ET Equalizer Circuit for Wideband RF Voltage Distortion
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Solution Overview
Problem
In mobile communication devices, envelope tracking (ET) systems experience distortions in high modulation bandwidth RF signals due to trace inductance and load impedance, leading to unwanted distortions in the ET voltage, which compromises power amplifier efficiency and user experience.
Innovation Solution
An equalizer circuit is introduced in the power management circuit to equalize the differential target voltage using a second-order complex-zero transfer function and a real-zero term, offsetting the inherent trace inductance and impedance, thereby reducing distortion in the ET voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If envelope tracking voltage is generated to track high modulation bandwidth RF signals, then power amplifier efficiency is improved, but voltage distortion occurs due to trace inductance and load impedance
Solution Approach 1:
The equalizer circuit pre-compensates the target voltage before it is applied to the power amplifier. By anticipating and correcting for the distorting effects of trace inductance and load impedance in advance, the system ensures that the voltage delivered to the power amplifier accurately tracks the RF signal envelope, thereby maintaining both efficiency and voltage accuracy
Solution Approach 2:
The equalizer circuit acts as an intermediary between the voltage source and the power amplifier. It introduces compensating impedance elements that counterbalance the harmful effects of trace inductance and load impedance, thereby mediating the interaction and preventing voltage distortion while preserving power amplifier efficiency
2Power
If higher output power is used to achieve higher data rates, then wireless communication performance is improved, but power consumption and thermal dissipation increase
Solution Approach 1:
The system dynamically adjusts the supply voltage to the power amplifier to match the instantaneous envelope of the RF signal. By changing the voltage parameter in real-time rather than maintaining a constant high voltage, the system enables high output power when needed while reducing power consumption during lower signal conditions, thereby improving overall energy efficiency
Data Source
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.