Frequency Scanning Radio Modulator with Single Antenna Interference Avoidance
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Solution Overview
Problem
Existing FM modulators face interference issues when the selected transmit frequency coincides with local FM broadcast stations, leading to degraded audio quality, and prior solutions require complex circuitry with separate transmitter and receiver circuits, increasing size, cost, and complexity, while not adapting well to changing interference environments.
Innovation Solution
A radio modulator with a frequency scan function that uses a single antenna for both transmission and reception, employing a controller to sequentially tune through the FM band, measure signal strength, and select a frequency with low interference, displayed for user adjustment, thereby minimizing circuit complexity and adapting to changing environments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a full receiver circuit and full transmitter circuit are implemented to scan the FM band and automatically select a frequency with low interference, then the adaptability to changing interference environments is improved, but the device complexity and circuit size increase significantly
Solution Approach 1:
The patent merges the receiver and transmitter circuits into a single integrated modulator unit, allowing the same device to perform both frequency scanning (receiver function) and audio transmission (transmitter function). This consolidation reduces the number of separate components while maintaining the automatic frequency selection capability that adapts to changing interference environments.
Solution Approach 2:
The modulator is designed with multi-functionality, serving both as a frequency scanner (detecting ambient signal levels) and as an FM transmitter. The single device performs multiple functions that would traditionally require separate dedicated receiver and transmitter circuits, thereby reducing overall system complexity while maintaining adaptability to different interference conditions.
2Device complexity
If the transmit frequency is manually selected from predetermined channels, then the device complexity is reduced, but the audio quality degrades when the selected frequency coincides with local broadcast stations
Solution Approach 1:
The modulator incorporates a feedback mechanism where the receiver circuit continuously monitors ambient FM signal levels and provides information to the control logic. Based on this feedback about local broadcast presence, the system automatically adjusts the transmit frequency selection to avoid interfering with or being interfered by local stations, thereby maintaining audio quality without requiring complex manual intervention.
Solution Approach 2:
The system performs self-service by automatically detecting interference conditions and selecting appropriate transmit frequencies without user intervention. The modulator autonomously scans the FM band, identifies frequencies with low ambient signal levels, and configures itself to operate on those frequencies, eliminating the need for manual frequency selection while avoiding broadcast interference.
3Object-affected harmful factors
If the entire FM band is scanned to find the quietest frequency, then the audio quality is improved by minimizing interference, but the scanning time increases
Solution Approach 1:
The system performs a complete scan of the entire FM band to ensure the quietest possible frequency is selected, accepting the time requirement as necessary to achieve optimal interference avoidance. This comprehensive scanning approach guarantees that no potentially suitable frequency is missed, prioritizing audio quality over scanning speed.
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
The solution effectively scans the entire FM band to find a quiet frequency, reducing interference and maintaining audio quality, while simplifying circuitry and reducing costs by using a single antenna and minimizing spurious emissions.
Implementation Method 1
a demodulator coupled to mix a received antenna signal with the RF signal to produce an indicia of signal strength at the receive frequency resulting from that mix
Data Source
AI summary
A radio modulator and method with a radio band scan function. The apparatus consists of a frequency selectable RF signal transmitter, a switch that couples the RF signal to an antenna, and a demodulator coupled to mix a received antenna signal with the RF signal to produce an indicia of signal strength at the receive frequency resulting from that mix. A channel memory is coupled to store plural indicia of signal strength values corresponding to plural receive frequencies. A controller is coupled to the transmitter, the switch, the channel memory, and a display. In operation, the controller enables the frequency scan function by decoupling the switch, tuning the transmitter RF signal to plural frequencies, which causes the demodulator to receive plural receive frequencies within the radio band. The controller also stores the resultant plural corresponding indicia of signal strength in the channel memory, and then compares the stored plural indicia of signal strength to select a present transmit frequency that has a low signal interfering level. Next, the controller couples the transmitter to the antenna, tunes the RF signal to the present transmit frequency, and displays the present transmit frequency on the display.