Miniature Quadrature Hybrid Coupler Using Multilayer Capacitive Stacking
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Solution Overview
Problem
Conventional directional couplers face challenges in miniaturization due to the large gap requirements between coupled transmission lines, which are difficult to fabricate using planar circuit technologies, and the resulting size of Lange couplers is still problematic, exceeding that of associated circuitry.
Innovation Solution
The design incorporates a first and second transmission line element with conductive coupling elements separated by a dielectric element to increase capacitive coupling, allowing for reduced spacing and size while maintaining effective signal division and phase separation, utilizing a multilayer metal interconnect structure to enhance coupling and reduce the electrical length required.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If two edge coupled transmission lines are used to implement a quadrature hybrid coupler, then the coupler can provide proper signal division and phase separation, but the gap between the two coupled lines is too small to be practically and reliably fabricated using conventional planar processes
Solution Approach 1:
The patent transitions from a planar two-dimensional layout to a three-dimensional structure by stacking transmission line elements on different substrate layers. This vertical arrangement allows sufficient spacing between coupled lines for reliable fabrication while maintaining the required coupling through controlled dielectric thickness between layers.
2Ease of manufacture
If transmission lines with large dimensions are used to achieve proper impedance ranges, then the impedance requirements are met, but the overall size of the coupler becomes excessively large
Solution Approach 1:
By utilizing the third dimension (vertical stacking), the patent achieves proper impedance matching without requiring large planar dimensions. The coupling between layers provides the necessary impedance transformation in a compact footprint.
Solution Approach 2:
The patent changes physical parameters including dielectric thickness, conductor width, and spacing to achieve proper impedance ranges. By adjusting these parameters in the vertical dimension, the coupler maintains impedance matching while reducing overall area.
3Manufacturing precision
If Lange couplers with two or more pairs of lines are used, then the gap problem for planar processing is alleviated, but the resulting size of the coupler still exceeds that of associated circuitry
Solution Approach 1:
The patent uses vertical stacking of transmission line elements on different substrate layers to achieve proper coupling without requiring multiple pairs of lines in the planar direction. This three-dimensional approach reduces the coupler area while maintaining fabrication feasibility.
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 approach enables the miniaturization of directional couplers, reducing the overall size by increasing capacitive coupling and allowing for reliable fabrication using conventional planar fabrication techniques, while maintaining the necessary impedance and signal characteristics.
Implementation Method 1
The first and the second plane can be separated by a pre-determined distance to increase a capacitive coupling between the first and the second transmission line elements
Data Source
AI summary
A radio frequency (RF) directional coupler (100) can include a first transmission line element (102) having a first end and a second end, and a second transmission line element (104) having a first end and a second end. The first and second transmission line elements (102, 104) can be disposed in a first plane, where at least a portion of said first and said second transmission line elements (102, 104) are adjacent along a path. The RF coupler (100) can also include a first series of conductive coupling elements (116) disposed along said path in a second plane parallel to the first plane and separated from said first and said second transmission line elements (102, 104) by a first dielectric element (114). The first and second plane can be separated by a pre-determined distance (t2) to increase a capacitive coupling between the first and second transmission line elements (102, 104).