Digital Compensation of Analog Filter Frequency Response
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Solution Overview
Problem
Conventional high-Q and high-order analog filters in communication devices result in longer settling times and require additional calibration due to fabrication process variations, leading to increased chip area and potential signal degradation.
Innovation Solution
A digital filter is used to calibrate an analog filter by transforming communication signals between domains and generating compensation parameters based on frequency-related characteristics of the analog filter, allowing for adjustment of the digital filter's frequency response to compensate for deviations in the analog filter's response.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high-Q and high-order analog filters are used to achieve high signal rejection, then the filtering performance is improved, but the settling time increases and chip area expands
Solution Approach 1:
The patent replaces the traditional mechanical analog filter system with a hybrid system that uses a simple analog filter combined with digital signal processing. The analog filter performs initial filtering, and the digital processor compensates for frequency response deviations, eliminating the need for complex high-order analog filters and reducing settling time.
Solution Approach 2:
The patent changes the operating parameters by using a low-order analog filter with digitally adjustable frequency response. Through digital compensation algorithms, the system achieves high-Q filtering performance without the physical constraints of high-order analog filters, thereby reducing settling time and chip area.
2Reliability
If high-Q and high-order analog filters are used to achieve high signal rejection, then the filtering performance is improved, but the chip area increases due to backup capacitances
Solution Approach 1:
The patent replaces the physical backup capacitance system with a digital compensation system. Instead of using additional hardware components to calibrate and maintain filter performance, the system uses digital algorithms to compensate for frequency response deviations, significantly reducing chip area.
Solution Approach 2:
The patent creates a digital model or representation of the filter's frequency response characteristics and uses this digital copy to compensate for deviations. This virtual calibration approach eliminates the need for physical backup capacitances and reduces chip area.
3Reliability
If high-Q and high-order analog filters are used to achieve high signal rejection, then the filtering performance is improved, but the device complexity increases
Solution Approach 1:
The patent divides the filtering function into two separate stages: a simple analog filter for initial signal separation and a digital processing stage for fine-tuning frequency response. This segmentation reduces the complexity of the analog filter structure while maintaining overall filtering performance.
Solution Approach 2:
The patent introduces a digital processor as an intermediary between the simple analog filter and the final output. This intermediary compensates for the analog filter's frequency response deviations, allowing the use of simpler analog filter structures without sacrificing filtering performance.
Data Source
AI summary
A processing apparatus for calibrating an analog filter of a communication device in a digital domain is disclosed, wherein the analog filter is arranged to perform a filtering operation upon a communication signal in an analog domain. The processing apparatus includes a signal processing circuit and a digital filter. The signal processing circuit is used for transforming the communication signal between the digital domain and the analog domain. The digital filter is coupled to the signal processing circuit, and used for performing a filtering operation upon the communication signal in the digital domain, wherein a frequency response of the digital filter is arranged to compensate a frequency response of the analog filter according to at least a compensation parameter generated with reference to a frequency-related characteristic of the analog filter.