US-12625512-B2 - Sine wave generation circuit and test device

US12625512B2US 12625512 B2US12625512 B2US 12625512B2US-12625512-B2

Abstract

A sine wave generation circuit includes: a first direct digital synthesizer generating a digital sine wave fundamental signal having a frequency f 0 in a normal operation mode and a calibration mode; a second direct digital synthesizer generating a digital second harmonic correction signal having a frequency 2f 0 in the normal operation mode; a correction circuit superimposing the digital second harmonic correction signal on the digital sine wave fundamental signal; a D/A converter converting an output of the correction circuit into an analog sine wave signal; an output buffer receiving the analog sine wave signal and outputting an analog sine wave output signal; an A/D converter converting the analog sine wave output signal into a digital signal in the calibration mode; and a processing circuit generating a spectrum based on the digital signal in the calibration mode and setting a parameter of the second direct digital synthesizer based on the spectrum.

Inventors

Keno SATO

Assignees

ROHM CO., LTD.

Dates

Publication Date: 20260512
Application Date: 20240709
Priority Date: 20230712

Claims (4)

1 . A sine wave generation circuit comprising: a first direct digital synthesizer configured to generate a digital sine wave fundamental signal having a frequency f 0 in a normal operation mode and a calibration mode; a second direct digital synthesizer configured to generate a digital second harmonic correction signal having a frequency 2f 0 in the normal operation mode; a correction circuit configured to superimpose the digital second harmonic correction signal on the digital sine wave fundamental signal; a Digital-to-Analog (D/A) converter configured to convert an output of the correction circuit into an analog sine wave signal; an output buffer configured to receive the analog sine wave signal and output an analog sine wave output signal; an Analog-to-Digital (A/D) converter configured to convert the analog sine wave output signal into a digital signal in the calibration mode; and a processing circuit configured to generate a spectrum by performing Fast Fourier Transform on the digital signal output by the A/D converter in the calibration mode and set a parameter of the second direct digital synthesizer based on information on the frequency 2f 0 in the spectrum, wherein the first direct digital synthesizer and the second direct digital synthesizer include a same configuration and operate based on a common clock signal, wherein the first direct digital synthesizer includes: a first integrator configured to integrate a first input value according to the clock signal; and a first waveform generator configured to include a sine wave table and output a value of a sine wave according to an output of the first integrator by referring to the sine wave table, and wherein the second direct digital synthesizer includes: a second integrator configured to integrate a second input value according to the clock signal; and a second waveform generator configured to include a sine wave table and output a value of a sine wave according to an output of the second integrator.
2 . The sine wave generation circuit of claim 1 , wherein the processing circuit performs Fast Fourier Transform on waveform data whose starting point is a peak of a waveform of the digital signal generated by the A/D converter.
3 . The sine wave generation circuit of claim 1 , further comprising: a third direct digital synthesizer configured to generate a digital third harmonic correction signal having a frequency 3f 0 in the normal operation mode, wherein the correction circuit superimposes the digital second harmonic correction signal and the digital third harmonic correction signal on the digital sine wave fundamental signal, and wherein the processing circuit sets a parameter of the third direct digital synthesizer based on information on the frequency 3f 0 in the spectrum.
4 . A test device, comprising: the sine wave generation circuit of claim 1 , which generates the analog sine wave output signal to be supplied to a device under test that includes the A/D converter; and an analyzer configured to analyze the digital signal output by the A/D converter in response to the analog sine wave output signal.

Description

CROSS-REFERENCE TO RELATED APPLICATION The present invention claims priority under 35 U.S.C. § 119 to Japanese Patent Application No. 2023-114748, filed on Jul. 12, 2023, the entire contents of which are incorporated herein by reference. TECHNICAL FIELD The present disclosure relates to a sine wave generation circuit. BACKGROUND Analog sine wave signals (trigonometric functions) are used in various applications such as semiconductor test devices and wireless communication circuits. As a method of generating an analog sine wave signal, a method is known in which a digital sine wave signal is generated by a direct digital synthesizer (DDS) and is converted into an analog sine wave signal by a D/A converter. BRIEF DESCRIPTION OF DRAWINGS The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the present disclosure. FIG. 1 is a block diagram of a sine wave generation circuit according to an embodiment. FIG. 2 is a diagram illustrating an operation of the sine wave generation circuit of FIG. 1 in a calibration mode. FIG. 3 is a diagram illustrating an operation of the sine wave generation circuit of FIG. 1 in a normal operation mode. FIG. 4 is a block diagram of a sine wave generation circuit according to one Example. FIG. 5 is a block diagram of a first direct digital synthesizer and a second direct digital synthesizer in FIG. 4. FIG. 6A and FIG. 6B are diagrams showing measurement results of the sine wave generation circuit of FIG. 4. FIG. 7A and FIG. 7B are diagrams comparing second harmonics of spectra before and after calibration. FIG. 8A and FIG. 8B are diagrams showing measurement results of the sine wave generation circuit of FIG. 4 by an external measuring device. FIG. 9A and FIG. 9B are diagrams comparing second harmonics of spectra before and after calibration. FIG. 10 is a block diagram of a sine wave generation circuit according to Modification 1. FIG. 11 is a block diagram of a test device according to an embodiment. DETAILED DESCRIPTION Reference will now be made in detail to various embodiments, examples of which are illustrated in the accompanying drawings. In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the present disclosure. However, it will be apparent to one of ordinary skill in the art that the present disclosure may be practiced without these specific details. In other instances, well-known methods, procedures, systems, and components have not been described in detail so as not to unnecessarily obscure aspects of the various embodiments. OVERVIEW OF EMBODIMENTS The overview of some exemplary embodiments of the present disclosure is described. This overview presents, in a simplified form, some concepts of one or more embodiments, as a prologue to the detailed description which is presented later, and for the purpose of basic understanding of the embodiments, but it is not intended to limit the scope of the disclosure. This overview is not a comprehensive overview of all possible embodiments, and it is intended to neither identify key elements of all embodiments nor delineate the scope of some or all aspects. For the sake of convenience, “an embodiment” may be used to refer to one embodiment (example or modification) or a plurality of embodiments (examples or modifications) disclosed herein. A sine wave generation circuit according to an embodiment includes: a first direct digital synthesizer configured to generate a digital sine wave fundamental signal having a frequency f0 in a normal operation mode and a calibration mode; a second direct digital synthesizer configured to generate a digital second harmonic correction signal having a frequency 2f0 in the normal operation mode; a correction circuit configured to superimpose the digital second harmonic correction signal on the digital sine wave fundamental signal; a D/A converter configured to convert an output of the correction circuit into an analog sine wave signal; an output buffer configured to receive the analog sine wave signal and output an analog sine wave output signal; an A/D converter configured to convert the analog sine wave output signal into a digital signal in the calibration mode; and a processing circuit configured to generate a spectrum by performing Fast Fourier Transform on the digital signal output by the A/D converter in the calibration mode and set a parameter of the second direct digital synthesizer based on information on the frequency 2f0 in the spectrum. In the calibration mode, the processing circuit detects a second harmonic generated due to distortion of the output buffer and determines a phase and an amplitude of the digital second harmonic correction signal to cancel the second harmonic. Then, in the normal operation mode, by digital signal processing, the digital second harmonic correction signal whose phase and amplitude have been optimized is superimposed onto