Planar Waveguide Air Channel PCB Microstrip Signal Loss
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Solution Overview
Problem
Existing waveguide technologies, such as PCB microstrip and metal cavity waveguides, face significant challenges in maintaining low signal loss and high precision at frequencies above 40 GHz, leading to increased costs and complexity.
Innovation Solution
A planar waveguide design utilizing a top and bottom PCB with shielding metal blocks and a metal plate, forming an air waveguide with microstrips, where the shielding metal blocks' dimensions and gaps optimize signal transmission with lower tolerance requirements and cost compared to traditional waveguides.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If PCB microstrip waveguide is used, then cost is reduced and processing is simplified, but signal loss increases significantly for frequencies above 40 GHz
Solution Approach 1:
The waveguide is divided into two separate PCB layers (top and bottom) with an air gap between them, forming an air-filled waveguide channel. This segmentation allows the waveguide to achieve low signal loss characteristics of air-filled structures while maintaining the manufacturing advantages of PCB technology.
Solution Approach 2:
Air is introduced as an intermediary medium between the top and bottom PCB layers to form the waveguide channel. This air-filled channel reduces signal loss compared to traditional PCB microstrip while the PCB structures provide the mechanical support and integration advantages.
2Ease of manufacture
If PCB microstrip waveguide is used, then manufacturing cost is reduced, but machining precision requirement increases sharply
Solution Approach 1:
The waveguide structure transitions from a planar 2D microstrip on a single PCB layer to a 3D structure utilizing two PCB layers separated by an air gap. This dimensional change allows the use of standard PCB manufacturing processes for both layers while the air gap provides the necessary electromagnetic performance without requiring high-precision machining of a single complex structure.
3Loss of energy
If metal cavity waveguide is used, then signal loss is reduced, but machining precision tolerance reaches micrometer level and costs increase sharply
Solution Approach 1:
The waveguide combines different materials and structures: PCB substrates for mechanical support and integration, air for low-loss electromagnetic propagation, and shielding metal blocks for signal containment. This composite approach achieves the low signal loss of metal cavity waveguides while using more manufacturable materials and processes.
Solution Approach 2:
Instead of using a single monolithic metal cavity requiring micrometer-level precision, the waveguide is segmented into two PCB layers with standardized tolerances, an air gap, and discrete shielding metal blocks. This segmentation distributes the precision requirements across multiple components that can be manufactured using less stringent processes.
4Loss of energy
If metal cavity waveguide is used, then signal loss is reduced, but device complexity and cost increase
Solution Approach 1:
The waveguide merges the low-loss electromagnetic propagation characteristics of air-filled metal waveguides with the manufacturing advantages and integration capabilities of PCB technology. The top and bottom PCB layers are merged to form a complete waveguide structure that can be integrated with other PCB-based 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 planar waveguide design achieves lower tolerance requirements and reduced costs while maintaining high system performance by converting signals from microstrips to an air waveguide, reducing signal loss and improving system performance.
Implementation Method 1
a waveguide is a pipeline that is capable of confining and guiding an electromagnetic wave to propagate in a lengthwise direction
Implementation Method 2
a waveguide formed of a printed circuit board (Printed Circuit Board, PCB for short) microstrip
Implementation Method 3
multiple shielding metal blocks with their upper surfaces contacting the top PCB and with their lower surfaces contacting the bottom PCB
Data Source
Figure 1~2
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AI summary
The present disclosure provides a planar waveguide, a waveguide filter, and an antenna. The planar waveguide includes a top printed circuit board PCB, a bottom PCB, multiple shielding metal blocks, and a metal plate, where the top PCB has a groove, the groove and the bottom PCB form an air waveguide, and microstrips are disposed on the lower surface of the top PCB; the microstrips are positioned at both ends of the groove and disposed along an extension line of the groove; the multiple shielding metal blocks are disposed along the extension direction of the microstrips and the groove and positioned on both sides of the microstrips and the groove; a first conversion piece for implementing signal transmission between the microstrips and the air waveguide is further disposed between the microstrips and the bottom PCB under the groove; and a working barycentric frequency of the planar waveguide is f0, a wavelength of an electromagnetic wave in the air under frequency f0 is λ = c/f0, 0.75 x λ/4 ≤ a height Hb of the shielding metal blocks ≤ 1.25 x λ/4, λ/8 ≤ a width Wb ≤ λ, and 0 < a gap Wg between the shielding metal blocks ≤ λ/2.