An experimental verification of the impulse-response method to evaluate the transient acoustic field of pulsed ultrasonic radiators is presented. Several piezoelectric disk radiators were constructed for the experiments. Transient pressure measurements were obtained at several field points for pulsed wide bandwidth electrical excitations of the radiators. The pressure data were processed via an iterative deconvolution method to obtain experimental impulse responses. The method ideally eliminates the effects of the dynamic response of the transmit and receive system on the impulse responses. A comparison of the experimental and theoretical impulse responses shows the responses to be in general agreement.
This paper describes the design of an archival temperature monitoring tag to be used to collect habitat information of Atlantic salmon during the marine phase of the species' natural history. The monolithic circuit should not exceed an average power dissipation of 3.4W, so that a small 3 V, 30 mAh lithium battery will provide the device with the expected lifetime of 3 years. The thermal sensor is realized by a p-njunction. The recorded junction voltages are digitized and stored in static RAM cells. The tag is programmed before deployment by an external computer via a serial interface. The device's temperature-monitoring protocol is defined at this stage. Upon retrieval of the tag, the stored temperature values will be transfered to a computer where the geographical location of the fish at the actual sampling time will be deduced through retrospective navigation based on known sea temperature distribution.
A b s t r a c tThe Arithmetic Fourier Transform(AFT) is a novel and promising algorithm for accurate high-speed Fourier analysis. It is based on the number-theoretic method of Mobius inversion. Its computations proceed in parallel and except for a small number of scalings in one stage of the computation, only multiplications by 0, -1, and +1 are required. In this paper we will show the implementation of an AFT channel by switchedcapacitor(SC) techniques. The circuit consists of one opamp, two capacitors (one for the sample and hold(S/H) stage and one for the data accumulation) and a couple of CMOS transmission gates which serve as switches. If necessary, the accumulated data, corresponding to the intermediate sums in the AFT algorithm, can be converted to digital signals for further processing. Note that this analog sampled data solution has eliminated the requirement for a fast A/D conversion at the input.
The Mobius Functionwhere ak(t) = Ak cos(2nkt + 0k)(3)Ak and are the amplitude and phase of the kth harmonic term. A(t) is assumed to be having a period one and has no constant term and all the harmonic terms above Nfh are assumed to be zero.Let us consider a bank of N delay line filters each with input a(t). The output of the nth filter is denoted by S(n,t) and is defined by the formulas n-1 S(n,t) = -zA(t-m/n) for n = 1,2,. . . ,N (4) m=O We can see that S(1,t) = A(t). By replacing t in (4) by (t + l/n) and using the periodicity of A(t),we can see that S(n,t) is periodic with period l l n for n = 1,2,. . .,N.
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