Envelope Tracking Circuit Notch Filtering for RF Voltage Ripple
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Solution Overview
Problem
Existing power management circuits in 5G-NR wireless communication devices face challenges in reducing voltage ripple, which leads to undesirable errors in RF signals due to interactions between output impedance and load current, affecting battery life and performance.
Innovation Solution
Incorporating a notch circuit in the envelope tracking integrated circuit (ETIC) to resonate at a notch frequency within the modulation bandwidth of the RF signal, combined with a smaller decoupling capacitor and feedback mechanisms to reduce output impedance and voltage ripple.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a traditional power management circuit is used without a notch circuit, then the circuit structure is simple, but voltage ripple is generated due to interaction between output impedance and load current
Solution Approach 1:
A notch circuit is introduced as an intermediary component between the ETIC and power amplifier circuit. This notch circuit specifically targets and attenuates the voltage ripple caused by the interaction between output impedance and modulated load current, without affecting the overall simplicity of the power management system.
2Object-affected harmful factors
If a larger decoupling capacitor is used to reduce voltage ripple, then voltage ripple is reduced, but the battery life is reduced due to increased power consumption
Solution Approach 1:
The invention changes the approach from using a larger capacitor (increasing energy storage) to using a notch circuit (changing the frequency response characteristics). The notch circuit selectively attenuates ripple frequencies without requiring increased capacitance, thereby maintaining lower power consumption and preserving battery life.
3Object-affected harmful factors
If output impedance is reduced to minimize voltage ripple, then voltage ripple is reduced, but the circuit complexity increases
Solution Approach 1:
Rather than modifying the output impedance of the existing circuits, a dedicated notch circuit is inserted as an intermediary stage. This approach reduces voltage ripple by filtering specific frequency components without requiring redesign of the power amplifier or ETIC output stages, thus minimizing overall circuit complexity.
4Speed
If fast voltage changes are enabled between OFDM symbols to improve communication performance, then data rates are improved, but voltage ripple increases due to rapid current modulation
Solution Approach 1:
The notch circuit is designed to resonate at specific frequencies corresponding to the OFDM symbol rates and modulation bandwidths. By creating a controlled resonant response that opposes the ripple frequencies, the circuit effectively cancels out voltage ripple while allowing fast voltage transitions necessary for high-speed 5G communication.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Minimizes root-mean-square error vector magnitude (RMS EVM) and improves battery life by effectively reducing voltage ripple, enabling fast voltage changes between OFDM symbols.
Implementation Method 1
The notch circuit is configured to resonate at a notch frequency within a modulation bandwidth of the RF signal to reduce the voltage ripple
Data Source
AI summary
Voltage ripple reduction in a power management circuit is disclosed. The power management circuit includes a power amplifier circuit configured to amplify a radio frequency (RF) signal based on a modulated voltage and an envelope tracking integrated circuit (ETIC) configured to provide the modulated voltage to the power amplifier circuit via a conductive path. Notably, an output impedance presenting at an input of the power amplifier circuit can interact with a modulated load current in the power amplifier circuit to create a voltage ripple in the modulated voltage to potentially cause an undesirable error in the RF signal. In this regard, a notch circuit is provided, preferably in the ETIC, to reduce the voltage ripple within a modulation bandwidth of the RF signal. As a result, it is possible to minimize the undesirable error, such as root-mean-square (RMS) error vector magnitude (EVM), within the modulation bandwidth of the RF signal.