Calibrating Analog I/Q-Modulator Using Lookup Table

Solution Overview

Problem

Existing digital communication systems face challenges in calibrating analog I/Q-modulators due to imbalances between I- and Q-branches, leading to insufficient image signal suppression and requiring excessive processing time and power.

Innovation Solution

A calibration method involving two steps, where a calibration signal is adjusted by complex compensation values, with output signals correlated with harmonics to determine optimal compensation coefficients for amplitude and phase imbalance and DC offsets, reducing the number of calibration stages to two.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If multiple calibration steps with iterative convergence are used to determine optimal compensation coefficients, then the calibration accuracy is improved, but the processing time and power consumption increase excessively

Engineering Contradiction:

Improvecalibration accuracyVSAvoidprocessing time

Core Design Contradiction:

Measurement precisionVSLoss of time

Solution Approach 1:

The patent applies preliminary action by using predetermined compensation coefficients that are pre-calculated and stored in a lookup table. During calibration, instead of performing iterative convergence calculations, the system directly retrieves the appropriate compensation coefficients from the lookup table based on measured I/Q imbalance characteristics. This pre-computation approach significantly reduces processing time while maintaining calibration accuracy.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent changes the parameter representation by transforming the calibration problem from solving for optimal compensation coefficients directly to measuring I/Q imbalance parameters and mapping them to predetermined coefficients. The system measures amplitude and phase imbalance parameters, then uses these measurements to index into a lookup table containing pre-computed compensation coefficients, avoiding iterative optimization while achieving accurate calibration.

Inventive Principle:

Principle #35Parameter changes

2Measurement precision

If multiple calibration steps with iterative convergence are used to determine optimal compensation coefficients, then the calibration accuracy is improved, but the power consumption increases excessively

Engineering Contradiction:

Improvecalibration accuracyVSAvoidpower consumption

Core Design Contradiction:

Measurement precisionVSUse of energy by moving object

Solution Approach 1:

The patent applies preliminary action by using predetermined compensation coefficients that are pre-calculated and stored in a lookup table. During calibration, instead of performing iterative convergence calculations, the system directly retrieves the appropriate compensation coefficients from the lookup table based on measured I/Q imbalance characteristics. This pre-computation approach significantly reduces processing time while maintaining calibration accuracy.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent changes the parameter representation by transforming the calibration problem from solving for optimal compensation coefficients directly to measuring I/Q imbalance parameters and mapping them to predetermined coefficients. The system measures amplitude and phase imbalance parameters, then uses these measurements to index into a lookup table containing pre-computed compensation coefficients, avoiding iterative optimization while achieving accurate calibration.

Inventive Principle:

Principle #35Parameter changes

3Reliability

If a detailed multi-step calibration process is used to compensate for I/Q imbalance and DC offsets, then the suppression of image signal is improved, but the device complexity increases

Engineering Contradiction:

Improveimage signal suppressionVSAvoidcalibration process complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent applies preliminary action by using predetermined compensation coefficients that are pre-calculated and stored in a lookup table. During calibration, instead of performing iterative convergence calculations, the system directly retrieves the appropriate compensation coefficients from the lookup table based on measured I/Q imbalance characteristics. This pre-computation approach significantly reduces processing time while maintaining calibration accuracy.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent introduces an intermediary element - the lookup table - that mediates between the measured I/Q imbalance parameters and the required compensation coefficients. The lookup table stores pre-computed compensation values indexed by imbalance characteristics, serving as an intermediary that eliminates the need for complex real-time optimization algorithms while achieving accurate compensation.

Inventive Principle:

Principle #24Intermediary (Mediator)

Data Source

PatentEP2067335B1Method and system for calibrating an analogue I/Q-modulator of a transmitter

Publication Date: 2013.01.09 NXP BV

Figure 1~2

AI summary

The invention relates to a method and a system for calibrating an analogue I/Q-modulator (2) of a transmitter (3), wherein a calibration signal (s(tk)) is transmitted and an in-phase signal (sI(tk)) and a quadrature-phase signal (sQ(tk)) of the calibration signal (s(tk)) are adjusted by at least one predetermined compensation coefficient (C, D, E) in two calibration steps in at least one compensation measurement set (un, Vn, Wn), whereby: - in a first calibration step, the calibration signal (s(tk)) is adjusted by a first complex compensation value (Cn, 1,