Low Power I/Q Modulator Using Sign Magnitude Processing

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Solution Overview

Problem

I/Q modulators in radio transmitters face inefficiencies due to high current consumption and noise generation in low-noise, low-power applications, primarily because traditional double-balanced mixers operate inefficiently and introduce noise.

Innovation Solution

The implementation of a sign and magnitude signal processing system that selectively applies input signals to mixers based on the sign of the current signal components, allowing only one differential pair to operate at a time and adjusting current consumption according to the input signal's amplitude, thereby reducing noise and current consumption.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If traditional double-balanced mixers are used in I/Q modulators, then modulation functionality is achieved, but current consumption is high and noise levels increase

Engineering Contradiction:

Improvecurrent consumptionVSAvoidnoise

Core Design Contradiction:

Use of energy by moving objectVSObject-generated harmful factors

Solution Approach 1:

The patent divides the mixer operation into two separate differential pairs (first and second differential pairs) that operate alternately. Each differential pair handles one polarity of the RF input signal, segmenting the traditional single mixer operation into two specialized paths. This segmentation allows each pair to be optimized for unipolar operation, reducing overall noise and power consumption while maintaining full modulation functionality.

Inventive Principle:

Principle #1Segmentation

2Productivity

If both differential pairs in a traditional mixer operate simultaneously, then full signal processing capability is maintained, but power consumption increases

Engineering Contradiction:

Improvesignal processing capabilityVSAvoidpower consumption

Core Design Contradiction:

ProductivityVSLoss of energy

Solution Approach 1:

The patent implements periodic action by using the RF input signal's own polarity to alternately activate the first and second differential pairs. When the RF signal is positive, one differential pair operates; when negative, the other operates. This periodic switching based on signal polarity maintains complete signal processing capability while ensuring that only one pair consumes power at any given moment, effectively halving average power consumption.

Inventive Principle:

Principle #19Periodic action

3Adaptability or versatility

If traditional mixers operate with bipolar signals, then complete modulation range is achieved, but efficiency decreases

Engineering Contradiction:

Improvemodulation rangeVSAvoidoperational efficiency

Core Design Contradiction:

Adaptability or versatilityVSUse of energy by moving object

Solution Approach 1:

The patent inverts the traditional approach by using the RF signal polarity to select which differential pair operates, rather than using a fixed bipolar configuration. By routing positive RF signals through one differential pair and negative RF signals through another, the system achieves complete modulation range while operating each pair in its optimal unipolar region, significantly improving efficiency.

Inventive Principle:

Principle #13The other way round (Inversion)

Data Source

PatentUS7839231B1Low power I/Q modulator

Publication Date: 2010.11.23 QUINTIC MICROELECTRONICS WUXI

AI summary

Apparatus and methods for improving the performance of a modulator, typically in an I/Q modulation system, are described. Input I and Q current modulation signals may be processed to generate a sign signal and a magnitude signal, with the magnitude signal selectively applied to the inputs of a mixer based on the sign signal so as to generate respective I and Q modulation signal components. These may then be combined to generate a composite modulation signal.