RF Filter for Mobile Audio Circuit Interference Reduction
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Solution Overview
Problem
Mobile wireless communications devices face interference issues due to conducted and radiated RF energy from power amplifiers and antennas, which affect audio quality and receiver sensitivity, and are exacerbated by components like LCDs and keyboards generating electromagnetic interference.
Innovation Solution
The implementation of RF shielding for microphones, EMI filters in LCD and keyboard circuits, and choke filters in audio and serial bus circuits to reduce interfering energy and improve RF immunity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If components are reduced in size and placed closer together to make the device smaller, then device size is reduced, but electromagnetic interference between components increases
Solution Approach 1:
The patent introduces filter circuits as intermediary elements between RF components (power amplifier, antenna) and audio components (microphone, speaker). These filter circuits act as mediators that block conducted and radiated electromagnetic interference while allowing audio signals to pass through, thus resolving the interference problem caused by compact component layout.
Solution Approach 2:
The patent extracts and removes interfering electromagnetic energy from the system by using filter circuits to separate RF interference signals from audio signals. The filters extract the harmful RF components from the conductors connecting various components, preventing them from coupling into the audio circuit.
2Object-affected harmful factors
If filter circuits are added to reduce electromagnetic interference, then interference is reduced, but device complexity increases
Solution Approach 1:
The patent applies filtering only at specific critical locations where interference coupling occurs - namely between RF components and audio components. Rather than filtering entire systems, the solution applies local quality control by placing filter circuits only where needed (at audio component connections), thus reducing interference without unnecessarily increasing overall device complexity.
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 effectively minimizes interference, enhancing audio quality and receiver sensitivity by isolating RF energy and reducing electromagnetic interference, thereby improving the overall performance of mobile wireless communications devices.
Implementation Method 1
A filter is operative with the audio connection lines and operatively connected to at least one of the microphone audio switch or receiver speaker audio switch to reduce conducted and radiated interfering RF energy from coupling into the audio circuitry
Data Source
AI summary
A mobile wireless communications device includes a housing and circuit board carried by the housing. RF circuitry and a processor are operative with each other and carried by the circuit board. A receiver speaker and microphone are carried by the housing. Audio circuitry is carried by the circuit board and operative with the RF circuitry and processor. A microphone audio switch and receiver speaker audio switch are carried by the circuit board and are connected with audio connection lines that interconnect the processor. A filter is operative with the audio connection lines and operatively connected to at least one of the microphone audio switch or receiver speaker audio switch to reduce conducted and radiated interfering RF energy from coupling into the audio circuitry.