the predetermined image signal, and adding these color difference signals to output as a color signal. It is possible to easily improve the image quality.

  The trigonometric function wave generating method according to claim 4 is a trigonometric function wave generating method for outputting a trigonometric wave signal having a predetermined frequency, wherein a phase increment value is calculated and the phase increment value is accumulated. A predetermined periodic signal is output based on the value, a predetermined trigonometric wave approximate signal is output based on the predetermined periodic signal, and an error between the predetermined trigonometric wave approximate signal and the trigonometric wave signal is A signal corrected for each phase based on the phase integration value is output.

  Then, a predetermined periodic signal is output based on the phase integrated value obtained by integrating the phase increment value, a predetermined trigonometric function wave approximate signal is output based on the output predetermined periodic signal, and the output predetermined By correcting the error between the trigonometric wave approximate signal and the trigonometric wave signal for each phase based on the phase integration value and outputting this corrected signal, for example, data is read from the ROM for each phase to generate a trigonometric wave Compared to the case of generating a trigonometric wave using Taylor series expansion, etc., it is possible to easily output a signal with suppressed error with respect to the trigonometric wave signal. It is suppressed.

  According to a fifth aspect of the present invention, there is provided a color signal output method that integrates one of the sine wave signal and the cosine wave signal output by the trigonometric function wave generation device according to the fourth aspect into a first color difference signal, and The other one of the wave signal and the cosine wave signal is integrated into a second color difference signal different from the first color difference signal, and either the sine wave signal or the cosine wave signal is integrated. The color difference signal is added to the second color difference signal obtained by integrating the other one of the sine wave signal and the cosine wave signal and output as a color signal.

  Further, by using the trigonometric function wave generation device according to claim 4, the cost is suppressed, and one of the sine wave signal and the cosine wave signal is added to the first color difference signal of the predetermined image signal. And adding the other one of the sine wave signal and the cosine wave signal to the second color difference signal different from the first color difference signal of the predetermined image signal, and adding these color difference signals to output as a color signal. It is possible to easily improve the image quality.

  According to the trigonometric function wave generator of claim 1, a predetermined periodic signal is output by the integrating circuit unit based on the phase integrated value obtained by integrating the phase increment value, and the predetermined signal output by the integrating circuit unit is output. Based on the periodic signal, a predetermined trigonometric wave approximate signal is output by the multiplication circuit unit, and an error between the predetermined trigonometric wave approximate signal and the trigonometric wave signal output by the multiplication circuit unit is based on the phase integration value. By correcting each phase and outputting the corrected signal at the error correction unit, for example, when reading data from the ROM for each phase to generate a trigonometric wave, or by using a Taylor series expansion, the trigonometric wave is generated. Compared with the case where it produces | generates etc., the signal which suppressed the error with respect to a trigonometric wave signal with a comparatively small circuit scale can be output easily, and cost can be suppressed.

  According to the trigonometric wave generator of claim 2, in addition to the effect of the trigonometric wave generator of claim 1, for x proportional to the phase of the predetermined periodic signal output from the integrating circuit unit Thus, by outputting the half wave y of the trigonometric function wave approximate signal at y = 8x (1-2x), the trigonometric function wave approximated signal approximated to the trigonometric function wave signal can be easily output.

  According to the color signal output device of the third aspect, the cost can be suppressed by including the trigonometric function wave generation device according to the first or second aspect, and the sine wave signal and the first color difference signal of the predetermined image signal can be reduced. One of the cosine wave signals is integrated, and either the sine wave signal or the cosine wave signal is integrated with the second color difference signal different from the first color difference signal of the predetermined image signal, and these color difference signals are obtained. By combining and outputting as a color signal, the image quality can be easily improved.

  According to the method for generating a trigonometric function wave according to claim 4, a predetermined periodic signal is output based on the phase integrated value obtained by integrating the phase increment values, and the predetermined trigonometric function is output based on the output predetermined periodic signal. By outputting a wave approximation signal, correcting an error between the output predetermined trigonometric wave approximation signal and the trigonometric wave signal for each phase based on the phase integration value, and outputting this corrected signal, for example, a ROM Compared with the case of generating trigonometric waves by reading data from each phase, or when generating trigonometric waves using Taylor series expansion, etc. It can be output easily and the cost can be reduced.

