Envelope Modulator Feedback Pulse Width Control for RF Linearity
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Solution Overview
Problem
Conventional envelope modulators in polar transmitters face limitations in flexibility, coding efficiency, and linearity, particularly due to fixed pulse widths and inability to compensate for processing errors and disturbances, which affect signal processing in RF communication systems.
Innovation Solution
An envelope modulator that determines pulse width based on both the amplitude signal and a feedback signal, allowing for varying pulse widths and dynamic error compensation, thereby enhancing linearity and coding efficiency by using a combination of amplitude and feedback signal processing, including an arcsin mapping function and a feedback loop for error correction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If fixed pulse width is used in conventional envelope modulators, then device complexity is reduced, but linearity and coding efficiency deteriorate
Solution Approach 1:
The patent implements dynamic pulse width adjustment by introducing a feedback signal that modifies the pulse width based on the amplitude signal characteristics. The envelope modulator transitions from fixed pulse width to variable pulse width operation, where the pulse width is dynamically adapted to maintain linearity and improve coding efficiency without excessive complexity increase
Solution Approach 2:
A feedback signal is introduced to the envelope modulator to compensate for processing errors and disturbances. The feedback mechanism enables the system to adjust pulse width dynamically based on actual signal conditions, improving linearity and coding efficiency while maintaining manageable device complexity through error correction
2Ease of operation
If fixed pulse width is used in conventional envelope modulators, then ease of operation is improved, but coding efficiency deteriorates
Solution Approach 1:
The system dynamically adjusts pulse width based on amplitude signal characteristics and feedback, enabling optimized coding efficiency for different signal conditions. This dynamic adaptation maintains ease of operation by automating the optimization process while significantly improving coding efficiency through variable pulse width modulation
3Device complexity
If processing errors are not compensated, then device complexity is reduced, but linearity deteriorates
Solution Approach 1:
The patent implements a feedback loop that detects processing errors and disturbances in the signal path. The feedback signal is used to generate corrective adjustments to the pulse width, compensating for non-linearities and processing errors. This feedback mechanism improves linearity while keeping device complexity manageable through efficient error correction algorithms
Data Source
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Figure 2c~3b
Figure 4a~4c
AI summary
The present invention relates to an envelope modulator (100, 100a, 100b, 100c), particularly for a polar transmitter (1000), wherein said envelope modulator (100) is configured to receive an amplitude signal (A, u) and a phase-modulated carrier signal (f_c_mod, fcm'), and to output for at least one clock cycle (T_c) of said phase-modulated carrier signal (f_c_mod, fcm') an output pulse (p1, p2, p3), wherein a pulse width of said output pulse (p1, p2, p3) is determined depending on said amplitude signal (A) and on a feedback signal (fb) derived from said amplitude signal (A).