PSEUDOZUFALLSZITTERVERFAHREN UND ZUFALLSZITTERVERFAHREN GEGEN FREQUENZSYNTHESE-RAUSCHEN

A method and apparatus for reducing spurious output noise in digital frequency synthesizers employing sine amplitude converters connected to Digital-to-Analog converters to generate analog waveforms from sine amplitude data. Random or pseudorandom numbers having a value equal to or less than plus or minus one-half of a minimum quantization step or value change for the sine amplitude data are generated and added to the sine amplitude data with the resulting sum being transferred to the Digital-to-Analog converter. In one embodiment, a summation circuit is connected between an output of the sine function converter and an input of the Digital-to-Analog converter and also has a second input connected to a pseudorandom number generator which provides Pseudorandom numbers varying in value over a range of +/-1/2n+1 times a least significant step value, or bit for base 2, of a corresponding Digital-to-Analog input data value where n is greater than or equal to 1.