RF Amplifier Impedance Matching Using Output Lead Inductance
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Solution Overview
Problem
High power radiofrequency amplifiers, particularly Doherty amplifiers, exhibit significant memory effects at frequencies above 1 GHz due to parasitic inductances between the power supply and the amplifier, leading to distortion and inefficiencies, which are exacerbated by the need for high inductances and additional components within the device package.
Innovation Solution
A radiofrequency amplifier design featuring a series high pass network on the active device and a low pass network with inductive shunt connections, where the second output lead forms part of the inductance, reducing the need for high inductances within the package and allowing for wideband impedance transformation without phase shift, thereby minimizing memory effects and package size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high inductances are used inside the device package to achieve impedance matching, then the impedance matching is improved, but the package size increases and losses increase
Solution Approach 1:
The patent moves the inductance function from the internal package structure to the external lead structure. The second output lead is designed to provide the required inductance value, effectively shifting the inductance provision to a different spatial dimension (outside the package) while maintaining the electrical function inside the package.
Solution Approach 2:
The patent extracts the inductance function from the internal package components and assigns it to the external output lead. This separation allows the package itself to be more compact while the lead structure provides the necessary inductance value for impedance matching.
2Reliability
If high inductances are used inside the device package, then the impedance matching is improved, but the losses within the package increase
Solution Approach 1:
The patent extracts the inductance function from internal package components where it would cause losses, and relocates it to the external output lead structure. This eliminates the source of losses while preserving the impedance matching function.
3Reliability
If additional components are added inside the device package to achieve impedance matching, then the impedance matching is improved, but the device complexity increases
Solution Approach 1:
The patent makes the second output lead serve multiple functions: it provides both the electrical connection and the required inductance value for impedance matching. This eliminates the need for separate inductance components, reducing device complexity while maintaining impedance matching performance.
Solution Approach 2:
The output lead structure itself provides the inductance function that would otherwise require additional components. The lead's physical dimensions and geometry are designed to inherently provide the necessary inductance value, making the system self-sufficient.
4Speed
If the amplifier operates at frequencies above 1 GHz with conventional designs, then the amplifier functionality is maintained, but memory effects and distortion increase
Solution Approach 1:
The patent changes the inductance parameter distribution by using the output lead's physical dimensions to provide the required inductance value. This parameter adjustment reduces parasitic effects and memory effects, enabling high-frequency operation with improved signal quality and reduced distortion.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution reduces losses and package size, enhances bandwidth, and improves the amplifier's compactness and efficiency by eliminating the need for high-value shunt inductances, allowing for increased applicability in high power amplifiers with reduced memory effects and phase rotation.
Implementation Method 1
This avoids any detrimental impedance inversion between the channel (the drain or collector) of the active device and the discrete power device output
Implementation Method 2
Memory effects are particularly problematic at frequencies of 1 GHz and above. These memory effects result from parasitic inductances between the power supply and the amplifier
Data Source
AI summary
The invention relates to high power radiofrequency amplifiers, in particular to amplifiers having output impedance matching networks, exemplary embodiments of which include a radiofrequency amplifier having an active device mounted on a substrate within a device package, the amplifier having an output impedance matching network comprising a high pass network provided at least partly on the active device and a low pass network having a first inductive shunt connection between an output of the active device and a first output lead and a second inductive shunt connection between the output of the active device and a second output lead, wherein part of the second output lead forms an inductance contributing to the inductance of the low pass network.