TIADC Polyphase FIR Correction for Channel Bandwidth Mismatch
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Solution Overview
Problem
Current techniques for correcting mismatches in Time Interleaved Analog to Digital Converters (TIADC) systems are complex and inefficient, particularly in the time domain, and often require large matrix inversions and complex filter designs, which increase computational complexity and reduce Spurious-Free Dynamic Range (SFDR) values.
Innovation Solution
The proposed solution involves a time domain correction method derived from frequency domain correction matrices, which simplifies the design of Finite Impulse Response (FIR) filters by reducing complexity and improving the correction of frequency-dependent mismatches, using a polyphase time-invariant filter structure and weighted least-squares optimization to minimize error in filter coefficients.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If frequency domain correction methods are used with matrix multiplication, then correction accuracy is improved, but computational complexity increases due to large matrix inversions
Solution Approach 1:
The patent segments the complex M x M correction matrix into M separate polyphase filters, each of size L x L where L << M. This segmentation transforms a single large matrix inversion problem into multiple smaller, independent filter design problems, significantly reducing computational complexity while maintaining correction accuracy through the polyphase structure.
Solution Approach 2:
The patent transitions from direct time-domain filter design to frequency-domain specification followed by inverse transformation. By specifying filter characteristics in the frequency domain and using inverse Fourier transformation, the patent simplifies the design process and reduces computational burden compared to direct time-domain optimization.
2Reliability
If large matrix inversions are performed for time domain correction, then correction effectiveness is improved, but processing time increases
Solution Approach 1:
The patent divides the large M x M matrix operation into M separate polyphase filter operations, each involving much smaller L x L computations. This segmentation dramatically reduces processing time while maintaining correction effectiveness, as the polyphase structure preserves the essential correction functionality through distributed processing.
Solution Approach 2:
The patent performs calibration and filter coefficient determination in advance during a setup phase, storing the computed polyphase filters for rapid application during normal operation. This preliminary action separates the computationally intensive filter design from the real-time correction process, reducing processing time during actual signal correction.
3Measurement precision
If complex filter designs are used for mismatch correction, then correction precision is improved, but device complexity increases
Solution Approach 1:
The patent segments the complex correction task into M simpler polyphase filters with fewer coefficients each. This segmentation reduces filter design complexity while maintaining overall correction precision, as each polyphase filter operates on a subset of the frequency spectrum with reduced computational requirements.
Solution Approach 2:
The patent changes the design parameters from direct time-domain coefficients to frequency-domain specifications. By defining filter characteristics in the frequency domain and transforming to time domain, the patent simplifies the design process and reduces the number of parameters that need to be optimized, thereby reducing device complexity while maintaining correction precision.
Data Source
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AI summary
A machine-implemented method can include receiving a common input signal over M parallel time-interleaved (TI) analog to digital converter (ADC) channels, determining a multiple-input, multiple-output finite impulse response (FIR) filter structure for correcting bandwidth mismatches between the M parallel TIADC channels, and providing a common output signal comprising TI data corresponding to the M parallel TIADC corrected channels.