Transformer Matching Circuit With Harmonic Rejection Filtering
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Solution Overview
Problem
Designing an impedance matching circuit that effectively rejects harmonic signals while minimizing spurious emissions is challenging, particularly in wireless communications circuitry.
Innovation Solution
A transformer-based impedance matching network with a primary coil, two secondary coils, and a capacitor configured to provide differential and single-ended ports, where the secondary coils have varying coupling coefficients and overlapping/non-overlapping configurations to reject harmonic frequencies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If a conventional impedance matching circuit is used, then power transfer is achieved, but harmonic signals leak into the antenna
Solution Approach 1:
The secondary winding is divided into two separate secondary windings (first secondary winding and second secondary winding) with different coupling coefficients to the primary winding. This segmentation allows each winding to handle different frequency components, with the capacitor selectively filtering harmonic frequencies while maintaining power transfer through the differentiated coupling paths.
Solution Approach 2:
The patent applies different coupling coefficients (k1 > k2) to different secondary windings, creating local quality differences in the magnetic coupling. The first secondary winding has stronger coupling for fundamental frequency power transfer, while the second secondary winding with weaker coupling combined with the capacitor provides harmonic rejection, achieving frequency-selective performance.
2Object-generated harmful factors
If harmonic rejection is enhanced, then spurious emission guidelines are met, but circuit complexity increases
Solution Approach 1:
The patent combines impedance matching and harmonic rejection functions into a single integrated transformer structure. The transformer provides both the impedance transformation needed for power transfer and the frequency-selective filtering for harmonic rejection, eliminating the need for separate matching and filtering circuits.
Solution Approach 2:
The transformer structure serves multiple functions simultaneously: it provides impedance matching between different stages, enables power transfer through magnetic coupling, and rejects harmonic frequencies through the capacitor-filtered secondary winding path. This multi-functionality reduces overall system 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 solution effectively filters spurious harmonic signals while maintaining optimal power transfer and minimizing in-band signal loss, enhancing wireless communications performance.
Implementation Method 1
a first secondary coil magnetically coupled to the primary coil by a first amount of coupling, and a second secondary coil magnetically coupled to the primary coil by a second amount of coupling different than the first amount of coupling
Data Source
AI summary
Wireless circuitry is provided that includes an antenna and an impedance matching circuit coupled to the antenna. The impedance matching circuit can include a primary coil, a first secondary coil magnetically coupled to the primary coil by a first amount of coupling, and a second secondary coil magnetically coupled to the primary coil by a second amount of coupling different than the first amount of coupling. The impedance matching circuit can further include a capacitor having a first terminal coupled to a node disposed between the first secondary coil and the second secondary coil and having a second terminal coupled to a ground power supply line. The capacitor can be configured as a harmonic rejection component for filtering spurious harmonic signals.