Microstrip Line Short Circuit ESD Protection

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Solution Overview

Problem

Existing ESD protection methods for RF and DC signal circuits introduce capacitance that reduces transmission performance, particularly in higher power applications, and do not effectively prevent damage from electrostatic discharges.

Innovation Solution

A system incorporating a microstrip line coupled to a radio frequency port and a short circuit with a higher characteristic impedance, positioned proximate to the radio frequency port, which acts as an open circuit for the operating frequency and suppresses harmonics, thereby providing effective ESD protection with minimal insertion loss and return loss.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If ESD protection diodes are coupled to the transmitter output to shunt ESD to ground, then ESD protection is provided, but capacitance is introduced onto the antenna port that reduces transmission performance

Engineering Contradiction:

ImproveESD protectionVSAvoidtransmission performance

Core Design Contradiction:

ReliabilityVSLoss of energy

Solution Approach 1:

The patent extracts the harmful capacitance effect from the ESD protection mechanism by removing the ESD protection diode and replacing it with a transmission line structure. The microstrip line with short circuit provides ESD protection through its impedance characteristics rather than through diode clamping, thereby eliminating the parasitic capacitance that degraded transmission performance.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent replaces the electronic component-based ESD protection (diodes) with a transmission line structure-based protection mechanism. The microstrip line with controlled impedance and short circuit creates an ESD protection effect through electromagnetic field distribution and impedance mismatch, substituting the mechanical/electronic diode structure with a distributed parameter transmission line system.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Reliability

If ESD protection diodes are used to shunt ESD, then discharge protection is achieved, but insertion loss increases

Engineering Contradiction:

Improvedischarge protectionVSAvoidinsertion loss

Core Design Contradiction:

ReliabilityVSLoss of energy

Solution Approach 1:

The patent removes the ESD protection diode component entirely and extracts its protective function into the transmission line structure itself. The microstrip line with short circuit at a specific distance from the antenna port creates an impedance discontinuity that reflects ESD energy back, providing protection without the insertion loss associated with diode-based protection.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The microstrip line acts as an intermediary element between the antenna port and the ESD event. By positioning the short circuit at a specific distance (quarter-wavelength or odd multiples thereof), the transmission line transforms the ESD energy through impedance transformation, mediating the protection function while maintaining low insertion loss for normal signal transmission.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Reliability

If ESD protection diodes are coupled to the transmitter output, then ESD current path is provided, but return loss increases

Engineering Contradiction:

ImproveESD protectionVSAvoidreturn loss

Core Design Contradiction:

ReliabilityVSLoss of energy

Solution Approach 1:

The patent substitutes the diode-based ESD protection mechanism with a transmission line-based mechanism. The microstrip line with short circuit provides an ESD current path through the distributed capacitance and inductance of the transmission line structure, replacing the discrete diode component. This substitution maintains impedance matching for normal signals while providing effective ESD protection, thereby reducing return loss compared to diode-based solutions.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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 effectively prevents damage from electrostatic discharges while maintaining low insertion loss and return loss, improving matching to 50 Ohms and reducing negative effects on passive intermodulation performance compared to previous designs.

Implementation Method 1

a short coupled to the microstrip line and a ground reference, wherein the short is coupled to the microstrip line proximate the radio frequency port

Methodology Applied

Scientific EffectElectromagnetic resonance: Resonance

Implementation Method 2

a microstrip line coupled to the radio frequency port and one or more components mounted on a printed circuit board

Methodology Applied

Scientific EffectElectromagnetic wave propagation:

Implementation Method 3

acts as an open circuit for the operating frequency and suppresses harmonics

Methodology Applied

Scientific EffectFrequency filtering:

Data Source

PatentUS11818836B2Systems for electrostatic discharge protection

Publication Date: 2023.11.14 OUTDOOR WIRELESS NETWORKS LLC

AI summary

In one example, a system includes a radio frequency port coupled to an external connector and a microstrip line coupled to the radio frequency port and one or more components mounted on a printed circuit board. The system further includes a short coupled to the microstrip line and a ground reference, wherein the short is coupled to the microstrip line proximate the radio frequency port.