PMIC Group Delay Detection for RF Power Amplifier Alignment
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Solution Overview
Problem
In 5G-NR mobile communication devices, the misalignment between modulated voltage and current at power amplifiers due to different group delays leads to degraded error vector magnitude (EVM) and adjacent channel leakage ratio (ACLR) in RF signals, which is challenging to measure accurately without complex calibration equipment.
Innovation Solution
A group delay determination circuit within the PMIC determines the relative group delay between modulated voltage and current based on known signals, allowing for time alignment and improving EVM and ACLR by using a group delay detection circuit that estimates the delay through signal conversion and edge detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If group delay compensation is implemented using complex calibration equipment, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The PMIC performs self-measurement of group delay by internally generating test signals and measuring the delay between voltage and current signals without requiring external calibration equipment. The group delay determination circuit uses the PMIC's own resources (oscillator, signal generation capabilities, and measurement circuits) to autonomously determine the group delay value, eliminating the need for complex external calibration equipment while maintaining measurement precision
Solution Approach 2:
A group delay determination circuit is introduced as an intermediary component within the PMIC that facilitates the measurement process. This circuit generates test signals, detects voltage and current signal edges, and calculates group delay values, serving as a mediator between the power amplifier circuit and the measurement process, thereby simplifying the overall system while improving measurement capability
2Measurement precision
If group delay determination is performed using external calibration equipment, then measurement accuracy is improved, but ease of operation deteriorates
Solution Approach 1:
The PMIC autonomously performs group delay determination by internally generating rectangular voltage and current signals, detecting their edges, and calculating the time difference. This self-service approach eliminates the need for external calibration equipment and complex calibration procedures, making the operation simple while maintaining high measurement accuracy through internal signal generation and measurement
3Reliability
If time alignment between modulated voltage and current is achieved, then EVM and ACLR performance are improved, but device complexity increases
Solution Approach 1:
The system performs preliminary group delay measurement and compensation before the actual power amplification and signal transmission. By determining the group delay value in advance using test signals and applying the appropriate delay compensation, the system ensures proper time alignment between voltage and current signals during normal operation, improving EVM and ACLR performance without requiring complex real-time adjustment mechanisms
Solution Approach 2:
The system adjusts the timing parameter (group delay) of the modulated voltage or current signals to achieve proper alignment. By changing the delay parameter based on measured values and applying compensation through delay elements or timing adjustments in the signal path, the system optimizes EVM and ACLR performance while maintaining relatively simple circuit architecture
Data Source
AI summary
Group delay determination in a communication circuit is disclosed. The communication circuit includes a power amplifier circuit that amplifies a radio frequency (RF) signal based on a modulated voltage and a power management integrated circuit (PMIC) that generates the modulated voltage. Herein, the PMIC includes a group delay determination circuit to determine a relative group delay between the modulated voltage and a modulated current, which is internal to the power amplifier circuit and unknown to the PMIC, solely based on signals known to the PMIC. The determined relative group delay can help to time align the modulated voltage with the modulated current at the power amplifier circuit to improve error vector magnitude (EVM) and/or adjacent channel leakage ratio (ACLR). Further, by determining the relative group delay based on known signals to the PMIC, it is possible to achieve good time alignment between the modulated voltage and the modulated current.