Power Amplifier Phase-Shifted Band-Pass Feedback Noise Suppression
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Solution Overview
Problem
Power amplifier systems in electronic devices face challenges in minimizing unwanted noise emissions, particularly in protected frequency bands like the GPS band, due to thermal noise and unwanted signals from other sources, which can interfere with nearby receivers.
Innovation Solution
A power amplifier system with a noise suppression feedback circuit that includes a directional coupler, a surface acoustic wave (SAW) or bulk acoustic wave (BAW) bandpass filter, and phase shifters to provide negative feedback and reduce gain in specific frequency bands, thereby minimizing noise emissions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If post-power-amplifier filters are used to suppress noise in protected frequency bands, then noise emissions are reduced, but device complexity and cost increase
Solution Approach 1:
The patent implements a feedback mechanism where a portion of the power amplifier output is fed back through a bandpass filter tuned to the protected frequency band (e.g., GPS band). This filtered feedback signal is then combined with the input signal to cancel out noise components in the protected band, thereby reducing noise emissions without requiring additional post-amplifier filters
Solution Approach 2:
The patent changes the gain parameter of the power amplifier specifically in the protected frequency band by utilizing the feedback path. The feedback loop introduces a frequency-dependent gain modification that reduces amplification in the protected band while maintaining normal amplification in other bands, effectively suppressing noise emissions through parameter modulation rather than physical filtering
2Object-affected harmful factors
If post-power-amplifier filters are used to suppress noise, then noise emissions are reduced, but power consumption increases
Solution Approach 1:
The feedback mechanism allows the system to suppress noise in protected bands by redirecting existing signal paths rather than adding new active filtering components. The feedback loop uses the already-amplified signal to generate cancellation, eliminating the need for additional power-hungry post-amplifier filters
Solution Approach 2:
The system uses its own output signal to generate the feedback needed for noise suppression. The power amplifier's output is fed back through the bandpass filter to create the cancellation signal, allowing the system to suppress its own noise emissions using internally-generated signals rather than requiring external suppression components
3Power
If the power amplifier amplifies all frequency bands equally, then signal strength is maximized, but noise in protected bands increases
Solution Approach 1:
The feedback path introduces frequency-selective gain modification through the bandpass filter. The filter is tuned to pass only the protected frequency band (e.g., GPS band), creating local quality changes where gain is reduced specifically in the protected band while other frequency bands maintain normal amplification, thereby achieving selective noise suppression without compromising overall signal strength
Solution Approach 2:
The system dynamically changes the gain parameter of the power amplifier in a frequency-selective manner. By utilizing the feedback loop with the bandpass filter, the effective gain in the protected frequency band is reduced while gain in other bands remains unchanged, achieving differential parameter control that simultaneously maintains signal strength and suppresses noise in protected bands
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution effectively reduces noise emissions in protected frequency bands without the need for post-power-amplifier filters, improving power efficiency and reducing the cost and power requirements of noise suppression.
Implementation Method 1
a surface acoustic wave (SAW) or bulk acoustic wave (BAW) bandpass filter
Implementation Method 2
an acoustic wave bandpass filter arranged in a feedback configuration with respect to the power amplifier
Data Source
AI summary
A power amplifier system can be configured to provide amplification to a radio frequency signal associated with a first frequency band and to output an amplified radio frequency signal. The system can include a bandpass filter arranged in a feedback loop with respect to the power amplifier and configured to pass through a portion of the amplified radio frequency signal corresponding to a second frequency band. A first shifter can be positioned in the feedback loop, and an output of the feedback loop can provide negative feedback to an input of the power amplifier.