Logarithmic Amplifier Demodulation Using Self-Quenching
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Solution Overview
Problem
Existing regenerative selective logarithmic detector amplifiers (LDAs) lack the ability to intrinsically demodulate phase and amplitude signals with high sensitivity and noise suppression, and have limited dynamic range and flexibility in receiver chain placement.
Innovation Solution
A regenerative logarithmic detector amplifier (LDA) with integrated amplitude and phase modulation capabilities, utilizing a phase lock loop (PLL) and automatic signal restart mechanism, enabling logarithmic amplification, signal regeneration, frequency conversion, noise filtering, and demodulation across a wide dynamic range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If super-regenerative receivers (SRO) are used for narrow band signals, then amplification gain is high, but selectivity deteriorates and output noise increases
Solution Approach 1:
The patent divides the amplification function into multiple stages: a super-regenerative amplifier stage for high gain amplification, followed by a logarithmic detector stage for signal processing. This segmentation allows each stage to optimize its function - the SRO provides high gain while the log detector provides selectivity and noise reduction, resolving the contradiction between amplification gain and selectivity.
2Quantity of substance
If logarithmic amplifiers are used to provide wide dynamic range amplification, then dynamic range is high, but the ability to reduce noise and demodulate phase modulation is lost
Solution Approach 1:
The patent merges the super-regenerative amplifier and logarithmic detector into a single integrated device. The SRO provides high gain amplification and the logarithmic detector provides noise reduction and phase modulation demodulation capabilities. This combination maintains the wide dynamic range of log amps while adding noise reduction and PM demodulation capabilities that pure log amps lack.
3Measurement precision
If super-regenerative receivers are placed upfront in the receive chain, then receive sensitivity is improved, but external quenching is required which increases device complexity
Solution Approach 1:
The patent implements self-quenching within the logarithmic detector stage, eliminating the need for external quenching circuits. The logarithmic detector naturally provides quenching action through its operating mechanism, allowing the super-regenerative amplifier to be placed upfront in the receive chain for maximum sensitivity without requiring additional external quenching components or circuitry.
Data Source
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AI summary
A logarithmic amplifier (LDA) is described that includes an amplifier configured to oscillate a modulated input signal, a feedback establishing a 180 degree phase shift between the amplifier input and the output and maintaining oscillation of the input signal, a parallel resonant circuit connected to the amplifier output causing the amplifier to resonate at or around a center frequency, and a controller connected to the amplifier input cyclically terminating oscillation of the input signal each time a pre-determined threshold of current is detected, the controller including a low pass filter configured to generate a second output signal having a repetition frequency. The LDA may be used for AM with or without a PLL and/or a superrsetiodyne. The LDA may be implemented as a mixer and used for phase demodulation. The LDA may be used for phase demodulation. The LDA may be used in place of a low noise amplifier.