ET Equalizer Circuit for Wideband Voltage Tracking Accuracy
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Solution Overview
Problem
In mobile communication devices, envelope tracking (ET) systems experience distortions in high modulation bandwidth scenarios due to inherent impedance and trace inductance, leading to misalignment of time-variant voltage envelopes with RF signal power envelopes, causing unwanted distortions such as amplitude clipping.
Innovation Solution
An equalizer circuit is introduced in the power management circuit, utilizing a second-order complex-zero transfer function combined with a real-zero term to offset the inherent impedance and trace inductance, thereby equalizing the differential target voltage and reducing distortions in the ET voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If envelope tracking voltage is generated to track high modulation bandwidth RF signals, then data rate performance is improved, but voltage distortions increase due to trace inductance and load impedance
Solution Approach 1:
The equalizer circuit performs preliminary compensation of voltage distortions before the voltage amplifier generates the envelope tracking voltage. By pre-equalizing the differential target voltage to counteract the effects of trace inductance and load impedance, the system ensures accurate voltage tracking throughout the high modulation bandwidth range without sacrificing data rate performance
Solution Approach 2:
The equalizer circuit acts as an intermediary component between the voltage amplifier and the power amplifier. It processes the differential target voltage to compensate for distortions that would otherwise be introduced by trace inductance and load impedance, thereby maintaining voltage tracking accuracy while enabling high data rate transmission
2Use of energy by moving object
If time-variant ET voltage tracks high modulation bandwidth power envelope, then amplifier efficiency is improved, but distortions such as amplitude clipping increase due to trace inductance
Solution Approach 1:
The equalizer circuit performs preliminary compensation of voltage distortions before the voltage amplifier generates the envelope tracking voltage. By pre-equalizing the differential target voltage to counteract the effects of trace inductance and load impedance, the system ensures accurate voltage tracking throughout the high modulation bandwidth range without sacrificing data rate performance
Solution Approach 2:
The equalizer circuit converts the harmful effects of trace inductance and load impedance into beneficial compensation. By designing the equalizer with transfer functions that have zeros corresponding to the poles introduced by trace inductance and load impedance, the circuit transforms these parasitic elements from sources of distortion into opportunities for precise compensation, maintaining both amplifier efficiency and signal fidelity
Data Source
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AI summary
An equalizer circuit and related power management circuit are provided. The power management circuit includes a voltage amplifier circuit configured to generate an envelope tracking (ET) voltage based on a differential target voltage and provide the ET voltage to a power amplifier circuit(s) via a signal path for amplifying a radio frequency signal(s). An equalizer circuit is provided in the power management circuit to equalize the differential target voltage prior to generating the ET voltage. Specifically, the equalizer circuit is configured to provide a transfer function including a second-order complex-zero term and a real-zero term for offsetting a transfer function of an inherent trace inductance of the signal path and an inherent impedance of the voltage amplifier circuit. By employing the second-order transfer function with the real-zero term, it is possible to reduce distortion in the ET voltage, especially when the RF signal(s) is modulated in a wide modulation bandwidth.