JPH01316009A - Signal generating circuit - Google Patents

Abstract

PURPOSE:To generate a highly stable signal at an optional frequency with simple circuit constitution by using a converter so as to convert a desired generating signal into a phase quantity, accumulating the phase quantity from the converter into an accumulator and converting the output into a sine or a cosine wave with a SIN/COS generator. CONSTITUTION:A phase of a reference frequency f0 is varied by 1/2 each for each sample by means of a sampling period Ts by a phase conversion table ROM (converter) 1 of a signal generating circuit. The phase quantity obtained by the table 1 is given to an accumulator 2, where the phase quantity is being accumulated and the output from the accumulator 2 is fed to a SIN/COS conversion table ROM 3. The generated signal is converted into optional information and an angular frequency is generated by the accumulator 2 from the converted phase quantity and the result is converted further into amplitude information thereby generating a highly stable signal at an optional frequency and simplifying the hardware constitution.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a signal generation circuit that generates a sine wave of an arbitrary frequency, and particularly to a reference signal generation circuit used in a digital signal processing circuit.

[Conventional technology]

In digital signal processing circuits, a reference signal with a stable frequency is required for frequency conversion and the like.

In the signal processing circuit shown in Fig. 3, the input signal is a sine wave (S
IN) circuit 30. An analog reference frequency signal f is passed through a cosine wave (CO3) circuit 31 and obtained from a frequency synthesizer. A sine wave (SIN) circuit 32, a cosine wave (C
These signals are passed through the A/D conversion circuits 34 to 37 based on the sample frequency signal F8, converted to A/1], and multiplied by the multiplier 38 to obtain signals of arbitrary frequencies. It has gained. Further, in the signal processing circuit shown in FIG. 4, the reference frequency signal f is manually inputted to the counter 39, the output thereof is stored in a read-only memory (ROM) 40 as waveform information of the reference signal, and the output is stored as the waveform information of the reference signal. Based on this, the stored contents are sequentially read into the register 41 and multiplied by the multiplier 38 to obtain a signal of an arbitrary frequency.

[Problem to be solved by the invention]

Although it is possible to obtain a high-quality basic signal with a stable frequency using the above-mentioned method, the example shown in Figure 3 requires complicated hardware scale, and the example shown in Figure 4 cannot be improved in terms of hardware scale. However, there was a problem in that it was not suitable for applications in which the frequency of the reference signal was arbitrarily changed.

An object of the present invention is to provide a signal generation circuit that solves the above problems.

[Means to solve the problem]

To achieve the above object, the present invention provides a signal generation circuit that generates a sine wave of an arbitrary frequency, which includes a converter that converts a desired generated signal into a phase amount, and an accumulator that accumulates the phase amount obtained from the converter. and an STN/COS generator that converts the output of the accumulator into a sine wave or a cosine wave.

〔Example〕

Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a diagram showing an example of a signal generating circuit according to the present invention.

In the figure, reference numeral 1 denotes a conversion table (converter) that converts a generated reference signal into a phase amount, and is composed of an RO8 and the like. 2 is an accumulator that accumulates the phase amount given by the phase conversion table ROM 1 for each sample period. 3 is a sine wave (SIN) or a cosine wave (C
O3) SIN/CO5 conversion table ROM (generator), which generates SIN and COS amplitude information, respectively, based on the phase information accumulated by the accumulator 2.

The frequency resolution of the generated signal is bj of accumulator 2
It is determined by the following formula depending on the t length.

Δfo=1/NXFs N=2 where Δf: Frequency resolution Fs: Sampling frequency n: Bit length of accumulator Also, the frequency stability depends on the stability of the sampling frequency F5, and this is usually a high-precision crystal oscillator, etc. It is possible to obtain a very stable signal.

Incidentally, when converting into a phase amount in the phase conversion table ROM 1, either an analog or digital method may be used. That is, in the example of FIG. 2, the signal generation circuit of the present invention does not simply read the reference signal from the ROM based on the value of a counter that operates at regular intervals, but generates the reference frequency signal f at the sampling frequency Fs. By reading out the value of an accumulator which sequentially accumulates the phase amount from the ROM, the frequency can be changed arbitrarily and a signal with good frequency accuracy and stability can be obtained.

FIG. 2 is a diagram showing the principle of the signal generation circuit of the present invention,
FIG. 2 shows the reference frequency signal f. (indicates the generated signal here) is the sampling period Ts (i.e., the sampling frequency F
s) shows the phase relationship when sampled at s). FIG. 2(a) shows the reference frequency signal f. When is FS/4, (b) is the reference frequency signal f. Each figure shows the case where is Fs/2. For example, in FIG. 2(a), the phase amount changes by π/2 for each sample, and in FIG. 2(b), it changes by π. Therefore, the angular frequency of the reference signal can be generated by converting the reference signal frequency to be generated into a phase change amount with respect to the sample frequency Fs and accumulating it for each sample period. Furthermore, by converting this phase information into amplitude information, a desired reference signal can be obtained.

〔Effect of the invention〕

As explained above, the present invention converts a generated signal into phase information, generates an angular frequency using an accumulator from the converted phase amount, and further converts this into =4-amplitude information. It has the advantage of being able to generate highly stable signals and realizing it with a simple hardware configuration.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing one embodiment of the present invention, and FIG. 2 (
a) and (b) are diagrams showing the principle of the present invention, FIG. 3; FIG. 4 is a block diagram showing a conventional example.

Claims (1)

[Claims] (1) In a signal generation circuit that generates a sine wave of an arbitrary frequency, a converter that converts a desired generated signal into a phase amount;
A signal generating circuit comprising: an accumulator that accumulates the phase amount obtained from the converter; and a SIN/COS generator that converts the output of the accumulator into a sine wave or a cosine wave.