Distributed Envelope Tracking Amplifier for RF Distortion Control
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Solution Overview
Problem
Envelope tracking (ET) power amplifiers in mobile communication devices face distortion issues due to trace inductance, especially when handling high modulation bandwidth RF signals, leading to misalignment of voltage and power envelopes and resulting in unwanted distortions such as amplitude clipping.
Innovation Solution
A distributed ET integrated circuit (DETIC) is used to generate a distributed ET voltage, which is selectively provided to either a higher-bandwidth or lower-bandwidth amplifier circuit, depending on which is activated, reducing distortion by minimizing trace inductance and isolating capacitive impedance between the circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single ET voltage source is used for both HB and LB amplifier circuits, then device complexity is reduced, but trace inductance causes voltage distortion and misalignment with power envelope
Solution Approach 1:
The patent divides the single ET voltage source into two separate distributed ET voltage sources, one dedicated to the HB amplifier circuit and another to the LB amplifier circuit. This segmentation eliminates the trace inductance problem by providing each amplifier with its own locally-generated voltage, ensuring precise voltage envelope alignment with the power envelope for each respective amplifier.
Solution Approach 2:
The patent implements local ET voltage generation by placing distributed ET voltage circuits in close proximity to each amplifier circuit (HB and LB). This local quality approach ensures that each amplifier receives a voltage envelope that is precisely aligned with its specific power envelope requirements, rather than sharing a compromised distant voltage source.
2Manufacturing precision
If separate distributed ET voltage circuits are provided for HB and LB amplifier circuits, then voltage envelope alignment is improved, but device footprint increases
Solution Approach 1:
The patent merges the control functions of the distributed ET voltage circuits into a unified distributed controller that manages both HB and LB amplifier circuits. This consolidation allows the system to achieve precise local voltage envelope alignment for each amplifier while sharing control logic and reducing overall device footprint through functional integration.
Solution Approach 2:
The distributed controller is designed with multi-functionality to manage both HB and LB amplifier circuits, generating appropriate ET voltages for each based on their respective power envelopes. This universal control approach eliminates the need for separate independent control circuits, thereby reducing the overall device area while maintaining precise voltage alignment for both amplifiers.
3Manufacturing precision
If trace length is reduced to minimize inductance, then voltage distortion is reduced, but device area increases
Solution Approach 1:
The patent segments the voltage delivery path by placing distributed ET voltage circuits immediately adjacent to each amplifier circuit they serve. This segmentation creates extremely short local connection traces that minimize inductance and voltage distortion, while the modular architecture prevents these local circuits from significantly increasing overall device footprint.
Data Source
AI summary
An envelope tracking (ET) amplifier apparatus is provided. The ET amplifier apparatus includes a distributed ET integrated circuit (DETIC) configured to generate a distributed ET voltage. The DETIC may be coupled to a higher-bandwidth (HB) amplifier circuit and a lower-bandwidth (LB) amplifier circuit configured to amplify an HB radio frequency (RF) signal and an LB RF signal, respectively. In examples discussed herein, the DETIC may be configured to selectively provide the ET voltage to one of the HB amplifier circuit and the LB amplifier circuit, depending on which of the HB amplifier circuit and the LB amplifier circuit is activated. By providing the DETIC in proximity to the HB amplifier circuit and the LB amplifier circuit, it may be possible to reduce potential distortion to the HB RF signal and the LB RF signal, without significantly increasing footprint of the ET amplifier apparatus.