Waveform synthesizers

摘要

The invention facilitates the calibration of VOR equipment by synthesis of a series of waveforms representative of different positions in azimuth. Digital data representative of a frequency modulated component of the VOR waveform is stored in a first memory area (1) and digital data representative of an added sine wave component of the waveform is stored in a second memory area (2). By appropriate cyclic data retrieval from the memory areas and combination of the data (7) together with digital to analogue conversion (8) and filtering (10) the VOR waveform corresponding to a particular azimuth may be synthesized.