Receiver Filter Circuit for Low-Frequency Noise Suppression
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Solution Overview
Problem
Conventional radio signal receivers experience signal quality deterioration due to low-frequency noise and offset current generated by amplifiers, particularly in the direct conversion method, which affects image interference reduction.
Innovation Solution
A receiver design that includes a current output unit generating a current signal with a predetermined offset current, a demodulation unit for high-frequency components, and a filter circuit causing high-frequency components to pass to the demodulation unit while routing low-frequency components to a reference potential, utilizing active inductors or bias circuits to minimize noise and offset current impact.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If an amplifier is disposed in the front stage of the quadrature mixer to amplify the received signal, then the signal strength is improved, but low-frequency noise and offset current are generated which deteriorate signal quality
Solution Approach 1:
The patent divides the signal processing into two frequency bands: low-frequency components (including noise and offset) are separated and filtered out, while high-frequency components (containing the actual signal) are passed to the demodulation unit. This segmentation allows the system to maintain signal amplification benefits while eliminating harmful low-frequency artifacts.
Solution Approach 2:
The filter circuit extracts and removes the harmful low-frequency noise and offset current from the amplified signal. By taking out only the problematic frequency components while preserving the useful high-frequency signal components, the system achieves both strong signal amplification and clean signal quality.
2Power
If the amplifier amplifies all frequency components including low-frequency components, then the overall signal gain is improved, but the low-frequency noise and offset current also get amplified which degrades image quality
Solution Approach 1:
The filter circuit applies different quality characteristics to different frequency components: low-frequency components are attenuated or blocked while high-frequency components are passed with minimal attenuation. This local quality approach ensures that signal gain is maintained for the useful frequency range while image quality is preserved by eliminating low-frequency degradation.
3Object-affected harmful factors
If a filter circuit is introduced to remove low-frequency noise, then signal quality is improved, but device complexity increases
Solution Approach 1:
The filter circuit acts as an intermediary element between the amplifier and the demodulation unit. This mediator selectively processes the signal by removing harmful low-frequency components while preserving useful high-frequency components, achieving noise reduction with minimal impact on the overall system architecture.
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
This approach effectively suppresses signal quality deterioration by isolating and reducing low-frequency noise and offset current, enhancing the demodulation process and maintaining signal integrity.
Implementation Method 1
a filter circuit configured to cause, in the current signal, the high-frequency component to pass from the current output unit to the demodulation unit and cause, in the current signal, the low-frequency component to flow from the current output unit to a predetermined reference potential point
Data Source
AI summary
In a receiver that demodulates a received signal, deterioration of signal quality is suppressed. A current output unit generates and outputs, from a voltage signal, a current signal including a predetermined offset current in a low-frequency component between a high-frequency component having a frequency higher than a predetermined frequency and the low-frequency component having a frequency lower than the predetermined frequency. A demodulation unit demodulates the high-frequency component. A filter circuit passes, in the current signal, the high-frequency component from a current output unit to the demodulation unit, and causes the low-frequency component to flow from the current output unit to a predetermined reference potential point.