Equalizer Circuit for Wideband Envelope Tracking Linearity
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Envelope tracking (ET) voltage in power amplifiers for mobile communication devices is susceptible to distortions caused by trace inductance and load impedance, especially at high modulation bandwidths, leading to unwanted distortions in RF signals.
Innovation Solution
An equalizer circuit is introduced in the power management circuit to equalize the differential target voltage using a transfer function with a second-order complex-zero term 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
1Productivity
If envelope tracking voltage is generated to track the time-variant power envelope of high modulation bandwidth RF signals, then data rates are improved, but voltage distortions occur 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 power envelope, thereby maintaining high data rates without voltage distortions
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 trace inductance and load impedance, thereby mediating the interaction and preventing voltage distortions while maintaining high-frequency performance for improved data rates
2Device complexity
If trace inductance and load impedance are present in the signal path, then circuit simplicity is maintained, but voltage distortions and amplitude clipping occur
Solution Approach 1:
The equalizer circuit serves as an intermediary component that compensates for the distorting effects of trace inductance and load impedance. By introducing equalizing impedance elements in parallel with the signal path, it counterbalances the harmful effects without requiring complete redesign of the existing circuit structure, thus maintaining relative simplicity while improving signal fidelity
Solution Approach 2:
The equalizer circuit modifies the impedance parameters of the signal path by introducing compensating elements. This changes the overall transfer function of the circuit to counteract the distorting effects of trace inductance and load impedance, thereby improving voltage accuracy and signal fidelity while maintaining practical circuit implementation
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.