RF Analog LSI Low-Pass Filter Calibration
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Solution Overview
Problem
Existing RF analog LSI systems face challenges in efficiently calibrating low-pass filters for both reception and transmission circuits, leading to degraded constellation characteristics and increased noise due to relative mismatches between I and Q signals, which affect the throughput and accuracy of wireless LAN communication, especially under the IEEE802.11n standard.
Innovation Solution
The implementation of a calibration controller (Cal_Cnt) that detects phase differences between the output signals of low-pass filters using a phase detector (PD) to calibrate relative mismatches in both reception and transmission low-pass filters, adjusting their cut-off frequencies and time constants to reduce interference and improve signal quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional RF analog LSI systems are used without dedicated calibration mechanisms, then device complexity is reduced, but manufacturing precision deteriorates due to relative mismatches between I and Q signals in low-pass filters
Solution Approach 1:
The patent implements self-calibration mechanisms where the RF analog LSI automatically detects and corrects relative mismatches between I and Q low-pass filters using built-in phase detectors and calibration controllers. The system performs self-diagnosis and self-adjustment during operation, eliminating the need for external calibration equipment and maintaining filter characteristic matching autonomously.
Solution Approach 2:
The patent incorporates preliminary calibration procedures that adjust low-pass filter characteristics before full operation begins. Calibration controllers pre-adjust the I and Q filter parameters based on detected phase differences, ensuring optimal matching is established prior to signal processing, thereby preventing performance degradation from the outset.
2Manufacturing precision
If calibration mechanisms are added to improve filter matching, then manufacturing precision is improved, but device complexity increases due to additional calibration circuits and control logic
Solution Approach 1:
The patent merges the calibration function with the existing signal processing pathway by integrating phase detectors and calibration controllers into the current I/Q signal flow. The calibration circuits share common components with the operational signal path, such as using the same low-pass filter outputs for both signal processing and calibration measurements, thereby improving signal accuracy without proportionally increasing overall circuit complexity.
Solution Approach 2:
The patent designs calibration circuits that serve multiple functions: the phase detectors operate during both normal signal reception and calibration modes, and the calibration controllers adjust filter parameters for both I and Q channels simultaneously. This multi-functionality allows a single calibration mechanism to address multiple potential mismatches, improving signal accuracy while minimizing the number of dedicated calibration components required.
3Reliability
If low-pass filters are calibrated to reduce noise and improve signal quality, then reliability is improved, but loss of time occurs during the calibration process
Solution Approach 1:
The patent implements periodic calibration cycles where the RF analog LSI automatically performs calibration at predetermined intervals during operation. The calibration controller activates phase detectors and adjusts filter parameters at regular time intervals, ensuring reliability is maintained through periodic optimization without requiring continuous calibration that would consume excessive time. This approach balances communication accuracy with operational efficiency.
Solution Approach 2:
The patent performs preliminary calibration during the initialization phase before full communication operations begin. By completing the majority of calibration adjustments in advance, the system establishes optimal filter characteristics before processing actual data, thereby ensuring high reliability from the start while minimizing the time lost to calibration during active communication periods.
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 enables efficient calibration of low-pass filters, enhancing the performance of receiving and transmitting circuits by reducing noise and improving signal accuracy, thereby supporting high-throughput wireless LAN communications according to the IEEE802.11n standard.
Implementation Method 1
a phase detector (PD) which detects a difference in phase between output signals of the low-pass filters
Data Source
AI summary
The present invention aims to efficiently calibrate the characteristics of a pair of reception or transmission low-pass filters by a receiving or transmitting circuit. A semiconductor integrated circuit includes an RF receiver that processes an RF reception signal, an RF transmitter that generates an RF transmission signal and a frequency synthesizer. A reception low-pass filter of the RF receiver suppresses undesired components contained in I and Q baseband reception signals. A transmission low-pass filter of the RF transmitter suppresses noise due to D/A conversion, which is contained in I and Q transmission analog baseband signals. A calibration test signal is supplied to the inputs of the pair of reception or transmission low-pass filters. A difference in phase between the pair of filters is detected by a phase detection unit. A calibration controller calibrates a relative mismatch between the cut-off frequencies of the pair of filters.