PCB Unit Cell Antenna Array With Waveguide Coupling and Low Grating Lobes
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Solution Overview
Problem
Ka-band antenna systems are large, heavy, and complex due to the need for physical separation of transmit and receive antennas to avoid radio interference and grating lobes, which increases size, weight, and production costs, and compromises gain-to-noise-temperature (G/T) performance.
Innovation Solution
A multilayer PCB antenna array is designed with a driven layer featuring unit cells with elements arranged in a square configuration, where the center of each element is equidistant from adjacent elements, and orientations vary in 90° increments, coupled with combiner layers and waveguide layers to efficiently interface with waveguides, reducing the overall footprint and minimizing grating lobes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If transmit and receive antennas are physically separated to avoid radio interference and grating lobes, then G/T performance is improved, but device size and weight increase
Solution Approach 1:
The patent combines transmit and receive antenna elements into a single integrated PCB array structure. Multiple antenna elements are densely packed on the same PCB substrate with sub-wavelength spacing, eliminating the need for separate physical antenna structures. This merging approach maintains G/T performance through proper element spacing while dramatically reducing overall system weight and size.
Solution Approach 2:
The patent transitions from traditional three-dimensional spatial separation of transmit and receive antennas to a two-dimensional planar integration on a PCB substrate. By arranging elements in a dense two-dimensional grid with sub-wavelength spacing, the system achieves the required isolation and performance without the vertical or lateral separation that would increase weight and size.
2Area of stationary object
If antenna elements are closely spaced to reduce footprint, then device size is reduced, but grating lobes occur that compromise G/T ratio
Solution Approach 1:
The patent changes the spacing parameter to be less than one wavelength (sub-wavelength spacing) between adjacent antenna elements. This parameter modification prevents the formation of grating lobes that occur at larger spacings, while still allowing dense integration to reduce footprint. The sub-wavelength spacing is the critical parameter change that simultaneously achieves compact size and maintains G/T ratio.
3Reliability
If traditional separate antenna structures are used for transmit and receive, then frequency separation is achieved, but manufacturing complexity and cost increase
Solution Approach 1:
The patent creates a universal antenna element design that serves both transmit and receive functions within the same PCB structure. The same PCB substrate, metal layers, and grounding structures support multiple antenna elements operating at different frequencies (e.g., 20 GHz receive and 30 GHz transmit). This multi-functional integration eliminates the need for separate antenna structures, reducing manufacturing complexity and cost while maintaining frequency separation through frequency-selective surfaces and element spacing.
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 enables a compact, cost-effective, and scalable antenna array that maintains high gain-to-noise-temperature (G/T) performance by efficiently coupling waveguides to a PCB stack, reducing the occurrence of grating lobes and minimizing the overall footprint.
Implementation Method 1
A compact unit cell PCB antenna system with waveguide coupling
Data Source
AI summary
An antenna assembly of PCB layers and waveguide layers includes a driven PCB layer with an array of unit cells. Each cell includes a central first element (e.g., a receive patch) and four second elements (e.g., transmit patches) evenly spaced around the first element in a square configuration. Distances between adjacent aligned first elements are equal, and less than the first elements' operating frequency. Distances between adjacent aligned second elements are equal, and less than the second elements' operating frequency. First and second combiner layer conductively couple first elements and second elements, respectively, to one or more first or second combiner pads to facilitate interfacing the elements with waveguides. First and second waveguides formed into separate plates communicatively coupled to their corresponding combiner layer.