IR Receiver Squelch Logic for Interference Discrimination
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing IR receiving units struggle to effectively implement squelch to filter out interference noise, particularly from sources like fluorescent lamps and plasma televisions, as they cannot be distinguished from IR transmitters in the relevant frequency range.
Innovation Solution
An IR receiver with a decision logic circuit that activates or deactivates squelch based on mean and variance values of frequency, audio amplitude, and signal strength of the receiver intermediate frequency, allowing for more precise determination of signal quality and interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If traditional squelch methods (RSSI evaluation or demodulated noise analysis) are used, then the receiving unit can filter some noise, but fluorescent lamps and plasma televisions cannot be distinguished from IR transmitters and interfere with reception
Solution Approach 1:
The patent segments the noise analysis into multiple frequency components by evaluating the variance of the demodulated noise at different frequency bands. This allows differentiation between broadband interference (fluorescent lamps) and narrowband signals (IR transmitters) by analyzing which frequency segments are affected.
Solution Approach 2:
Instead of analyzing the entire noise spectrum equally, the patent applies partial action by focusing analysis on specific frequency ranges where IR transmission occurs. The variance evaluation is performed selectively on relevant frequency components rather than uniformly across all frequencies.
2Object-affected harmful factors
If squelch is activated to filter interference, then noise during transmission breaks is reduced, but legitimate IR signals may also be blocked
Solution Approach 1:
The patent implements feedback by continuously monitoring the variance of demodulated noise and dynamically adjusting the squelch decision. The system compares the calculated variance against threshold values and adapts the squelch activation state based on this feedback, allowing discrimination between noise patterns characteristic of interference versus those of legitimate signals.
Solution Approach 2:
The patent changes the parameter used for squelch decision from simple signal strength (RSSI) to the variance of demodulated noise. This parameter transformation enables better differentiation between types of signals, as variance captures the statistical properties of noise that distinguish fluorescent lamp interference from modulated IR signals.
3Measurement precision
If multiple parameters (frequency mean, frequency variance, audio amplitude) are evaluated for squelch decision, then signal discrimination improves, but device complexity increases
Solution Approach 1:
The patent merges multiple evaluation parameters (frequency mean, frequency variance, audio amplitude mean, audio amplitude variance) into a unified squelch decision logic. By combining these parameters and comparing them against threshold values, the system achieves comprehensive signal discrimination without requiring separate independent decision circuits for each parameter.
Data Source
AI summary
An IR receiver having a decision logic circuit for activating or deactivating a squelch. Activation or deactivation of the squelch is effected in dependence on a mean value of the frequency, a variance of the receiver intermediate frequency, a mean value of the audio amplitude, a variance of the audio amplitude and/or a signal strength of the receiver intermediate circuit frequency.