Adjustable Filter Choke Circuit for Faster Tuning and RF Isolation
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Solution Overview
Problem
Existing tractable filters in radiocommunication systems face challenges in achieving fast frequency response times without degrading the station's speed characteristics, especially when exposed to high levels of interference from nearby jammers.
Innovation Solution
Incorporating a series resistance and inductance with specific relationships, such as Rp = Q * L * ω0 and Cp = 1 / (L * ω0^2), and adding a series resistor to the choke, allowing for faster tuning times while minimizing resonances and isolating the RF part from DC control voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a tractable filter is used to achieve fast frequency response, then the filter can respond quickly to control voltage changes, but resonances in the choke degrade the frequency response and slow down tuning time
Solution Approach 1:
The patent introduces an intermediary circuit consisting of a series resistance and inductance between the control voltage source and the choke. This intermediary network acts as a mediator that suppresses resonances while allowing the choke to maintain its DC blocking function. The series resistance specifically dampens the resonant oscillations in the choke, thereby improving frequency response quality without sacrificing the fast tuning capability of the tractable filter.
Solution Approach 2:
The patent modifies the electrical parameters of the choke circuit by adding specific series resistance and inductance values. By carefully selecting these parameter values, the resonance characteristics of the choke are altered to reduce unwanted oscillations. This parameter adjustment allows the system to maintain fast tuning response while improving the overall quality of the frequency response by suppressing resonant peaks.
2Reliability
If the choke is used to isolate RF from DC control voltage, then DC isolation is achieved, but resonances in the choke frequency response slow down the tuning time
Solution Approach 1:
The patent segments the choke circuit into multiple functional parts: the original choke for DC isolation, and an additional series resistance-inductance network for resonance control. This segmentation allows each component to perform its specific function independently - the choke maintains DC blocking while the added series resistance suppresses resonances that would otherwise slow down tuning. The segmentation enables both DC isolation and fast tuning to coexist.
3Device complexity
If standard choke values are used for DC isolation, then simple design is achieved, but resonances degrade frequency response and increase tuning time
Solution Approach 1:
Rather than completely redesigning the choke, the patent introduces a simple intermediary series resistance-inductance network. This minimal addition serves as a mediator that suppresses resonances without requiring complete redesign of the existing choke. The approach maintains design simplicity while effectively reducing tuning time by damping resonant oscillations in the frequency response.
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
This configuration enables fast tuning times for the filter, limits resonances in the frequency response, and improves isolation between the RF and DC parts, maintaining the station's speed characteristics.
Implementation Method 1
limiting the resonances of the choke in its frequency response
Implementation Method 2
a series resistance r series whose value is determined from the expression: where Rp corresponding to the parallel resistance of the choke
Implementation Method 3
isolating the RF part from the DC part better known under the expression 'choker' the control voltage
Data Source
Figure 1
Figure 2~3
AI summary
The invention relates to a device associated with he control of a adjustable filter, characterised in that it comprises a combination of at least the following members: a self having an inductance Ls and a resistance Rs; a serial resistor rsérie having a value determined based on the expression (I), where Rp is the parallel resistance of the self, Lo is the inductance at the resonance frequency, and ?0 is the resonance frequency, by selecting the lowest resistance value and subtracting rsérie from R = rsérie + Rs.