Dynamic Threshold Adjustment for FM Detection in Weak Fields
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Solution Overview
Problem
Existing receivers and transceivers struggle to accurately detect FM signals in weak electric fields, leading to erroneous detection due to increased noise levels in FM detection voltage.
Innovation Solution
A receiver and transceiver design that includes a detection voltage output unit and a threshold change unit, which dynamically adjusts the threshold for FM detection based on the noise level in the FM detection voltage, allowing correct output of FM detection voltage even in weak electric fields.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a fixed threshold is used for FM detection, then the detection circuit is simple, but FM is erroneously detected in weak electric fields due to increased noise levels
Solution Approach 1:
The patent applies dynamics by making the threshold variable rather than fixed. The threshold changes dynamically based on the received electric field strength - it is set to a first value when the electric field is strong and a second value (smaller than the first) when the electric field is weak. This dynamic adjustment allows the detection system to adapt to different signal conditions, preventing erroneous FM detection in weak electric fields while maintaining simple circuit operation.
Solution Approach 2:
The patent applies parameter changes by modifying the threshold parameter based on the noise level in the FM detection voltage. When the noise amount exceeds a predetermined value (indicating weak electric field), the threshold is changed from a first value to a second value. This parameter adjustment resolves the contradiction by enabling accurate detection in varying conditions without requiring complex additional circuitry.
2Measurement precision
If the threshold is lowered to detect weak FM signals, then detection sensitivity improves, but noise-induced erroneous detection increases
Solution Approach 1:
The patent applies parameter changes by adjusting the threshold based on the received electric field strength. When the electric field is weak (noise amount > predetermined value), the threshold is set to a second value (smaller than the first value), enabling detection of weak FM signals. When the electric field is strong, the threshold is set to a first value, preventing noise-induced erroneous detection. This conditional parameter adjustment resolves the contradiction between detection sensitivity and reliability.
Solution Approach 2:
The patent applies feedback by using the noise amount (detected from the FM detection voltage) to control the threshold setting. The system continuously monitors the noise level and adjusts the threshold accordingly - when noise exceeds a predetermined value, the threshold is lowered to detect weak signals; when noise is low, the threshold is raised to prevent false detection. This feedback mechanism ensures both high sensitivity and reliability.
Data Source
AI summary
Provided is a receiver capable of receiving an FM radio wave and an AM radio wave in a same frequency band (same channel). The receiver includes: a detection voltage output unit that outputs FM detection voltage obtained by detecting the FM radio wave when the FM detection voltage is determined to be at or above a first threshold; and a threshold change unit that sets the first threshold to a first value when a noise amount included in the FM detection voltage before threshold determination by the detection voltage output unit is larger than a predetermined value, and that sets the first threshold to a second value smaller than the first value when the noise amount is smaller than the predetermined value.