Cavity-Backed Coplanar Waveguide Transition for Millimeter-Wave
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing transition methods from planar transmission lines to rectangular waveguides at millimeter-wave and terahertz frequencies are complex and difficult to implement accurately due to their 3-D geometries, and previous solutions like impedance-tapering techniques face challenges in fabrication and performance stability due to micromachining tolerances.
Innovation Solution
A cavity-backed coplanar waveguide with a suspended microstrip over a metallic trench and an in-plane transition waveguide design that uses a three-step taper to convert the TEM mode to the TE01 mode, optimized for minimal insertion loss and wideband response, facilitating easy fabrication with silicon micromachining.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If complex 3-D transition geometries are used from planar transmission lines to rectangular waveguides, then the transition functionality is achieved, but the manufacturing precision and ease of fabrication deteriorate due to micromachining tolerances
Solution Approach 1:
The patent transitions from complex 3-D geometries to a 2.5-D fully micromachined structure by removing the need for assembly of multiple parts. The transition is realized using two resonant structures (a shorted section of transmission line with a pin inside the waveguide and an E-plane step discontinuity) that can be fabricated in a planar manner on silicon wafers, eliminating the need for complex 3-D assembly while maintaining transition functionality.
Solution Approach 2:
The transition structure is divided into two separate resonant structures that can be independently fabricated and then assembled. This segmentation allows each component to be optimized for micromachining processes while maintaining the overall transition functionality, reducing the complexity of fabricating a single complex 3-D structure.
2Ease of manufacture
If resonant-based transitions are used, then the transition can be fully micromachined without assembly, but the bandwidth is limited to 17%
Solution Approach 1:
The patent merges two resonant structures (the shorted transmission line section with pin and the E-plane step discontinuity) into a single integrated transition design. This combination allows the transition to maintain full micromachining compatibility while achieving a significantly broader bandwidth than either resonant structure could provide alone, overcoming the 17% bandwidth limitation of individual resonant-based transitions.
3Reliability
If impedance-tapering technique with ridged-waveguide is used, then the mode conversion is achieved, but the fabrication difficulty increases due to geometry incompatibility with micromachining
Solution Approach 1:
The patent replaces the traditional 3-D ridged-waveguide impedance taper with a 2.5-D fully micromachined resonant-based transition. This dimensional simplification allows the transition to be fabricated using planar micromachining techniques on silicon wafers, eliminating the fabrication difficulties associated with the ridged-waveguide geometry while maintaining mode conversion functionality through the resonant structures.
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 provides a reliable, low-loss transition with improved bandwidth and reduced sensitivity to fabrication errors, enabling efficient integration of active and passive components in high-frequency systems.
Implementation Method 1
an in-plane transition waveguide design that uses a three-step taper to convert the TEM mode to the TE01 mode
Data Source
AI summary
A broadband fully micromachined transition from rectangular waveguide to cavity-backed coplanar waveguide line for submillimeter-wave and terahertz application is presented. The cavity-backed coplanar waveguide line is a planar transmission line that is designed and optimized for minimum loss while providing 50 Ohm characteristic impedance. This line is shown to provide less than 0.12 dB/mm loss over the entire J-band. The transition from cavity-backed coplanar waveguide to a reduced-height waveguide is realized in three steps to achieve a broadband response with a topology amenable to silicon micromachining. A novel waveguide probe measurement setup is also introduced and utilized to evaluate the performance of the transitions.