Differential RSSI Rectifier Circuit for Small AC Signals
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Solution Overview
Problem
Existing RSSI systems struggle to rectify signals with amplitudes below the threshold voltage of diode circuits, as diodes require a minimum voltage to function, making it impossible to measure small AC signals effectively.
Innovation Solution
The use of PMOS and NMOS transistors in conjunction with capacitors to achieve differential signaling, where the transistors are coupled in a manner that allows effective rectification of small AC signals by coupling capacitors to the signal only during the positive or negative half-cycle, thereby enabling the measurement of signal strength indicators.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a diode circuit is used for rectification, then the circuit structure is simple, but small AC signals with amplitude below the threshold voltage cannot be rectified
Solution Approach 1:
The patent changes the electrical parameters of the rectification circuit by replacing the diode with a transistor-based differential amplifier. This allows the circuit to operate with much lower threshold voltages, enabling rectification of small AC signals that would otherwise be below the diode's threshold voltage. The transistor's transconductance characteristic enables the circuit to convert small voltage variations into proportional current signals.
Solution Approach 2:
The patent substitutes the nonlinear diode rectification mechanism with a linear transistor-based differential amplification mechanism. Instead of relying on the diode's threshold voltage drop for rectification, the invention uses the transistor's linear region operation with capacitive coupling to achieve signal rectification, thereby extending the measurable signal range to include very small amplitudes.
2Measurement precision
If a diode circuit is used for rectification, then the threshold voltage is fixed at around 0.6V, but this prevents measurement of small AC signals
Solution Approach 1:
The patent changes the operational parameters by using transistors biased in their linear region rather than relying on diode threshold voltage. The differential amplifier configuration with capacitive coupling allows the circuit to respond to voltage changes much smaller than 0.6V, thereby improving measurement precision for weak signals while maintaining a relatively simple circuit structure.
Solution Approach 2:
The patent introduces capacitors as intermediary elements that couple the AC signal to the transistor gates without requiring direct conduction through a threshold voltage barrier. These capacitors allow small voltage variations to be transmitted to the transistor gates, which then convert them into proportional current signals, enabling precise measurement of small AC signals.
3Measurement precision
If the threshold voltage is reduced to detect smaller signals, then small AC signals can be measured, but the circuit complexity increases
Solution Approach 1:
The patent replaces the diode's threshold voltage mechanism with a transistor-based differential amplification system. This substitution allows the circuit to detect much smaller voltage changes without requiring complex signal conditioning or multiple stages, as the transistor's transconductance directly converts small voltage variations into measurable current signals.
Solution Approach 2:
The patent uses capacitors as intermediary coupling elements that enable small AC signals to be transmitted to the transistor gates without being blocked by threshold voltage effects. This capacitive coupling mechanism, combined with the differential amplifier configuration, achieves high measurement precision for weak signals while maintaining circuit simplicity through the use of standard electronic components.
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 allows for the effective rectification and measurement of small AC signals, overcoming the limitations of diode-based systems by ensuring that the capacitors are only engaged when the signal is above or below the threshold, thus enabling accurate RSSI measurement across a wider range of signal amplitudes.
Implementation Method 1
Rectification is the conversion of an AC signal into a DC (direct current) signal. In prior art systems, rectification is usually accomplished by using a diode circuit.
Implementation Method 2
a first capacitor, and a second capacitor, wherein: a first terminal of the PMOS transistor is coupled to a first signal
Data Source
AI summary
An apparatus includes a PMOS (p-channel metal-oxide semiconductor) transistor, a NMOS (n-channel metal-oxide semiconductor) transistor, a first capacitor, and a second capacitor, wherein: a first terminal of the PMOS transistor is coupled to a first signal; a second terminal of the PMOS transistor is coupled to a second signal; a third terminal of the PMOS transistor is coupled to the first capacitor; a first terminal of the NMOS transistor is coupled to the second signal; a second terminal of NMOS transistor is coupled to the first signal; and a third terminal of the NMOS transistor is coupled to the second capacitor.