Frequency Domain Error Compensation for IQ Modulators
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Direct conversion IQ-modulators in wireless communication transmitters generate unwanted spectrum components and DC offset, leading to signal-to-noise ratio degradation due to distortion and imbalance in quadrature channels, which existing methods fail to effectively compensate for.
Innovation Solution
Processing base band signals in the frequency domain to determine transfer functions for In-phase and Quadrature channels, calculating correction coefficients to modify the signal and compensate for frequency-dependent distortion, thereby suppressing LO leakage and image frequency components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If direct conversion IQ-modulators are used to convert base band signals to radio frequency, then integration with circuits is improved, but unwanted spectrum components and DC offset are generated causing signal-to-noise ratio degradation
Solution Approach 1:
The patent applies preliminary action by pre-calculating and storing compensation coefficients in a lookup table before signal transmission. These coefficients are used to compensate for distortion and LO leakage in advance, resolving the contradiction by preparing correction data beforehand rather than attempting real-time correction of the harmful effects
Solution Approach 2:
The patent converts the harmful distortion and LO leakage effects into beneficial information by measuring them and using them to generate compensation coefficients. The unwanted spectrum components and DC offset characteristics are transformed into useful correction data that improves signal quality, directly addressing the signal-to-noise ratio degradation while maintaining integration benefits
2Object-affected harmful factors
If frequency domain processing is applied to compensate for distortion, then signal-to-noise ratio is improved, but computational complexity increases
Solution Approach 1:
The patent performs frequency domain processing and compensation coefficient calculation in advance, storing results in lookup tables. During actual signal transmission, only table lookup and simple multiplication are required, dramatically reducing real-time computational complexity while maintaining the signal-to-noise ratio improvement benefits
Solution Approach 2:
The patent introduces lookup tables as an intermediary structure that stores pre-computed compensation data. This intermediary eliminates the need for complex real-time frequency domain processing by providing pre-prepared correction coefficients, resolving the contradiction between signal quality improvement and computational complexity
Data Source
AI summary
The invention is related to an apparatus which includes a first generator configured to generate transfer function values of in-phase and quadrature channels. The apparatus further includes a determiner configured to determine compensation coefficients on the basis of the generated transfer function values of in-phase and quadrature channels. The apparatus further includes a second generator configured to generate compensated frequency domain symbols for at least one frequency pair by using the compensation coefficients.