  According to the color signal output method described in claim 5, by using the trigonometric function wave generation device according to claim 4, the cost can be suppressed and a sine wave signal is added to the first color difference signal of the predetermined image signal. One of the sine wave signal and the cosine wave signal, and one of the sine wave signal and the cosine wave signal is added to the second color difference signal different from the first color difference signal of the predetermined image signal. Can be added and output as a color signal to easily improve the image quality.

  Hereinafter, the configuration of the color signal output apparatus according to the embodiment will be described with reference to the drawings.

  In FIG. 2, reference numeral 1 denotes a color signal output device. This color signal output device 1 is used for a digital video encoder, for example, and a red color difference signal Cr as a first color difference signal in a predetermined image signal and a second color signal. The blue color difference signal Cb as the color difference signal is converted into a video chroma signal C as the color signal and output.

  The color signal output device 1 includes a first input unit 2, a second input unit 3, and a DDS (Direct Function) as a trigonometric function wave generating device that outputs a sine wave signal W 1 as a trigonometric wave having a predetermined frequency. Digital Synthesizer) circuit 4 and output unit 5 are provided. Since the DDS circuit 4 can generate the cosine wave signal W2 by shifting the phase of the sine wave signal W1 by ¼ period, generation of the sine wave signal W1 will be described below.

  The first input unit 2 is an input terminal, for example, and receives a red difference signal Cr of a predetermined image signal.

  The second input unit 3 is an input terminal, for example, and receives a blue difference signal Cb of a predetermined image signal.

The DDS circuit 4 will be described below with respect to the output of the sine wave signal W1. As shown in FIG. 1, the DDS circuit 4 includes an integration circuit unit 11 having an integrator and the like. The integrating circuit 11, the number of bits accumulator A, the frequency of the sine wave signal W1 which generates f _0, the sampling frequency is taken as f _c,
θ = 2 ^A × f ₀ / f _c
Calculating a phase increment theta sought with this phase increment by integrating the theta outputs the phase integrated value theta _1, outputs a sawtooth SW is a predetermined periodic signal based on the phase accumulation value theta ₁ To do. Here, the phase integration value θ ₁ is θ ₁ (n) = n × θ where n is the number of counts.
It is. Also, sawtooth SW is expressed as the remainder of the phase accumulation value theta ₁ by 2 ^A. That is,
SW (n) = (θ ₁ (n) mod 2 ^A )
It is. Here, (a mod b) indicates a remainder when a is divided by b.

Further, the multiplication circuit unit 12 is connected to the integration circuit unit 11. The multiplication circuit unit 12 outputs a parabola signal P as a predetermined trigonometric function wave approximation signal based on the sawtooth wave SW output from the integration circuit unit 11. Here, the parabolic signal P is, for example, y = 8x (1-2x)
The half wave y is obtained. At this time, x is based on each phase of the sawtooth wave SW, that is, the phase integrated value θ ₁ .
x (n) = (1/2) × (SW (n) / 2 ^A )
(0 ≦ x). Note that the half wave of x <0 is generated by inverting the sign of the half wave y.

  Further, an error correction unit 13 is connected to the multiplication circuit unit 12. The error correction unit 13 corrects an error from a preset ideal sine wave for each phase x (n) of the parabolic signal P by a program, and outputs the corrected signal as a sine wave signal W1. It is.

  Then, the DDS circuit 4 outputs and multiplies the sine wave signal W1, which is a carrier wave, to the blue difference signal Cb of the second input unit 3 and generates the cosine generated by shifting the phase of the sine wave signal W1 by ¼ period. The wave signal W2 is output to the red difference signal Cr of the first input unit 2 and multiplied, and output to the output unit 5, respectively.

  The output unit 5 is, for example, an output terminal, adds the red color difference signal Cr multiplied by the cosine wave signal W2 and the blue color difference signal Cb multiplied by the sine wave signal W1, and outputs the result as a video chroma signal C.

  Next, a method for generating a sine wave by the DDS circuit 4 of the present invention will be described.

