An Eifficient Method for Generating Coherent Digital Sweep Signals

In this paper a new method for generating coherent digital sweep signals is proposed. The proposed system is a hybrid of the digital sweep generator with the system using interpolation based direct digital frequency synthesis. The interpolator uses predetermined interpolation coefficients to fit the sine wave from the calculated phase instead of using a predetermined waveform stored in a big size memory. The sweep oscillators are expected to have extremely low sweep rates and at the same time reduce both the hardware complexity and the spurious harmonic distortion associated with fractional addressing of the LUT. The new size of the ROM will be reduced, as expected, by factor more than e.g.128 when using 12 address lines and 15 bits word size. Consequently, the output of this sweep generator is expected to be seriously comparable with other methods that implement the look-up table method.