Envelope Tracking Voltage Transitions With Pulse-Shaped MLS Modulation
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Solution Overview
Problem
Existing multi-level switch (MLS) envelope tracking systems generate high frequency edge distortion that requires filtering, which leads to power loss and increased footprint, while maintaining fast settling times and efficiency is challenging.
Innovation Solution
Implement a multi-level switch modulator with an analog component during transitions and a digital component following transitions, combined with a pulse shaping filter to control bandwidth and reduce noise, using a multi-level switch matrix and programmable digital filters to generate a pulse train that noise shapes the envelope signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If filtering is applied to remove high frequency edge distortion in MLS envelope tracking systems, then noise levels are reduced, but power loss increases and footprint increases
Solution Approach 1:
The patent applies pulse shaping filtering to the envelope signal before it reaches the MLS modulator. This preliminary action pre-shapes the voltage transitions, reducing high frequency edge distortion at the source and thereby eliminating the need for subsequent filtering that would cause power loss.
Solution Approach 2:
The patent extracts and addresses the high frequency edge distortion problem at the envelope signal generation stage rather than dealing with it later in the power supply chain. By taking out the pulse shaping function and applying it early, the system avoids the power loss associated with filtering the power supply output.
2Object-affected harmful factors
If filtering is applied to remove high frequency edge distortion, then noise levels are reduced, but device footprint increases
Solution Approach 1:
By applying pulse shaping filtering to the envelope signal before modulation, the patent reduces high frequency content at the source. This eliminates the need for large footprint filters in the power supply path, as the distortion is already minimized by the preliminary pulse shaping action.
3Loss of time
If fast settling times are achieved in MLS envelope tracking, then efficiency is improved, but high frequency edge distortion increases
Solution Approach 1:
The patent applies pulse shaping filtering to the envelope signal before it enters the MLS modulator. This preliminary action prepares the signal with controlled rise and fall times, enabling fast settling without generating excessive high frequency edge distortion that would otherwise require filtering.
Solution Approach 2:
The patent modifies the envelope signal parameters by applying pulse shaping filtering with specific time constants. This changes the frequency content and transition characteristics of the envelope signal, allowing fast settling times while controlling high frequency edge distortion through parameter optimization.
Data Source
AI summary
Systems and methods for pulse shaping voltage transitions in envelope tracking systems are provided. In one aspect, a radio frequency module includes a power amplifier configured to receive a radio frequency input signal and a voltage source. The power amplifier further configured to amplify a radio frequency input signal using the voltage source to generate an output radio frequency signal. The radio frequency module further includes a multi-level switch modulator configured to receive an envelope signal indicative of an envelope of the radio frequency input signal and generate the voltage source based on the envelope signal at one of a plurality of discrete voltage levels. The multi-level switch modulator is further configured to generate the voltage source using an analog component during transitions between discrete voltage levels and a digital component following the transitions.