Dual-Mixer Linearity Correction for Full-Duplex Frequency Mixing
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Full-duplex wireless communication systems face challenges due to self-interference, which existing frequency mixing technologies struggle to address effectively, leading to performance limitations and increased circuit complexity or cost.
Innovation Solution
A system for enhanced linearity mixing, comprising a primary mixer, a distortion-source mixer, signal couplers, a phase shifter, a scaler, and harmonic shorting circuits, which models and subtracts distortion to improve the linearity of frequency mixers without significant increases in complexity or cost.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If traditional frequency mixing is used to address self-interference in full-duplex systems, then the basic mixing function is achieved, but linearity performance is insufficient leading to higher-order distortion
Solution Approach 1:
The mixing function is divided into two separate mixer stages: a first mixer that performs the primary frequency conversion, and a second mixer that corrects distortion by mixing the input signal with a corrected local oscillator signal. This segmentation allows each mixer to handle specific aspects of the signal processing, improving overall linearity.
Solution Approach 2:
A distortion correction signal is generated as an intermediary component. This correction signal is derived from the local oscillator signal and is used to compensate for non-linearities in the mixing process. The correction signal acts as a mediator between the local oscillator and the final mixed output, reducing higher-order distortion.
2Manufacturing precision
If distortion correction components are added to improve linearity, then higher-order distortion is reduced, but circuit complexity increases
Solution Approach 1:
The second mixer serves multiple functions: it performs additional frequency conversion and simultaneously applies distortion correction. By combining these functions in a single mixing stage, the circuit avoids the need for separate correction circuits, thereby reducing overall complexity while maintaining improved linearity.
Solution Approach 2:
The distortion correction functionality is merged into the second mixing stage rather than being implemented as a separate correction circuit. The corrected local oscillator signal is directly combined with the input signal in the second mixer, integrating the correction function with the frequency conversion function in a unified circuit architecture.
Data Source
Figure 1
Figure 2
Figure 3
AI summary
A system for enhanced linearity mixing includes an input-source signal coupler; a local oscillator (LO) signal coupler; a primary mixer that combines, via heterodyning, the primary-mixer-input signal and the primary-mixer-LO signal to generate a primary-mixer-output signal; a distortion-source mixer that combines, via heterodyning, the distortion-mixer-input signal and the distortion-mixer-LO signal to generate a distortion-mixer-output signal; and an output signal coupler that combines the primary-mixer- output signal and the distortion-mixer-output signal to generate an output signal with reduced non-linearity.