Controlled Single Pole Filter for Adjacent Channel Interference
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Solution Overview
Problem
Current communication systems face challenges in effectively rejecting adjacent channel interferers, leading to saturation of downstream components and variability in in-band attenuation, which degrades receiver performance and error vector magnitude.
Innovation Solution
A controlled single pole filter is introduced to reject adjacent channel components, causing a predetermined attenuation in the in-band signal, which can be precisely compensated for in the digital domain, and a bypass circuit is used to avoid noise at low signal levels, ensuring a flat in-band frequency response.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a filter is used to reject adjacent channel components, then adjacent channel rejection is improved, but in-band signal attenuation varies and downstream components may saturate
Solution Approach 1:
The filtering function is divided into two separate stages: an analog controlled single pole filter that provides fixed attenuation and rejects adjacent channels, and a digital signal processor that provides variable gain control to compensate for the fixed attenuation. This segmentation allows each stage to optimize its function independently, preventing saturation while maintaining reliability.
Solution Approach 2:
The controlled single pole filter acts as an intermediary component with fixed attenuation characteristics that prevents adjacent channel components from saturating downstream components. By placing this fixed-attenuation filter before the variable-gain amplifier, it mediates between the strong adjacent channel signals and the sensitive downstream components.
2Object-affected harmful factors
If strong attenuation is applied to adjacent channels, then adjacent channel rejection is improved, but in-band signal level decreases
Solution Approach 1:
The signal processing chain is segmented into distinct functional blocks: a fixed-attenuation filter stage for adjacent channel rejection, and a separate variable-gain amplification stage for in-band signal level restoration. This allows the system to apply strong attenuation to adjacent channels while independently compensating for the in-band signal loss through digital control.
Solution Approach 2:
The system changes the attenuation parameter in a controlled manner by using a fixed attenuation value in the analog filter stage, then compensates by adjusting the gain parameter in the digital signal processor stage. This parameter control approach allows precise management of both adjacent channel rejection and in-band signal level.
3Power
If variable gain control is applied to in-band signal, then signal level is maintained, but system complexity increases
Solution Approach 1:
The system replaces complex analog variable gain control circuits with a simpler digital signal processing approach. The controlled single pole filter provides fixed attenuation through passive components, and the variable gain compensation is achieved through digital signal processing, which is less complex than implementing variable gain control entirely in the analog domain.
Data Source
AI summary
A circuit and method for filtering adjacent channel interferers. One embodiment of an adjacent channel filtering circuit for reducing adjacent channel interference with an in-band signal, includes: (1) a radio frequency (RF) circuit configured to receive and down-convert an RF signal to a baseband signal containing an in-band signal and adjacent channel components, (2) a controlled single pole filter electrically coupled to the RF circuit and configured to reject the adjacent channel components and cause a predetermined attenuation in the in-band signal, (3) a baseband circuit coupled to the controlled single pole filter and configured to condition the baseband signal for conversion to a digital signal, and (4) a digital circuit coupled to the baseband circuit and configured to receive the digital signal and compensate for the predetermined attenuation.