RF PCB Ground Cage Layout for Resonance-Free Connector Transitions
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Solution Overview
Problem
Conventional printed circuit board (PCB) connectivity for radio frequency (RF) connectors suffers from signal resonance modes, leading to insertion loss and return loss notches, particularly in the millimeter waveband, causing system failures and bandwidth bottlenecks in high-speed telecommunications.
Innovation Solution
The implementation of a PCB with a dielectric layer structure and a ground cage structure around RF signal pads and traces, using WSMP, G3PO, or SMPS connectors with reduced bends and a blind via for electrical conductivity, maintains constant transmission line impedance and reduces parasitic parameters, ensuring efficient RF signal transition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional GPO or GPPO connectors are surface-mounted or edge-mounted on PCB, then connector assembly is achieved, but signal resonance modes are excited causing insertion loss and return loss notches
Solution Approach 1:
The patent introduces an intermediary transition structure between the connector and PCB trace that includes a coaxial section with controlled impedance. This transition structure acts as a mediator to smoothly couple the connector to the PCB trace while maintaining constant impedance, thereby preventing resonance mode excitation and eliminating insertion/return loss notches.
Solution Approach 2:
The patent changes the geometric parameters of the transition structure, specifically designing a coaxial section with optimized dimensions (outer conductor diameter, inner conductor diameter, dielectric thickness) to achieve constant 50-ohm impedance throughout the transition. This parameter optimization ensures resonance-free operation across the millimeter-wave frequency range.
2Ease of manufacture
If connectors with multiple bends are used to achieve PCB mounting, then connector assembly is achieved, but parasitic parameters increase degrading RF performance
Solution Approach 1:
The patent extracts the bends from the signal path by designing a connector with a straight inner conductor that transitions directly to the PCB trace through the coaxial transition structure. By removing unnecessary bends from the RF signal path, parasitic inductance and capacitance are minimized, preserving signal integrity at millimeter-wave frequencies.
3Ease of manufacture
If air gap is introduced between connector body and PCB cut-out for assembly, then connector installation is facilitated, but impedance discontinuity is created causing resonance
Solution Approach 1:
The patent introduces a coaxial transition structure as an intermediary element that bridges the connector body and PCB trace. This transition structure includes a dielectric material that fills the space between the connector outer conductor and PCB ground plane, ensuring continuous impedance matching and eliminating resonance caused by air gaps.
4Productivity
If conventional PCB trace transition structures are used for RF connector coupling, then signal transmission is achieved, but resonance modes are excited causing system failure
Solution Approach 1:
The patent changes the transition structure from a conventional PCB trace design to a controlled-impedance coaxial configuration. By optimizing the geometric parameters (conductor diameters, dielectric thickness, ground plane dimensions) to maintain constant 50-ohm impedance, the transition structure eliminates resonance modes while preserving high-speed signal transmission capability.
Data Source
AI summary
A Printed Circuit Board (PCB) and methods for manufacturing the PCB board are provided. The PCB includes a plurality of layers; a signal pad, at a first layer of the plurality of layers, connected to a signal transmission trace strip line, at a second layer of the plurality of layers, wherein the signal pad is configured to connect to a surface mount Radio Frequency (RF) connector that is configured to interface an RF signal with the signal pad; a PCB ground cage structure through the plurality of layers, surrounding the signal pad; and extended ground reference planes located at the first layer and a third layer of the plurality of layers, wherein the extended ground reference planes extend into a volume of the PCB ground cage structure.