RF Squarer Detector Feedback for Low-Power Signal Sensitivity
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Solution Overview
Problem
Existing RF detectors face challenges with sensitivity for low power RF input levels, often requiring calibration or complex digital loops to achieve necessary sensitivity and dynamic range, especially in RF AGC closed loop systems.
Innovation Solution
A radiofrequency detector with a squarer circuit configured to feed back a feedback signal, functionally related to the difference voltage between the output and reference voltages, to the control electrode of a second reference transistor, enhancing sensitivity without the need for calibration or complex digital loops.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If existing RF detectors are used for low power RF input levels, then detection function is provided, but sensitivity is insufficient and calibration or complex digital loops are required
Solution Approach 1:
The patent implements a feedback mechanism where a portion of the output signal is fed back to the control electrode of the reference transistor. This feedback loop automatically adjusts the reference transistor's conductance to match the squarer transistor's conductance, enabling the detector to maintain high sensitivity for low power RF inputs without requiring external calibration or complex digital processing. The feedback signal ensures the reference transistor dynamically tracks the squarer transistor's characteristics across different input power levels.
2Measurement precision
If existing RF detectors are used for low power RF input levels, then detection function is provided, but sensitivity is insufficient and complex digital loops are required
Solution Approach 1:
The detector circuit performs self-adjustment through the feedback mechanism, where the reference transistor automatically adapts its characteristics to match the squarer transistor based on the feedback signal derived from the output. This self-service capability eliminates the need for external calibration procedures or complex digital loops, as the circuit autonomously maintains optimal operating conditions for high sensitivity detection across varying input power levels.
3Measurement precision
If a feedback signal is fed back to the control electrode of the second reference transistor, then sensitivity for low power input levels is improved, but circuit complexity increases
Solution Approach 1:
The feedback signal is derived directly from the existing output node of the squarer circuit, requiring only an additional connection to the control electrode of the reference transistor. This minimal additional circuitry provides automatic gain control and sensitivity enhancement without requiring complex feedback networks, making the complexity increase acceptable given the significant improvement in low power detection capability.
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 proposed solution improves sensitivity for RF low power input levels without requiring trimming or calibration procedures, and maintains dynamic DC offset recovery, ensuring stable RMS detection and AGC operations.
Implementation Method 1
The squarer circuit uses nonlinear elements such as diodes or transistors to perform the squaring operation. These nonlinear elements generate harmonics and effectively multiply the input signal by itself.
Implementation Method 2
said circuit is configured to feed back to a control electrode of said second reference transistor a feedback signal which is function of said difference voltage
Data Source
Figure 1A~1B
Figure 2
Figure 3
AI summary
A radiofrequency detector comprising a squarer circuit (21) comprising a first (B1) and second (B2) branch coupled between a voltage supply and ground, said first branch (B1) comprising at least a first squarer transistor (M1) receiving a RF sinusoidal input voltage, said first squarer transistor (M1) being coupled to the voltage supply (Vcc) through a respective load (ZL21), said second branch (B2) comprising a second reference transistor (M2), said second reference transistor (M2) being coupled to the voltage supply (Vcc) through a respective load (ZL22), an output voltage (Vout) being formed at an output node of said first branch (B1) and a reference voltage (Vref) being formed at a respective output node, in particular a squared voltage being obtained by a difference voltage (Vdiff) of said output voltage (Vout) and reference voltage (Vref), wherein said circuit (21) is configured to feed back to a control electrode of said second reference transistor (M2) a feedback signal (Vref_fbk) which is function of said difference voltage (Vdiff).