RF EVM Prediction Using Harmonic Balance Power Sweeps
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Solution Overview
Problem
Existing methods for determining error vector magnitude (EVM) in RF devices are time-consuming and sensitive to convergence issues related to power amplifier compression and saturation states.
Innovation Solution
A computer-implemented method for fast EVM prediction using a single-tone harmonic balance AM-AM/PM power sweep simulation, based on the statistics of the modulated IQ waveform, and performed within a simulator without external post-processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional transient simulation methods are used to determine EVM, then measurement precision is improved, but productivity deteriorates due to computation time taking hours
Solution Approach 1:
The patent transforms the EVM calculation from time-domain transient simulation to frequency-domain harmonic balance simulation by changing the simulation parameters and mathematical approach. This allows EVM to be calculated directly from amplitude and phase data at different power levels, bypassing the need for time-consuming transient analysis while maintaining accuracy.
Solution Approach 2:
The patent creates a simplified mathematical model that copies the essential characteristics of the complex transient simulation. By using harmonic balance to represent the amplitude and phase relationships, it produces equivalent EVM results without requiring full transient waveform analysis, significantly reducing computation time.
2Measurement precision
If transient simulation with external post-processing is used, then EVM calculation accuracy is improved, but device complexity increases due to multiple processing steps
Solution Approach 1:
The patent merges the EVM calculation process into the simulation environment itself by using harmonic balance to directly compute amplitude and phase data. This eliminates the need for separate external post-processing steps, reducing process complexity while maintaining calculation accuracy through integrated computation.
Solution Approach 2:
The patent extracts only the essential amplitude and phase information needed for EVM calculation from the simulation process, removing unnecessary transient waveform processing steps. This simplifies the overall process by focusing only on the critical parameters required for accurate EVM determination.
3Reliability
If traditional simulation methods are used, then EVM measurement reliability is improved, but loss of time increases due to convergence issues and long computation times
Solution Approach 1:
The patent replaces the mechanical transient simulation process with a frequency-domain harmonic balance approach. This substitution eliminates convergence issues associated with transient simulation while maintaining measurement reliability, as harmonic balance directly solves for steady-state amplitude and phase relationships without requiring iterative time-domain convergence.
Data Source
AI summary
Methods and systems for determining the error vector magnitudes for an RF device by fitting voltage magnitudes to a Rayleigh distribution to produce weighting parameters for an EVM calculation, either in simulation for designing the RF device or as validation measurements from a physical RF device.