Graded-Ground Millimeter-Wave RF Module Substrate Design
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Solution Overview
Problem
Conventional RF module designs for millimeter wave communications are limited by the need to implement active antennas on one side of the substrate, which restricts the number of antennas and leads to signal losses due to inadequate ground plane references, making it difficult to achieve efficient signal propagation and meet constraints of size, power consumption, and cost.
Innovation Solution
The RF module employs a multilayer substrate with a graded-ground plane and double graded-ground plane structure, providing a reference ground to each antenna sub-array, allowing for a compact stack-up and reduced signal losses, while enabling independent control and beam-forming capabilities for increased antenna diversity and coverage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If active antennas are implemented on one side of the substrate, then the substrate area is reduced, but the number of antennas is limited and signal losses increase due to inadequate ground plane references
Solution Approach 1:
The patent transitions from a single-sided antenna implementation to a multi-layer substrate structure with antennas distributed across multiple layers. This dimensional change allows more antennas to be packed into the same footprint area while providing adequate ground plane references for each antenna, thereby resolving the contradiction between substrate area and signal propagation efficiency.
Solution Approach 2:
The patent divides the ground plane into multiple segmented ground layers (first ground layer and second ground layer) that are distributed across different substrate layers. Each antenna sub-array is provided with dedicated ground plane references through these segmented layers, which reduces signal losses and improves reliability while maintaining compact substrate area.
2Adaptability or versatility
If the number of antennas is increased, then antenna diversity and coverage are improved, but the substrate area and device complexity increase
Solution Approach 1:
The patent utilizes multiple substrate layers to accommodate increased antenna diversity. By distributing antenna sub-arrays across different layers (front layer, back layer, and middle layers) with corresponding ground layers, the design achieves higher antenna count and diversity without proportionally increasing the substrate footprint area.
Solution Approach 2:
The patent implements a nested multi-layer structure where antenna sub-arrays and ground layers are arranged in concentric or stacked configurations. The first ground layer and second ground layer are positioned at different depths, with transmission lines routed through intermediate layers, creating a compact nested arrangement that maximizes antenna density within the substrate volume.
3Loss of energy
If a graded-ground plane structure is implemented, then signal losses are reduced and reference ground is provided to each antenna, but the manufacturing complexity increases
Solution Approach 1:
The graded-ground plane is segmented into multiple discrete ground layers (first ground layer and second ground layer) positioned at different substrate levels. Each ground layer is connected to antennas through controlled impedance transmission lines, providing dedicated reference grounds that reduce signal losses. This segmentation approach makes the complex graded-ground structure manufacturable using standard multi-layer PCB fabrication processes.
4Reliability
If multiple ground layers are used to provide reference ground to each antenna sub-array, then signal propagation efficiency is improved, but the device complexity and material costs increase
Solution Approach 1:
The patent resolves the complexity issue by organizing multiple ground layers in a systematic vertical arrangement across different substrate layers. The first ground layer and second ground layer are positioned at different depths with defined connectivity patterns to antenna sub-arrays, creating a manageable three-dimensional structure that improves signal propagation while maintaining manufacturing feasibility through standardized multi-layer construction methods.
Data Source
AI summary
A millimeter-wave radio frequency (RF) module is provided. The RF module includes a multilayer substrate having at least a front layer, a back layer, a plurality of middle layers, a first ground layer, and a second ground layer, wherein the first ground layer includes a graded-ground plane having a pair of non-overlapping ground lines connected at a single connection point through a graded connection, and wherein the second ground layer includes a double graded-ground plane having a pair of overlapping ground lines connected at a single connection point through a graded connection, wherein the first ground layer and the second ground layer provide a reference ground to a transmission line included in the multilayer substrate.