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Maximum Constrained Directivity of Oversteered End-Fire Sensor Arrays.

Trucco A, Traverso F, Crocco M - Sensors (Basel) (2015)

Bottom Line: Moreover, we verify that the maximized oversteering performance is very close to the optimum end-fire performance.We conclude that optimized oversteering is a viable method for designing end-fire arrays that have better constrained directivity than broadside arrays but with a similar implementation complexity.A numerical simulation is used to perform a statistical analysis, which confirms that the maximized oversteering performance is robust against sensor mismatches.

View Article: PubMed Central - PubMed

Affiliation: Department of Electrical, Electronic, Telecommunications Engineering, and Naval Architecture (DITEN), University of Genoa, 5-16126 Genova, Italy. andrea.trucco@unige.it.

ABSTRACT
For linear arrays with fixed steering and an inter-element spacing smaller than one half of the wavelength, end-fire steering of a data-independent beamformer offers better directivity than broadside steering. The introduction of a lower bound on the white noise gain ensures the necessary robustness against random array errors and sensor mismatches. However, the optimum broadside performance can be obtained using a simple processing architecture, whereas the optimum end-fire performance requires a more complicated system (because complex weight coefficients are needed). In this paper, we reconsider the oversteering technique as a possible way to simplify the processing architecture of equally spaced end-fire arrays. We propose a method for computing the amount of oversteering and the related real-valued weight vector that allows the constrained directivity to be maximized for a given inter-element spacing. Moreover, we verify that the maximized oversteering performance is very close to the optimum end-fire performance. We conclude that optimized oversteering is a viable method for designing end-fire arrays that have better constrained directivity than broadside arrays but with a similar implementation complexity. A numerical simulation is used to perform a statistical analysis, which confirms that the maximized oversteering performance is robust against sensor mismatches.

No MeSH data available.


Normalized end-fire beam patterns for an array of 10 sensors with a spacing d = 0.15 λ without oversteering (solid line) and with oversteering (dashed line), using a uniform weighting window.
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sensors-15-13477-f003: Normalized end-fire beam patterns for an array of 10 sensors with a spacing d = 0.15 λ without oversteering (solid line) and with oversteering (dashed line), using a uniform weighting window.

Mentions: In this paper, we demonstrate that an oversteered end-fire array, if adequately optimized, yields a constrained directivity that is similar to the maximum directivity (achieved by complex weight coefficients) and circumvents the previously mentioned implementation difficulties. Oversteering [3,4,5,7,10,12,13] is a technique applied to increase the directivity of an end-fire array by pushing its main-lobe peak past the end-fire, outside the visible region. The main lobe is steered past the end-fire (or oversteered) by inserting additional delays. If the sensors are spaced less than λ/2 and the beam pattern shift is adequately tuned, a reduction in the width of the main lobe in the visible region is obtained and the appearance of grating lobes is avoided. Unfortunately, the main-lobe absolute level is reduced, whereas the absolute levels of the side lobes are not modified. Thus, as shown in Figure 3, the oversteering operation reduces the main-lobe width but increases the side-lobe level relative to the main-lobe [10]. In particular, if the weight coefficients are held constant, a gradual increase in the oversteering amount causes a progressive decrease in the WNG (this statement can be easily demonstrated by the equation that defines the WNG, which is introduced in Section 2) (i.e., a robustness reduction).


Maximum Constrained Directivity of Oversteered End-Fire Sensor Arrays.

Trucco A, Traverso F, Crocco M - Sensors (Basel) (2015)

Normalized end-fire beam patterns for an array of 10 sensors with a spacing d = 0.15 λ without oversteering (solid line) and with oversteering (dashed line), using a uniform weighting window.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4507652&req=5

sensors-15-13477-f003: Normalized end-fire beam patterns for an array of 10 sensors with a spacing d = 0.15 λ without oversteering (solid line) and with oversteering (dashed line), using a uniform weighting window.
Mentions: In this paper, we demonstrate that an oversteered end-fire array, if adequately optimized, yields a constrained directivity that is similar to the maximum directivity (achieved by complex weight coefficients) and circumvents the previously mentioned implementation difficulties. Oversteering [3,4,5,7,10,12,13] is a technique applied to increase the directivity of an end-fire array by pushing its main-lobe peak past the end-fire, outside the visible region. The main lobe is steered past the end-fire (or oversteered) by inserting additional delays. If the sensors are spaced less than λ/2 and the beam pattern shift is adequately tuned, a reduction in the width of the main lobe in the visible region is obtained and the appearance of grating lobes is avoided. Unfortunately, the main-lobe absolute level is reduced, whereas the absolute levels of the side lobes are not modified. Thus, as shown in Figure 3, the oversteering operation reduces the main-lobe width but increases the side-lobe level relative to the main-lobe [10]. In particular, if the weight coefficients are held constant, a gradual increase in the oversteering amount causes a progressive decrease in the WNG (this statement can be easily demonstrated by the equation that defines the WNG, which is introduced in Section 2) (i.e., a robustness reduction).

Bottom Line: Moreover, we verify that the maximized oversteering performance is very close to the optimum end-fire performance.We conclude that optimized oversteering is a viable method for designing end-fire arrays that have better constrained directivity than broadside arrays but with a similar implementation complexity.A numerical simulation is used to perform a statistical analysis, which confirms that the maximized oversteering performance is robust against sensor mismatches.

View Article: PubMed Central - PubMed

Affiliation: Department of Electrical, Electronic, Telecommunications Engineering, and Naval Architecture (DITEN), University of Genoa, 5-16126 Genova, Italy. andrea.trucco@unige.it.

ABSTRACT
For linear arrays with fixed steering and an inter-element spacing smaller than one half of the wavelength, end-fire steering of a data-independent beamformer offers better directivity than broadside steering. The introduction of a lower bound on the white noise gain ensures the necessary robustness against random array errors and sensor mismatches. However, the optimum broadside performance can be obtained using a simple processing architecture, whereas the optimum end-fire performance requires a more complicated system (because complex weight coefficients are needed). In this paper, we reconsider the oversteering technique as a possible way to simplify the processing architecture of equally spaced end-fire arrays. We propose a method for computing the amount of oversteering and the related real-valued weight vector that allows the constrained directivity to be maximized for a given inter-element spacing. Moreover, we verify that the maximized oversteering performance is very close to the optimum end-fire performance. We conclude that optimized oversteering is a viable method for designing end-fire arrays that have better constrained directivity than broadside arrays but with a similar implementation complexity. A numerical simulation is used to perform a statistical analysis, which confirms that the maximized oversteering performance is robust against sensor mismatches.

No MeSH data available.