Dual-Mode APT Loop Filter for Fast Power Tracking With Low Ripple
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Solution Overview
Problem
Conventional average power tracking (APT) circuits in wireless communication devices face challenges in rapidly changing transmission power levels, leading to frequent control signal changes that introduce unwanted ripples and inefficiencies, particularly in 5G-NR systems where power changes occur quickly, affecting noise performance and efficiency.
Innovation Solution
A dual-mode APT controller that quickly adjusts the control voltage in a first mode to reach a target value and then switches to a second mode with reduced ringing, using changes in resistance and capacitance values in the loop filter, and optionally employs a pulse shaper circuit to facilitate rapid changes, ensuring a clean control voltage during transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the size of capacitors and inductors in the control circuit is reduced to enable faster control signal changes, then the speed of control signal change is improved, but unwanted ripples are introduced in the control signal
Solution Approach 1:
The patent applies dynamics by making the loop filter parameters (resistance and capacitance values) changeable over time. The loop filter transitions between different operational modes with different parameter sets: a first mode with parameters optimized for fast response and a second mode with parameters optimized for low ripple. This dynamic adjustment allows the system to achieve both fast control signal changes and clean signals at different times in the transmission cycle.
Solution Approach 2:
The patent directly applies parameter changes by modifying the resistance and capacitance values in the loop filter based on the operational phase. During certain phases, the loop filter uses parameter combinations that enable rapid control voltage transitions, while in other phases, it uses different parameter combinations that minimize ripples and ringing. This parameter switching resolves the contradiction between speed and signal quality.
2Productivity
If frequent power level changes are implemented to meet 5G-NR data rate requirements, then data transmission performance is improved, but control signal ripples and inefficiencies increase
Solution Approach 1:
The loop filter dynamically adjusts its parameters in response to power level change requirements. When frequent power changes are needed for high data rates, the loop filter switches to a mode with parameters that enable fast response. When power levels are stable, it switches to a mode that minimizes ripples, thus maintaining high productivity without continuous ripple generation.
Solution Approach 2:
The system employs periodic switching between different loop filter modes synchronized with the transmission time slots. During active transmission periods requiring power changes, the fast-response mode is activated. During idle or stable transmission periods, the low-ripple mode is activated. This periodic action allows the system to achieve high data transmission rates when needed while minimizing harmful ripples during stable operation.
3Device complexity
If a single mode is used in the APT controller, then device complexity is reduced, but the ability to achieve both fast response and clean control voltage is compromised
Solution Approach 1:
The loop filter is designed as a multi-functional component that can operate in multiple modes. By incorporating variable resistance and capacitance elements, the same loop filter structure can provide both fast-response operation and low-ripple operation. This universal design avoids the need for separate dedicated circuits for each function, thus not significantly increasing device complexity while improving control voltage quality.
Data Source
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Figure 2A~2B
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AI summary
A dual-mode average power tracking (APT) controller operates in a first mode to move the control voltage quickly without concern for ripple or ringing. When this coarse adjustment takes the control voltage to within a desired margin of a target, the controller may switch to a second mode, where the APT controller more slowly approaches the target, but has reduced ringing or ripples. The mode is changed by changing resistance and capacitance values in a loop filter within the APT circuit. In a further aspect, a pulse shaper circuit may inject a pulse to force the control voltage to change more rapidly. By switching modes in this fashion, the control voltage may quickly reach a desired target, and then remain in the second mode during a transmission time slot such that the control voltage is clean throughout.