Digital Pre-emphasis Filter for Quadrature Imbalance Compensation
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Solution Overview
Problem
Modern transmitters face inefficiencies and increased complexity in supporting multiple bandwidths due to filtering requirements, leading to higher power consumption, silicon area usage, and design complexity when using either multiple narrow filters or a single wide bandwidth filter.
Innovation Solution
A pre-emphasis digital filter is used to compensate for impairments caused by differences between filter bandwidth and transmit signal bandwidth, allowing a single narrow bandwidth filter to be used, which simplifies design and reduces power consumption by adapting to changing analog filter performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If multiple narrow bandwidth filters are used to support different signal bandwidths, then filtering accuracy is improved, but device complexity and power consumption increase
Solution Approach 1:
The patent applies pre-emphasis filtering in the digital domain before DAC conversion to pre-compensate for the narrow bandwidth filter's frequency response limitations. This preliminary digital processing allows a single narrow filter to effectively support multiple bandwidth requirements without needing multiple physical filters, thereby reducing device complexity while maintaining filtering accuracy.
Solution Approach 2:
The patent introduces a pre-emphasis digital filter as an intermediary processing stage between the modem and DAC. This digital filter acts as a mediator that compensates for the bandwidth limitations of the narrow analog filter, enabling the system to support multiple signal bandwidths with a single analog filter and reducing overall system complexity.
2Manufacturing precision
If multiple narrow bandwidth filters are used to support different signal bandwidths, then filtering accuracy is improved, but silicon area usage increases
Solution Approach 1:
The patent makes a single narrow bandwidth analog filter universal by combining it with a pre-emphasis digital filter that can be configured for different bandwidths. The digital filter adapts its characteristics based on the required signal bandwidth, allowing the same analog filter hardware to serve multiple bandwidth functions (20MHz, 40MHz, 80MHz, 160MHz), thereby reducing silicon area usage while maintaining filtering accuracy.
Solution Approach 2:
The patent changes the parameters of the digital pre-emphasis filter (coefficients, tap weights, filter order) dynamically based on the required signal bandwidth. By adjusting these digital parameters rather than changing the physical analog filter, the system achieves different bandwidth support with the same analog filter hardware, reducing silicon area while preserving filtering precision.
3Device complexity
If a single wide bandwidth filter is used to support multiple bandwidths, then device complexity is reduced, but manufacturing precision deteriorates
Solution Approach 1:
The patent applies pre-emphasis filtering in the digital domain before DAC conversion to pre-compensate for the narrow bandwidth filter's frequency response limitations. This preliminary digital processing allows a single narrow filter to effectively support multiple bandwidth requirements without needing multiple physical filters, thereby reducing device complexity while maintaining filtering accuracy.
Solution Approach 2:
The patent employs an estimator that analyzes the frequency response characteristics and dynamically adjusts the pre-emphasis filter parameters to compensate for the narrow bandwidth filter's limitations across different operating conditions. This feedback mechanism ensures that filtering accuracy is maintained despite using a single narrow analog filter for multiple bandwidths.
4Device complexity
If a single wide bandwidth filter is used to support multiple bandwidths, then device complexity is reduced, but power consumption increases
Solution Approach 1:
The patent applies pre-emphasis filtering in the digital domain before DAC conversion to pre-compensate for the narrow bandwidth filter's frequency response limitations. This preliminary digital processing allows a single narrow filter to effectively support multiple bandwidth requirements without needing multiple physical filters, thereby reducing device complexity while maintaining filtering accuracy.
Data Source
AI summary
A transmitter includes a pre-emphasis digital filter configured to filter a series of respective digital input data samples according to a plurality of coefficients to generate a series of respective corresponding pre-emphasized data samples. The transmitter also includes a digital-to-analog converter (DAC) configured to sample the series of pre-emphasized data samples to generate an analog signal and an analog filter configured to filter the analog signal to generate a filtered signal. Estimator circuitry is configured to input a pre-emphasized data sample; input a corresponding sample of the filtered signal; and calculate the plurality of coefficients based on the sample of the filtered signal and the pre-emphasized data sample.