Digital AGC Circuit for Disturbance-Resistant Wideband Reception
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Solution Overview
Problem
Existing automatic gain control methods in wireless communication devices face challenges in reducing the effect of disturbances superimposed on wideband and small received signals, particularly due to the large circuit size and difficulty in accurately controlling analog filters used to mitigate these disturbances.
Innovation Solution
An automatic gain control method that employs a variable gain amplifier and an analog-to-digital converter, where a frequency selection circuit identifies a frequency bandwidth free from disturbance effects, and a control signal generation circuit determines the gain based on the signal strength of the selected frequency, allowing for reduced circuit size and effective disturbance reduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If an analog filter is used to reduce disturbance effects on wideband small received signals, then the disturbance reduction effect is improved, but the circuit size increases and control accuracy becomes difficult to achieve
Solution Approach 1:
The patent replaces the mechanical/analog filter system with a digital signal processing system. Specifically, it uses an ADC to convert the analog signal to digital, then employs digital filtering and frequency domain processing to remove disturbances. This substitution eliminates the need for complex analog filters while achieving better disturbance reduction through software-based signal processing.
Solution Approach 2:
The patent changes the operating parameters by moving from analog domain to digital domain processing. It transforms the signal into the frequency domain using FFT (Fast Fourier Transform), allowing selective removal of disturbance frequencies while preserving the desired wideband signal characteristics. This parameter transformation enables precise control without the physical constraints of analog filters.
2Object-affected harmful factors
If an analog filter is used to mitigate disturbances, then the disturbance reduction effect is improved, but the control accuracy deteriorates due to difficulty in accurate control
Solution Approach 1:
The patent replaces manual analog filter tuning with automated digital signal processing. The system uses ADC to digitize the signal, then applies digital filtering algorithms that can be precisely controlled through software. This eliminates the manual adjustment errors inherent in analog filter control while maintaining high disturbance reduction effectiveness.
Solution Approach 2:
The patent implements feedback mechanisms where the processed signal is continuously monitored and adjusted. The digital signal processing system can detect disturbance levels and automatically adjust filtering parameters to optimize performance, ensuring high control accuracy without manual intervention.
3Illumination intensity
If the gain of variable gain amplifier is increased to maintain signal level, then the signal level is improved, but the disturbance level also increases causing ADC saturation
Solution Approach 1:
The patent segments the signal processing into distinct stages: first amplification of the received signal, then digital filtering to remove disturbances, and finally output to ADC. By separating the amplification and disturbance removal operations into different stages (analog amplification followed by digital filtering), the system can increase gain without proportionally increasing disturbance levels that would cause saturation.
Solution Approach 2:
The patent introduces digital signal processing as an intermediary between the variable gain amplifier and the ADC. This intermediary stage processes the amplified signal to remove disturbances before the signal reaches the ADC, preventing saturation while maintaining high signal levels throughout the processing chain.
Data Source
AI summary
This automatic gain control circuit is provided with a variable gain amplifier for amplifying a received signal, has a small circuit size, and makes it possible to reduce the effect of superimposed external noise input within the frequency bandwidth of a received signal. The automatic gain control circuit supplies the output of the variable gain amplifier to an analog/digital converter and comprises: a frequency selection circuit that is connected to the output of the analog/digital converter and that selects a signal within the frequency bandwidth of a received signal, said signal having a narrower bandwidth than the frequency bandwidth; and a control signal generation circuit that generates a control signal for the variable gain amplifier on the basis of the strength of the signal selected by the frequency selection circuit.