CPW-to-Air Waveguide Vertical Transition With Half-Mode Excitation
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Solution Overview
Problem
Traditional coplanar waveguide (CPW) to waveguide transitions face challenges such as high insertion loss, radiation issues, and high fabrication costs, particularly in implementing sparse antenna arrays for automotive radar systems, which require low loss and wide bandwidth for efficient radar beam calibration and long-range detection.
Innovation Solution
A vertical transition from coplanar waveguide to air waveguide using half-mode excitation, implemented with a three-layer printed circuit board (PCB) structure, providing a compact, low-loss, and wide-band transition suitable for mass production, with a two-piece waveguide board design that reduces radiation and fabrication costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If traditional transmission lines (Microstrip, CPW, SIW) are used for routing, then the routing can be implemented on the same side of the antenna array, but the routing loss becomes significant which reduces detection range and accuracy
Solution Approach 1:
A waveguide structure is introduced as an intermediary component between the CPW transmission line and the antenna array. The waveguide acts as a low-loss transmission medium that bridges the gap between the planar CPW structure and the three-dimensional antenna elements, enabling long routing traces with minimal energy loss while maintaining structural integrity
Solution Approach 2:
The routing structure transitions from a two-dimensional planar configuration (CPW on PCB) to a three-dimensional waveguide structure. This dimensional change allows the routing trace to extend further without proportionally increasing loss, as the waveguide confines electromagnetic energy more effectively in multiple spatial dimensions, reducing radiation and ohmic losses
2Object-generated harmful factors
If CPW transmission lines with bending sections are used, then the routing flexibility is improved, but radiation occurs which distorts antenna pattern and downgrades radar beam calibration
Solution Approach 1:
The waveguide serves as an intermediary that eliminates radiation from bending sections. By transitioning the signal from CPW into the waveguide structure, the electromagnetic energy is confined within the waveguide walls, preventing radiation even when the routing path contains bends or changes in direction
Solution Approach 2:
The harmful radiation effect is extracted and eliminated by transitioning from the radiating CPW structure to the non-radiating waveguide structure. The waveguide walls contain the electromagnetic fields, removing the radiation problem while preserving routing flexibility through the waveguide's three-dimensional path capability
3Ease of manufacture
If conventional CPW to waveguide transitions with metal posts are used, then the transition can be implemented, but mass production fabrication becomes difficult
Solution Approach 1:
The transition structure is segmented into discrete, manufacturable components including via openings, conductive patterns, and dielectric layers that can be fabricated using standard PCB processes. This segmentation eliminates the need for complex metal post assemblies while achieving the same electromagnetic transition function
Solution Approach 2:
The mechanical metal post transition structure is replaced with an integrated PCB-based transition using via openings and conductive patterns. This substitution enables the transition to be fabricated using standard PCB manufacturing processes (drilling, plating, etching) rather than requiring precision mechanical assembly of metal components
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 achieves low insertion loss and high radiation efficiency across an ultra-wide bandwidth, enabling high-resolution data acquisition for automotive radar systems with reduced module costs and power consumption, while maintaining detection range and accuracy.
Implementation Method 1
Vertical transition from coplanar waveguide to air waveguide using half-mode excitation
Implementation Method 2
A radio frequency (RF) waveguide is a structure that guides an electromagnetic (EM) wave by restricting the transmission of energy to one direction
Implementation Method 3
The first through via openings and the second through via openings may provide a through via between the first layer, the second layer and the third layer
Data Source
AI summary
An apparatus comprising a first layer, a second layer and a third layer. The first layer may comprise a plurality of first through via openings, a plurality of first blind openings and a coplanar waveguide input. The second layer may comprise a plurality of second through via openings, a plurality of second blind via openings and an aperture. The third layer may comprise a ground. The coplanar waveguide input may comprise a vertical transition to a waveguide. The first through via openings and the second through via openings may provide a through via between the first, second and third layer. The first blind via openings may provide a blind via from the first to the second layer. The second blind via openings may provide a blind via from the second to the third layer. The coplanar waveguide input may transmit an output from a circuit to the waveguide.