Digital Signal Equalization Without Cross-Term Complexity
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Solution Overview
Problem
Conventional equalizers for analog circuits like time-interleaved Analog-to-Digital Converters (ADCs) face increased complexity and power consumption due to the need for cross-terms as basis functions, which complicates meeting performance targets while maintaining low power and area consumption.
Innovation Solution
A digital equalization method using a system with parallel filters and a combiner circuit that omits cross-terms, employing fractional delay filters and a non-linear equalization function to generate the equalized signal, thereby reducing complexity and power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional equalizer uses cross-terms as basis functions, then equalization performance is improved, but device complexity increases
Solution Approach 1:
The patent extracts and removes the cross-terms from the equalizer's basis functions. By using only linear terms (y[n-k]) instead of cross-terms (y[n-i]y[n-j]), the invention simplifies the equalizer structure while maintaining effective equalization performance for time-interleaved ADC impairments.
Solution Approach 2:
The patent segments the equalization function into separate linear components that can be independently calculated and combined. Each filter processes the input signal separately using simple linear coefficients, avoiding the need to compute complex cross-terms while achieving the same equalization effect.
2Measurement precision
If conventional equalizer uses cross-terms as basis functions, then equalization performance is improved, but power consumption increases
Solution Approach 1:
The patent extracts and removes the computationally intensive cross-terms from the equalization process. By using only linear terms, the number of multiplications and additions is dramatically reduced, leading to lower power consumption in the digital signal processor while maintaining equalization performance.
Solution Approach 2:
The patent changes the mathematical parameters of the equalization function from quadratic cross-terms to linear terms. This parameter change reduces the computational complexity from O(M^2) to O(M) where M is the number of taps, directly reducing power consumption.
3Reliability
If analog component's power consumption is increased to meet performance targets, then performance is improved, but power consumption increases
Solution Approach 1:
The patent substitutes the analog equalization approach with a digital equalization approach. Instead of increasing analog component power consumption to meet performance targets, the invention uses a digital equalizer that processes the ADC output signal, achieving the same performance improvement with lower overall power consumption.
4Device complexity
If digital equalization simplifies the combination operation by omitting cross-terms, then device complexity is reduced, but equalization performance may deteriorate
Solution Approach 1:
The patent changes the mathematical model parameters to match the actual impairment characteristics of time-interleaved ADCs. By using linear terms that correspond to the physical impairments (buffer nonlinearity, DC offset mismatch, frequency response mismatch), the simplified equalizer achieves effective correction without needing cross-terms.
Data Source
AI summary
An apparatus for equalizing a digital input signal is provided. The apparatus includes an input node configured to receive the digital input signal. Further, the apparatus includes a plurality of filters coupled in parallel to the input node. The plurality of filters are configured to filter the digital input signal and generate a respective filtered signal. Additionally, the apparatus includes a combiner circuit coupled to the plurality of filters. The combiner circuit is configured to receive the respective filtered signal from the plurality of filters, and to generate an equalized signal by combining the received filtered signals according to a non-linear equalization function.