Variable Filter Feedback Loop for Independent Q and Frequency Tuning
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Solution Overview
Problem
Existing bandpass filters lack the ability to electronically adjust their pass-band center frequency and bandwidth efficiently, limiting their control and flexibility in frequency filtering applications.
Innovation Solution
A variable filter design featuring a signal loop with a frequency tunable resonator and an adjustable scaling block, controlled by a controller to achieve desired frequency responses, allowing for positive and negative gain adjustments and Q-enhancement or Q-spoiling of resonators.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If feedback gain is increased to achieve narrower bandwidth, then bandwidth is reduced, but the filter becomes an oscillator when loop gain exceeds unity
Solution Approach 1:
The patent implements a feedback path that feeds a portion of the output signal back to the input, with the feedback amount controlled by a controllable component. This feedback mechanism enables bandwidth control while maintaining stability by adjusting the feedback gain to remain below unity, preventing oscillation. The feedback path includes a controllable component that can be adjusted to achieve the desired bandwidth without causing the filter to oscillate.
Solution Approach 2:
The patent changes the feedback gain parameter to control bandwidth while maintaining stability. By adjusting the feedback gain parameter to be less than unity, the system achieves variable bandwidth control without transitioning into oscillation mode. The controllable component in the feedback path allows dynamic adjustment of this parameter.
2Ease of operation
If resonator Q is increased to achieve narrower bandwidth, then bandwidth is reduced, but tuning range is limited
Solution Approach 1:
The feedback path with controllable gain allows bandwidth control independent of resonator Q. By using feedback to control bandwidth rather than relying solely on high-Q resonators, the system achieves narrow bandwidth when needed while maintaining the ability to tune over a broader frequency range by adjusting the feedback gain and resonator frequency.
Solution Approach 2:
The system dynamically adjusts the feedback gain and resonator frequency to achieve different bandwidths and tuning ranges as needed. The controllable component in the feedback path and the frequency-tunable resonator work together to provide adaptive control, allowing the filter to transition between narrowband and broadband operation modes.
3Device complexity
If passive elements are used for frequency adjustment, then circuit complexity is reduced, but electronic control capability is insufficient
Solution Approach 1:
The feedback path includes a controllable component that can be adjusted electronically to control the feedback amount. This provides electronic control capability while maintaining a relatively simple circuit structure. The controllable component may be implemented using standard electronic devices that can be controlled by external signals.
Solution Approach 2:
The feedback-based architecture provides multiple functions including bandwidth control, frequency tuning, and potential gain control, all within a single circuit structure. The frequency-tunable resonator and controllable feedback component work together to provide versatile electronic control for various filtering applications.
4Measurement precision
If filter bandwidth is reduced for better selectivity, then frequency selectivity is improved, but adaptability to different applications is reduced
Solution Approach 1:
The system dynamically adjusts the feedback gain to control bandwidth, allowing the filter to adapt to different applications. When high frequency selectivity is needed, the feedback gain is increased to narrow the bandwidth. When broader bandwidth is needed for different applications, the feedback gain is reduced. This dynamic control provides both high selectivity when needed and adaptability to various applications.
Solution Approach 2:
The feedback gain parameter is changed to control bandwidth adaptively. By adjusting this parameter, the system can achieve narrow bandwidth for high selectivity applications or wider bandwidth for applications requiring broader frequency acceptance, providing versatility across different use cases.
Data Source
AI summary
A variable filter has a signal loop defined between a signal input and a signal output. A plurality of circuit elements connected in the signal loop, the plurality of circuit elements comprising a frequency tunable resonator, and an adjustable scaling block that applies a gain factor that is adjustable in a range that comprises a positive gain and a negative gain. A controller is connected to 1) tune the frequency tunable resonator; and to 2) adjust the gain factor of the adjustable scaling block between a negative gain factor to a positive gain factor providing for variable Q independent of frequency.