First, to calculate the phase increment theta at integrating circuit 11, after calculating the phase accumulation value theta ₁ by accumulating the phase increment theta, based on the phase accumulation value theta _1, multiplied by the sawtooth SW Output to the circuit unit 12.

  Next, the multiplication circuit unit 12 calculates a parabolic signal P for each phase of the sawtooth wave SW and outputs the parabolic signal P to the error correction unit 13.

  Then, an error between the parabola signal P and a preset ideal sine wave is corrected by the error correction unit 13 for each phase x (n) and output as a sine wave signal W1.

  Next, a color signal output method by the color signal output apparatus 1 of the present invention will be described.

  First, the cosine wave signal W2 generated by the DDS circuit 4 is added to the red color difference signal Cr in the predetermined image signal input to the first input unit 2, and the predetermined input input to the second input unit 3 is performed. The sine wave signal W1 generated by the DDS circuit 4 is added to the blue difference signal Cb in the image signal.

  Next, the output unit 5 adds the red color difference signal Cr integrated with the cosine wave signal W2 and the blue color difference signal Cb integrated with the sine wave signal W1, and outputs the result as a video chroma signal C.

As described above, according to the DDS circuit 4 of the above embodiment, and outputs the sawtooth wave SW based on the phase accumulation value theta ₁ obtained by integrating the phase increment theta, predetermined parabola based on this sawtooth SW The signal P is output, the error between the parabolic signal P and the ideal sine wave is corrected for each phase, and the corrected signal is output as the sine wave signal W1, for example, data is read from the ROM for each phase. Compared to the case of generating a sine wave or the case of generating a sine wave using Taylor series expansion, etc., it is possible to generate an ideal sine wave with a relatively small circuit scale without improving bit accuracy. Thus, the sine wave signal W1 with suppressed errors can be easily output, and the cost can be reduced.

  Further, by outputting the half wave y of the parabola signal P at y = 8x (1-2x) with respect to the phase x (n) proportional to the phase of the sawtooth wave SW outputted by the integrating circuit unit 11, A parabolic signal P approximated to a sine wave signal can be easily output by a relatively simple process, and combined with the error correction unit 13, a sine wave having a small error with respect to an ideal sine wave while suppressing manufacturing costs. Signal W1 can be output.

  Furthermore, the color signal output device 1 includes the DDS circuit 4 so that the cost can be reduced, and the cosine wave signal W2 is added to the red difference signal Cr of the predetermined image signal, and the blue difference signal Cb of the predetermined image signal. By integrating the sine wave signal W1 and synthesizing these data and outputting them as color signals, the image quality can be improved easily.

Incidentally, in the embodiment described above, the frequency f ₀ of the signal generated by the DDS circuit 4 can be arbitrarily set in a range not exceeding the half of the sampling frequency f _c.

  Further, the half wave y of the parabola signal P can be calculated by an arbitrary parabola.

  In addition to the parabolic signal P, any signal approximated to a trigonometric wave can be used as the trigonometric wave approximate signal.

  Further, the DDS circuit 4 can be used not only for the color signal output device 1 but also for various other signal processing devices.

  A configuration is also possible in which the sine wave signal W1 is integrated with the red color difference signal Cr and the cosine wave signal W2 is integrated with the blue color difference signal Cb.

  Further, as the first color difference signal and the second color difference signal, U and V, RY and RB, or NTSC (National TV Standards Committee) type I and Q can be used.

  Hereinafter, an example of the trigonometric function wave generating apparatus according to the above-described embodiment will be described with reference to FIGS.

As an example, a sine wave signal W1 having a frequency of 3.58 MHz was output from the DDS circuit 4 having 32 bits of the integrator of the integrating circuit unit 11 and a sampling frequency of 13.5 MHz. That is, the phase increment value θ is
θ = 2 ³² × 3.58 / 13.5
The number of gates at this time was 6.2k.

  As a comparative example, a signal based on a third-order Taylor expansion of a sine wave having a frequency of 3.58 MHz was generated and output with a bit number of 32 and a sampling frequency of 13.5 MHz. The number of gates in the comparative example at this time was 8.8k.

  When the frequency spectrum of the parabolic signal P of the embodiment shown in FIG. 3 is compared with the frequency spectrum of the comparative example shown in FIG. 4, unnecessary frequency components are generated in the vicinity of 2.75 MHz and 4.41 MHz in common. Yes. At this time, the error value between the parabolic signal P and the ideal sine wave is as shown in FIG.

