Parallel RF Amplifier Chain Matching Network Biasing
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Solution Overview
Problem
Parallel RF amplifiers face challenges in coupling high and low power sides while maintaining impedance matching, leading to issues with voltage swings that degrade linearity and efficiency, particularly due to large signal voltage swings causing anomalous behavior in the low power side.
Innovation Solution
A parallel RF amplifier circuit with a chain matching network that disables either the high power side or low power side output, incorporating LPS bias circuitry to minimize the impact of negative voltage swings, including a bias impedance network or LPS bias power enable circuit to limit currents during large signal swings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a chain matching network couples the LPS output to the HPS output for improved efficiency, then efficiency at lower output power is improved, but large voltage swings from the HPS may be multiplied through the chain matching network causing negative voltage swings at the LPS collector that degrade linearity and efficiency
Solution Approach 1:
The patent introduces an intermediary coupling mechanism (the chain matching network) between the LPS and HPS amplifiers that allows efficient power transfer while isolating the LPS from harmful voltage swings. The matching network acts as a mediator that enables the LPS to drive the HPS without directly exposing the LPS to the large voltage swings generated by the HPS collector.
Solution Approach 2:
The patent extracts or removes the harmful effect (large voltage swings) from the LPS amplifier by using the chain matching network to prevent these swings from reaching the LPS collector. The LPS is effectively decoupled from the voltage swing problems of the HPS while maintaining the efficiency benefits of the coupled architecture.
2Reliability
If separate impedance matching circuitry is provided for each side and the two sides are isolated using multiple one-quarter wavelength transmission lines, then proper impedance matching is maintained, but PCB space requirements increase which may be prohibited by space constraints
Solution Approach 1:
The patent merges the impedance matching functions for both the LPS and HPS amplifiers into a single integrated chain matching network. This combined matching network performs the impedance transformation for both amplifiers simultaneously, eliminating the need for separate matching circuits and reducing the overall PCB space required while maintaining proper impedance matching for both sides.
Solution Approach 2:
The chain matching network serves multiple functions: it provides impedance matching for both the LPS and HPS amplifiers, enables efficient power transfer from LPS to HPS, and isolates the LPS from harmful voltage swings. This multi-functional design replaces what would otherwise require multiple separate circuits, reducing PCB space while maintaining all necessary functions.
3Loss of energy
If the LPS is selected for transmission at lower output power levels, then efficiency is maintained with a relatively simple architecture, but coupling the HPS to the LPS while preserving proper impedance matching for both sides becomes challenging
Solution Approach 1:
The patent implements a dynamic coupling architecture where the chain matching network enables the LPS to dynamically drive the HPS based on power level requirements. The matching network is designed to accommodate the varying operating conditions of both amplifiers, allowing efficient power transfer when the LPS is active while maintaining proper impedance matching across different power levels and operating states.
Data Source
AI summary
The present invention is a parallel RF amplifier circuit that selects between a high power side (HPS) and a low power side (LPS), depending upon output power. A chain matching network couples an LPS output to an HPS output for improved efficiency at lower output power. When the HPS is selected, the LPS output is disabled, and when the LPS is selected, the HPS output is disabled When the HPS is selected, large signal voltage swings from the collector of the HPS amplifier may be multiplied through the chain matching network, and may cause negative voltage swings at the LPS collector, which may degrade linearity and efficiency of the HPS amplifier by driving currents into the disabled LPS amplifier. Therefore, the present invention includes LPS bias circuitry to minimize impacts of negative voltage swings at the LPS output.