Direct Conversion Receiver Phase Correction Using Asymmetric FIR
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Solution Overview
Problem
Direct conversion receivers suffer from inherent phase imbalance between in-phase and quadrature channels, which existing methods fail to effectively correct, especially the frequency-dependent component of this imbalance.
Innovation Solution
A method involving a phase estimation mechanism and an interpolating mechanism using an asymmetric Finite Impulse Response (FIR) filter, which applies a phase imbalance correction value to sampled signals to correct the frequency-dependent phase imbalance, allowing for minimal hardware changes and efficient phase alignment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If existing phase correction methods are used, then some phase imbalance correction is achieved, but the frequency-dependent component of phase imbalance remains uncorrected
Solution Approach 1:
The patent applies parameter changes by using an asymmetric FIR filter with specifically designed tap coefficients that vary according to frequency-dependent phase imbalance characteristics. The filter coefficients are calculated to compensate for frequency-dependent phase errors, transforming the correction approach from fixed to adaptive based on frequency parameters
Solution Approach 2:
The patent introduces an interpolating mechanism as an intermediary between the ADC and DSP components. This interpolating mechanism uses the asymmetric FIR filter to generate corrected quadrature channel samples by interpolating between actual samples, thereby mediating the frequency-dependent phase imbalance correction without requiring complete redesign of the receiver architecture
2Measurement precision
If complex correction mechanisms are implemented, then phase imbalance correction improves, but hardware complexity and acquisition time increase
Solution Approach 1:
The patent applies partial action by implementing correction only for the frequency-dependent component of phase imbalance using the asymmetric FIR filter, rather than attempting to correct all aspects of phase imbalance. This selective approach achieves sufficient correction for frequency-dependent errors without the complexity of comprehensive correction systems
Solution Approach 2:
The patent uses copying by generating corrected quadrature channel samples through interpolation based on in-phase and quadrature channel samples. The asymmetric FIR filter creates a copied and corrected version of the quadrature signal by combining actual samples with interpolated values, avoiding the need for additional physical hardware components
3Device complexity
If frequency-dependent phase imbalance is not corrected, then hardware remains simple, but signal processing accuracy deteriorates
Solution Approach 1:
The patent replaces mechanical or hardware-based correction mechanisms with a digital signal processing approach using an asymmetric FIR filter. Instead of adding complex hardware circuits for phase correction, the solution substitutes a digital filtering and interpolation mechanism that achieves frequency-dependent phase correction through computational algorithms
Solution Approach 2:
The asymmetric FIR filter serves multiple functions simultaneously: it acts as a phase correction filter, an interpolating mechanism, and a frequency-dependent equalizer. This multi-functional approach improves signal processing accuracy without requiring separate dedicated hardware components for each function
Data Source
AI summary
A direct conversion receiver and a method for correcting phase imbalance including applying an input signal to an in-phase channel and a quadrature channel of the receiver. The input signal is processed by the receiver to obtain an in-phase zero intermediate frequency (IF) signal in the in-phase channel and a quadrature zero-IF signal in the quadrature channel. The in-phase zero-IF signal and the quadrature zero-IF signal are filtered to obtain a fixed band signal. A phase imbalance correction value is obtained for the fixed-band quadrature zero-IF signal as a function of the frequency of the fixed-band in-phase zero-IF signal and the fixed-band quadrature zero-IF signal. The in-phase zero-IF signal and the quadrature zero-IF signal are sampled and the phase imbalance correction value is applied using an interpolation to the sampled quadrature zero-IF signal or to the sampled in-phase zero-IF signal to correct the phase imbalance in the direct conversion receiver.