Circulator Impedance Matching for Front End Circuit Signal Loss
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current front end circuits for small-sized mobile communication devices require matching circuits to match the low radiation resistance of small antennas to standard 50Ω circuits, leading to signal loss and band narrowing, and necessitate large variable capacitive elements, increasing circuit size and complexity.
Innovation Solution
A front end circuit utilizing a circulator with impedance settings between ports allows impedance matching between the antenna and the circuit without a separate matching circuit, using different coil turns, diameters, or conductor patterns to set the impedance of the second port to a value different from the first and third ports, and incorporating filters for enhanced isolation and high-band signal support.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a matching circuit is added to match the low radiation resistance of small antennas to 50Ω circuits, then impedance matching is improved, but signal loss increases and band width narrows
Solution Approach 1:
The patent combines the circulator with an impedance transformation function by setting different impedance values at different ports. The circulator is merged with the impedance matching function, eliminating the need for a separate matching circuit and reducing signal loss while maintaining matching performance.
Solution Approach 2:
The circulator is designed to perform multiple functions: signal isolation in addition to impedance transformation. By setting the second port impedance differently from the first and third ports, the circulator simultaneously achieves signal directionality and impedance matching, reducing overall system complexity and component count.
2Reliability
If a variable capacitive element is added to suppress impedance change, then impedance stability is improved, but circuit size and complexity increase
Solution Approach 1:
The patent merges the impedance stabilization function into the circulator structure itself by configuring different impedance values at different ports. This eliminates the need for separate variable capacitive elements and their associated control circuits, thereby reducing circuit complexity while maintaining impedance stability.
Solution Approach 2:
The patent changes the impedance parameter distribution across the circulator ports, specifically setting the second port impedance to a value different from the first and third ports. This parameter configuration enables the circulator to inherently provide impedance transformation and stabilization without requiring additional active components.
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 enables impedance matching without a matching circuit, providing a broadband antenna, simplifying the circuit, and reducing the size of the communication apparatus while minimizing signal loss and maintaining low-band performance.
Implementation Method 1
The circulator can include a first coil connected to the first port, a second coil connected to the second port, and a third coil connected to the third port. The number of turns of the second coil can be different from the number of turns of the first coil and the third coil.
Data Source
AI summary
A front end circuit includes a circulator having a first port into which a transmission signal is input, a second port into/from which a transmission/reception signal is input/output, and a third port from which a reception signal is output. The impedance of the second port of the circulator is set to a value different from the impedance value of the first port and the third port. With his configuration, the narrowing of a frequency band and the increase in loss, which occur when an impedance matching circuit is additionally provided, are prevented.