Envelope Tracking Amplifier Delay Compensation for RF Linearity
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Solution Overview
Problem
Envelope tracking systems in mobile communication devices suffer from linearity and efficiency degradation due to inherent bandwidth limitations, particularly with the advent of 5G-NR technology, which modulates RF signals at higher bandwidths than the system can handle, leading to temporal misalignment between voltage and signal envelopes and resulting in reduced amplifier performance.
Innovation Solution
An ET amplifier circuit with a voltage processing circuit that operates in both low-bandwidth and high-bandwidth modes, modifying the ET modulated voltage to improve delay tolerance and reduce linearity degradation by dynamically adjusting the voltage differential between the time-variant voltage and signal envelopes, thereby maintaining efficient amplification of RF signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If envelope tracking system operates at higher bandwidth to support 5G-NR technology, then data rate and communication capability are improved, but linearity and efficiency degradation occur due to temporal misalignment between voltage and signal envelopes
Solution Approach 1:
The voltage processing circuit pre-modulates the ET modulated voltage to anticipate and compensate for the temporal delay that will occur during amplification. By performing the voltage modulation in advance with adjusted timing, the system ensures that the voltage envelope and signal envelope remain aligned despite the inherent delay in the amplifier circuit, thus maintaining linearity at higher bandwidths
Solution Approach 2:
The system dynamically adjusts the modulation bandwidth of the ET modulated voltage based on the operating conditions. By changing the bandwidth parameter of the voltage envelope to match the signal envelope characteristics, the system maintains optimal alignment between voltage and signal envelopes across different bandwidth operations, preventing linearity degradation
2Adaptability or versatility
If envelope tracking system increases bandwidth handling capability to support 5G-NR, then adaptability to new technology is improved, but efficiency and linearity are reduced due to inherent bandwidth limitations
Solution Approach 1:
The voltage processing circuit operates in different modes (low-bandwidth mode and high-bandwidth mode) depending on the operating conditions. By dynamically switching between modes and adjusting the modulation bandwidth accordingly, the system adapts to different bandwidth requirements while maintaining optimal efficiency and linearity performance in each operating regime
3Reliability
If temporal delay in ET amplifier circuit is reduced to improve alignment, then linearity is improved, but inherent processing delay cannot be eliminated
Solution Approach 1:
Instead of attempting to reduce the inherent processing delay, the system performs voltage modulation in advance before the signal enters the amplifier circuit. By pre-modulating the ET modulated voltage with adjusted timing, the system compensates for the unavoidable processing delay, ensuring that the voltage envelope arrives aligned with the signal envelope at the output
Data Source
AI summary
An envelope tracking (ET) amplifier circuit is provided. The ET amplifier circuit includes an amplifier circuit configured to amplify a radio frequency (RF) signal based on an ET modulated voltage. The ET modulated voltage corresponds to a time-variant voltage envelope, which can be misaligned from a time-variant signal envelope of the RF signal due to inherent temporal delay in the ET amplifier circuit. As a result, the amplifier circuit may suffer degraded linearity performance. In this regard, a voltage processing circuit is provided in the ET amplifier circuit and configured to operate in a low-bandwidth mode and a high-bandwidth mode. In the high-bandwidth mode, the voltage processing circuit is configured to cause the ET modulated voltage to be modified to help improve delay tolerance of the ET amplifier circuit. As a result, it may be possible to reduce linearity degradation of the amplifier circuit to a predetermined threshold.