Pre-Distortion Signal Processing for CIM3 Reduction
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Solution Overview
Problem
In wireless communication systems, the non-linear characteristics of transmitters cause distortion, particularly CIM3 (Counter 3rd order intermodulation) folding back distortion, which affects transmission quality and adjacent channels, especially when data rate is reduced.
Innovation Solution
A pre-distortion method using a signal transmitting apparatus with a processing device that generates pre-distortion signals based on specific combinations of in-phase and quadrature digital signals, combined with compensation coefficients and phases, to reduce CIM3 signal power by pre-distorting the signals before amplification.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the power and bandwidth of wireless signal are increased to extend transmission range and improve transmission rate, then transmission performance is improved, but non-linear distortion including CIM3 folding back distortion becomes more severe
Solution Approach 1:
The patent applies pre-distortion technology that performs preliminary action by pre-compensating the transmitted signal with inverse non-linear characteristics before transmission. The processing device generates pre-distortion signals that counteract the expected non-linear distortion from passive mixers and amplifiers, so that after passing through these non-linear components, the signal maintains low distortion even at high power and bandwidth levels.
2Loss of energy
If data rate is reduced and only partial resource blocks are used, then energy consumption is reduced, but CIM3 effect becomes more severe and affects adjacent channels
Solution Approach 1:
The pre-distortion mechanism performs preliminary compensation specifically tailored to the active resource blocks. The processing device generates pre-distortion signals based on the actual transmission configuration, ensuring that even when only partial resource blocks are used, the CIM3 distortion is pre-compensated to prevent interference to adjacent channels while maintaining energy efficiency.
3Object-generated harmful factors
If pre-distortion signals are generated using complex combinations of in-phase and quadrature digital signals, then CIM3 distortion is reduced, but device complexity increases
Solution Approach 1:
The patent segments the pre-distortion process into distinct functional modules: a first converting device for generating pre-distorted in-phase signals, a second converting device for quadrature signals, and a processing device for generating pre-distortion signals. This segmentation allows each module to perform a specific function, making the complex pre-distortion process more manageable and implementable while effectively reducing CIM3 distortion.
Data Source
AI summary
A signal transmitting apparatus includes: a first converting device arranged to generate an up-converted in-phase signal according to an in-phase digital signal and a first pre-distortion signal; a second converting device arranged to generate an up-converted quadrature signal according to a quadrature digital signal and a second pre-distortion signal; an amplifying device arranged to generate an amplified signal according to the up-converted in-phase signal and the up-converted quadrature signal; and a processing device arranged to generate the first pre-distortion signal according to a first combination signal combined by a cube of the in-phase digital signal and a multiplication of the in-phase digital signal and a square of the quadrature digital signal, and to generate the second pre-distortion signal according to a second combination signal combined by a cube of the quadrature digital signal and a multiplication of the quadrature digital signal and a square of the in-phase digital signal.