Low-Noise RF Peak Detector Using Feedback Noise Cancellation
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Solution Overview
Problem
Radio-frequency signals at relatively low signal levels in electronic devices can exhibit excessive noise, interfering with satisfactory reception and measurement, particularly in environments with significant propagation loss and electromagnetic interference.
Innovation Solution
Incorporating a peak detector with a pair of square law transistors and diode-connected transistors in parallel, coupled between a power supply voltage and ground, to cancel out noise from the DC voltage output, and a differential pair of transistors to enhance noise cancellation in wireless circuitry.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a peak detector is used to measure radio-frequency signal levels, then measurement capability is provided, but noise interferes with satisfactory reception and measurement at low signal levels
Solution Approach 1:
The patent implements feedback loops that sense noise currents generated by square law transistors during signal peak detection and actively cancel them. The feedback mechanism monitors the output of square law transistors and injects counter-phase signals to neutralize noise, thereby maintaining measurement precision at low signal levels without sacrificing detection capability
Solution Approach 2:
The patent converts the harmful noise currents generated by square law transistors into beneficial information by sensing and measuring them through feedback loops. The noise currents are detected, processed, and used to generate correction signals that improve overall measurement accuracy, transforming a detrimental effect into a useful component of the measurement system
2Measurement precision
If square law transistors are used in the peak detector, then signal peak detection is enabled, but excessive noise is generated at low signal levels
Solution Approach 1:
The patent extracts and separates the noise current component from the useful signal peak detection function. By using dedicated feedback loops that specifically target and isolate noise currents generated by square law transistors, the system removes this harmful element while preserving the beneficial peak detection capability. The noise extraction is achieved through selective sensing and counter-phase signal injection
Solution Approach 2:
The patent introduces feedback loops as intermediary elements between the square law transistors and the output. These feedback loops act as mediators that sense the noise currents generated by the transistors and introduce correction signals that cancel the noise without interfering with the primary peak detection function. The intermediary feedback mechanism enables coexistence of noise-generating transistors with low-noise measurement requirements
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 effectively minimizes noise in signal peak measurements, allowing accurate detection of radio-frequency signals even at low signal levels by canceling noise current through feedback loops, thereby improving signal differentiation and measurement accuracy.
Implementation Method 1
The diode-connected transistors may cause noise current to flow in a single direction along feedback loop paths from the source-drain terminals onto the gate terminals of the pair of square law transistors. This may serve to cancel out noise from the DC voltage output by the peak detector.
Data Source
AI summary
An electronic device may include an antenna, a receiver, and a transmission line path that couples the antenna to the receiver. A peak detector may receive a radio-frequency signal from the transmission line path and may output a DC voltage indicative of a peak voltage level of the signal. The peak detector may include a pair of square law transistors having source-drain terminals coupled to an output of the peak detector. The peak detector may include a differential pair of transistors coupled between a power supply voltage and the output. The peak detector may include diode-connected transistors coupled between the source-drain terminals and gate terminals of the square law transistors. The diode-connected transistors may cause noise current to flow along feedback loop paths from the source-drain terminals onto the gate terminals of the square law transistors. This may remove noise from the output of the peak detector.