Multifinger FET Power Amplifier Harmonic Impedance Control
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Solution Overview
Problem
High-frequency power amplifiers used in microwave and milliwave communication struggle to achieve low-impedance load conditions for harmonics, especially for large-gate-width transistor elements, leading to inefficiencies and distortion, particularly when trying to control input load across a wide frequency band.
Innovation Solution
Incorporating multiple series resonance circuits with different resonance frequencies corresponding to second and higher harmonics, shunt-connected between the control terminals and constant-potential ends of the transistor element, to effectively manage impedance and reduce distortion across a wide frequency band.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a large-gate-width transistor element is formed by connecting multiple gate-finger-type transistors in parallel to achieve high-power amplification, then the output power is improved, but the input and output impedances are necessarily decreased making impedance matching extremely difficult
Solution Approach 1:
The gate of the power transistor is divided into multiple fingers, with each finger having its own series resonance circuit connected between the finger gate and ground. This segmentation allows independent control of harmonic impedances for each finger while collectively achieving the desired overall impedance characteristics for high-power operation
Solution Approach 2:
Series resonance circuits are introduced as intermediary elements between the transistor gate fingers and ground. These resonance circuits act as mediators that provide the necessary low-impedance paths for harmonic frequencies without affecting the fundamental frequency impedance matching, thereby resolving the impedance conflict
2Power
If the impedance of the matching circuit load is set to an extremely low value with respect to the fundamental frequency to accommodate large-gate-width transistors, then the output power is improved, but it becomes extremely difficult to provide a low-impedance load condition for the second harmonic
Solution Approach 1:
The series resonance circuits are connected locally between each gate finger and ground, creating localized low-impedance paths specifically for harmonic frequencies at the gate node. This local quality enhancement allows harmonic control without affecting the overall low-impedance matching required for high-power operation at the fundamental frequency
Solution Approach 2:
Series resonance circuits are employed to create resonant conditions at harmonic frequencies, analogous to mechanical vibration principles. By tuning the L and C values of each series resonance circuit, the gates experience resonant grounding at specific harmonic frequencies, providing the necessary low-impedance load conditions for efficient power amplification
3Loss of energy
If a series resonance circuit is connected between the gate and ground to control the second harmonic impedance, then the efficiency is improved, but the distortion characteristics deteriorate when operating across a wide frequency band
Solution Approach 1:
Multiple series resonance circuits are distributed across the gate fingers, each capable of being tuned to different harmonic frequencies. This segmentation enables the system to maintain efficient harmonic control across a wide frequency band by appropriately configuring the resonance frequencies of individual circuits
Solution Approach 2:
The series resonance circuits are designed to serve multiple functions: controlling second harmonics, controlling third harmonics, and providing adaptive impedance transformation. By configuring the L and C values appropriately, the same circuit structure can address multiple harmonic control requirements across different operating frequencies
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
This configuration allows for stable and improved distortion characteristics throughout a wide frequency band by controlling high-frequency loads to low impedance, enhancing the operating efficiency and output of the power amplifier.
Implementation Method 1
a plurality of series resonance circuits, shunt-connected between control terminals of the respective unit transistors and constant-potential ends
Data Source
AI summary
A high-frequency power amplifier has an FET element having a unit FETs in multifinger form, and having a gate pad through which a signal is input, a source pad that is grounded, and a drain pad through which a signal is output. A high-frequency processing circuit includes series resonance circuits shunt-connected between the gate pads of the unit FETs and grounding ends. Two of the series resonance circuits have respective different resonance frequencies which correspond to second and higher harmonics of a frequency included in the operating frequency band of the FET element.