Angle Estimation Using Zero-Padded DFT for Radio Signals
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Solution Overview
Problem
Conventional angle estimation methods for radio signals are ineffective when the radiated power is low, leading to incomplete measurement of power on receiving paths, and down-sampling in amplitude goniometers results in spectrum folding and ambiguous frequency measurements, limiting the accuracy of angle of arrival estimation.
Innovation Solution
An angle estimation method that determines a subset of receiving paths with measured power, attributes non-measured powers with optimized values, and applies discrete Fourier transform to calculate transformed values for improved angle estimation, using a reference index and stored values from radiation patterns.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If down-sampling is used in amplitude goniometers to reduce bit rate, then the processing speed is improved, but spectrum folding occurs leading to ambiguous frequency measurements
Solution Approach 1:
The patent applies preliminary action by performing zero-padding on the received signal before down-sampling. This preparatory step increases the signal length, which prevents spectrum folding during the subsequent down-sampling process. The zero-padding is done in advance to maintain spectral accuracy while still achieving the desired reduction in bit rate for efficient processing.
2Reliability
If only a subset of receiving paths with adjacent antennas delivers measurable power, then the detection threshold is satisfied, but the number of available measurements is reduced, limiting angle estimation accuracy
Solution Approach 1:
The patent applies copying by creating a virtual extended array through mathematical reconstruction. When only a subset of adjacent antenna elements provides measurable power, the algorithm reconstructs the missing power measurements by exploiting the spatial correlation and symmetry properties of the antenna array. This virtual copying of measurement information from available elements enables accurate angle estimation as if all N elements were measured, thereby maintaining measurement precision despite limited physical measurements.
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
Enhances the accuracy of angle of arrival estimation by effectively utilizing non-measured power values, improving the method's performance even when only a subset of receiving paths provide measurable power, and addressing issues related to spectrum folding and ambiguity in down-sampling.
Implementation Method 1
a set of N receiving paths comprising directional antennas pointing in N different receiving directions
Implementation Method 2
calculation, by applying a discrete Fourier transform to the said completed power signal, of at least one transformed value
Data Source
AI summary
The invention relates to a method and a device for estimating an angle of arrival of an incident radio signal in relation to a predetermined reference direction by using a set of N receiving paths comprising at least one directional antenna pointing in N different receiving directions, wherein only one sub-set of at least two receiving paths with adjacent antenna directions in said set of antennas delivers a measured power at reception.The device comprises modules suitable for: determining a number of receiving paths delivering a measured power forming said sub-set, and a reference index corresponding to a first receiving path in a direction in which extends the set of antenna directions of said sub-set; selecting the measured powers and obtaining a value to attribute to the non-measured powers to form a completed power signal; by applying a discrete Fourier transform (DFT) to said completed power signal, calculating at least one transformed value among the transformed values corresponding to a first, second, and third frequency line of the DFT; and, using the transformed value(s), applying an estimator of the angle of arrival, depending on the reference index.