Multi-Level APT Voltage Circuit for OFDM Power Ramp Timing
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Solution Overview
Problem
In 5G-NR wireless communication systems, existing power amplifier technologies face challenges in adjusting average power tracking (APT) voltage in a timely manner to accommodate power fluctuations across OFDM symbols, leading to degraded error vector magnitude (EVM) due to insufficient ramp-up time for APT voltage.
Innovation Solution
A multi-level voltage circuit that independently increases APT voltage from a present value to a future value ahead of a predetermined effective time, using a control circuit to manage a command sequence with a voltage indicator and trigger, allowing for timely voltage adjustments independent of traditional triggers, thereby improving linearity and efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If traditional trigger-based voltage adjustment is used, then the control circuit waits for the voltage change trigger before adjusting APT voltage, but the voltage adjustment is too slow to accommodate power fluctuations across OFDM symbols
Solution Approach 1:
The control circuit receives the voltage indicator in advance and begins ramping up the APT voltage before the voltage change trigger is received. This preliminary action allows the voltage to be adjusted ahead of time, reducing the ramp-up time and preventing power envelope clipping while maintaining compatibility with the traditional trigger-based interface.
2Reliability
If APT voltage is adjusted in real-time to follow power fluctuations, then linearity and efficiency improve, but the voltage adjustment cannot keep up with the rapid transitions between OFDM symbols
Solution Approach 1:
By receiving the voltage indicator in advance and initiating voltage ramp-up before the trigger, the system prepares the APT voltage in advance, ensuring that the voltage transition completes in time to maintain linearity and prevent clipping, thus improving EVM performance without requiring faster hardware response.
Solution Approach 2:
The system dynamically adjusts the APT voltage ramp-up timing and rate based on the received voltage indicator and trigger timing, optimizing the voltage transition to match the specific power fluctuation requirements of each OFDM symbol while adapting to different modulation schemes and power conditions.
Data Source
AI summary
A multi-level voltage circuit and related apparatus are provided. The multi-level voltage circuit is configured to provide an average power tracking (APT) voltage to an amplifier circuit for amplifying a radio frequency (RF) signal, which can be modulated in a number of orthogonal frequency division multiplexing (OFDM) symbols. The RF signal may experience power fluctuations from one OFDM symbol to another and the multi-level voltage circuit may need to adjust the APT voltage accordingly. In examples discussed herein, when the APT voltage needs to increase from a present value to a higher future value at a predetermined effective time, the multi-level voltage circuit may start increasing the APT voltage from the present value toward the future value ahead of the predetermined effective time. As such, it may be possible to ramp up the APT voltage in a timely fashion to help improve linearity and efficiency of the amplifier circuit.