Digital Step Attenuator Temperature Compensation

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Solution Overview

Problem

Digital step attenuators (DSAs) experience significant relative attenuation errors due to temperature variations, as their components (transistors, resistors, and capacitors) exhibit different electrical properties with temperature changes, leading to performance issues.

Innovation Solution

The use of resistors with coordinated first-order resistance temperature (FORT) coefficients in attenuator cells, such as T-type and bridged-T attenuator cells, to minimize temperature variations by compensating or offsetting each other, allowing for consistent attenuation across temperature ranges without relying on negative FORT coefficients.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional resistors with varying FORT coefficients are used in DSA, then the device can be manufactured with standard components, but the attenuation performance varies significantly with temperature

Engineering Contradiction:

Improveattenuation consistencyVSAvoidtemperature variation

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent applies parameter changes by selecting resistors with specific FORT coefficient values and configuring them in particular circuit topologies (T-type, π-type, bridged-T) to achieve temperature compensation. By changing the resistance temperature parameters of individual resistors, the overall attenuation remains stable across temperature variations.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent uses composite resistor configurations where multiple resistors with different FORT coefficients are combined in specific arrangements. This creates a composite attenuator cell that leverages the different temperature characteristics of individual resistors to achieve overall temperature stability without requiring negative FORT coefficient materials.

Inventive Principle:

Principle #40Composite materials

2Reliability

If resistors with negative FORT coefficients are used to compensate temperature variation, then attenuation stability improves, but manufacturing complexity and cost increase

Engineering Contradiction:

Improveattenuation stabilityVSAvoidresistor selection complexity

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The patent changes the approach from using negative FORT coefficient resistors to using positive FORT coefficient resistors with carefully selected values. By adjusting the parameter values (resistance and FORT coefficients) of readily available positive coefficient resistors and arranging them in specific circuit configurations, temperature compensation is achieved without the manufacturing complexities of negative coefficient components.

Inventive Principle:

Principle #35Parameter changes

3Adaptability or versatility

If multiple attenuator cells are cascaded to achieve higher attenuation, then the attenuation range increases, but temperature variation effects accumulate

Engineering Contradiction:

Improveattenuation rangeVSAvoidtemperature sensitivity

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The patent segments the overall attenuation function into multiple attenuator cells, each designed with temperature compensation. By dividing the total attenuation requirement into smaller compensated stages, each cell maintains stability independently, preventing the accumulation of temperature effects that would occur in a single large-stage attenuator.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent combines multiple temperature-compensated attenuator cells in cascade, where each cell is designed with balanced FORT coefficients. The combination merges the attenuation capabilities while the temperature compensation characteristics of each cell work together to maintain overall stability across the extended attenuation range.

Inventive Principle:

Principle #5Merging (Combining)

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 results in attenuators with reduced temperature variations, maintaining consistent attenuation performance across a wide temperature range, thereby improving the overall performance of DSAs.

Implementation Method 1

By coordinating first-order resistance temperature (FORT) coefficients of resistors, embodiments of attenuator or attenuator cells are capable of achieving desired attenuation with reduced or minimized temperature variation

Methodology Applied

Scientific EffectFirst-order resistance temperature (FORT) coefficient: Thermal Expansion

Data Source

PatentUS20210313967A1Digital step attenuator

Publication Date: 2021.10.07 CHENGDU SICORE SEMICON CORP LTD

AI summary

Various embodiments of the invention relate to attenuators with reduced temperature variation. By coordinating first-order resistance temperature (FORT) coefficients of resistors, embodiments of attenuator or attenuator cells are capable of achieving desired attenuation with reduced or minimized temperature variation. Such achievements in reducing temperature variation may be obtained without relying on resistors with large negative FORT coefficients. Attenuator cells may be configured as T-type attenuator cells, π-type attenuator cells, bridged-T attenuator cells, or shunt attenuators with various FORT coefficient combinations for the resistors incorporated within the attenuator cells. Furthermore, various attenuator cells may be cascaded together into a digital step attenuator with the temperature variation of those cells compensating or offsetting each other for an overall minimum temperature variation.