Polar Transmitter Phase Selection for Reduced FM Range
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Solution Overview
Problem
Existing RF transmitters face inefficiencies due to IQ imbalance in direct conversion architectures, leading to cross-carrier interference and reduced Error Vector Magnitude (EVM) performance, particularly in polar transmitters.
Innovation Solution
Implement a polar transmitter with a frequency modulation (FM) reduction module that determines phase selections and generates modified phases to reduce FM range, using a cartesian to polar conversion module, a local oscillator, quadrature generator, and a power amplifier to generate RF signals with reduced FM.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If direct conversion architecture is used with separate I and Q channels, then transmitter structure is implemented, but IQ imbalance occurs causing cross-carrier interference and reduced EVM performance
Solution Approach 1:
The patent introduces an intermediary coordinate conversion process that transforms the problematic I/Q domain signals into polar coordinates (magnitude and phase). This intermediary representation eliminates the direct I/Q imbalance issue by using magnitude-phase decomposition, where the magnitude carries amplitude information and phase carries frequency information, avoiding the cross-carrier interference inherent in direct I/Q mixing architectures.
Solution Approach 2:
The patent changes the parameter representation from Cartesian coordinates (I, Q) to polar coordinates (magnitude, phase). This parameter transformation fundamentally alters how signal information is encoded: instead of using orthogonal I and Q components that suffer from imbalance, the system uses magnitude for amplitude modulation and phase for frequency modulation, thereby resolving the EVM performance degradation caused by IQ imbalance.
2Reliability
If polar transmitter is used to avoid IQ imbalance, then EVM performance is improved, but frequency modulation range increases causing efficiency loss
Solution Approach 1:
The patent extracts the frequency modulation component from the main signal path and handles it separately through phase selection. Instead of requiring the power amplifier to handle wide frequency swings through full FM, the system extracts phase information and uses a phase selector to choose from predefined phase states, significantly reducing the FM range requirement and improving PA efficiency.
Solution Approach 2:
The patent segments the phase component into discrete selectable states rather than requiring continuous phase control. By dividing the phase domain into distinct regions and selecting representative phase values from each region, the system reduces the frequency modulation range while maintaining acceptable EVM performance, thereby improving power amplifier efficiency and reducing power consumption.
3Measurement precision
If full phase range is used in polar transmitter, then signal accuracy is maintained, but FM range and power consumption increase
Solution Approach 1:
The patent applies partial action by using only the necessary portion of the full phase range. Instead of utilizing the complete 360-degree phase range, the system divides the phase domain into regions and selects representative phase values that provide sufficient signal accuracy for the application, thereby reducing the FM range and power consumption while maintaining acceptable performance through selective phase representation.
Data Source
AI summary
Systems and techniques are provided for a polar transmitter using a reduced frequency modulation (FM) range. Baseband complex data can be converted into magnitude and phase components by a cartesian-to-polar conversion module. For each respective phase of the phase component, a phase selection can be determined from a plurality of phase selection candidates and used to generate a phase select parameter and a modified phase for the respective phase. A set of clock signals includes a clock signal with a frequency controlled by the modified phase, and one or more shifted clock signals with phase shifts relative to the clock signal. An input clock signal can be selected from the set using the phase select parameter. A power amplifier can be driven by the magnitude component according to the input clock signal to generate a RF signal for transmission by the polar transmitter on a wireless medium.