Frequency Offset Compensation Using FFT Data Reordering
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Solution Overview
Problem
The circuit scale of digital signal processing units in optical communication systems increases due to the need for complex multipliers and memories during frequency offset compensation, leading to issues like increased power consumption and reduced chip yield.
Innovation Solution
A frequency offset compensation method that uses first and second FFT means to perform discrete-time Fourier transforms and changes the order of output data according to the frequency offset compensation amount, eliminating the need for new complex multipliers or memories.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If frequency offset compensation is performed using complex multipliers and memories in digital signal processing, then compensation accuracy is improved, but circuit scale increases
Solution Approach 1:
The patent changes the computational domain from time domain to frequency domain by using FFT (Fast Fourier Transform). This parameter change allows frequency offset compensation to be achieved through simple frequency shifting in the frequency domain rather than complex multiplication in the time domain, thereby maintaining compensation accuracy while reducing circuit complexity
Solution Approach 2:
The patent replaces the traditional time-domain complex multiplication mechanism with a frequency-domain FFT-based mechanism. By substituting the computational approach from time-domain processing to frequency-domain processing, the system achieves the same compensation function with reduced hardware requirements
2Reliability
If frequency offset compensation is performed using complex multipliers and memories, then compensation effectiveness is improved, but power consumption increases
Solution Approach 1:
The patent changes the processing domain from time domain to frequency domain using FFT, which transforms the computational operations. This parameter change reduces the number of complex multiplications required, thereby maintaining compensation effectiveness while significantly reducing power consumption associated with complex arithmetic operations
3Speed
If the number of complex multipliers is increased to compensate for speed limitations, then processing speed is improved, but circuit scale increases
Solution Approach 1:
The patent substitutes time-domain complex multiplication with frequency-domain FFT processing. This substitution changes the fundamental approach from parallel complex multiplication to sequential frequency transformation, achieving high-speed processing without proportionally increasing circuit scale by leveraging the efficiency of FFT algorithms
Data Source
AI summary
A frequency offset compensation apparatus includes: first FFT means for performing a discrete-time Fourier transform of an input signal; second FFT means for performing a discrete-time Fourier transform; and offset compensation means for changing an order of output data of the first FFT means according to a frequency offset compensation amount, and rearranging the output data, and then inputting the output data to the second FFT means. This makes possible a frequency offset compensation without needing a new complex multiplier or a new memory in optical communication.