Webb 1 described what could be considered as the basis of DDS mechanics to generate various types of analog waveforms, including sine waves, simply with the use of a few digital logic modules.
#SINE WAVE U HE DIVA GENERATOR#
The digital signal generator synthesizer patent filed in April 1970 by Joseph A. Taking the benefit of the full-word data length of the SHARC core architecture either in 32-bit or 64-bit fixed-point format for the NCO phase accumulation and the proprietary, 40-bit, floating-point, extended precision to execute the sine approximation function and the digital filters used to shape the spectrum, the quantization effects (rounding and truncation noise) are drastically reduced to be considered negligible compared to the digital-to-analog converter (DAC) imperfections used for the signal reconstruction. A reasonably fast floating-point DSP will meet real-time expectations and fulfill all the arithmetic and processing conditions to achieve the distortion and noise performance level set up by the most advanced SAR ADCs.
#SINE WAVE U HE DIVA FULL#
The DDFS makes the whole measurement system fully digital with a lot of benefits including full flexibility and coherent sampling acquisition.Īt a fraction of the cost of an audio precision analyzer, it is possible to design a very accurate sine wave generator based on the direct digital frequency synthesis (DDFS) principle, but implemented in software onto a floating-point DSP processor such as the SHARC ® processor. Processing chain of a typical ADC (ac) test setup based upon the IEEE 1241 standard. The most critical component is the sine wave generator (single or multitone) and here a software-based direct digital synthesizer (DDS) can provide full flexibility with extremely fine frequency resolution and clock synchronization with the data acquisition system to perform coherent sampling to avoid leakage and FFT window filtering.įigure 1. A typical configuration of a typical bench test setup suited for high resolution wideband ADCs is illustrated on the Figure 1. Similarly, the noise and distortion level of this ac generator should be much better than the specifications of these ADCs, resulting in a noise floor level well below –140 dBc and distortion lower than –120 dBc with an input tone frequency of 1 kHz or 2 kHz and up to 20 kHz according to most supplier specifications. Most of the time, modern high speed SAR and wideband sigma-delta (Σ-Δ) ADCs exhibiting 24 bits or more feature single-supply and full-differential inputs, and therefore require the signal source used for the DUT to be dc and ac accurate, while providing full differential outputs (180° out of phase). Usually, expensive laboratory instruments are used to perform these evaluations and characterizations such as the audio analyzer AP27xx or APx5xx series from Audio Precision.
#SINE WAVE U HE DIVA VERIFICATION#
The test and verification of ac performance of high precision fast analog-to-digital converters (ADCs) with resolution better than 16 bits require a near perfect sine wave generator capable of covering a 0 kHz to 20 kHz audio bandwidth at least. An Almost Pure DDS Sine Wave Tone Generator