Power Amplifier Feedback Circuit for GPS Band 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 and a surface acoustic wave (SAW) or bulk acoustic wave (BAW) bandpass filter configured in a feedback loop to reduce the gain of the power amplifier within specific frequency bands, using phase shifters to provide negative feedback and minimize noise emissions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If post-power-amplifier filters are used to reduce noise emissions in protected frequency bands, then noise emissions are reduced, but power efficiency decreases and power requirements increase
Solution Approach 1:
The patent implements a feedback loop that taps a portion of the power amplifier output, filters it through a bandpass filter to extract noise in protected bands, phase-shifts it by 180 degrees, and feeds it back to the amplifier input. This negative feedback mechanism actively suppresses noise emissions in protected frequency bands without requiring external post-amplifier filters, thereby maintaining power efficiency while reducing harmful emissions.
Solution Approach 2:
The patent introduces a feedback network as an intermediary mechanism between the power amplifier output and input. This network includes a bandpass filter tuned to protected bands and a phase shifter that mediates the noise suppression process by creating a counter-phase signal, eliminating the need for direct post-amplifier filtering and associated power losses.
2Object-affected harmful factors
If post-power-amplifier filters are used to reduce noise emissions, then noise emissions are reduced, but device complexity increases
Solution Approach 1:
The feedback network serves multiple functions simultaneously: it provides noise suppression in protected bands, maintains amplifier stability, and eliminates the need for separate post-amplifier filter stages. By integrating these functions into a single feedback loop, the patent reduces overall system complexity despite adding feedback circuitry.
Solution Approach 2:
The feedback mechanism consolidates noise suppression functionality within the existing amplifier control loop, avoiding the need for separate post-amplifier filter stages and their associated control circuits. This integrated approach reduces device complexity compared to external filtering solutions.
3Object-affected harmful factors
If the power amplifier gain is reduced in protected frequency bands, then noise emissions are reduced, but signal amplification in desired bands may be affected
Solution Approach 1:
The bandpass filter in the feedback loop is specifically tuned to pass only the frequency components in protected bands while blocking desired frequency bands. This ensures that the negative feedback action is applied locally only to noise frequencies, leaving signal amplification in desired bands unaffected and maintaining reliable signal transmission.
Solution Approach 2:
The frequency-selective feedback mechanism ensures that only noise components in protected bands are fed back to suppress amplifier gain at those specific frequencies. The desired signal bands experience no feedback effect, maintaining their amplification and ensuring reliable signal transmission while reducing noise emissions.
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 power requirements of the system.
Implementation Method 1
a surface acoustic wave (SAW) bandpass filter configured to pass through a portion of the amplified radio frequency signal corresponding to a second frequency band
Data Source
AI summary
A power amplifier system can include a power amplifier that provides amplification to a radio frequency signal associated with a first frequency band and outputs an amplified radio frequency signal. An acoustic wave bandpass filter such as a surface acoustic wave or bulk acoustic wave bandpass filter is arranged in a feedback configuration with respect to the power amplifier. The filter can pass through a portion of the amplified radio frequency signal corresponding to a second frequency to provide negative feedback to the power amplifier, resulting in a reduction in an amount of gain from the power amplifier within the second frequency band.