FM Detector Signal Interpolation Using Valid Phase Samples
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Solution Overview
Problem
Existing FM detectors suffer from significant signal distortion due to prolonged signal interpolation during noise detection, as they interpolate signals independently of pulse noise duration and use outdated methods that do not account for current signal validity.
Innovation Solution
An FM detector employing a quadrature detection system, phase converter, power calculator, threshold-based decider, and signal interpolator to assess signal validity and implement interpolation only when necessary, using valid samples preceding invalid ones to minimize distortion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If signal interpolation is implemented using a gate circuit closed for a fixed time upon noise detection, then pulse noise is eliminated, but the interpolation duration becomes excessively long independent of actual noise duration, causing signal distortion
Solution Approach 1:
The gate circuit closure time is made dynamic rather than fixed. The closure duration now adapts to the actual noise characteristics by monitoring when the noise condition persists, allowing the system to close the gate only as long as necessary to eliminate the noise while minimizing unnecessary signal interpolation and associated distortion.
Solution Approach 2:
The system incorporates feedback by continuously monitoring the noise condition during gate closure. The gate remains closed only as long as the noise condition is detected, and opens automatically when the noise subsides, creating a closed-loop control mechanism that optimizes the interpolation duration based on actual signal conditions.
2Ease of manufacture
If signal interpolation uses only the output signal immediately before gate closure, then implementation is simple, but significant signal distortion occurs due to outdated signal information
Solution Approach 1:
The system performs preliminary actions by storing multiple successive output signal values in a buffer before gate closure occurs. This allows the system to have pre-prepared, more current signal information available for interpolation, reducing the time gap between the actual signal state and the interpolation reference point.
Solution Approach 2:
The system changes the parameter of signal information freshness by using multiple successive signal samples rather than a single outdated sample. This parameter change from using one old value to using multiple more recent values significantly reduces signal distortion while maintaining reasonable implementation complexity.
Data Source
AI summary
A received FM wave signal is subjected to quadrature detection to generate baseband I and Q signals. The baseband I and Q signals are converted into a sequence of samples of phase information. An FM-detection-result signal is generated in response to a variation between two successive samples of the phase information. A power of the baseband I and Q signals is computed. A decision is made as to whether the baseband I and Q signals are valid or invalid by referring to the computed power and at least one threshold value. Signal interpolation is implemented with respect to the FM-detection-result signal in cases where it is decided that the baseband I and Q signals are invalid.