Polar Modulator Origin-Passing Trajectory Bandwidth Reduction

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Solution Overview

Problem

Polar transmitters face challenges in wider band radio systems like LTE due to high bandwidth requirements for phase and amplitude modulation signals, leading to increased spectral growth and noise, and difficulties in generating wide frequency deviations and supporting multiple bands.

Innovation Solution

A modulator that detects high bandwidth events and adapts in-phase and quadrature-phase components to ensure the modulation signal trajectory passes through the origin, inverting the amplitude component and adding a 180-degree phase offset to the differentiated phase component, reducing bandwidth and peak frequency deviation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If polar modulation is used in LTE systems, then power efficiency is improved, but bandwidth requirements increase significantly

Engineering Contradiction:

Improvepower efficiencyVSAvoidbandwidth

Core Design Contradiction:

Use of energy by moving objectVSLength of stationary object

Solution Approach 1:

The patent inverts the conventional approach by forcing the signal trajectory to pass through the origin rather than avoiding it. This inversion causes the amplitude to reach zero at specific points, which reduces the bandwidth of the amplitude modulation signal while maintaining the power efficiency benefits of polar modulation in LTE systems

Inventive Principle:

Principle #13The other way round (Inversion)

2Stability of the object's composition

If the signal trajectory avoids the origin, then phase continuity is maintained, but bandwidth increases

Engineering Contradiction:

Improvephase continuityVSAvoidbandwidth

Core Design Contradiction:

Stability of the object's compositionVSLength of stationary object

Solution Approach 1:

Instead of avoiding the origin to maintain phase continuity, the patent inverts the approach by deliberately passing through the origin. The phase discontinuity that occurs is managed through the specific modulation scheme, allowing bandwidth reduction while maintaining acceptable phase continuity through the origin-passing trajectory

Inventive Principle:

Principle #13The other way round (Inversion)

3Adaptability or versatility

If high frequency deviation is used to support multiple bands, then adaptability is improved, but device complexity increases

Engineering Contradiction:

Improvemulti-band supportVSAvoidfrequency deviation range

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The patent changes the parameter of frequency deviation by reducing it through the origin-passing trajectory approach. This parameter change allows the system to support multiple bands with lower frequency deviation requirements, thereby reducing the complexity of the DCO and frequency synthesis components while maintaining multi-band adaptability

Inventive Principle:

Principle #35Parameter changes

4Object-generated harmful factors

If timing alignment is made very accurate, then spectral growth is reduced, but manufacturing precision requirements increase

Engineering Contradiction:

Improvespectral growthVSAvoidtiming alignment accuracy

Core Design Contradiction:

Object-generated harmful factorsVSManufacturing precision

Solution Approach 1:

The patent inverts the conventional timing alignment approach by designing the modulation scheme to pass through the origin, which naturally creates zero-crossing points. This inversion reduces the sensitivity to timing misalignment because the amplitude is zero at these points, thereby reducing spectral growth while lowering the stringent timing precision requirements

Inventive Principle:

Principle #13The other way round (Inversion)

Data Source

PatentEP2627053B1Polar modulation

Publication Date: 2016.04.20 TELEFONAKTIEBOLAGET LM ERICSSON (PUBL)

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AI summary

A modulator (100) comprises a polar generation stage (120) arranged for generating an amplitude component and a phase component of a modulation signal, a differentiator stage (150) arranged for generating a differentiated phase component by differentiating the phase component; and an event detection stage (170) arranged for detecting a high bandwidth event by detecting at least one of the amplitude component and the differentiated phase component meeting an event criterion. An inversion stage (130) is arranged for generating a modified amplitude component by inverting the amplitude component in response to detecting the high bandwidth event. A phase offset stage (150) is arranged for generating a modified differentiated phase component by, in response to detecting the high bandwidth event, adding to the differentiated phase component a phase offset having a magnitude of 180 degrees and a sign opposite to a sign of the differentiated phase component. An amplitude modulation stage (300) is arranged for employing the modified amplitude component to modulate the amplitude of a carrier signal, and a phase modulation stage (200) is arranged for employing the modified differentiated phase component to modulate the frequency of the carrier signal.