Sub-Threshold MOS RF Detector for Low-Power Signal Demodulation
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Solution Overview
Problem
Existing radio-frequency signal demodulators consume high power, especially at increased transmission rates, making them inefficient for battery-powered devices and those relying on remote high-frequency power supply, which decreases with distance from the reader.
Innovation Solution
A MOS transistor-based circuit that biases the transistor below its threshold voltage, using a series of MOS transistors as diodes and current mirrors to detect radio-frequency signals with low power consumption, and includes a low-pass filter to determine the average current for demodulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If an amplifier is interposed upstream and/or downstream of the diode to detect signals modulated with lower amplitude, then the detection capability for low-amplitude signals is improved, but the power consumption increases
Solution Approach 1:
The patent changes the operating parameters of the MOS transistor by biasing it below the threshold voltage and using it in the sub-threshold region, which allows the transistor to operate with extremely low power consumption while still providing sufficient gain for detecting low-amplitude signals. This parameter change eliminates the need for additional amplifiers that would increase power consumption.
Solution Approach 2:
The MOS transistor itself is configured to provide the necessary signal amplification and detection functionality through its sub-threshold operation characteristics, eliminating the need for separate amplifier components. The transistor's inherent properties in the sub-threshold region provide the required gain and detection capability without external assistance.
2Productivity
If the transmission rate is increased, then the communication speed is improved, but the power consumption increases
Solution Approach 1:
The patent exploits the frequency-dependent characteristics of MOS transistors in the sub-threshold region, where the transistor's transconductance and other parameters vary with frequency. By operating in this regime, the circuit can achieve higher transmission rates while maintaining low power consumption, as the transistor's natural response to high-frequency signals provides the necessary bandwidth without requiring additional power-hungry amplification stages.
3Measurement precision
If a coherent demodulation technique using a differential amplifier and multiplier is used, then the demodulation accuracy is improved, but the circuit power consumption increases
Solution Approach 1:
The patent extracts and utilizes the sub-threshold operation characteristics of the MOS transistor, which inherently provide the necessary signal processing functionality. By focusing on this specific operational regime, the complex coherent demodulation circuit with differential amplifiers and multipliers is simplified into a single transistor-based detector that achieves comparable accuracy with much lower power consumption.
4Measurement precision
If a super-regenerative technique using an oscillator and differential amplifier is used, then the signal detection sensitivity is improved, but the power consumption increases
Solution Approach 1:
The MOS transistor in sub-threshold operation provides inherent signal regeneration and detection capabilities through its non-linear characteristics and frequency-dependent behavior. This self-service mechanism eliminates the need for external oscillators and differential amplifiers required by super-regenerative techniques, achieving similar detection sensitivity with dramatically reduced power consumption.
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 reduces power consumption while effectively detecting low-amplitude signals and electromagnetic fields, maintaining efficiency even at higher carrier frequencies and varying supply voltages, and is insensitive to temperature and technological variations.
Implementation Method 1
The detector comprises at least one first MOS transistor with a channel of a first type, having its gate coupled to an input terminal capable of receiving said signal; a circuit for biasing the first transistor, capable of biasing it to a level lower than its threshold voltage
Implementation Method 2
a circuit for determining the average value of the current in the first transistor
Data Source
AI summary
A method and a circuit for detecting a radio-frequency signal, including at least one first MOS transistor with a channel of a first type, having its gate coupled to an input terminal capable of receiving said signal; a circuit for biasing the first transistor, capable of biasing it to a level lower than its threshold voltage; and a circuit for determining the average value of the current in the first transistor.