Parametric Filter Blending for First Adjacent Cancellation
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Solution Overview
Problem
The HD Radio system faces interference from FM signals in adjacent radio channels, which affects the quality of digitally modulated carriers in hybrid IBOC signals, and existing methods like the First Adjacent Canceller (FAC) do not effectively mitigate this interference across the entire signal bandwidth.
Innovation Solution
A method and apparatus that utilize notch filtering and parametric filtering to remove FM interferer components from the FM in-band on-channel radio signal, weighting the filtered signals, and combining them to produce an output signal, with a parametric filter controlled by the relative levels of the desired digital sideband and FM interferer to suppress interference near the center frequency more than inner subcarriers, and vectorizing operations for efficient implementation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If notch filtering is used to remove FM interferer components, then the interference removal effectiveness is improved, but the signal processing complexity increases
Solution Approach 1:
The signal processing is divided into multiple stages: notch filtering for interferer removal, parametric filtering for spectral shaping, and weighting for optimization. Each stage handles a specific aspect of interference mitigation, allowing the system to achieve effective interference removal while managing complexity through modular processing steps.
Solution Approach 2:
The patent employs parametric filtering with adjustable parameters to adapt the filter characteristics to different signal conditions. By changing filter parameters dynamically, the system can effectively suppress FM interferers across varying bandwidth conditions without requiring overly complex fixed-filter designs.
2Object-affected harmful factors
If parametric filter is used to suppress interference near center frequency, then the interference suppression effectiveness is improved, but the processing time increases
Solution Approach 1:
The system performs preliminary notch filtering to remove the majority of FM interferer components before applying the more computationally intensive parametric filtering. This preliminary action reduces the processing burden on subsequent stages, thereby reducing overall processing time while maintaining effective interference suppression.
Solution Approach 2:
The parametric filter is applied selectively to suppress interference near the center frequency where it is most problematic, rather than uniformly processing the entire spectrum. This localized approach to interference suppression reduces the total processing time while maintaining effectiveness in the critical frequency region.
3Reliability
If weighting is applied to the filtered signals, then the signal-to-noise ratio is improved, but the device complexity increases
Solution Approach 1:
The weighting operation uses feedback from the signal processing stages to optimize the combination of filtered signals. By adjusting weights based on signal characteristics and interference levels, the system improves the signal-to-noise ratio while the feedback mechanism allows for adaptive complexity management.
Solution Approach 2:
The patent combines multiple filtered signals (notch-filtered signal and parametric-filtered input signal) through weighted summation to produce the final output. This merging operation integrates the benefits of different filtering approaches while the weighting provides optimization, achieving improved signal-to-noise ratio through coordinated signal combination.
4Object-affected harmful factors
If FAC technique is used to mitigate first-adjacent FM interference, then the interference mitigation effectiveness is improved, but the blending performance is insufficient
Solution Approach 1:
The patent enhances the FAC technique by introducing parametric filtering with adjustable parameters that control the blending characteristics. By optimizing filter parameters and weighting factors, the system achieves superior blending performance while maintaining the interference mitigation effectiveness of the FAC technique.
Solution Approach 2:
The system creates a composite signal processing approach by combining multiple filtering techniques (notch filtering, parametric filtering) and weighting operations. This composite approach integrates the strengths of different processing methods to achieve both effective interference mitigation and superior blending performance.
Data Source
AI summary
A method for processing a radio signal includes: receiving an FM in-band on-channel radio signal including a plurality of digitally modulated subcarriers in upper and lower sidebands; sampling the FM in-band on-channel radio signal to produce an input signal including complex digital samples of a combination of a desired one the upper and lower sidebands and an FM interferer; removing FM interferer components from the first signal by notch filtering to produce a notch-filtered signal; weighting the notch-filtered signal to produce a weighted notch-filtered signal; using a parametric filter to filter the input signal to produce a parametric-filtered input signal; and combining the weighted notch-filtered signal and the parametric-filtered input signal to produce an output signal. A radio receiver that implements the method is also included.