A low cost downconverter for a 1.7-2.3 GHz analog radio system has been implemented using -the fiberglass printed-circuitry technique. A maximum 1.9db SSB noise figure and minimum 31dB conversion gain were achieved. The design and performance of such a low cost-unit are also presented.
Sound spectrography , the visual portrayal of the audiofrequency spectrum, has been employed in seismology, acoustics, and speech studies. Visible speech' not only presents word picture patterns, but also characterizes one's voice as "voice prints"' (FIGURE 1). Use of this technique in the analysis of cardiovascular. sound is called spectral phonocardiography .3 Contour spectral phonocardiography' is a new threedimensional method for analyzing cardiovascular sound. The result of the analysis is the portrayal of the audio frequency spectrum of heart sounds and murmurs in a three-dimensional plot. Qualitative and quantitative data concerning frequency, intensity, and time previously unattainable by other methods are clearly displayed. The aim of this report is to present the nlethod, its capabilities, and its use in the assessment of aortic valve disease. Nine cases are presented.
METHOD AND EQUIPMENTUsing suitable microphones and amplifiers, recordings are made on a four
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