  Further, as shown in FIG. 6, the frequency spectrum of the sine wave signal W1 corrected by the error correction unit 13 in the embodiment is close to the ideal frequency spectrum of the sine wave because unnecessary frequency components are reduced.

  On the other hand, the comparative example increases the number of gates to correct the error, increases the order of Taylor expansion, improves the bit accuracy, etc. Cannot be brought close to the ideal frequency spectrum of a sine wave.

  Therefore, it was shown that the embodiment can output the sine wave signal W1 closer to an ideal sine wave with a smaller number of gates than that of the comparative example, that is, a circuit scale smaller than that of the comparative example.

It is a block diagram which shows the trigonometric function wave generator of one embodiment of this invention. It is a block diagram which shows the color signal output device provided with the same trigonometric function wave generator same as the above. It is a graph which shows the frequency spectrum of the parabola signal by one Example of a trigonometric function wave generator same as the above. It is a graph which shows the frequency spectrum before correction | amendment of the signal by the comparative example with respect to one Example of a trigonometric function wave generator same as the above. It is a graph which shows the relationship between the error value and phase of an ideal sine wave and parabola signal by one Example of a trigonometric function wave generator same as the above. It is a graph which shows the frequency spectrum of the output signal by one Example of a trigonometric function wave generator same as the above.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Color signal output device 2 1st input part 3 2nd input part 4 DDS circuit as a trigonometric function wave generator 5 Output part
11 Integration circuit
12 Multiplier circuit
13 Error correction section

Claims (5)

A trigonometric wave generator that outputs a trigonometric wave signal of a predetermined frequency,
An integration circuit unit that calculates a phase increment value and outputs a predetermined periodic signal based on a phase integration value obtained by integrating the phase increment value;
A multiplication circuit unit that outputs a predetermined trigonometric wave approximate signal based on the predetermined periodic signal output by the integration circuit unit;
An error correction unit that corrects an error between the predetermined trigonometric wave approximate signal output from the multiplication circuit unit and the trigonometric wave signal for each phase based on the phase integration value, and outputs the corrected signal; A trigonometric function wave generator characterized by comprising: The multiplication circuit unit converts the half wave y of the trigonometric function wave approximation signal to y = 8x with respect to x (0 ≦ x ≦ 1/2) proportional to the phase of the predetermined periodic signal output from the integration circuit unit. The trigonometric function wave generation device according to claim 1, wherein the output is (1-2x). A first input unit to which a first color difference signal of a predetermined image signal is input;
A second input unit to which a second color difference signal different from the first color difference signal of the predetermined image signal is input;
One of the sine wave signal and the cosine wave signal is output to the first color difference signal and integrated, and the other of the sine wave signal and the cosine wave signal is output to the second color difference signal. The trigonometric function wave generating device according to claim 1 or 2, wherein the trigonometric function wave generating device is integrated,
The first color difference signal obtained by integrating one of the sine wave signal and the cosine wave signal is added to the second color difference signal obtained by integrating the other one of the sine wave signal and the cosine wave signal. And a color signal output device comprising: an output unit that outputs the signal as a color signal. A method of generating a trigonometric wave that outputs a trigonometric wave signal of a predetermined frequency,
Calculate the phase increment value,
A predetermined periodic signal is output based on the phase integration value obtained by integrating the phase increment value,
Based on the predetermined periodic signal, a predetermined trigonometric wave approximate signal is output,
A method of generating a trigonometric function wave, comprising: outputting a signal obtained by correcting an error between the predetermined trigonometric wave approximate signal and the trigonometric wave signal for each phase based on the phase integration value. One of the sine wave signal and the cosine wave signal output by the trigonometric function wave generating device according to claim 4 is integrated with the first color difference signal,
Integrating the other of the sine wave signal and the cosine wave signal with a second color difference signal different from the first color difference signal;
The first color difference signal obtained by integrating one of the sine wave signal and the cosine wave signal is added to the second color difference signal obtained by integrating the other one of the sine wave signal and the cosine wave signal. And outputting it as a color signal.

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