Envelope Tracking RF Amplifier Layout to Cut Packaging Parasitics
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Solution Overview
Problem
Conventional RF power amplifiers using envelope tracking face challenges in achieving good overall performance due to parasitics from transistor package housings, which affect bandwidth and efficiency, especially in multi-stage amplifiers where delay compensation of the envelope tracking bias voltage and RF signal is difficult to achieve across separate stages.
Innovation Solution
The solution involves unpackaging the RF power transistor unit and envelope tracking modulator, arranging them on a common circuit board, and using a single, unbranched supply voltage line to minimize delay differences between stages, thereby reducing parasitics and improving positioning and size efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the RF power transistor unit and envelope tracking modulator are packaged separately in conventional housings, then the components can be manufactured and assembled using standard packaging processes, but parasitic capacitances and inductances are introduced that degrade RF power amplifier bandwidth and envelope tracking system bandwidth
Solution Approach 1:
The patent merges the RF power transistor unit and envelope tracking modulator into a single integrated package housing. This integration eliminates the need for external bonding wires and interconnect structures between separate housings, thereby removing the parasitic capacitances and inductances that would otherwise degrade RF bandwidth and envelope tracking performance. The merged design allows direct connection of the modulator output to the power amplifier input without intermediate packaging parasitics.
Solution Approach 2:
The patent extracts and eliminates the harmful packaging structures (separate housings, bonding wires, and interconnect elements) that introduce parasitics. By removing these conventional packaging elements and replacing them with an integrated monolithic structure, the design eliminates the source of bandwidth degradation while maintaining manufacturability through advanced semiconductor fabrication processes.
2Device complexity
If a single envelope tracking modulator is used for multi-stage RF power amplifiers, then the system complexity is reduced, but it becomes difficult to guarantee that the delay between the modulated supply voltage and the RF signal is in phase for both the final stage and preceding stages
Solution Approach 1:
By merging the envelope tracking modulator and RF power transistor unit into a single integrated package, the patent creates a unified structure where the modulator and power amplifier stages are physically co-located. This integration allows for precise control and matching of signal paths, enabling phase alignment between the modulated supply voltage and RF signal across multiple amplifier stages within the same package, thereby resolving the phase synchronization issue while maintaining single-modulator simplicity.
3Ease of repair
If separate packaged modules are used for the envelope tracking modulator and RF power transistor unit, then component replacement and repair are easier, but the positioning accuracy between modules deteriorates and overall size increases
Solution Approach 1:
The patent combines the modulator and power transistor unit into a single integrated package, eliminating positioning accuracy issues by making the components physically unified rather than separate modules. While this reduces replaceability of individual components, it achieves superior overall performance through the elimination of inter-module parasitics and improved electrical connectivity, which is the primary design goal for RF envelope tracking systems.
Data Source
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AI summary
The present invention relates to an envelope tracking RF power amplifier unit (80), comprising: an RF power transistor unit (20) for amplification of an RF input signal (RF in), and an envelope tracking modulator (100) for feeding a supply voltage (Drain supply) to the RF power transistor unit (20), wherein the RF power transistor unit (20), preferably also the envelope tracking modulator (100), is unpackaged, and wherein the envelope tracking modulator (100) and the RF power transistor unit (20) are arranged on a common circuit board, in particular on an common RF line card (120). The invention also relates to a base station (300) comprising at least one envelope tracking RF power amplifier unit (80), to a communication network (400) comprising at least one such RF base station, and to a method for power amplification of an RF input signal (RF in). The benefit of this approach is that parasitics caused by a packaged RF power amplifier circuit may be dispensed with, thus allowing to improve overall envelope tracking performance and, possibly, to achieve an improved feeding of a driver transistor stage and of a final transistor stage of the RF power transistor unit by the same modulator (100).