Frequency generator for nmr - applications with direct digital frequency synthesis (dds), a method for operation of such a dds - generator as well as a method for the operation of an nmr - spectrometer with dds - generator

摘要

A method for the operation of a high-resolution nmr - spectrometer with a dds - generator, the one nco φ l φ for generating a lo - frequency, wherein the frequency of the nco φ l φ in the dds - generator by means of an input of a numerical value z is defined, is characterized in that this numerical value z assumes only such values, which the equation z = n been n / m, and z, n, n and m are whole numbers and positive numbers, n is a power of 2, with an integer, positive exponent and the exponent the maximum number of bits in the computing operation means m is approximately equal to 2 been f φ s φ / delta b, n is approximately equal to m been f φ out φ / f φ s φ and m, in addition, a gemeisamer, integral divisor of n been n, and f φ s φ the clock frequency of the nco φ l φ, delta b the desired bandwidth with high spectral purity, and f φ out φ the output frequency of the nco φ l φ denote. As a result, a dds - generator also be used without problems, in which a very high spectral purity is required, wherein, in particular, the quantization noise for nmr - measurements by means of the relevant frequency range as far as possible is largely eliminated.