IQ Mismatch Pre-compensator Using Real-valued Filters
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Quadrature transmitters face interference due to in-phase (I) and quadrature (Q) branch imbalances, leading to frequency-dependent IQ mismatch (FD-IQMM) that degrades signal-to-interference ratio and system performance.
Innovation Solution
A transmit in-phase and quadrature mismatch compensator (IQMC) is implemented, comprising TX delay elements, complex-valued filters, and adders to pre-compensate signals, reducing computational complexity and effectively canceling FD-IQMM in the transmitter path.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional IQMC architectures are used, then FD-IQMM can be compensated, but hardware complexity increases
Solution Approach 1:
The patent extracts only the necessary components for FD-IQMM compensation by using real-valued filters instead of complex-valued filters. This extraction approach removes unnecessary computational complexity while retaining the essential compensation functionality, directly addressing the contradiction between achieving reliable FD-IQMM compensation and reducing hardware complexity.
Solution Approach 2:
The patent changes the parameter type of the filter from complex-valued to real-valued. This parameter change fundamentally alters the computational requirements, reducing the number of multiplications and additions needed while maintaining the ability to compensate for frequency-dependent IQ mismatch, thus resolving the contradiction between compensation reliability and hardware complexity.
2Measurement precision
If complex-valued filters are used in IQMC, then compensation accuracy improves, but computational complexity increases
Solution Approach 1:
The patent changes the filter parameter from complex-valued to real-valued, which reduces computational complexity while maintaining compensation accuracy. This parameter transformation allows the system to achieve the same FD-IQMM cancellation effect with fewer computational resources, directly resolving the contradiction between precision and complexity.
Solution Approach 2:
The patent uses simpler real-valued filters that are computationally cheaper than complex-valued filters. These simplified filters achieve sufficient compensation accuracy without the high computational cost, effectively replacing expensive complex-valued processing with more efficient real-valued processing.
3Reliability
If more filter taps are used, then compensation performance improves, but device complexity increases
Solution Approach 1:
The patent changes the filter implementation from complex-valued to real-valued, which reduces the number of required filter taps for achieving the same compensation performance. This parameter change allows the system to maintain high compensation performance with fewer taps, thereby reducing device complexity while preserving reliability.
Data Source
AI summary
An in-phase and quadrature mismatch compensator for a quadrature transmitter includes a delay element, a complex-valued filter and an adder. The delay element receives an input transmit signal and outputs a delayed transmit signal. The complex-valued filter receives the input transmit signal and outputs a selected part of a filtered output transmit signal. The adder adds the delayed transmit signal and the selected part of the filtered output transmit signal and outputs a pre-compensated transmit signal. In one embodiment, the selected part of the filtered output transmit signal includes the real part of the complex-valued output transmit signal. In another embodiment, the selected part of the filtered output transmit signal includes the imaginary part of the complex-valued output transmit signal. Two transmit real-valued compensators are also disclosed that combine the in-phase and quadrature signals before being filtered.