Set Up Signal Detection Using Butterworth Filtering and Autocorrelation
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Solution Overview
Problem
Existing methods for detecting set up signals in data communication over communication networks, such as those described in U.S. Pat. No. 7,003,093, are not accurate enough to achieve high Call Connect Reliability (CCR) for all standard telephone lines and require additional processing overhead, particularly due to the reliance on Goertzel Filters and automatic gain control (AGC).
Innovation Solution
A method and apparatus that utilize a combination of Butterworth filters, Goertzel algorithms, and autocorrelation techniques to detect answer tone signals and phase reversals, ensuring accurate identification of set up signals by comparing energy levels and analyzing signal patterns, thereby enabling reliable data communication without distortion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If Goertzel Filters and automatic gain control (AGC) are used to detect set up signals, then detection capability is provided, but processing overhead increases and measurement precision is insufficient
Solution Approach 1:
The patent segments the detection process into distinct functional modules: a signal conditioning stage that applies Butterworth filtering to preprocess the input signal, followed by a Goertzel algorithm stage that targets specific frequency components. This segmentation allows each module to specialize in one aspect of signal analysis, improving overall detection precision while making the processing overhead more manageable through modular design.
Solution Approach 2:
The patent merges multiple detection approaches by combining Butterworth filter-based signal conditioning with Goertzel algorithm-based frequency analysis in a unified detection system. This merging leverages the strengths of both methods: the Butterworth filter provides robust noise rejection and smooth frequency response, while the Goertzel algorithm efficiently identifies specific frequency components, together achieving high detection accuracy without requiring overly complex processing.
2Reliability
If existing detection methods are used, then set up signal detection is enabled, but Call Connect Reliability cannot reach 100% for all standard telephone lines
Solution Approach 1:
The patent applies parameter changes by adjusting the Butterworth filter order and cutoff frequencies to optimize performance across different telephone line standards. By dynamically adapting filter parameters and Goertzel algorithm frequency targets based on the detected signal characteristics and line type, the system achieves consistent high detection accuracy and 100% Call Connect Reliability across all standard telephone lines regardless of varying line conditions.
Data Source
AI summary
A method of detecting a set up signal having a predetermined frequency and used for data transmissions over a communication network comprises comparing an energy level of a filtered received signal with a first predetermined value and providing a first detect signal, comparing an energy level of a component of the received signal at a predetermined frequency with a second predetermined value and providing a second detect signal. In addition, an autocorrelation function is performed on the received signal to discriminate between the set up signal and other signals in the received signal, and a check signal is provided when the autocorrelation function identifies the set up signal. The set up signal in the received signal is detected in response to the first and the second detect signals and the check signal. A method of detecting phase reversals in the set up signal is also disclosed.