AGC Circuit for Accurate RSSI Under Signal Distortion
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Solution Overview
Problem
Existing systems for determining received signal strength indicators (RSSI) of magnetic fields in vehicle access systems are prone to inaccuracies due to signal distortion, leading to incorrect distance measurements.
Innovation Solution
An automatic gain control (AGC) circuit comprising a pre-divider circuit, pre-amplifier, post-divider circuit, analog-to-digital converter, and logic to sample and set divider settings, generating accurate RSSI values by improving carrier-to-noise ratio and signal linearity, and allowing for fast envelope tracking and noise reduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a continuous waveform signal is used for RSSI measurement, then the measurement process is simple, but signal distortion causes the constant envelope to vary leading to inaccurate RSSI information
Solution Approach 1:
The patent implements dynamic gain adjustment through multiple gain stages that can be individually controlled. The system transitions from a static measurement approach to a dynamic one where gain settings are continuously adjusted based on signal conditions, allowing the measurement system to adapt to varying signal strengths while maintaining envelope stability.
Solution Approach 2:
The patent changes the parameter of gain control by introducing multiple adjustable gain stages with different gain values. By varying the gain parameters dynamically according to signal conditions, the system maintains accurate RSSI measurements across different signal strengths without being affected by envelope variations.
2Measurement precision
If multiple gain stages are used to improve signal processing accuracy, then measurement precision improves, but device complexity increases
Solution Approach 1:
The patent divides the gain control function into multiple independent gain stages, each with its own control mechanism. This segmentation allows each stage to be optimized independently and controlled separately, improving measurement precision while keeping the complexity manageable through modular design.
Solution Approach 2:
The patent implements feedback control where the system monitors signal conditions and automatically adjusts the gain stage settings. This feedback mechanism enables the complex multi-stage gain control system to operate autonomously, reducing the need for manual intervention and simplifying the overall control complexity.
3Measurement precision
If gain control settings are adjusted dynamically, then RSSI measurement accuracy improves, but processing time increases
Solution Approach 1:
The patent pre-configures multiple gain stages with predetermined gain values and settings. When a measurement is needed, the system can quickly select from these pre-prepared configurations rather than calculating optimal settings in real-time, thus maintaining high measurement accuracy while minimizing processing time.
Solution Approach 2:
The patent employs periodic sampling and measurement cycles where gain settings are adjusted at specific intervals rather than continuously. This periodic approach allows the system to maintain accurate measurements while reducing the overall processing time by avoiding constant adjustments.
Data Source
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AI summary
In some implementations, an automatic gain control (AGC) circuit comprises: a pre-divider circuit operable to pre-divide an input signal according to a pre-divider circuit setting and output a pre-divided signal; a pre-amplifier operable to pre-amplify the pre-divided signal and output a pre-amplified signal; a post-divider circuit operable to post-divide the pre-amplified signal according to a post-divider circuit setting; an analog-to-digital converter (ADC) operable to generate a digital data stream from the post-divided signal; logic operable to sample the digital data stream; determine a pre-divider circuit setting and a post-divider circuit setting based on the sampled data stream; set the pre-divider circuit and the post-divider circuit based on the determined settings; and generate a received signal strength value based on the pre-divider circuit setting and the post-divider circuit setting.