Characteristics of a high power ultrasonic array transmitter in air
A high-power ultrasonic array transmitter with 144 transmitting elements for 3D measurements in air has been developed. The sound pressure level of 126 dB was obtained at a distance of 5 m in the air with an ultrasonic frequency of 40 kHz. This value is approximately 32 dB higher than that obtained using a single transmitting element. The characteristics of the array transmitter were studied and compared with simulation results. The experimental results were in good agreement with the simulation results.
Long‐range measurement system using ultrasonic range sensor with high‐power transmitter array in air
HighlightsConcept of portable high power 144 elements ultrasonic transmitter array.Concept of high sensitive 32 elements ultrasonic receiver array.Delay‐and‐sum operations for image sensing and detection of an object.Concept of ranging and three dimensional imaging in adverse conditions. &NA; A long‐range measurement system comprising an ultrasonic range sensor with a high‐power ultrasonic transmitter array in air was investigated. The system is simple in construction and can be used under adverse conditions such as fog, rain, darkness, and smoke. However, due to ultrasonic waves are well absorbed by air molecules, the measurable range is limited to a few meters. Therefore, we developed a high‐power ultrasonic transmitter array consisting of 144 transmitting elements. All elements are arranged in the form of a 12 × 12 array pattern. The sound pressure level at 5 m from the transmitter array was >30 dB higher than that of a single element. A measuring range of over 25 m was achieved using this transmitter array in conjunction with a receiver array having 32 receiving elements. The characteristics of the transmitter array and range sensor system are discussed by comparing simulation and experimental results.
Quiescent pattern control in linearly constrained adaptive arrays
When an adaptive array operates in the presence of white noise only, the resulting beam pattern is referred to as the quiescent response. Typically, these patterns have mainlobe and sidelobe shapes differing from those designed for use in deterministic, nonadaptive arrays. This paper describes a simple method which allows nearly arbitrary specification of the quiescent response in a linearly constrained power minimization adaptation array. The only restriction on the quiescent is that it must meet the constraints defined for the adaptive array. Since many well-known deterministic designs such as Chebychev are not likely to meet the linear constraint conditions used in adaptive arrays for mainlobe and other pattern control functions, a procedure is presented which modifies the deterministic design to force it to meet the linear constraints in a least-squares manner. Once this has been accomplished, the methods outlined in this paper can be used to cause the modified deterministic design to become the quiescent response of the adaptive array. As a result, the adaptive array can be configured to closely resemble a deterministic array when the noise is white. Under conditions of correlated interference, or jamming, however, the response changes so as to effectively steer nulls in the appropriate directions. The method is based on the use of a generalized side-lobe canceller and requires one additional linear constraint for both narrow-band and broad-band arrays.