Antenna Array Calibration Using Orthogonal Pilot Signals
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing antenna array calibration methods face challenges in accurately synchronizing transmitter paths due to interference from wanted signals, leading to instability and inefficiency in blind calibration methods and prolonged calibration processes in pilot-based methods.
Innovation Solution
The implementation of a pilot-based online calibration technique that cancels interference from wanted signals by generating orthogonal calibration signals, summing transmission signals, estimating interference, and applying correction factors to improve signal-to-noise ratio and calibration accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a low-power calibration signal is used to minimize interference with the wanted signal, then interference with the wanted signal is reduced, but the calibration accuracy deteriorates due to insufficient signal energy
Solution Approach 1:
The patent employs periodic pseudo-noise calibration signals with known sequences that are transmitted at specific time intervals. The receiver correlates the received signal with the known calibration sequence, accumulating energy over the periodic transmissions. This allows the use of low-power signals that do not interfere with wanted signals while achieving sufficient calibration accuracy through temporal integration of the periodic signal energy.
Solution Approach 2:
The patent introduces an intermediary correlation process between the received calibration signal and the known pseudo-noise sequence. This correlation operation acts as a mediator that extracts the weak calibration signal from the background noise and wanted signals, effectively amplifying the calibration signal's detectability without increasing its transmitted power. The correlation peak provides a clear indication of calibration signal presence and enables accurate magnitude and phase measurement.
2Measurement precision
If pseudo-noise sequences are used to spread calibration signal energy over time and frequency, then calibration accuracy is improved, but the calibration process duration becomes unfeasibly long
Solution Approach 1:
The patent uses periodic repetitions of shorter pseudo-noise calibration sequences instead of single long sequences. By transmitting the calibration signal periodically and accumulating correlation results across multiple periods, the system achieves the same calibration accuracy as a single long sequence but in a much shorter total time. The periodic structure allows parallel processing and faster convergence of the calibration algorithm.
Solution Approach 2:
The patent performs preliminary correlation operations on each periodic calibration signal transmission and accumulates the results. This preliminary processing of individual periodic segments allows the system to build up the total correlation energy incrementally, avoiding the need to wait for a single extremely long pseudo-noise sequence to complete. The preliminary correlation results from each period are combined to achieve the final calibration accuracy.
3Device complexity
If blind calibration methods are used to avoid interfering pilot signals, then system complexity is reduced, but calibration stability deteriorates for larger magnitude and phase deviations
Solution Approach 1:
The patent introduces an intermediary known calibration signal as a mediator between the transmitter and receiver paths. This calibration signal serves as a reference that carries information about the transmitter path characteristics without requiring complex blind estimation algorithms. The known calibration sequence enables direct correlation-based measurement of magnitude and phase deviations, providing stable calibration results even for large deviations while maintaining relatively simple system implementation.
Data Source
AI summary
An antenna array (10) for the transmission of signals (20) is disclosed. The antenna array (10) comprises: a plurality of transmission paths (30-1, 30-2, 30-K) for transmitting a plurality of wanted signals (25) and at least one calibration signal generator (40-1, 40-2, 40-K) for the generation of at least one calibration signal (45). A plurality of calibration signal mixers (50-1, 50-2, 50-K) mixes the at least one calibration signal (45) with the plurality of wanted signals (25) to produce a plurality of transmission signals (20). A path sum signal device (60) sum the plurality of transmission signals (20) to produce a summed transmission signal (65); and an interference estimator (90) accepts the at least one calibration signal (45) and generates an estimated interference signal (92). An estimation signal mixer (95) subtracts from the summed transmission signal (65) the estimated interference signal (92) to produce a difference signal (97); and a on signal detection unit (70) for comparing the signal (97) with the at least one calibration signal (45).