Frequency Shift Estimation via Deconvolution

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Solution Overview

Problem

Existing methods for determining motion-induced frequency shifts in signals, particularly those modulated with continuous-phase frequency-shift-keying (CP-FSK), are unreliable due to their broadband frequency spectrum, leading to poor estimates when cross-correlating against templates in the frequency domain.

Innovation Solution

A receiving apparatus and method that deconvolve the received signal with templates shifted in frequency by different amounts, evaluating signal-to-noise measures to identify an impulse response function with a peak criterion, which provides a reliable estimate of the motion-induced frequency shift.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If cross-correlation in the frequency domain is used to estimate frequency shift, then the method is simple to implement, but the estimation reliability deteriorates for broadband signals like CP-FSK

Engineering Contradiction:

Improveease of implementationVSAvoidfrequency shift estimation reliability

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The patent introduces an intermediary deconvolution process between signal reception and frequency shift estimation. Instead of directly cross-correlating the received signal with templates, the system first performs deconvolution to generate impulse response functions, then evaluates signal-to-noise measures on these intermediate results. This intermediary step transforms the broadband CP-FSK signal into a form where frequency shift can be reliably estimated, resolving the contradiction between implementation simplicity and estimation reliability.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If deconvolution with frequency-shifted templates is performed, then frequency shift estimation reliability improves for broadband signals, but computational complexity increases

Engineering Contradiction:

Improvefrequency shift estimation reliabilityVSAvoidprocessing complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent segments the frequency shift estimation process into multiple discrete steps: generating frequency-shifted templates at different hypothesized shift values, performing deconvolution for each template, evaluating signal-to-noise measures, and identifying the impulse response function with the peak criterion. This segmentation transforms a single complex estimation problem into a series of manageable sub-tasks, improving reliability while making the increased computational complexity systematic and controllable.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The system performs preliminary generation of multiple frequency-shifted templates before the actual deconvolution and estimation process. By pre-computing templates for various frequency shift values, the system prepares all necessary reference signals in advance, which streamlines the subsequent deconvolution operations and reduces overall processing complexity despite the increased computational burden.

Inventive Principle:

Principle #10Preliminary action

3Speed

If frequency domain cross-correlation is used, then processing speed is fast, but measurement precision deteriorates for signals with broadband spectrum

Engineering Contradiction:

Improveprocessing speedVSAvoidfrequency shift measurement precision

Core Design Contradiction:

SpeedVSMeasurement precision

Solution Approach 1:

The patent substitutes the direct frequency domain cross-correlation mechanism with a deconvolution-based approach. Instead of relying on the mechanical cross-correlation operation that fails for broadband signals, the system uses deconvolution to generate impulse response functions, then evaluates signal-to-noise measures to identify the correct frequency shift. This substitution maintains processing efficiency while dramatically improving measurement precision for broadband CP-FSK signals.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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 approach effectively discriminates between signal and noise peaks in the impulse response function, providing a robust estimation of the frequency shift even for signals with less peaked frequency characteristics, such as CP-FSK, thereby improving decoding accuracy in environments with overlapping echoes.

Implementation Method 1

generate data representative of a plurality of impulse response functions by deconvolving the received signal with each of a plurality of templates

Methodology Applied

Scientific EffectDeconvolution:

Implementation Method 2

the frequency and phase of the received signals may be distorted due to Doppler shift

Methodology Applied

Scientific EffectDoppler shift: Doppler Effect

Data Source

PatentUS12117551B2Frequency-shift determination

Publication Date: 2024.10.15 SONITOR TECH AS

AI summary

A receiving apparatus (7) that can estimate a motion-induced frequency shift in a received signal comprises a processing system (205) and a receiver (204) configured to receive a signal comprising one or more instances of a transmitted signal. The processing system (205) is configured to generate data representative of a plurality of impulse response functions by deconvolving the received signal with each of a plurality of templates representative of the transmitted signal shifted in frequency by a different respective frequency shift. The processing system (205) is further configured to evaluate a signal-to-noise measure for each of the plurality of impulse response functions, and to identify an impulse response function of the plurality of impulse response functions for which the signal-to-noise measure satisfies a peak criterion.