DAC Linearity Correction Using Band-Based Frequency Calibration

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Solution Overview

Problem

In mobile terminal test systems, acquiring calibration values for all frequencies in the desired frequency bandwidth is time-consuming, necessitating a method to efficiently create and apply correction data for signal linearity across a limited frequency range.

Innovation Solution

A signal generation apparatus comprising a signal generation unit, level conversion unit, DA converter, amplifier, frequency conversion unit, correction data storage unit, and control unit, which creates and stores correction data based on actual output signal levels at predetermined frequencies and applies it to convert input signals, focusing on ranges with poor linearity for efficient correction.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If calibration values are acquired for all frequencies in the entire frequency bandwidth, then the linearity correction accuracy is improved, but the time required to acquire calibration data increases significantly

Engineering Contradiction:

Improvelinearity correction accuracyVSAvoidtime to acquire calibration data

Core Design Contradiction:

Measurement precisionVSLoss of time

Solution Approach 1:

The frequency bandwidth is divided into multiple frequency bands, with only representative frequencies measured in each band. The correction data obtained from these representative frequencies is then applied to all frequencies within each band, segmenting the measurement task to reduce time while maintaining accuracy.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Correction data obtained from measured representative frequencies is copied and applied to all other frequencies within the same frequency band. This allows the system to use limited measurement data to correct linearity across the entire bandwidth without measuring every frequency point.

Inventive Principle:

Principle #26Copying

2Reliability

If correction data is created for all frequencies, then the linearity correction comprehensiveness is improved, but the device complexity and processing burden increase

Engineering Contradiction:

Improvelinearity correction comprehensivenessVSAvoidcorrection data processing complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The correction process is segmented by frequency bands, with correction data generated independently for each band based on representative frequencies. This reduces the overall complexity by breaking down the large-scale correction task into smaller, manageable band-specific tasks.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The correction data structure and application method are designed to be universal across all frequency bands. The same correction approach used for representative frequencies can be universally applied to all frequencies within each band, simplifying the overall system design.

Inventive Principle:

Principle #6Universality (Multi-functionality)

3Measurement precision

If the level conversion unit corrects all frequency ranges, then the linearity correction accuracy is improved, but the processing time increases

Engineering Contradiction:

Improvelinearity correction accuracyVSAvoidcorrection operation speed

Core Design Contradiction:

Measurement precisionVSProductivity

Solution Approach 1:

The level conversion unit applies correction selectively based on local needs. Correction is performed using band-specific correction data only for frequencies within each band, allowing the system to optimize processing by treating different frequency regions with appropriate local correction characteristics rather than uniform global correction.

Inventive Principle:

Principle #3Local quality

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 approach enables rapid and simplified correction of signal linearity across all frequencies, utilizing data from a limited frequency range to improve output signal accuracy and speed up the correction process, even with inexpensive DA converters.

Implementation Method 1

a DA converter that converts the digital signal of which the level is converted by the level conversion unit into an analog signal having a predetermined frequency

Methodology Applied

Scientific EffectDigital-to-Analog Conversion:

Implementation Method 2

an amplifier that amplifies the analog signal converted by the DA converter

Methodology Applied

Scientific EffectSignal Amplification:

Implementation Method 3

a frequency conversion unit that converts the frequency of the analog signal amplified by the amplifier

Methodology Applied

Scientific EffectFrequency Conversion:

Data Source

PatentUS11909420B2Signal generation apparatus and linearity correction method thereof

Publication Date: 2024.02.20 ANRITSU CORP

AI summary

There are provided a signal generation unit that generates a predetermined digital signal, a level conversion unit that converts a level of the digital signal generated by the signal generation unit, a DA converter that converts the digital signal of which the level is converted by the level conversion unit into an analog signal in a predetermined intermediate frequency bandwidth, and a control unit that creates correction data for correcting a linearity of a level of an output signal of the DA converter for all frequencies to be used, based on actual data which is data of a level of an actual output signal when a setting of the level of the output signal of the DA converter is changed at a predetermined level interval, at a predetermined frequency, and converts a level of an input signal of the DA converter with the correction data.