Polar Transmitter Phase-to-Frequency Conversion for Cleaner Spectrum
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Solution Overview
Problem
Current polar transmission methods face challenges in optimizing the trade-off between phase signal update rate and spectrum purity, particularly in wireless communication systems like OFDM, where high peak-to-average ratios demand high linearity, leading to inefficiencies in power amplifiers.
Innovation Solution
A polar transmitter architecture that employs a phase-to-frequency converter to interpolate and down-sample phase components, allowing a lower update rate for the digitally controlled oscillator while utilizing surplus phase samples for better spectrum approximation, and includes a frequency calculator to minimize Euclidean distance and avoid local minima, with optional switching for linear approximation during sudden phase changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the phase signal update rate is increased to improve spectrum purity, then the spectrum purity is improved, but the power consumption and device complexity increase
Solution Approach 1:
The patent applies preliminary action by pre-calculating and storing phase-to-frequency conversion values in lookup tables before transmission. The frequency values are prepared in advance based on expected phase changes, allowing the system to use lower update rates while maintaining spectrum purity, thus reducing power consumption without sacrificing performance
Solution Approach 2:
The patent changes the parameter of update rate dynamically by using variable update intervals instead of fixed high-rate updates. The system adjusts the phase signal update rate based on actual signal conditions and requirements, allowing operation at lower rates when possible to reduce power consumption while maintaining adequate spectrum purity
2Measurement precision
If the phase signal update rate is increased to improve spectrum purity, then the spectrum purity is improved, but the device complexity increases
Solution Approach 1:
The patent replaces complex real-time computational mechanisms with pre-computed lookup tables. Instead of performing complex phase-to-frequency conversions in real-time at high update rates, the system uses stored tables that map phase values to frequency values, significantly reducing computational complexity while maintaining spectrum purity
Solution Approach 2:
The patent creates simplified copies of the phase-to-frequency conversion relationship in the form of lookup tables. These tables contain pre-calculated frequency values corresponding to various phase values, allowing the system to retrieve frequencies quickly without performing complex calculations, thus reducing device complexity
3Reliability
If linear operation is required for high peak-to-average ratios in OFDM, then the linearity is improved, but the power amplifier efficiency deteriorates
Solution Approach 1:
The patent segments the modulation process into separate amplitude and phase components that can be processed independently. The power amplifier handles only the phase component in a non-linear efficient manner, while amplitude control is applied separately, allowing the PA to operate efficiently without requiring linear operation for the entire signal
Solution Approach 2:
The patent applies dynamic phase adjustment through frequency offsets that are calculated and applied in real-time based on the instantaneous phase requirements. This dynamic approach allows the system to maintain signal integrity and linearity where needed while allowing the power amplifier to operate in its non-linear efficient region for the majority of the signal processing
Data Source
AI summary
The present invention relates to a polar transmission method and a polar transmitter for transmitting phase and amplitude components derived from in-phase (I) and quadrature-phase (Q) components of an input signal. A first conversion is provided for converting the in-phase (I) and quadrature-phase (Q) components into the phase and amplitude components at a first sampling rate. Additionally, a second conversion is provided for converting the phase component into a frequency component, wherein the second conversion comprises a rate conversion for converting the first sampling rate into a lower second sampling rate at which the frequency component is provided. Thereby, the second sampling rate can be used as a lower update rate in a digitally controlled oscillator in order to save power or because of speed limitations, while the surplus phase samples obtain due to the higher first sampling rate enable better approximation of the phase component after the digitally controlled oscillator. This better approximation accounts for a cleaner spectrum around the synthesized channel.