Doppler Correlator Bank Phase Rotation Clock Offset Compensation
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Solution Overview
Problem
Clock offset/frequency errors between a spread spectrum transmitter and receiver degrade correlation results, leading to poor decoding performance in spread spectrum communication systems.
Innovation Solution
A Doppler correlator bank with successive butterfly elements and phase rotation is used to correlate samples against a code sequence, compensating for clock offset/frequency errors by applying phase rotations across the correlators, thereby improving timing synchronization and decoding efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a spread spectrum receiver correlates a receive signal against a known code sequence to find time lag, then timing synchronization is achieved, but computational burden increases significantly
Solution Approach 1:
The patent divides the correlation process into multiple stages: coarse time lag estimation followed by fine time lag refinement. This segmentation reduces the computational complexity at each stage while maintaining overall timing synchronization accuracy, addressing the contradiction between measurement precision and device complexity.
Solution Approach 2:
The patent performs preliminary coarse time lag estimation before fine time lag refinement. By establishing an initial time lag estimate first, the system reduces the search space for subsequent precise correlation, thereby reducing computational burden while achieving accurate timing synchronization.
2Measurement precision
If clock offset compensation is performed in spread spectrum correlation, then correlation accuracy improves, but computational complexity increases
Solution Approach 1:
The patent changes the approach to clock offset compensation by using phase rotation in the frequency domain rather than time-domain adjustment. This parameter change in the compensation method maintains correlation accuracy while reducing computational complexity through efficient frequency-domain operations.
Solution Approach 2:
The patent replaces direct time-domain clock offset compensation with frequency-domain phase rotation. This substitution uses Fourier transform relationships to achieve the same compensation effect with reduced computational burden, addressing the contradiction between correlation accuracy and computational complexity.
3Measurement precision
If phase rotation is applied across Doppler correlators to compensate for frequency errors, then timing synchronization improves, but device complexity increases
Solution Approach 1:
The patent implements a unified Doppler correlator bank structure where multiple correlators share common components and processing stages. The phase rotation mechanism is applied universally across all correlators in a systematic way, reducing overall device complexity while maintaining improved timing synchronization through multi-frequency offset compensation.
Data Source
AI summary
Doppler correlators are configured to receive samples of a signal sampled based on a frequency. Each Doppler correlator includes successive butterfly elements. Each butterfly element includes cross-coupled first and second branches that include a sample delay that doubles for each successive butterfly element, and a sample inversion selectively placed in one of the first and second branches to encode into the successive butterfly elements of each Doppler correlator the same code sequence. Each Doppler correlator is configured with a respective phase rotation that varies across the Doppler correlators. Each Doppler correlator is configured to correlate the samples against the code sequence and apply the respective phase rotation to the samples as the samples are shifted through the successive butterfly elements, to produce respective correlation results from each Doppler correlator centered on a respective frequency offset from the frequency that varies across the Doppler correlators based on the phase rotations.