Microscale Plasma Limiter in Coplanar Waveguides for RF Power Protection
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Solution Overview
Problem
Diode limiters are unable to handle very high levels of power, posing a risk to sensitive RF circuits during adversary jamming or ally co-site transmission.
Innovation Solution
A microscale plasma limiter integrated into a RF transmission line that generates plasma at a controlled power threshold, altering the characteristic impedance to reflect excessive power back to the source and protect downstream circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If diode limiters are used to protect RF circuits, then low power levels are limited effectively, but the device cannot handle very high levels of power
Solution Approach 1:
The patent transitions from using diode limiters (solid-state semiconductor devices) to plasma limiters (ionized gas devices). This fundamental parameter change in the limiting mechanism enables the system to handle very high power levels while maintaining protection capabilities, as plasma can dissipate high energy without the thermal and breakdown limitations of semiconductor diodes.
Solution Approach 2:
The invention replaces the electronic/mechanical diode limiter system with a plasma-based electromagnetic field interaction system. The plasma limiter uses ionized gas to create a reflective barrier through electromagnetic field interactions rather than physical contact or semiconductor junctions, enabling high power handling.
2Power
If plasma limiter is integrated into RF transmission line, then high power handling is achieved, but device complexity increases
Solution Approach 1:
The patent integrates the plasma limiter directly into the RF transmission line structure, merging the limiting function with the transmission path. This integration approach reduces the number of discrete components and interconnections, thereby reducing overall device complexity despite the advanced plasma-based technology.
Solution Approach 2:
The plasma limiter structure serves multiple functions: it acts as both a transmission line conductor and a power limiting device. The same structural elements that guide RF signals also generate and contain the plasma for limiting, eliminating the need for separate limiting components and reducing system complexity.
3Reliability
If plasma limiter reflects excessive power, then power transmission is limited effectively, but insertion loss increases
Solution Approach 1:
The plasma limiter dynamically adjusts its characteristics based on the incident power level. At low power levels, the plasma is not fully ionized and the transmission line maintains low insertion loss. When excessive power is detected, the plasma becomes highly ionized and creates a reflective barrier, effectively limiting power transmission only when necessary.
Solution Approach 2:
The plasma is generated locally at specific points in the transmission line where high power levels are detected, rather than throughout the entire transmission path. This localized plasma generation minimizes the impact on signal transmission and insertion loss while providing effective power limiting at critical locations.
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
Effectively limits power transmission to protect sensitive RF equipment by reflecting excessive power, maintaining low insertion loss and high return loss, while integrating with minimal size, weight, and cost impact.
Implementation Method 1
A microscale plasma limiter integrated into a RF transmission line that generates plasma at a controlled power threshold
Implementation Method 2
altering the characteristic impedance to reflect excessive power back to the source
Data Source
Figure 1A
Figure 1B
Figure 1C
AI summary
A radio frequency (RF) transmission line (100) is described. The RF transmission line includes a first ground line (106a), a second ground line (106b), and a signal line (104) disposed on a substrate (102) and forming a coplanar waveguide. A plasma limiter feature (108) is integrated into an internal surface of one or more of the first ground line (106a), the second ground line (106b), and the signal line (104). The plasma limiter (108) decreases a gap distance between the signal line (104) and the associated ground line. The gap distance is selected, together with a gas pressure, to control a voltage at which the gas within the gap breaks down, targeted at a breakdown power of 1 W across a wide bandwidth. The plasma limiter (108) thus limits a power transmitted by way of the RF transmission line (100) for protecting a sensitive integrated circuit (306).