Output Matching Circuit for Broadband Second-Harmonic Suppression
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Solution Overview
Problem
Conventional power amplifiers face difficulties in impedance control of broadband second-order harmonics due to their narrow resonance width, which affects the fundamental frequency component, leading to increased complexity and cost in circuit design.
Innovation Solution
A single output matching circuit using two second-order harmonic trap circuits with different resonance frequencies, one with large inductance and small capacitance, and the other with small inductance and large capacitance, to suppress broadband second-order harmonics while minimizing the impact on the fundamental frequency component.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single output matching circuit is used for broadband range, then circuit complexity is reduced, but impedance control of broadband second-order harmonic becomes difficult
Solution Approach 1:
The patent divides the broadband second-order harmonic suppression task into two separate frequency ranges: low frequency range (first band) and high frequency range (second band). Each range is handled by a dedicated trap circuit with optimized L and C values, allowing precise impedance control in each segment while maintaining overall circuit simplicity
Solution Approach 2:
The patent applies different component characteristics to different frequency regions: the first trap circuit uses specific L1 and C1 values optimized for low frequency second-order harmonics, while the second trap circuit uses different L2 and C2 values optimized for high frequency second-order harmonics. This local optimization enables precise impedance control across the entire broadband range
2Object-generated harmful factors
If conventional second-order harmonic trap circuit with large inductance and small capacitance is used, then low frequency second-order harmonic is suppressed, but resonance width is narrow affecting fundamental frequency component
Solution Approach 1:
The patent segments the harmonic suppression function into two independent trap circuits: the first trap circuit (L1, C1) handles low frequency second-order harmonics with narrow resonance width, while the second trap circuit (L2, C2) handles high frequency second-order harmonics. This segmentation prevents the narrow resonance width from affecting the fundamental frequency component across the entire broadband range
Solution Approach 2:
The patent changes the resonance frequency parameters of the trap circuits by using different L and C values: the first trap circuit has resonance frequency matched to low frequency second-order harmonic, while the second trap circuit has resonance frequency matched to high frequency second-order harmonic. This parameter differentiation allows each circuit to suppress its target frequency without affecting the fundamental frequency
3Object-generated harmful factors
If multiple trap circuits are added to suppress broadband second-order harmonic, then harmonic suppression improves, but circuit complexity and cost increase
Solution Approach 1:
The patent segments the broadband second-order harmonic suppression into two discrete frequency bands, each handled by a simple LC trap circuit. This segmentation achieves broadband suppression functionality while maintaining each individual circuit's simplicity, avoiding the need for a single complex broadband trap circuit
Solution Approach 2:
The patent creates a universal solution for broadband second-order harmonic suppression by combining two simple trap circuits that together cover the entire broadband range. Each trap circuit is simple in structure but the combination provides universal broadband suppression capability, achieving multi-functionality without excessive complexity
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 approach enables efficient impedance control of broadband second-order harmonics, reducing the influence on the fundamental frequency and achieving a simple, low-cost power amplifier with improved power efficiency over a broad range.
Implementation Method 1
a conventional second-order harmonic trap circuit (first second-order harmonic trap circuit) in which an inductor having an inductance of 1 nH or larger is connected in series to a capacitor and a second second-order harmonic trap circuit which is composed of an inductor having an inductance of 1 nH or lower and a large capacitor and has a resonance frequency different from the first second-order harmonic trap circuit
Data Source
AI summary
A power amplifier amplifies an input signal having a fundamental frequency of which band width ranges between a first fundamental frequency F1 and a second fundamental frequency F2. The power amplifier includes a power amplifier transistor for amplifying the input signal and an output matching circuit for suppressing a harmonic component included in an output signal from the power amplifier transistor. The output matching circuit includes: a first second-order harmonic series resonant circuit including a first inductor and a first capacitor and having a frequency twice as large as F1 as a resonance frequency; and a second second-order harmonic series resonant circuit including a second inductor and a second capacitor and having a frequency twice as large as F2 as a resonance frequency.