Directional Coupler Power Detection Using 90-Degree Phase Shift
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Solution Overview
Problem
Existing power detection techniques using single directional couplers result in complex and large structures, making it difficult to achieve a miniature directional coupler with decent directivity for integration into MMIC circuits or modules, and rely on high directivity which is costly and bulky.
Innovation Solution
A power detection system utilizing a pair of directional couplers with a 90° phase shift between them, combined with two power detectors to provide accurate power detection independent of load phase, allowing for a compact design that can be integrated into MMIC circuits and modules.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If prior art techniques use single directional coupler with improved directivity, then measurement precision is improved, but device complexity and size increase
Solution Approach 1:
The patent divides the power detection function into two separate directional couplers instead of using one complex high-directivity coupler. Each coupler operates at a different phase point (0° and 90°), and their outputs are combined to achieve accurate power detection. This segmentation allows each coupler to be simpler and smaller while maintaining overall measurement precision.
Solution Approach 2:
The patent introduces a phase dimension by using two directional couplers with 90° phase difference between them. Instead of relying on a single coupler with high directivity, the system measures power at two different phase points and combines the results. This dimensional approach (adding phase diversity) enables accurate power detection with simpler individual components.
2Measurement precision
If prior art techniques use single directional coupler with improved directivity, then measurement precision is improved, but the device becomes large in size
Solution Approach 1:
The patent segments the power detection task across two smaller directional couplers rather than using one large high-directivity coupler. Each coupler can be compact since they don't need to achieve high directivity individually, and their combined output provides accurate power measurement. This enables miniaturization of the overall detection system.
Solution Approach 2:
By introducing phase diversity with two couplers separated by 90°, the patent eliminates the need for each coupler to be large and complex. The phase difference provides the additional information needed for accurate power detection, allowing each physical component to be smaller while maintaining or improving measurement precision.
3Measurement precision
If prior art techniques focus on high directivity directional coupler, then measurement precision is improved, but ease of manufacture decreases
Solution Approach 1:
The patent divides the high-directivity requirement into two separate, lower-directivity couplers. Each coupler is easier to manufacture since they don't need to achieve high directivity individually, and the combination of their outputs provides the accurate power detection that would require a complex high-directivity coupler. This segmentation simplifies the manufacturing process.
Solution Approach 2:
The patent uses phase diversity (two couplers with 90° phase difference) to achieve accurate power detection without requiring each coupler to have high directivity. This approach relaxes manufacturing tolerances and makes the system easier to fabricate, as standard directional couplers can be used rather than specialized high-directivity designs.
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 system achieves accurate power detection by combining power from both couplers, eliminating the need for high directivity and enabling integration into small form factors, with the combined power being independent of load phase and allowing for calibration of constant offsets.
Implementation Method 1
a transmission line disposed between the directional couplers providing a 90° phase shift between the directional couplers
Data Source
AI summary
A power detection system implemented using a pair of directional couplers and a transmission line (or equivalent) disposed between the directional couplers, wherein the transmission line (or equivalent) provides a 90° phase shift between the directional couplers. Accurate power detection is provided by combining the powers detected at each of the directional couplers, whereby the combined power is independent of load phase. The total power in the forward case is given by Pc1=2*Pf*C, where Pf is the forward power and C is the coupling coefficient the directional couplers. The total power in the reflected case is given by Pc1=2*Pf*C*(ρ2+D2), where Pf is the forward power, C is the coupling coefficient of said directional couplers, ρ is the reflection coefficient, and D is the directivity of the directional couplers.