Envelope Tracking Circuit Ripple Suppression Without Large Decoupling Caps
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Solution Overview
Problem
In 5G-NR wireless communication systems, the large source impedance presented by the envelope tracking integrated circuit (ETIC) and the conductive path can cause voltage ripple in the modulated voltage supplied to the power amplifier circuit, potentially distorting the RF signal. Conventional solutions using large decoupling capacitors increase voltage switching time and battery current drain.
Innovation Solution
The ETIC determines and applies a correction term to the modulated voltage to suppress ripple without requiring a large decoupling capacitor. This is achieved through a voltage modulation circuit and a control circuit that generate and apply the correction term based on feedback signals, thereby modifying the modulated voltage to reduce ripple.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a large decoupling capacitor is used to isolate the large source impedance, then voltage ripple is suppressed, but voltage switching time increases and battery current drain increases
Solution Approach 1:
The patent changes the impedance characteristics of the conductive path by introducing a series resonant circuit that transforms the inductive impedance into a capacitive impedance at the operating frequency. This parameter transformation allows the system to achieve low output impedance without requiring large decoupling capacitors, thereby suppressing voltage ripple while maintaining fast voltage switching and reducing battery current drain.
Solution Approach 2:
The patent introduces an intermediary series resonant circuit between the ETIC and the power amplifier circuit. This intermediary circuit acts as an impedance transformer that converts the high inductive impedance of the conductive path into a low capacitive impedance at the operating frequency, thereby suppressing voltage ripple without requiring large decoupling capacitors.
2Reliability
If a large decoupling capacitor is used to isolate the large source impedance, then voltage ripple is suppressed, but battery current drain increases
Solution Approach 1:
The patent changes the impedance characteristics of the conductive path by introducing a series resonant circuit that transforms the inductive impedance into a capacitive impedance at the operating frequency. This parameter transformation allows the system to achieve low output impedance without requiring large decoupling capacitors, thereby suppressing voltage ripple while reducing battery current drain.
3Reliability
If the source impedance is reduced to suppress voltage ripple, then signal quality is maintained, but voltage switching speed decreases
Solution Approach 1:
The patent changes the impedance characteristics by introducing a series resonant circuit that transforms the inductive impedance into a capacitive impedance at the operating frequency. This allows the system to maintain low output impedance for signal quality while the capacitive nature enables fast voltage switching speeds.
Solution Approach 2:
The patent makes the impedance dynamic by using a resonant circuit whose impedance characteristics change with frequency. The circuit is designed to provide capacitive impedance at the specific operating frequency while maintaining the ability to switch voltages rapidly, thus achieving both signal quality and fast switching speed.
Data Source
AI summary
Voltage ripple suppression in a transmission circuit is disclosed. The transmission circuit includes a power amplifier circuit coupled to an envelope tracking integrated circuit (ETIC) via a conductive path. Notably, the ETIC and the conductive path can present a large source impedance to the power amplifier circuit, which can cause a ripple in the modulated voltage received by the power amplifier circuit. In a conventional approach, the large source impedance may be isolated by a large decoupling capacitor at the expense of increased voltage switching time and battery current drain. In contrast, the ETIC disclosed herein can determine and apply a correction term to the modulated voltage generated by the ETIC to thereby suppress the ripple without requiring the large decoupling capacitor. By eliminating the large decoupling capacitor, the transmission circuit can thus achieve fast voltage switching with lower battery current drain.