Filter Bank for CPM Signal Reception

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Solution Overview

Problem

Existing receivers for continuous phase modulated signals face issues with non-orthogonal decomposition components, extended symbol duration interference, and non-Gaussian noise, leading to increased complexity and interference between symbols.

Innovation Solution

A method for generating a filter bank that evaluates and constructs filters with temporal responses limited to a symbol duration, using trellis representation to determine complex pseudo-symbols and reduce the number of components, thereby eliminating symbol interference and ensuring Gaussian white noise output.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If decomposition into amplitude modulated signals is used to simplify receiver structure, then implementation complexity is reduced, but inter-component interference and symbol interference are generated

Engineering Contradiction:

Improvereceiver implementation complexityVSAvoidinter-component interference and symbol interference

Core Design Contradiction:

Device complexityVSObject-generated harmful factors

Solution Approach 1:

The invention changes the time support parameter of the filter responses from extended duration to exactly one symbol duration. This parameter change ensures that filters process only the current symbol without contributions from previous or future symbols, thereby eliminating symbol interference while maintaining the simplified decomposition structure.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The invention segments the continuous filter response into discrete symbol-duration segments. By designing filter responses that are exactly one symbol duration long, the continuous interference problem is segmented into discrete, non-overlapping symbol periods, eliminating inter-symbol interference.

Inventive Principle:

Principle #1Segmentation

2Measurement precision

If filter responses extend beyond symbol duration to capture full signal components, then signal decomposition accuracy is improved, but interference between symbols increases

Engineering Contradiction:

Improvesignal decomposition accuracyVSAvoidinter-symbol interference

Core Design Contradiction:

Measurement precisionVSObject-generated harmful factors

Solution Approach 1:

Inventive Principle:

Principle #35Parameter changes

3Loss of information

If traditional filter bank is used with extended duration components, then signal decomposition is achieved, but noise correlation occurs and Gaussian white noise assumption is violated

Engineering Contradiction:

Improvesignal decomposition capabilityVSAvoidnoise statistical properties

Core Design Contradiction:

Loss of informationVSReliability

Solution Approach 1:

The invention changes the time support parameter of the filter responses to exactly one symbol duration. This parameter change ensures that noise samples at the filter outputs are uncorrelated, satisfying the Gaussian white noise assumption required for accurate Viterbi and BCJR algorithms.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The invention extracts only the essential symbol-duration portion of the filter response, discarding the extended tails that cause noise correlation. By taking out only the necessary one-symbol-duration component, the filter maintains signal decomposition capability while eliminating the harmful correlated noise.

Inventive Principle:

Principle #2Taking out (Extraction)

4Reliability

If high modulation order and long modulation memory are used to improve signal properties, then phase continuity and bandwidth efficiency are enhanced, but receiver implementation complexity increases significantly

Engineering Contradiction:

Improvephase continuity and bandwidth efficiencyVSAvoidreceiver implementation complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The invention changes the time support parameter of the filter responses to exactly one symbol duration, which decouples the receiver complexity from the modulation memory length. This allows high modulation orders and long modulation memories to be used without proportionally increasing receiver complexity, as the filter bank structure remains manageable.

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentEP2993847B1Method for generating a filter bank for receiving cpm signals and a receiver comprising the generated filterbank

Publication Date: 2019.05.22 THALES SA

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AI summary

A method for generating a filter bank (301, 302, ... 30K) for receiving a signal modulated by continuous-phase modulation, said modulated signal being decomposable as a sum of a plurality of amplitude-modulated signals, each amplitude-modulated signal being expressed as a product between a complex pseudo-symbol and a time-domain component of a predefined waveform based on the modulation parameters, said method comprising the following steps: - Evaluating, over a duration T equal to the duration of a symbol, all possible waveforms of the signal from the parameters of the continuous-phase modulation and the decomposition as a sum of a plurality of amplitude-modulated signals, - Retaining all evaluated waveforms that are different from each other, - Constructing a filter bank (301, 302, ...30K) composed of a plurality of filters whose time responses are equal to the selected waveforms, limited to a duration equal to the duration of a symbol.