Programmable Squelch Circuit for Fair Low-Level Signal Gating
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Solution Overview
Problem
Existing squelch systems in telecommunications lack sufficient control resolution for high-quality audio, unfairly discriminate against low audio level signals with good carrier-to-noise ratios, and are not suitable for on-chip integration, leading to high power consumption and cost.
Innovation Solution
A squelch system with a noise signal block, full signal block, ATT block, and logic block that processes audio signals to determine noise and signal power, using a programmable gain control to attenuate signals based on noise and signal power ratios, ensuring finer threshold control and integration in a mixed-signal DSP environment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If existing squelch systems use simple power detectors and comparators, then the device complexity is reduced, but the control resolution is insufficient for high quality audio systems
Solution Approach 1:
The patent changes the parameter of threshold control from fixed to programmable by implementing a lookup table with multiple threshold values that can be selected based on different operating conditions. This allows fine control resolution without requiring complex analog circuitry, resolving the contradiction between measurement precision and device complexity.
Solution Approach 2:
The patent replaces traditional analog power detectors and comparators with a digital signal processing approach using a mixed-signal DSP environment. This substitution enables programmable threshold control and finer resolution while maintaining integration efficiency, addressing both the precision and complexity concerns.
2Adaptability or versatility
If existing squelch systems use fixed thresholds, then the device complexity is reduced, but they unfairly discriminate against received signals with low audio level but sufficient carrier-to-noise ratio
Solution Approach 1:
The patent implements dynamic threshold selection by providing multiple programmable threshold values in a lookup table that can be adjusted based on different operating conditions and signal characteristics. This dynamic adaptability ensures fair discrimination of low audio level signals with good carrier-to-noise ratio while maintaining manageable device complexity through systematic organization.
Solution Approach 2:
The patent creates a universal squelch control mechanism that can handle multiple signal conditions (different audio levels, carrier-to-noise ratios, and operating scenarios) through a single programmable lookup table structure. This multi-functionality approach improves adaptability without proportionally increasing device complexity.
3Ease of manufacture
If existing squelch systems use power detectors not suitable for on-chip integration, then the measurement precision is maintained, but the power consumption increases and on-chip integration becomes difficult
Solution Approach 1:
The patent replaces traditional power detectors with a mixed-signal DSP implementation that is suitable for on-chip integration in CMOS processes. This substitution significantly reduces power consumption while maintaining the necessary measurement capabilities through efficient digital signal processing techniques.
Solution Approach 2:
The patent merges the squelch control function with the DSP processing environment, integrating multiple functions (signal processing, threshold comparison, and control) into a unified on-chip implementation. This consolidation improves ease of manufacture and reduces power consumption by eliminating separate discrete components.
Data Source
AI summary
A method, system, and apparatus for squelching a signal in telecommunications systems. The apparatus includes a filter, two power detectors, a divider, two comparators, a logic gate, and a gain control block. The apparatus receives an input signal, and the power of the signal is detected. The input signal is also filtered to pass only the noise portion of the signal, and the power of the filtered signal is detected. A ratio between the filtered signal power and the input signal power is determined. A first comparator receives the filtered signal power and a second comparator receives the ratio of the filtered signal power and the input signal power. The logic gate receives the outputs from the first and second comparators. The gain control block receives as inputs the logic gate's output and the input signal to the apparatus. The gain control block may attenuate the input signal based on the logic gate's output. The gain control block generates the output signal of the apparatus.