Frequency Selective Canceler Stripline Impedance Matching
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Solution Overview
Problem
Frequency selective limiters (FSLs) struggle to effectively attenuate high-power RF signals while allowing low-power signals to pass through without significant attenuation, often requiring external matching structures that degrade bandwidth and increase insertion loss.
Innovation Solution
A frequency selective canceler (FSC) design incorporating a circulator, a direct signal path with a reflective element, and a conditioning path with amplitude and phase control circuitry, which redirects and phase-shifts above-threshold signals to cancel them out, allowing below-threshold signals to propagate unattenuated.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an external matching structure is used to improve impedance match, then return loss is improved, but bandwidth is reduced and insertion loss increases
Solution Approach 1:
The patent extracts the impedance matching function from a separate external matching structure and integrates it into the stripline transmission structure itself through geometric design (width, length, and positioning of the stripline), eliminating the need for additional matching components that would reduce bandwidth and increase insertion loss
Solution Approach 2:
The patent combines the impedance matching function with the transmission function in a single integrated stripline structure, where the stripline's physical dimensions are optimized to simultaneously achieve proper impedance matching and broadband performance, merging what were previously separate functions
2Power
If a lower-impedance stripline is used to reduce threshold power level, then power handling is improved, but return loss degrades
Solution Approach 1:
The patent changes the impedance parameter of the stripline to a lower value to reduce the threshold power level for frequency selective limiting, while simultaneously optimizing other geometric parameters (width, length, positioning) to compensate for the return loss degradation, achieving both power handling improvement and acceptable impedance matching
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 FSC achieves strong rejection of above-threshold signals while minimizing attenuation of below-threshold signals, improving power handling and maintaining bandwidth, with optional tunable components for further adjustments.
Implementation Method 1
a circulator having a first port coupled to an input port of the FSC; a direct signal path comprising a reflective element coupled between a second port of the circulator and a first input port of a combiner
Implementation Method 2
In response to RF signals having a power level above a threshold power level provided to the direct path, the reflective element (e.g. a reflective FSL) reflects or otherwise re-directs the above-threshold portion of the RF signals to the circulator
Implementation Method 3
The conditioning path of the FSC comprises RF amplitude and/or phase control circuitry. In response to signals provided to the input of the conditioning path, the conditioning path adjusts or otherwise sets the phase of the signals propagating therethrough such that the signal has phase which is shifted (e.g. 180 degrees shifted) from like frequency signals propagating in the direct path
Implementation Method 4
The outputs of both the direct path and conditioning path are coupled such that the interfering signals in each path cancel each other. In embodiments, the outputs of both the direct path and conditioning path are coupled to inputs of an RF combiner. In response to the interfering signal and the redirected signal being provided to inputs of the RF combiner, the RF combiner combines the signals provided thereto
Implementation Method 5
a frequency selective limiter (FSL) is a nonlinear passive device that attenuates radio frequency (RF) signals provided to an input thereof having a power level which is above a predetermined threshold power level. RF Signals having a power level below the predetermined threshold power, on the other hand, propagate from the FSL input port to the FSL output port substantially unattenuated
Data Source
AI summary
Described is a frequency selective canceler, which uses signals reflected from a reflective element (e.g. a frequency selective limiter) to selectively reject only signals having a power level above a threshold power level while simultaneously allowing signals having a power level below the threshold power level to pass without rejection.