Coupler Circuit Phase Compensation for RF Impedance Mismatch
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Solution Overview
Problem
Existing coupler circuits in RF front-end modules face challenges in maintaining accurate output power detection due to variations in antenna impedance, leading to errors from reflected waves, and struggle with size reduction and frequency band changes, which affect directivity and coupling accuracy.
Innovation Solution
A coupler circuit with a phase compensation function, incorporating a coupling adjusting circuit that includes impedance circuits with resistors and capacitors to reduce phase differences between coupling and isolation ports, maintaining constant coupling across frequency bands and enhancing directivity by minimizing the impact of reflected waves.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a coupled line coupler is used to achieve constant coupling value, then the coupling value increases with frequency due to parasitic capacitance, but the circuit size becomes larger than the wavelength
Solution Approach 1:
The patent introduces a phase compensation circuit that changes the electrical parameters (capacitance and resistance) to compensate for the frequency-dependent coupling variations. By adjusting the phase relationship between coupling and isolation ports through reactive components, the circuit maintains constant coupling values across different frequency bands without requiring the physical dimensions to scale with wavelength.
Solution Approach 2:
The phase compensation circuit acts as an intermediary between the coupled line coupler and the signal ports. It introduces additional reactive elements (capacitors and resistors) that mediate the phase relationship, allowing the main coupler structure to remain compact while achieving frequency-independent coupling through the compensating phase shift.
2Volume of moving object
If the coupler is implemented as an IC with reduced size, then the circuit size is smaller, but it becomes difficult to provide constant coupling value according to frequency
Solution Approach 1:
The patent uses phase compensation circuits with adjustable capacitive and resistive parameters to counteract the frequency-dependent effects in compact IC implementations. By carefully selecting and tuning the values of capacitors and resistors in the compensation network, the circuit achieves constant coupling values despite the reduced physical size and integrated structure.
3Adaptability or versatility
If the coupler is implemented as a module on PCB, then the directivity performance is deteriorated due to impedance mismatch and asymmetry, but the structure is more flexible
Solution Approach 1:
The patent intentionally introduces asymmetric phase compensation elements to counterbalance the inherent asymmetries in PCB module implementations. By strategically placing capacitors and resistors with specific values on different sides of the coupler structure, the compensation network corrects impedance mismatches and restores symmetry in the electrical characteristics, thereby improving directivity performance.
4Adaptability or versatility
If the coupler is used in multiple frequency bands, then the amount of coupling changes with frequency band, but the system needs to handle multiple bands
Solution Approach 1:
The patent employs phase compensation circuits designed to operate across multiple frequency bands by using reactive components whose impedance characteristics change with frequency. The compensation network is configured to provide the appropriate phase correction at each operating frequency, allowing the coupler to maintain accurate coupling measurements throughout the entire multi-band frequency range.
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 reduces changes in coupling due to frequency band variations, maintains constant coupling levels, and improves directivity and isolation characteristics, even when implemented in compact forms or across multiple frequency bands.
Implementation Method 1
a coupling line disposed between a coupling port and an isolation port such that the coupling line is coupled to the signal line and is configured to extract a coupling signal from the signal line
Implementation Method 2
a coupling adjusting circuit connected to the coupling port and the isolation port, and configured to reduce changes in an amount of coupling according to a change in a frequency band of a signal passing through the signal line
Data Source
AI summary
A coupler circuit includes: a signal line disposed between a first terminal and a second terminal; a coupling line disposed between a coupling port and an isolation port such that the coupling line is coupled to the signal line and is configured to extract a coupling signal from the signal line; and a coupling adjusting circuit connected to the coupling port and the isolation port, and configured to reduce changes in an amount of coupling according to a change in a frequency band of a signal passing through the signal line.