Signal Generator Circuit Without ROM Tables or Op-Amp Distortion
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Solution Overview
Problem
Existing signal generators require large memory capacity and high power consumption to improve noise characteristics, and they suffer from waveform distortion due to the use of operational amplifiers in linear interpolation methods.
Innovation Solution
A signal generator that integrates digital values to generate sawtooth and triangular waveforms, differentiates them to produce rectangular waves, and uses D/A conversion and integration to output an analog frequency signal, eliminating the need for a ROM table and operational amplifiers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the resolution for data in the ROM table is increased to improve noise characteristics, then the noise characteristics such as spurious are improved, but the memory capacity and consumption current increase
Solution Approach 1:
The invention extracts and eliminates the ROM table from the signal generation system. Instead of storing waveform data in a ROM table with high resolution, the system generates waveforms through mathematical operations (integration and differentiation) on digital signals, thereby removing the need for large memory capacity while maintaining good noise characteristics
Solution Approach 2:
The invention replaces the mechanical/memory-based ROM table storage system with a computational system using integration and differentiation circuits. This substitution eliminates the direct relationship between noise characteristics and memory resolution, allowing good noise performance without large memory capacity
2Measurement precision
If the resolution for data in the ROM table is increased to improve noise characteristics, then the noise characteristics such as spurious are improved, but the consumption current increases
Solution Approach 1:
The invention extracts and eliminates the ROM table from the signal generation system. Instead of storing waveform data in a ROM table with high resolution, the system generates waveforms through mathematical operations (integration and differentiation) on digital signals, thereby removing the need for large memory capacity while maintaining good noise characteristics
Solution Approach 2:
The invention replaces the mechanical/memory-based ROM table storage system with a computational system using integration and differentiation circuits. This substitution eliminates the direct relationship between noise characteristics and memory resolution, allowing good noise performance without large memory capacity
3Manufacturing precision
If an operational amplifier is used in the sample hold circuit for linear interpolation, then the zero cross timing can be fixed, but waveform distortion occurs due to gain fluctuation
Solution Approach 1:
The invention replaces the operational amplifier-based sample hold circuit with a digital signal processing approach using integration and differentiation. This substitution eliminates the gain fluctuation problem of operational amplifiers while maintaining accurate zero cross timing through digital control, thereby preventing waveform distortion
Solution Approach 2:
The invention changes the approach from analog linear interpolation using operational amplifiers to digital integration and differentiation. This parameter change from analog to digital domain eliminates the gain stability issues of operational amplifiers while preserving timing accuracy through digital signal processing
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration provides excellent noise characteristics with a simple circuit design, reduced power consumption, and minimizes waveform distortion, allowing for accurate digital signal processing and ignoring quantization noise.
Implementation Method 1
an integrated waveform generation unit receiving an inputted digital signal having a digital value according to a set frequency and integrating the digital value to generate an integrated waveform in a sawtooth shape
Implementation Method 2
a triangular wave generation unit inverting a digital value outputted from the integrated waveform generation unit to generate a waveform in a triangular wave shape
Implementation Method 3
a differential circuit unit differentiating an output of the triangular wave generation unit to generate a waveform in a rectangular wave shape
Implementation Method 4
a digital/analog conversion unit digital/analog converting an output of the differential circuit unit
Implementation Method 5
an integration circuit unit integrating an analog output of the digital/analog conversion unit and outputting an integrated waveform in a triangular wave shape
Implementation Method 6
a comparator comparing an output of the integration circuit unit and a preset threshold value and outputting a rectangular wave of an objective frequency being a comparison output
Data Source
AI summary
There is provided a signal generator outputting an analog frequency signal based on a digital value according to a set frequency, which provides excellent noise characteristics, requires no ROM table corresponding to waveform data, and has a simple configuration. A digital signal having a digital value according to a set frequency is integrated to generate a waveform in a sawtooth shape, a waveform in a triangular wave shape is generated based on the waveform, and this waveform output is differentiated and then D/A converted and integrated. A comparator using, for example, the voltage at a midpoint of the triangular wave as a threshold value is used for the integrated output, and a frequency signal of an objective frequency is obtained from the comparator.