Dual Class-AB Amplifier Switching for Wider Receiver Dynamic Range
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Solution Overview
Problem
Radio frequency receiver systems face challenges in dynamic range improvement due to gain compression, reciprocal mixing noise, and in-band blocker-induced noise, particularly when handling large blocker signals, which degrade signal-to-noise ratio and increase hardware costs.
Innovation Solution
The implementation of a dual-class AB amplifier circuit, where two class AB amplifiers are cascaded, with one amplifier turning off during the on-state of the other when the input signal exceeds a threshold, reducing gain and noise during high-amplitude blocker signals, thereby enhancing dynamic range without increasing average current consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a SAW filter is added to filter out the blocker signal, then the dynamic range is improved, but the wanted signal level is degraded and the bill of material cost increases
Solution Approach 1:
The invention extracts and removes the blocker signal component from the received signal by detecting its presence and selectively disabling the amplifier during blocker signal periods, thereby improving dynamic range without adding external filtering hardware
Solution Approach 2:
The amplifier circuit performs its own blocker signal mitigation by using its output signal to detect blocker presence and controlling its own operation state, eliminating the need for separate SAW filter components
2Reliability
If the amplifier operates in class-AB mode to handle large blocker signals, then the dynamic range is improved, but the current consumption increases during blocker signal periods
Solution Approach 1:
The amplifier operates periodically in class-AB mode during detected blocker signal periods and returns to normal class-AB operation during normal signal periods, thereby managing current consumption in a time-varying manner that balances dynamic range requirements with power efficiency
Solution Approach 2:
The amplifier dynamically switches between different operating states (normal class-AB and blocker-handling class-AB) based on real-time signal conditions, allowing current consumption to adapt to the actual signal environment rather than maintaining a fixed high-consumption state
3Measurement precision
If the amplifier gain is increased to amplify weak wanted signals, then the signal to noise ratio is improved, but the gain compression occurs when large blocker signals are present
Solution Approach 1:
The amplifier applies high gain periodically during normal signal periods to improve SNR for weak wanted signals, and reduces gain during blocker signal periods to avoid gain compression, thereby achieving both objectives through time-varying gain control
Solution Approach 2:
The amplifier dynamically changes its gain parameter based on the detected signal conditions, switching between high-gain mode for weak signals and reduced-gain mode for blocker signals, thereby adapting to different operating scenarios
Data Source
AI summary
The invention provides an amplifier circuit. In one embodiment, the amplifier circuit includes a first class-AB amplifier and a second class-AB amplifier. The first class-AB amplifier amplifies an input signal to generate the first output signal. The second class-AB amplifier amplifies the first output signal to generate a final output signal on an output node. When the power of the input signal is greater than a threshold level, the second class-AB amplifier is in a turned-off state during a turned-on duration period of the first class-AB amplifier, and the first class-AB amplifier is in a turned-off state during a turned-on duration period of the second-class AB amplifier.