Transformer Matching Network With LC Resonance for Harmonic Suppression
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Solution Overview
Problem
Power amplifier circuits in mobile communication devices experience harmonic distortion due to nonlinear gain and phase characteristics, particularly when using differential amplifiers and transformers, which limits their ability to support multiple frequency bands and wide bandwidths.
Innovation Solution
A matching network is introduced that includes a transformer and LC series resonant circuits connected in parallel with the transformer windings, where the resonant frequencies of these circuits are aligned with harmonic frequencies to suppress harmonic output.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a differential amplifier and transformer are used for output matching, then wide frequency band matching is achieved, but harmonic output increases due to nonlinear characteristics
Solution Approach 1:
LC series resonant circuits are introduced as intermediary elements connected in parallel with the transformer windings. These resonant circuits act as frequency-selective mediators that target specific harmonic frequencies generated by the nonlinear differential amplifier, providing a controlled path for harmonic suppression without disrupting the broadband matching function of the transformer.
Solution Approach 2:
The resonant frequencies of the LC series resonant circuits are specifically designed to coincide with harmonic frequencies of the amplifier output. By adjusting the inductance and capacitance values, the circuits are tuned to create high impedance at harmonic frequencies, effectively blocking harmonic output while maintaining broadband matching capability across the operating frequency range.
2Object-generated harmful factors
If LC series resonant circuits are added to suppress harmonics, then harmonic output is reduced, but device complexity increases
Solution Approach 1:
The LC series resonant circuits are integrated into the existing transformer structure, where each winding of the transformer is equipped with a corresponding resonant circuit. This multi-functional design allows the same circuit topology to suppress multiple harmonic frequencies simultaneously by configuring different L and C values, reducing the need for separate filtering stages and minimizing overall circuit 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
The matching network effectively reduces harmonic distortion, enabling the power amplifier circuit to support multiple frequency bands and wide bandwidths while maintaining efficient operation.
Implementation Method 1
an output-side winding that is coupled to the input-side winding via an electromagnetic field
Implementation Method 2
resonant frequencies of the first LC series resonant circuit and the second LC series resonant circuit are caused to coincide with the frequency of any harmonic of a plurality of harmonics, and thus the matching network can effectively suppress a harmonic output
Data Source
AI summary
A matching network is a matching network of a power amplifier circuit that outputs a signal obtained by a differential amplifier amplifying power of a high-frequency signal. The matching network includes an input-side winding connected between differential outputs of the differential amplifier; an output-side winding that is coupled to the input-side winding via an electromagnetic field and whose one end is connected to a reference potential; a first LC series resonant circuit including a capacitive element and an inductive element connected in series with each other, and being connected in parallel with the input-side winding; and a second LC series resonant circuit including a capacitive element and an inductive element connected in series with each other, and being connected in parallel with the output-side winding.