Zero-Insertion FIR Filtering for IQ Mismatch Correction
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Solution Overview
Problem
Existing zero intermediate frequency (zero IF) wireless architectures face challenges in correcting IQ mismatch errors due to gain, phase, and filter mismatches, which lead to side-band leakage, and require increased filter length and power for DPD bandwidth expansion, making current IQ mismatch correction methods inefficient.
Innovation Solution
A zero-insertion FIR filter architecture is introduced, which configures an L-tap FIR filter with a defined coefficient sequence that includes zero-inserted coefficients, allowing the filter to be reconfigured as an M-tap FIR filter with an extended length, optimizing for IQ mismatch correction in both the target and secondary bands.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the FIR filter length is increased to accommodate DPD bandwidth expansion, then the IQ mismatch correction performance is improved, but the device complexity and power consumption increase
Solution Approach 1:
The patent divides the FIR filter into multiple sub-filters, each handling a specific frequency band (target band and secondary bands). This segmentation allows the system to achieve comprehensive IQ mismatch correction across the entire bandwidth without requiring a single excessively long filter, thereby reducing overall device complexity while maintaining correction performance.
Solution Approach 2:
The patent applies different filter characteristics to different frequency bands. The first sub-filter is optimized for the target band while the second sub-filter handles the secondary bands. This local optimization allows each sub-filter to be more efficient and shorter in length compared to a single universal filter, reducing overall complexity.
2Measurement precision
If the FIR filter length is increased to accommodate DPD bandwidth expansion, then the IQ mismatch correction performance is improved, but the power consumption increases
Solution Approach 1:
By segmenting the filter into multiple sub-filters that operate in parallel on different frequency bands, the computational burden is distributed. Each sub-filter processes only its assigned band, reducing the total number of operations required compared to a single long filter processing the entire bandwidth, thereby lowering power consumption.
Solution Approach 2:
The patent applies filtering selectively to different frequency bands based on their specific requirements. The first sub-filter addresses the target band with appropriate filtering, while the second sub-filter handles secondary bands. This partial action approach avoids the excessive computation that would result from applying a single long filter uniformly across all bands, reducing power consumption.
3Device complexity
If a single FIR filter is used for both target and secondary bands, then the device complexity is reduced, but the IQ mismatch correction performance deteriorates due to frequency-dependent impairments
Solution Approach 1:
The patent implements different filter characteristics for different frequency bands. The first sub-filter is designed with parameters optimized for the target band, while the second sub-filter is designed for the secondary bands. This local quality approach ensures that each band receives the appropriate filtering treatment, maintaining high correction performance across all bands despite using multiple filters.
Solution Approach 2:
By segmenting the frequency spectrum into target band and secondary bands, and assigning dedicated sub-filters to each segment, the system can optimize each sub-filter's characteristics for its specific band. This segmentation enables precise frequency-dependent impairment correction that would be impossible with a single uniform filter.
Data Source
AI summary
A zero-insertion FIR filter architecture for filtering a signal with a target band and a secondary band. Digital filter circuitry includes an L-tap FIR (finite impulse response) filter, with a number L filter tap elements (L=0, 1, 2, . . . (L−1)), each with an assigned coefficient from a defined coefficient sequence. The L-tap FIR filter is configurable with a defined zero-insertion coefficient sequence of a repeating sub-sequence of a nonzero coefficient followed by one or more zero-inserted coefficients, with a number Nj of nonzero coefficients, and a number Nk of zero-inserted coefficients, so that L=Nj+Nk. The L-tap FIR filter is configurable as an M-tap FIR filter with a nonzero coefficient sequence in which each of the L filter tap elements is assigned a non-zero coefficient, the M-tap FIR filter having an effective length of M=(Nj+Nk) non-zero coefficients.