Antenna Arrangement for DOA Estimation Using Dual-Frequency Grating Lobe Separation
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Solution Overview
Problem
Existing DOA estimation methods lack the accuracy needed for precise direction finding in wireless communication systems, particularly due to the ambiguity introduced by grating lobes at higher frequencies, which affects the accuracy of user terminal positioning through triangulation.
Innovation Solution
An antenna arrangement comprising at least two antenna functions, each covering a specific angular sector, performs DOA estimations at both a lower and higher frequency, with the latter resulting in grating lobes. By separating these grating lobes from the main lobe using results from the lower frequency estimation, the method forms a more accurate DOA estimation, ensuring unambiguous results.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If DOA estimation is performed at a higher frequency to achieve a narrower main lobe and higher precision, then measurement precision is improved, but grating lobes appear causing ambiguity and reducing reliability
Solution Approach 1:
The patent performs a preliminary DOA estimation at a lower frequency before the higher frequency estimation. This preliminary estimate is then used to identify and exclude grating lobes from the higher frequency results, allowing the system to achieve high precision without the ambiguity caused by grating lobes.
Solution Approach 2:
The lower frequency DOA estimation acts as an intermediary that mediates between the high frequency estimation and the final DOA result. By using the lower frequency estimate to filter the higher frequency results, the system combines the advantages of both frequencies while avoiding the disadvantages of each.
2Measurement precision
If a single high frequency is used for DOA estimation, then the main lobe becomes narrower improving precision, but grating lobes create ambiguity reducing measurement accuracy
Solution Approach 1:
The system performs a preliminary DOA estimation at a lower frequency that does not produce grating lobes in the angular sector of interest. This preliminary estimate provides a reference direction that is then used to identify the correct main lobe among multiple lobes at the higher frequency, eliminating ambiguity.
Solution Approach 2:
The patent segments the DOA estimation process into two distinct frequency stages: a lower frequency stage for obtaining an unambiguous preliminary estimate, and a higher frequency stage for achieving narrow main lobe precision. The results from both stages are then combined to produce the final accurate DOA estimate.
3Reliability
If multi-frequency DOA estimation is performed to resolve grating lobe ambiguity, then reliability is improved, but device complexity increases due to multiple frequency processing
Solution Approach 1:
The antenna arrangement is designed to operate universally across multiple frequency bands, using the same hardware infrastructure for both lower and higher frequency DOA estimations. This multi-functionality allows the system to achieve reliable DOA estimation without requiring separate dedicated systems for each frequency.
Solution Approach 2:
The system uses feedback from the lower frequency DOA estimation to guide the higher frequency estimation process. The preliminary estimate serves as feedback that helps identify and select the correct main lobe at the higher frequency, reducing the complexity of processing multiple frequency results by providing a clear selection criterion.
Data Source
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AI summary
The present invention relates to an antenna arrangement (1) comprising at least two antenna functions (2, 3, 4, 5) arranged to cover a certain angular sector (6). Each antenna function (2, 3, 4, 5) comprises a corresponding antenna port. The antenna arrangement (1) is arranged to perform a first direction of arrival, DOA, estimation for a transmitting device (12) at a first frequency (f1). The antenna arrangement (1) is furthermore arranged to perform a second DOA estimation for the transmitting device (12) at a second frequency (f2), the second frequency (f2) being of larger magnitude than the first frequency (f1). At least one second frequency grating lobe (13, 14; 31, 32, 33, 34, 35, 36) is apparent in the angular sector (6) at the second frequency (f2). The antenna arrangement (1) is arranged to separate said second frequency grating lobe (13, 14; 31, 32, 33, 34, 35, 36) from a second frequency main lobe (15, 15') by means of results from the first DOA estimation, a pointing direction (17, 17') of the second frequency main lobe (15, 15') forming a resulting DOA estimation. The present invention also relates to a corresponding method.