Adaptive Frequency Tracking for Burst Signal Reception

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Solution Overview

Problem

Wireless receivers face challenges in accurately tracking burst transmission frequencies due to carrier frequency errors and low signal-to-noise ratios, particularly in mobile stations with crystal oscillator references, leading to significant clock drift and interference issues.

Innovation Solution

A method and system for tracking burst signal frequencies by determining the quality and carrier frequency of received signals, demodulating based on the carrier frequency, and calculating a drift window when signal quality exceeds a threshold, allowing for precise frequency adjustment and improved signal recovery in low SNIR conditions.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If the detection bandwidth is widened to account for carrier frequency error, then the frequency tracking range is improved, but the noise level at the receiver input increases proportionally with bandwidth

Engineering Contradiction:

Improvefrequency tracking rangeVSAvoidnoise level

Core Design Contradiction:

Adaptability or versatilityVSObject-affected harmful factors

Solution Approach 1:

The patent implements dynamic bandwidth adjustment where the detection bandwidth is adapted based on the current frequency offset estimate. The bandwidth is widened only when necessary to accommodate frequency errors, and narrowed when frequency alignment is good, thus maintaining frequency tracking capability while minimizing noise accumulation.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The system changes the detection bandwidth parameter dynamically based on frequency offset conditions. By adjusting this key parameter according to the estimated frequency error, the system optimizes the trade-off between capturing frequency-shifted signals and rejecting out-of-band noise.

Inventive Principle:

Principle #35Parameter changes

2Device complexity

If a fixed preamble is used for frequency correction, then the frequency tracking mechanism is simplified, but the system cannot adapt to significant clock drift after long periods of signal loss

Engineering Contradiction:

Improvefrequency tracking mechanism complexityVSAvoidfrequency accuracy after signal loss

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The patent performs preliminary frequency offset estimation using the fixed preamble before actual data reception. This preliminary action allows the system to establish an initial frequency reference that can be refined later, enabling the system to handle both simple cases and scenarios with significant drift.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system implements feedback mechanisms where the frequency offset estimated from the preamble is continuously refined during signal reception. The frequency tracking loop uses feedback from the received signal to adjust and correct the initial frequency estimate, maintaining accuracy even after long periods of signal loss.

Inventive Principle:

Principle #23Feedback

3Device complexity

If the receiver uses a crystal oscillator reference, then the device complexity is reduced, but significant clock drift occurs after long periods of no reception

Engineering Contradiction:

Improveclock reference system complexityVSAvoidfrequency accuracy

Core Design Contradiction:

Device complexityVSMeasurement precision

Solution Approach 1:

The patent enables the receiver to self-correct frequency drift by using the transmitted preamble and pilot signals as reference. Instead of relying solely on the crystal oscillator's inherent stability, the system uses the received signal itself to service and adjust its frequency reference, compensating for crystal drift without additional complex hardware.

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

The system dynamically adjusts the frequency reference parameter by comparing the received signal frequency with the expected frequency from the preamble. This parameter adjustment compensates for crystal oscillator drift, maintaining measurement precision while keeping the clock reference system simple.

Inventive Principle:

Principle #35Parameter changes

4Object-affected harmful factors

If the bandwidth is kept minimum to reduce noise, then the noise level is minimized, but the receiver cannot track signals with frequency errors

Engineering Contradiction:

Improvenoise levelVSAvoidfrequency error tolerance

Core Design Contradiction:

Object-affected harmful factorsVSAdaptability or versatility

Solution Approach 1:

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The system performs preliminary frequency offset estimation using the fixed preamble before actual data reception. This preliminary action allows the system to establish an initial frequency reference and set appropriate bandwidth, enabling narrow bandwidth operation during data reception while having already compensated for frequency errors.

Inventive Principle:

Principle #10Preliminary action

Data Source

PatentUS9923749B2Adaptive frequency tracking mechanism for burst transmission reception

Publication Date: 2018.03.20 SR TECH INC

AI summary

A method and wireless communication device for tracking frequencies of transmitted burst signals. The method includes receiving a burst signal, determining a quality of the burst signal and a carrier frequency of the burst signal, demodulating the burst signal based upon the determined carrier frequency, determining a frequency offset of the burst signal based on the determined carrier frequency, and when the quality of the burst signal exceeds a threshold, calculating a drift window based on the determined frequency offset.