Dynamic RF Filter Coefficient Selection for Noise Rejection
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Solution Overview
Problem
High-frequency electronic circuits face challenges in effectively filtering out noise signals from received RF signals, especially when frequency shifting is required to prevent interference, as existing methods are inefficient in dynamically adapting to frequency changes.
Innovation Solution
Modulating the frequency of the RF signal at the transmitter and using modulation information to retrieve filter coefficients stored in memory at the receiver, allowing for dynamic filtering of noise signals by varying filter characteristics or sampling rates to match the frequency shift of the transmitted signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If frequency shifting is performed to prevent interference, then interference from other RF transceivers is reduced, but noise signals at different frequencies cannot be effectively filtered out
Solution Approach 1:
The patent implements dynamic filter coefficient adjustment based on the transmitted frequency. The receiver uses the known transmit frequency to dynamically select or calculate appropriate filter coefficients from stored sets, allowing the filter characteristics to adapt in real-time to the current operating frequency. This dynamic adaptation enables effective noise rejection while maintaining the frequency-shifted signal integrity.
Solution Approach 2:
The system changes filter parameters (coefficients) based on the transmit frequency. Multiple sets of filter coefficients are stored in memory, each corresponding to a specific transmit frequency. When the transmit frequency changes, the receiver switches to the corresponding filter coefficient set, thereby adjusting the filter's frequency response to match the current operating conditions and effectively reject noise signals.
2Object-affected harmful factors
If a fixed bandpass filter is used to attenuate noise, then noise attenuation is achieved, but the system cannot adapt to frequency changes
Solution Approach 1:
The filter system transitions from static to dynamic operation. The receiver dynamically selects filter coefficients based on the current transmit frequency, which is known to both transmitter and receiver. This dynamic selection process allows the filter to adapt its characteristics (center frequency, bandwidth) to match the frequency-shifted signal while maintaining effective noise rejection.
Solution Approach 2:
Multiple sets of filter coefficients are pre-calculated and stored in memory before operation. Each set corresponds to a specific transmit frequency. When the system operates at a particular frequency, the appropriate pre-prepared coefficient set is retrieved and applied, eliminating the need for real-time calculation and enabling rapid adaptation to frequency changes.
3Speed
If synchronous sampling is used to downconvert RF signal, then RF signal is converted to audio frequency signal, but noise signals are also downconverted and cannot be distinguished
Solution Approach 1:
The patent applies localized filtering in the frequency domain by using specific filter coefficients that are tailored to the particular transmit frequency and corresponding audio frequency range. The filter selectively processes only the relevant frequency components while leaving other components (noise) unaffected or attenuated. This localized approach allows the system to distinguish the desired signal from noise even after downconversion.
Solution Approach 2:
The system uses feedback from the known transmit frequency information to determine the appropriate filter coefficients. Since both transmitter and receiver know the transmit frequency (either through modulation or predefined algorithm), the receiver can use this information to select the correct filter coefficients that will pass the desired audio frequency signal while rejecting downconverted noise signals.
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 approach enables efficient filtering of noise signals by dynamically tracking the frequency of the transmitted signal, ensuring that only desired audio frequency components pass through, thereby enhancing target detection and reducing interference.
Implementation Method 1
a synchronous sampler, such as used in a microwave impulse radar (MIR), is used to downconvert the received RF signal to an audio frequency signal by a scale factor
Implementation Method 2
a bandpass having a frequency characteristics shown with dashed line 45 is used
Data Source
AI summary
The frequency of an RF signal to be transmitted is modulated at the transmitting unit, and the modulation information is used by the receiving unit to filter out any unwanted noise. The modulation information may be used to retrieve associated filter coefficients that are used by the receiver to filter out the noise. Accordingly, for each transmit frequency, a multitude of filter coefficients stored in a memory are applied by the receiver to filter out the noise. The filtering operation may be performed after the received signal is downconverted from an RF to an audio signal.