Location

La Jolla, CA

Start Date

1979 12:00 AM

Description

Noise as a transmitted signal has been used in radar, ultrasonic Doppler flow measurement, and ultrasonic flaw detection. In each of these applications, the unique properties of noise have mainly influenced the design and operation of the signal processing portions of the system in which it was used. Our present work shows that the use of noise as a transmitted signal may also benefit the properties of phased array transducers used in imaging systems. Some imaging systems excite the transducer array sequentially in several modes. The echoes resulting from each of the transmitted modes are stored separately and then processed together to yield an effective beam pattern which cannot be realized by any elementary mode of the array. Although phased arrays are frequently used to simultaneously receive in a number of modes, it has not, up to now, been possible for an array to transmit more than one mode at a time. A technique is described which allows several modes to be transmitted simultaneously from a transducer array. This is achieved by exciting each mode with its own independent random signal. The echoes corresponding to each transmitted signal can then be unambiguously identified by correlation with the desired reference signal. This technique generally leads to simplified system design and permits operation in real time. Preliminary results for a small random signal phased array system will be described.

Book Title

Proceedings of the ARPA/AFML Review of Progress in Quantitative NDE

Chapter

12. Techniques for Flaw Reconstruction Using Short Wavelengths

Pages

473-475

Language

en

File Format

application/pdf

Share

COinS
 
Jan 1st, 12:00 AM

The Use of Noise Signals for Multi-Mode Beam Shaping

La Jolla, CA

Noise as a transmitted signal has been used in radar, ultrasonic Doppler flow measurement, and ultrasonic flaw detection. In each of these applications, the unique properties of noise have mainly influenced the design and operation of the signal processing portions of the system in which it was used. Our present work shows that the use of noise as a transmitted signal may also benefit the properties of phased array transducers used in imaging systems. Some imaging systems excite the transducer array sequentially in several modes. The echoes resulting from each of the transmitted modes are stored separately and then processed together to yield an effective beam pattern which cannot be realized by any elementary mode of the array. Although phased arrays are frequently used to simultaneously receive in a number of modes, it has not, up to now, been possible for an array to transmit more than one mode at a time. A technique is described which allows several modes to be transmitted simultaneously from a transducer array. This is achieved by exciting each mode with its own independent random signal. The echoes corresponding to each transmitted signal can then be unambiguously identified by correlation with the desired reference signal. This technique generally leads to simplified system design and permits operation in real time. Preliminary results for a small random signal phased array system will be described.