Distributed Antenna Array Time Synchronization via Cross-Correlation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In long-distance communications, such as those between satellites and ground-based locations or aircraft, high gain antennas are required, but existing methods for combining signals from spatially distributed sub-arrays are inadequate due to inaccuracies in time synchronization and dynamic changes in sub-array positions, leading to degraded performance.
Innovation Solution
A method is introduced where one sub-array is selected as a reference, and composite output signals are formed by combining its output with permutations of other sub-array outputs, either with no time delay or a time delay equivalent to half a wavelength, to determine the signal's relative arrival time, allowing for accurate time synchronization and optimal signal combination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If sub-arrays are spaced further apart to increase antenna gain, then antenna gain is improved, but time synchronization precision deteriorates due to increased difficulty in determining relative positions and direction to remote station
Solution Approach 1:
The patent applies feedback by having each sub-array transmit reference signals and receiving signals from all sub-arrays, then using cross-correlation to measure actual signal arrival times. These measured times are fed back to the processor which calculates actual relative positions and adjusts time delay settings accordingly, continuously improving synchronization precision despite large separations between sub-arrays
Solution Approach 2:
The patent replaces mechanical measurement of sub-array positions with electromagnetic signal-based measurement. Instead of relying on mechanical position sensors or pre-calibrated geometric relationships, the system uses signal propagation time measurements from reference signals to determine relative positions, enabling accurate timing even when sub-arrays are far apart and mechanical measurement becomes impractical
2Ease of operation
If sub-arrays are placed in fixed positions to simplify time delay calculation, then ease of operation is improved, but adaptability deteriorates due to inability to compensate for dynamic position changes from vibrations or bending
Solution Approach 1:
The patent implements dynamics by transitioning from static, fixed time delay calculations to dynamic, real-time adjustment. The system continuously measures actual signal arrival times using reference signals and cross-correlation, then updates time delay settings in response to measured position changes caused by vibrations or structural bending, maintaining synchronization despite dynamic conditions
Solution Approach 2:
The patent applies self-service by having the antenna array automatically measure its own relative positions and adjust time delays without external intervention. Each sub-array transmits reference signals and the system uses cross-correlation to self-determine position relationships and update synchronization parameters, eliminating the need for external position monitoring systems or manual recalibration
3Device complexity
If coarse time delay settings are used for widely separated sub-arrays, then device complexity is reduced, but signal combining accuracy deteriorates leading to degraded communications performance
Solution Approach 1:
The patent applies preliminary action by having sub-arrays transmit reference signals before actual communications to establish accurate time delay settings. These preliminary measurements of signal arrival times using cross-correlation provide the basis for calculating precise time delays that will be used during actual data transmission, ensuring accuracy without requiring complex real-time adjustments during communications
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 maximizes antenna gain in the direction of the satellite by ensuring time-synchronized signal addition, improving signal-to-noise ratio and maintaining a high gain beam, even in scenarios with uncertain sub-array positions or dynamic changes.
Implementation Method 1
Cross correlation is then performed between the trial beam and each sub-array output beam to determine the relative arrival time of the signal at each sub-array
Implementation Method 2
Time delay needs to be applied to the signal collected from a sub-array which is closer to the signal source to compensate for the extra journey time of the signal reaching a sub-array further from the signal source
Implementation Method 3
In some narrow band systems it is satisfactory to implement the time delay correction as a phase correction
Data Source
AI summary
A method of processing signals received and transmitted between a satellite and sub-arrays of an antenna array. The satellite emits an analog signal received by the sub-arrays, each sub-array in turn produces a corresponding output. The array's total output is approximated by designating one of the sub-array's output as a reference output, and digitally forming a series of beams that consist of the reference output and permutations of the other sub-array outputs with either no time delay or with a time delay applied. A high power beam from the series is selected for cross correlation with each sub-array output to determine the signal's relative arrival time at each sub-array. Each sub-array output is time delayed based on the signal arrival time at that sub-array. The time delayed outputs are combined to form a high gain beam.