Digital RF Modulator Delay Compensation for Phase Linearity
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Solution Overview
Problem
Conventional digital wireless transmitters and digital power amplifiers suffer from phase distortion due to non-ideal switches with finite impedance, leading to non-linear amplitude and phase distortion, which affects the efficiency and linearity of RF signal transmission, especially in multi-band and multi-standard applications like 5G and 802.11ax.
Innovation Solution
The introduction of a delay circuit in the RF signal path before the digital-to-RF modulator, where the duration of the delay is adjusted based on the digital input code to cancel out phase distortion, using a combination of delay cells and a controller to implement the necessary delay, allowing for on-chip correction without complex signal processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If conventional digital wireless transmitters use non-ideal switches with finite impedance, then device complexity is reduced, but phase linearity deteriorates causing non-linear amplitude and phase distortion
Solution Approach 1:
The patent applies preliminary action by measuring the phase distortion characteristics of each switch before operation and storing compensation values in lookup tables. During transmission, the pre-computed delay values are retrieved and applied to compensate for phase distortion, eliminating the need for real-time complex calculations while maintaining phase linearity.
Solution Approach 2:
The patent changes the parameter of signal delay based on the digital input code and switch state. By dynamically adjusting the delay amount according to the specific switch configuration and input signal, the system compensates for phase distortion without requiring complex real-time processing, thus maintaining both simplicity and accuracy.
2Use of energy by moving object
If digital transmitters integrate all blocks in a single block to reduce area and power, then energy efficiency improves, but phase distortion increases due to non-ideal switches
Solution Approach 1:
The patent converts the harmful phase distortion caused by non-ideal switches into a beneficial compensation mechanism. By measuring and characterizing the distortion, then applying pre-computed delay compensation, the system transforms the inherent limitation of integrated switches into an opportunity for optimized performance without additional power overhead.
Solution Approach 2:
The integrated transmitter performs self-characterization by measuring its own phase distortion properties during manufacturing or initialization. The measured data is stored in lookup tables, enabling the system to self-compensate for its inherent non-idealities without requiring external calibration equipment or complex real-time processing.
3Manufacturing precision
If delay compensation is implemented dynamically based on digital input code, then phase linearity improves, but device complexity increases due to additional delay circuits and control logic
Solution Approach 1:
The patent uses preliminary action by pre-computing and storing delay compensation values in lookup tables during manufacturing or initialization. The measured phase distortion characteristics are converted into lookup tables that map digital input codes to appropriate delay values, eliminating the need for complex real-time calculations and reducing runtime complexity.
Solution Approach 2:
The patent introduces lookup tables as an intermediary between the digital input code and the delay compensation mechanism. The lookup tables serve as a pre-computed reference that simplifies the control logic, allowing the system to retrieve appropriate delay values through simple address lookup rather than complex real-time computation.
4Productivity
If high linearity is achieved through conventional methods to support high data throughput, then productivity improves, but energy consumption increases due to multiple analog/RF blocks
Solution Approach 1:
The patent replaces complex analog/RF signal processing with digital signal processing and lookup table-based compensation. By performing phase distortion correction in the digital domain using pre-computed values, the system eliminates the need for multiple power-hungry analog blocks while maintaining the linearity required for high data throughput applications.
Data Source
AI summary
A technique is presented for correcting phase distortion in a digital wireless transmitter. The technique includes: receiving an RF signal in an analog domain by a digital-to-RF modulator; amplitude modulating, the RF signal in accordance with a digital input code; and introducing delay in a signal path traversed by the RF signal before the digital-to-RF modulator using a delay circuit. The duration of the delay depends upon the value of the digital input code and substantially cancels out the phase distortion introduced by the digital wireless transmitter.