Dual-Output Amplifier AGC for WiFi Interference Immunity
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Solution Overview
Problem
Wireless signal receivers face interference from unwanted signals, particularly from strong WiFi signals in the 2.4 GHz ISM band, which degrades their performance in receiving weak but desired signals, such as those in Bluetooth Low Energy and IEEE 802.15.4 standards, due to insufficient immunity to noise and linearity issues, and the need for effective automatic gain control.
Innovation Solution
The amplifier design includes two output terminals, one operating in current mode and the other in voltage mode, with an impedance-modifying circuit that provides greater voltage variation at the second output terminal, allowing for effective automatic gain control through a power level detector, enhancing the receiver's ability to distinguish and amplify weak signals amidst strong interferers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single output terminal is used in conventional amplifiers, then the circuit complexity is low, but the automatic gain control precision deteriorates due to insufficient voltage variation for power level detection
Solution Approach 1:
The amplifier is segmented into two parallel output paths: a first output terminal providing a first output signal and a second output terminal providing a second output signal. The impedance-modifying circuit further segments the second output path by introducing a parallel impedance configuration. This segmentation enables separate optimization of signals for different purposes (e.g., one for mixing, one for power detection), thereby improving power level detection precision without overwhelming complexity
Solution Approach 2:
The impedance-modifying circuit acts as an intermediary element between the amplifier output and the power level detector. By introducing this intermediate circuit with specific impedance characteristics (parallel combination of impedance elements), the voltage variation is enhanced without requiring direct modification of the amplifier core, thus improving detection precision while containing complexity growth
2Object-affected harmful factors
If the amplifier operates in strong interference environments like 2.4 GHz WiFi, then the receiver must handle high power signals, but the linearity deteriorates causing degradation in receiving weak signals like Bluetooth Low Energy
Solution Approach 1:
The amplifier employs dynamic automatic gain control enabled by the enhanced voltage variation at the second output terminal. The power level detector continuously monitors the output signal level and dynamically adjusts the gain of the amplifier stages. This dynamic adjustment allows the receiver to maintain optimal linearity across varying signal conditions, whether dealing with strong WiFi interference or weak Bluetooth signals, thereby preserving reception reliability across different interference scenarios
Solution Approach 2:
The impedance-modifying circuit changes the electrical parameters (voltage variation, impedance level) of the second output signal specifically for power detection purposes. By altering these parameters, the power level detector can accurately measure output power even in the presence of strong interference, enabling effective AGC that maintains linearity and reliability across different operating conditions
Data Source
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AI summary
An amplifier (101) comprising: a supply voltage terminal (201) and a reference voltage terminal (202) and an input terminal (102); an amplifier arrangement comprising a first (203) and second (204) branch coupled between the supply and reference voltage terminals, and one or more transistors configured to provide current flow through each of the branches based on the input signal at the input terminal; a first output terminal (103) coupled to the first branch to provide a first output signal based on the current flow (207) therethrough; and a second output terminal (104) coupled to the second branch to provide a second output signal based on the current flow (2012) therethrough, wherein an impedance-modifying circuit (220) is coupled to the second output terminal to provide a voltage variation in the second output signal in response to the input signal greater than a voltage variation in the first output signal in response to the input signal.