Digital Transmitter I/Q Assignment With Phase-Preserving Clipping
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Solution Overview
Problem
Conventional RF digital transmitters and power amplifiers with static I and Q assignments suffer from limited output power due to separate clipping of in-phase (I) and quadrature (Q) signal magnitudes, which restricts transmission range and introduces phase distortion.
Innovation Solution
A dynamic assignment scheme with phase-preserving clipping technique, where I and Q magnitudes are scaled equally and clipped together, allowing each RF cell to transmit either I or Q signals based on the summation of I and Q samples, thereby increasing output power and maintaining signal phase integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If separate clipping of I and Q signal magnitudes is applied, then device complexity is reduced, but output power is limited and phase distortion occurs
Solution Approach 1:
The patent merges the separate clipping operations of I and Q signals into a single unified clipping operation. By computing a combined magnitude M = sqrt(I² + Q²) and applying a single threshold comparison, the system achieves phase-preserving clipping that maximizes output power without requiring complex separate clipping circuits for each signal component.
Solution Approach 2:
The patent changes the clipping parameter from separate I and Q thresholds to a unified magnitude threshold. By transforming the clipping decision from individual signal components to the overall signal magnitude, the system achieves higher output power (3 dB improvement) while maintaining phase integrity through scaled clipping of I and Q components based on the same threshold ratio.
2Length of moving object
If static I and Q assignment is used, then device complexity is reduced, but transmission range is limited
Solution Approach 1:
The patent implements dynamic I and Q cell assignment based on the instantaneous signal magnitude M = sqrt(I² + Q²). Instead of fixed assignments, the system dynamically determines which unary cells are active for I and Q components by comparing M against thresholds, allowing optimal power utilization across varying signal conditions and extending transmission range.
Solution Approach 2:
The patent changes the assignment parameter from static cell allocation to dynamic threshold-based allocation. By using the signal magnitude M and its relationship to reference values (MREF, MREF/2, MREF/4) to dynamically assign unary cells, the system achieves higher effective output power and extended transmission range without significantly increasing device complexity.
3Manufacturing precision
If I and Q unary cells are equally divided, then device complexity is reduced, but phase integrity is compromised
Solution Approach 1:
The patent changes the clipping operation from separate I and Q magnitude clipping to unified magnitude-based clipping. By computing M = sqrt(I² + Q²) and using the ratio M/MREF to determine scaled clipping factors for both I and Q components, the system preserves the phase relationship between I and Q signals while achieving higher output power and better phase precision.
Data Source
AI summary
A transmitter includes a first digital-to-analog converter (DAC) circuit consisting of a first set of unary cells to mix a first set of digital input data with a first clock signal. A second DAC circuit includes a second set of unary cells to mix a second set of digital input data with a second clock signal. A third circuit provides signals to the first DAC circuit and the second DAC circuit to implement an assignment scheme to assign either an in-phase (I) component or a quadrature (Q) component to the first set of unary cells and the second set of unary cells. Based on the assignment scheme, the first set of digital input data include I-data and Q-data, and the second set of digital input data include I-data and Q-data.