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FIRST MEASUREMENTS OF AC-COUPLED JOSEPHSON WAVEFORM SYNTHESIZER.



NIST (National Institute of Standards & Technology, Washington, DC, www.nist.gov) The standards-defining agency of the U.S. government, formerly the National Bureau of Standards. It is one of three agencies that fall under the Technology Administration (www.technology.  researchers have completed preliminary rms voltage measurements of the Josephson waveform synthesizer synthesizer

Machine that electronically generates and modifies sounds, frequently with the use of a digital computer, for use in the composition of electronic music and in live performance.
 when it is biased using a new ac-coupled technique. AC coupling allows us to use distributed arrays of more than 4000 junctions that have larger output voltage as compared to the previously used lumped arrays with only 250 junctions. More importantly, this technique allows researchers to ground the Josephson array output voltage so that it can be directly measured using low impedance instruments, such as spectrum analyzers and thermal voltage converters. Direct connection to measurement instrumentation is required for optimum performance of calibrations because it avoids the possible gain and distortion errors that can be induced by intermediate amplifiers. NIST researchers have made the first spectral measurements of a directly coupled array and found that harmonic distortion In communications, unwanted frequencies that are generated as multiples of the original frequency due to irregularities in the transmission line. In audio amplifiers, harmonic distortion comes from non-uniform operation (non-linearity) in the amplifier circuits. See harmonic.  was more than 80 dB below the amplitude of synthesized fundamental frequencies of I kHz and 50 kHz. This measurement was likely limited by distortion in the spectrum analyzer. They also used a thermal transfer See thermal wax transfer printer and direct thermal printer.  standard to compare the rms voltages of synthesized sine waves A continuous, uniform wave with a constant frequency and amplitude. See wavelength.



A Sine Wave _title>
Sine wave 
 at 3 kflz, 10 kHz, 20 kHz, and 50 kHz with a synthesized 1 kHz sine wave. The measured Type A uncertainty for each comparison was no more than one-tenth that of previous comparisons using lower voltage lumped arrays.
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Publication:Journal of Research of the National Institute of Standards and Technology
Article Type:Brief Article
Geographic Code:1USA
Date:Nov 1, 2000
Words:214
Previous Article:IMPROVED SPECTRAL IRRADIANCE SCALE OFFERED BY NIST.
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