Waveguide to Microstrip Transition Structure
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Solution Overview
Problem
Current multi-layer circuit boards with waveguide to microstrip transitions face challenges in efficiently coupling signals between waveguides and microstrip transmission lines, leading to suboptimal performance in microwave and millimeter wave circuits.
Innovation Solution
A multi-layer circuit board design featuring a laminated structure with dielectric layers, top and bottom metal frames, and conductors connecting them, which includes a waveguide cavity and microstrip line that extends into the cavity, optimizing signal transition through a waveguide to microstrip transition structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional waveguide to microstrip transition structures are used, then signal coupling between waveguides and microstrip transmission lines is achieved, but insertion loss is high and return loss is suboptimal
Solution Approach 1:
The transition structure is divided into multiple functional segments: a waveguide section, a transition section with tapered geometry, and a microstrip section. This segmentation allows each part to be optimized for its specific function, reducing overall insertion loss while maintaining signal coupling efficiency.
Solution Approach 2:
The transition structure employs varying local properties along its length, with the taper ratio and dimensions changing progressively from the waveguide end to the microstrip end. This local variation in geometry creates optimal impedance matching at each point, minimizing reflections and improving return loss.
2Reliability
If conventional waveguide to microstrip transition structures are used, then signal coupling is achieved, but return loss is suboptimal
Solution Approach 1:
The transition is achieved by modifying the structure in the transverse dimension through tapering, rather than using complex multi-layer or three-dimensional structures. The gradual change in width along the longitudinal axis provides effective impedance transformation with relatively simple geometry.
3Reliability
If the microstrip line extends into the waveguide cavity, then signal coupling efficiency is improved, but the structure complexity increases
Solution Approach 1:
The microstrip line is nested within the waveguide cavity structure, with the microstrip substrate positioned inside the waveguide boundaries. This nesting allows the microstrip to extend into the cavity volume, improving coupling efficiency while containing the complexity within a compact integrated structure.
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 design achieves low insertion loss and optimized return loss, enabling efficient signal coupling and performance across various frequency ranges, as demonstrated by simulated and measured frequency response diagrams.
Implementation Method 1
Microwave and millimeter wave circuits may use a combination of rectangular and/or circular waveguides and planar transmission lines such as striplines, microstrips
Implementation Method 2
Transition devices are used to couple signals between microstrip transmission lines and waveguides
Data Source
AI summary
A multi-layer circuit board with a waveguide to microstrip transition structure includes a laminated structure having a plurality of dielectric layers, a top metal frame disposed over the laminated structure, a microstrip line disposed over the laminated structure, a bottom metal frame underlying the laminated structure, and a plurality of conductors electrically connecting the top metal frame and the bottom metal frame. The top metal frame defines a top cavity, the bottom metal frame defines a bottom cavity corresponding to the top cavity, and the microstrip line extends into the top cavity. The laminated structure includes an upper dielectric layer and at least one lower dielectric layer, wherein top cavity exposes a top surface of the upper dielectric layer, and the bottom cavity exposes a bottom surface of the at least one lower dielectric layer.