Power Amplifier Timing Alignment with Low-Skew Clocking
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Solution Overview
Problem
In electronic devices with wireless communications circuitry, the temporal misalignment of radio-frequency signals and control signals at the power amplifier can degrade performance due to variations in temperature and voltage, leading to inefficiencies and signal distortion.
Innovation Solution
The implementation of a circuit design that includes a common clocking interface with low skew reference clock and constant latency control and clock domain crossing circuits to synchronize data streams to the radio-frequency and control inputs of the power amplifier, ensuring stable timing alignment despite temperature and voltage variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If separate clock trees are used for radio-frequency and control signal paths, then each signal path can be independently designed, but temporal misalignment occurs between the signals at the power amplifier input
Solution Approach 1:
The patent merges the clock synchronization function into a unified clocking interface that serves both the radio-frequency and control signal paths. The constant latency control circuits in both paths are synchronized to the same reference clock, ensuring temporal alignment without requiring complex inter-path synchronization mechanisms.
Solution Approach 2:
The patent introduces constant latency control (CLC) circuits as intermediary elements between the clocking interface and the digital-to-analog converters. These CLC circuits act as mediators that absorb timing variations and ensure that both radio-frequency and control signals arrive at the power amplifier with precise temporal alignment, regardless of path length differences.
2Measurement precision
If constant latency control circuits are implemented in both signal paths, then precise timing alignment is achieved, but circuit complexity increases
Solution Approach 1:
The patent applies constant latency control locally at each digital-to-analog converter in both the radio-frequency and control signal paths. Each CLC circuit is tailored to its specific path requirements, adjusting latency independently to achieve precise alignment at the power amplifier input without requiring global recalibration.
Solution Approach 2:
The patent dynamically adjusts the latency parameter of the constant latency control circuits based on measured timing offsets between the radio-frequency and control signal paths. By changing the latency parameter adaptively, the system maintains precise timing alignment under varying operating conditions without increasing structural complexity.
3Measurement precision
If a shallow clock tree with fewer buffer stages is used, then clock skew is reduced, but clock signal distribution capability is limited
Solution Approach 1:
The patent segments the clock distribution function by using a shallow clock tree that distributes only the reference clock signal to the constant latency control circuits. The actual timing adjustment is then performed locally at each CLC circuit, dividing the clock distribution task between the central clock tree and local timing circuits to achieve low skew without requiring a deep, area-intensive clock tree.
Data Source
AI summary
A radio-frequency amplifier can have a radio-frequency input configured to receive a radio-frequency signal and a control input for receiving a control signal. The radio-frequency signal can be generated using a first group of digital-to-analog converters (DACs), whereas the control signal can be generated using a second set of DACs. Data intended for the first group of DACs can be fed through a first set of retiming circuits and a first crossbar circuit. Data intended for the second group of DACs can be fed through a second set of retiming circuits and a second crossbar circuit. A low skew clocking interface and constant latency control and clock domain cross circuits can be employed to ensure that data streams arriving at the first group of DACs are time aligned with data streams arriving at the second group of DACs.