2-D Phased Array Processing In Bulk Wave Acoustic Media

R M Montgomery; J W Watkins

doi:10.1117/12.944194

12 April 1988 2-D Phased Array Processing In Bulk Wave Acoustic Media

R M Montgomery, J W Watkins

Proceedings Volume 0886, Optoelectronic Signal Processing for Phased-Array Antennas; (1988) https://doi.org/10.1117/12.944194
Event: 1988 Los Angeles Symposium: O-E/LASE '88, 1988, Los Angeles, CA, United States

Abstract

As a starting point for understanding the utility of focused acoustic wave devices it is useful to consider the operation of the electromagnetic antenna array. The aperture of the array can be considered as the aperture of a large camera lens. If such a lens were present, the electromagnetic radiaton received by the array would be imaged in the focal plane at a point corresponding to the location of the source. This concept is illustrated in Figure(1). The widely used parabolic dish antenna is a limited embodiment of this principle with a single image point or beam on the reflector axis. In the case of an array the antenna elements in the aperture sample the fields at discrete points (really smaller subapertures) and use various methods of combining the resulting signals to form approximations to the "images" at various angular locations or beam directions. In most cases it is simply not practical to put a physical lens or imaging reflector in the aperture location and place real sensors (feed horns) at the image points. Acoustic wave devices can be used to reduce the scale of the problem so that wave imaging approaches to beam forming become practical. Suppose that an array of acoustic radiating elements is arranged in a manner that exactly corresponds to the physical arrangement of the electromagnetic array elements. That is; the frequency is the same and the acoustic radiator spacing measured in acoustic wavelengths is identical to the electromagnetic element spacing measured in electromagnetic wavelengths. Under these circumstances the acoustic wave reconstructed from the aperture samples is a scaled replica of the electromagnetic wave incident on the array. The scale factor is equal to the ratio of the electromagnetic wave velocity to the acoustic wave velocity. This ratio is typically on the order of ten to the power five for useful acoustic materials. The possibility of forming an image of the far field source distribution becomes much more attractive when this scale factor is applied. This paper will deal with the design parameters of such an imaging system for a modest size (on the order of 10 X 10 elements) two dimensional array operating in the low gHz range.

Citation Download Citation

R M Montgomery and J W Watkins "2-D Phased Array Processing In Bulk Wave Acoustic Media", Proc. SPIE 0886, Optoelectronic Signal Processing for Phased-Array Antennas, (12 April 1988); https://doi.org/10.1117/12.944194

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KEYWORDS

Acoustics

Transducers

Antennas

Electromagnetism

Phased arrays

Signal processing

Reflectors

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