AWG-2000 Series | Low Noise Waveform Generator

Introduction

The Active Technologies AWG-2000 Series instrument has an internal 10x Attenuator that lets the user generate signals with a very low amplitude without sacrificing the DAC resolution. For that reason AWG-2000 can be classified as a low noise waveform generator
When the user has to generate a small amplitude signal, if the instrument would not be equipped with an internal attenuator, it could happen that the waveform would be generated by the least significant bits of the DAC.

The AWG-2000 Arbitrary waveform generator has 16 Bits of vertical resolution and a full scale range of 6Vpp 50 Ohms into 50 Ohms: the resolution (DAC step size) is 6Vpp / 2^16 = 0.09155 mV.
If the attenuator is turned OFF, with 1mVpp waveform amplitude the DAC uses 4 bits only.
When you turn ON the attenuator, the DAC step size becomes
0.6Vpp/2^16 =0.009155 mV and it means that when you need to generate a sine waveform with 1mVpp amplitude, the DAC uses 7 bits.
Those considerations united to an analog front end with an excellent harmonic distortion, lead to the possibility of generating signals with very low amplitude and a good Signal-to-Noise Ratio.

Low Noise Waveform Generator

Real-world cardiac signals typically are very low in amplitude — often only a couple of millivolts or even less. This poses a problem for simulation using AWGs because typically their lowest amplitude setting is between 10 mV and 1 mV. When they are used at their lowest amplitude, the AWG’s signal-to-noise ratio can become a problem.
One way to overcome this drawback is to use a voltage divider at the output of the AWG, but when constructing the voltage divider, it is important to remember that the amplitude accuracy of the divider’s output signal depends on the precision of the resistors used in the divider.

Active Technologies AWG-2000 Series overcome this problem with the built-in internal 10x attenuator and by using an analog output stage able to provide an extremely high signal fidelity.
In this paper we’ve performed several measurements on very low amplitude signals using a Spectrum Analyzer and an oscilloscope; you can see the different tests and results in the pictures below.

Please note that when the signal is “too small”, the oscilloscope’s background noise is comparable to the signal amplitude.

1. AWG-2000 | Sine Wave | 2mVpp Amplitude | Attenuator ON | Spectrum Analyzer

2. AWG-2000 | Sine Wave | 0.2 mVpp Amplitude | Attenuator ON | Spectrum Analyzer

   

3. AWG-2000 | Sine Wave | 0.02 mVpp Amplitude | Attenuator ON | Spectrum Analyzer

   

4. AWG-2000 | Sine Wave | 2 mVpp Amplitude | Attenuator OFF | Spectrum Analyzer

   

5. AWG-2000 | Sine Wave | 5 mVpp Amplitude | Attenuator ON | OSCILLOSCOPE

   

6. AWG-2000 | Sine Wave | 0.5 mVpp Amplitude | Attenuator ON | OSCILLOSCOPE
   

   Important Note:

   when the signal is “too small”, the oscilloscope’s background noise is comparable to the signal amplitude.

   

   Conclusion
   The Active Technologies AWG-2000 Series first-class hardware architecture coupled with the built-in 10x attenuator offers the ability to generate unmatched performance and high signal fidelity when you need to generate real-world very low amplitude signals, making the ideal generator to simplify the job of engineers and researchers.