Broadband Impedance Matching Circuit with Variable Capacitance
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Solution Overview
Problem
Existing impedance matching circuits in mobile communication devices are limited to a single frequency band, failing to enable effective transmission and reception in multiple frequency bands due to their inability to adaptively match impedance across different frequency ranges.
Innovation Solution
An impedance matching circuit with a signal path containing a node connected by variable-capacitance capacitive elements and inductive elements, allowing for adaptive impedance matching in one frequency band while enabling reception in a second frequency band without adaptive matching, featuring a simpler design with fewer variable-impedance elements and a robust algorithm for adjustment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple variable-impedance elements are used for broadband matching, then frequency band coverage is improved, but device complexity increases
Solution Approach 1:
The circuit divides the impedance matching function into two parallel paths with different configurations. The main path uses variable-capacitance elements for adaptive matching, while the parallel path uses a fixed third inductive element for broadband reception. This segmentation reduces the need for multiple variable-impedance elements while achieving multi-band operation.
Solution Approach 2:
The third inductive element acts as an intermediary that provides an alternative signal path for the second frequency band. By introducing this intermediate element in parallel, the circuit achieves broadband coverage without requiring multiple variable-impedance elements, thus reducing overall device complexity.
2Adaptability or versatility
If variable-capacitance elements are placed throughout the circuit for adaptive matching, then impedance matching adaptability is improved, but manufacturing cost increases
Solution Approach 1:
The variable-capacitance elements are strategically placed only in the main signal path where adaptive impedance matching is required for the first frequency band. The parallel path uses fixed elements, creating local quality differences that reduce the total number of variable-impedance elements needed, thereby lowering manufacturing costs while maintaining adaptability where required.
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
Enables simultaneous transmission and reception in one frequency band and reception in another, maintaining communication quality across different frequency bands with improved insertion loss and reflection coefficient profiles, while being cost-effective and adaptable to varying antenna impedances.
Implementation Method 1
a first variable-capacitance capacitive element (KE1) connected between the signal port (SPO) and a node (K) in the signal path (SPF) and a second variable-capacitance capacitive element (KE2) connected between the node (K) and the load port (LP)
Implementation Method 2
a first inductive element (IE1) connecting the node (K) to ground (GND), a second inductive element (IE2) connecting the load port (LP) to ground (GND) and a third inductive element (IE3) connecting the signal port (SPO) and the load port (LP)
Data Source
AI summary
A broadband-operable impedance filter has capacitive elements of variable capacitance in the signal path, an inductive element in a parallel path connected in parallel to the signal path, and inductive elements in the ground path. The impedance filter allows communication in a first frequency band and the reception of HF signals in a second frequency band.