FM Demodulation PLL Feedback for Frequency Offset Detection
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Solution Overview
Problem
FM broadcast receiving apparatuses face challenges in detecting frequency and phase changes due to low energy or poor signal quality, leading to low sensitivity and poor audio demodulation performance.
Innovation Solution
The FM demodulation device incorporates a phase converter, phase-locked loop (PLL) circuit, and frequency offset/shift detector to perform signal alignment and compensation, generating a frequency offset/shift determining signal that allows automatic adjustment of the receiving frequency band or audio volume to maintain high sensitivity and quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional demodulation methods are used, then the device structure remains simple, but sensitivity to low energy or poor signal quality data is low
Solution Approach 1:
The patent introduces a phase-locked loop circuit as an intermediary component between the phase converter and the frequency offset/shift detector. This PLL circuit generates a phase adjustment signal that compensates for phase variations in the input signal, thereby improving sensitivity to low energy or poor signal quality data without excessively complicating the overall device structure
Solution Approach 2:
The patent implements a feedback mechanism where the phase-locked loop circuit continuously adjusts the phase signal based on detected phase variations. The phase adjustment signal is fed back to compensate for phase errors in real-time, enhancing the device's ability to handle low energy or poor signal quality inputs
2Manufacturing precision
If frequency offset/shift compensation is not performed, then the device complexity is low, but audio quality deteriorates when frequency offset/shift is excessive
Solution Approach 1:
The patent performs preliminary frequency offset/shift detection and compensation before the main demodulation process. The frequency offset/shift detector analyzes the phase adjustment signal from the PLL circuit and generates a determining signal that triggers frequency band adjustment or volume reduction in advance, preventing audio quality deterioration before it occurs
Solution Approach 2:
The patent introduces dynamic adjustment capabilities where the receiving frequency band and audio volume are automatically adjusted based on the frequency offset/shift determining signal. This dynamic response allows the system to adapt to varying frequency conditions in real-time, maintaining audio quality without requiring a completely complex fixed-structure design
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 the sensitivity of FM demodulation devices to received data with low energy or poor signal quality, ensuring good audio quality by automatically adjusting the frequency band or reducing audio volume when excessive frequency offset/shift is detected.
Implementation Method 1
The phase-locked loop circuit is coupled to the phase converter to generate a phase adjustment signal according to the phase signal, and the phase-locked loop circuit adjusts the phase signal according to the phase adjustment signal, to perform demodulation of the input signal
Implementation Method 2
The frequency offset/shift detector is coupled to the phase-locked loop circuit and generates a frequency offset/shift determining signal according to the phase adjustment signal obtained from the phase-locked loop circuit. The frequency offset/shift determining signal is related to a phase frequency offset/shift of the input signal
Data Source
AI summary
A frequency modulation demodulation device and a control method thereof are provided. The frequency modulation demodulation device includes an input terminal, a phase converter, a phase-locked loop circuit, and a frequency offset/shift detector. The phase converter receives an input signal to obtain a phase signal. The phase-locked loop circuit generates a phase adjustment signal according to the phase signal and adjusts the phase signal according to the phase adjustment signal to perform demodulation of the input signal. The phase-locked loop circuit performs signal alignment and signal compensation on the phase signal to generate a filtered phase signal. The phase adjustment signal provides a feedback of and adjusts the phase signal. The frequency offset/shift detector generates a frequency offset/shift determining signal according to the phase adjustment signal. The frequency offset/shift determining signal is related to a phase frequency offset/shift of the input signal.