Programmable FIR Audio Filtering for Multi-Standard TV Sound
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Solution Overview
Problem
The challenge lies in designing TV systems that are compatible with various video and audio standards used across different countries, such as NTSC and PAL, which require processing of TV audio signals with different frequencies and standards like FM-Mono, NICAM, and FM-Stereo, necessitating a flexible sound signal processing system.
Innovation Solution
A sound signal processing system utilizing a Finite Impulse Response (FIR) filter and a down-conversion device, comprising a mixer, Cascade Integrator Comb (CIC) filter, and a programmable FIR filter, to adaptively process digital input signals and generate compatible digital output signals, enabling compatibility with multiple audio standards by adjusting decimation ratios and tap coefficients.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a fixed sound signal processing system is designed for a specific audio standard, then the processing performance for that standard is optimized, but the system cannot be compatible with multiple different audio standards
Solution Approach 1:
The patent implements dynamic configurability in the sound signal processing system by making the tap coefficients of the FIR filter and the decimation ratio of the CIC filter adjustable according to different audio standards. This allows the system to adapt its parameters dynamically to match NICAM, FM-Stereo, or other standards, resolving the contradiction between fixed optimization and multi-standard compatibility.
Solution Approach 2:
The patent changes key parameters (tap coefficients and decimation ratio) based on the selected audio standard. By storing different tap coefficient sets for different standards and selecting appropriate decimation ratios, the system achieves multi-standard compatibility without requiring completely separate processing chains for each standard.
2Reliability
If separate processing systems are designed for each audio standard, then each standard is processed optimally, but the overall system complexity and resource requirements increase
Solution Approach 1:
The patent creates a universal sound signal processing system that can handle multiple audio standards (NICAM, FM-Stereo, and others) through a single integrated architecture. The universal FIR filter and CIC filter are configured with adjustable parameters that allow them to perform optimally for different standards, eliminating the need for multiple separate processing systems while maintaining high processing quality for each standard.
Solution Approach 2:
The patent segments the audio processing into distinct functional blocks (FIR filter stage and CIC filter stage) with independent parameter control. This segmentation allows each block to be optimized independently for different standards through parameter adjustment, maintaining processing reliability while reducing overall system complexity compared to having completely separate systems for each standard.
3Measurement precision
If the FIR filter uses a large number of tap coefficients to achieve high filtering precision, then the filtering accuracy improves, but the computational complexity and processing time increase
Solution Approach 1:
The patent implements dynamic adjustment of the decimation ratio in the CIC filter based on the audio standard being processed. By optimizing the decimation ratio (e.g., using different ratios for NICAM vs. FM-Stereo), the system achieves high filtering accuracy with reduced computational burden, balancing precision and processing speed according to the specific standard requirements.
Solution Approach 2:
The patent segments the filtering function into two stages: an FIR filter for precise signal conditioning and a CIC filter for decimation and anti-aliasing. This segmentation allows the FIR filter to use a moderate number of taps for accurate filtering while the CIC filter handles the computationally intensive decimation function, distributing the computational load efficiently to maintain both accuracy and productivity.
Data Source
AI summary
The invention discloses a finite impulse response (FIR) filter for processing a digital input signal to generate a digital output signal. The FIR filter has a tap amount N and a decimation ratio D. The FIR filter includes a first memory, a multiplier, and an accumulation module. For each input sample of the digital input signal, the first memory provides N/D corresponding tap coefficients from a plurality of tap coefficients in turn. The multiplier multiplies the input sample with the N/D corresponding tap coefficients in turn to generate N/D product values. The accumulation module adds the N/D product values to N/D previous accumulation values to generate N/D renewed accumulation values respectively. If one of the accumulation values has already accumulated N product values, the accumulation module outputs the accumulation value as an output sample of the digital output signal.