MIMO Beamforming Phase Correction via Feedback Loop
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Solution Overview
Problem
Beamforming MIMO communication systems face challenges in accurately measuring and correcting phase and frequency offsets between transmitters, particularly when Local Oscillator signals are unsynchronized, leading to differential phase noise and errors in directional signal formation.
Innovation Solution
The system employs a communication terminal with transmitters and receivers that produce and process phase-shifted RF signals, using a phase correction unit, such as a Differential Phase-Locked Loop, to measure and correct beamforming phase offsets. Additionally, pilot symbols with interleaved sub-sequences are used to estimate and adjust the beamforming phase, allowing for real-time correction of errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If phase-shifted RF signals are transmitted from multiple antennas to produce directional high-gain transmission, then transmission gain and directionality are improved, but sensitivity to phase and frequency offsets increases
Solution Approach 1:
The patent implements feedback mechanisms where received signals are processed to generate phase correction information that is fed back to the transmitters. The phase correction unit measures phase differences between signals from different antennas and adjusts the beamforming phase offsets accordingly, creating a closed-loop system that continuously compensates for phase and frequency offsets.
Solution Approach 2:
The patent replaces mechanical synchronization methods with electronic phase correction mechanisms. Instead of using synchronized local oscillators or mechanical phase alignment, the system uses digital signal processing to measure and correct phase offsets electronically, substituting complex mechanical synchronization systems with flexible electronic correction.
2Stability of the object's composition
If synchronized Local Oscillator signals are used in all transmitters, then phase consistency is improved, but system complexity and synchronization requirements increase
Solution Approach 1:
The patent extracts the synchronization function from the transmitter side and relocates it to the receiver side. Instead of requiring transmitters to maintain synchronized local oscillators, the receiver measures the actual phase differences and feeds correction information back, separating the complexity of synchronization from the transmission function.
Solution Approach 2:
The system implements self-service phase correction where each transmitter adjusts its own phase based on feedback from the receiver. The transmitters use their local unsynchronized oscillators but automatically correct their phase offsets based on measured errors, making each component self-adjusting without requiring external synchronization control.
3Device complexity
If unsynchronized Local Oscillator signals are used in transmitters, then system complexity is reduced, but differential phase noise increases
Solution Approach 1:
The patent converts the harmful effect of unsynchronized oscillators into a beneficial measurement opportunity. The differential phase noise generated by unsynchronized oscillators is not suppressed but rather measured and used as the basis for phase correction. The system embraces the phase differences as useful information for adjusting beamforming parameters.
Solution Approach 2:
The patent uses feedback loops to continuously measure and correct phase offsets caused by unsynchronized oscillators. The receiver measures phase differences in received signals and feeds correction information back to transmitters, creating a closed-loop system that compensates for the phase noise generated by unsynchronized local oscillators.
4Measurement precision
If beamforming phase offsets are corrected using traditional methods, then measurement accuracy is improved, but correction speed and adaptability to channel changes decrease
Solution Approach 1:
The patent implements preliminary phase correction by continuously measuring and maintaining phase offset information in the feedback loop. Instead of waiting for channel changes to occur and then correcting them, the system proactively measures and corrects phase offsets in real-time, preparing the system for upcoming channel variations.
Solution Approach 2:
The patent transforms the static beamforming phase offset correction into a dynamic process. The phase correction unit continuously adapts beamforming parameters based on real-time channel conditions and measured phase offsets, making the system dynamically responsive to changing environmental conditions rather than relying on fixed pre-calibrated values.
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 effectively cancels out differential phase noise and corrects beamforming phase errors, ensuring high-gain directional transmission in MIMO systems, even when transmitters use unsynchronized Local Oscillator signals, and adapts to changes in channel response and phase/frequency deviations.
Implementation Method 1
the phase correction unit includes a Differential Phase-Locked Loop (DPLL), which is coupled to measure the phase shift
Data Source
AI summary
A communication terminal includes first and second transmitters, which are coupled to produce respective first and second Radio Frequency (RF) signals that are phase-shifted with respect to one another by a beamforming phase offset, and to transmit the RF signals toward a remote communication terminal. The terminal includes a reception subsystem including first and second receivers and a phase correction unit. The first and second receivers are respectively coupled to receive third and fourth RF signals from the remote communication terminal. The phase correction unit is coupled to produce, responsively to the third and fourth RF signals, a phase correction for correcting an error component in the beamforming phase offset.