Headphone Cable Filter for FM Radio Noise
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Solution Overview
Problem
Mobile electronic devices often fail to adequately filter out-of-band noise, particularly from PLC networks, which interferes with FM broadcast radio reception, as they lack sufficient filtering for VHF radio bands, leading to disturbances in audio reproduction.
Innovation Solution
The integration of an electronic filter unit in the headphone cable arrangement that attenuates frequencies outside the VHF radio band, specifically between the audible frequency range and the VHF radio band, effectively suppressing interferences by acting as a common mode filter, ensuring only VHF frequencies are passed through.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If mobile electronic devices use headphone cable as FM antenna to pick up radio signals, then radio reception capability is improved, but out-of-band noise from PLC networks interferes with reception
Solution Approach 1:
An electronic filter unit is introduced as an intermediary component between the headphone cable and the VHF receiver. This filter unit selectively passes VHF radio band frequencies while attenuating out-of-band noise from PLC networks, thereby enabling clear radio reception without interference. The filter acts as a mediator that separates desired signals from harmful noise.
Solution Approach 2:
The filter unit changes the frequency parameter characteristics of signals transmitted through the headphone cable. It allows VHF radio band frequencies (87.5-108 MHz) to pass through while attenuating frequencies below and above this band, including PLC network interference. This selective frequency parameter modification enables reliable radio reception.
2Object-affected harmful factors
If electronic filter unit is integrated in headphone cable arrangement, then noise interference is reduced, but device complexity increases
Solution Approach 1:
The filter unit is designed to be self-contained and self-powered, drawing power from the audio signal itself or from the connected device without requiring additional power sources. This self-service capability reduces system complexity while maintaining effective noise filtering functionality.
Solution Approach 2:
The filter unit is designed to work with any headphone cable and VHF receiver combination, providing universal compatibility. It performs multiple functions: filtering PLC noise, passing VHF radio signals, and maintaining audio signal transmission. This multi-functionality reduces the need for separate components.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution enhances audio reproduction quality by filtering out unwanted frequencies, reducing noise interference and maintaining clear FM broadcast radio reception, thereby providing a more pleasant listening experience.
Implementation Method 1
The integration of an electronic filter unit in the headphone cable arrangement that attenuates frequencies outside the VHF radio band, specifically between the audible frequency range and the VHF radio band, effectively suppressing interferences by acting as a common mode filter
Data Source
Figure 1~2
Figure 3A~3B
Figure 3C~4
AI summary
A headphone cable (150) is connected to a headphone set (190) with one, two or more loudspeakers (191, 192). The headphone cable (150) includes at least a first signal wire (151) and at least one reference line (152, 154). An electronic filter unit (110) performs a filtering, e.g. a common mode filtering, which is effective on at least one of the signal wires and reference lines (151, 153). A differential audio signal between a signal wire and a reference line (152, 154) is passed. Common mode signals except signals within a VHF radio band may be attenuated. The electronic filter unit (110) may be arranged in a connector case (129) of a headphone connector (120) provided at a connector end of the headphone cable (150) or in a pluggable filter assembly (130) provided between the mobile electronic device (200) and the headphone cable (150).