Analog Discovery 3 and Analog Discovery 2 / Spectrum Analyzer, Network Analyzer, and Impedance Analyzer Bandwidth specifications

[Satian Anantapanyakul]

For specification of Analog Discovery 3

Spectrum Analyzer Bandwidth: 0 Hz to 62.5 MHz. Is this specification with or without BNC Adapter?

Network Analyzer Bandwidth: 20 uHz to 9 MHz. Is this specification with or without BNC Adapter?

Impedance Analyzer Bandwidth: 20 uHz to 31.25 MHz. Is this specification with or without BNC Adapter?

Why is the Bandwidth of Network Analyzer 9 MHz but not 31.25 MHz?

 

For specification of Analog Discovery 2

Spectrum Analyzer Bandwidth: 0 Hz to 50 MHz. Is this specification with or without BNC Adapter?

Network Analyzer Bandwidth: 1 mHz to 10/25 MHz. Is this specification with or without BNC Adapter?

Impedance Analyzer Bandwidth: 100 uHz to 10/25 MHz. Is this specification with or without BNC Adapter?

 

[JColvin]

Hi @Satian Anantapanyakul,

Those specifications are the frequency range that the device accepts, not the bandwidth, https://digilent.com/reference/test-and-measurement/analog-discovery-3/specifications#additional_features.

In all cases, whether using a Digilent Test and Measurement device, or Keysight or Tektronix, or any other competitors, you will be beholden the analog input bandwidth of the device as these additional features use the analog input hardware of the device. If you measure at a higher frequency than is supported by the bandwidth, you will experience signal attenuation.

As for the specific question on the Network Analyzer frequency, it is listed at 9 MHz because that feature in the WaveForms uses the Analog Outputs, which are specified at 9 MHz output bandwidth. There is a note within the specifications, https://digilent.com/reference/test-and-measurement/analog-discovery-3/specifications#refnotes:7:ref1, that explains that you can select higher frequencies up to one quarter of the system frequency (this is the 31.25 MHz frequency value you are quoting as that is 25% of the maximum 125 MHz system clock frequency).
If you instead use an external analog signal generation source (selectable as a dropdown in the Source option within the Network instrument within WaveForms), you'll be limited to the bandwidth of that external source, or the bandwidth of the analog inputs, whichever is lesser.

Thinking about it, the Impedance Analyzer section should have this similar limitation as it also uses the analog output hardware, so I will make this adjustment.

Similarly for the AD2, the frequency ranges should instead be:
Spectrum - 0 Hz to 50 MHz (i.e. half of the system frequency)
Network - 20 uHz to 25 MHz
Impedance - 20 uHz to 25 MHz

as those are the values selectable in WaveForms, but again the "accurate" values, much like the Analog Discovery 3, are also constrained to the bandwidth of the device. I will check the listed frequency ranges for the Analog Discovery 2 and change them to match what the user can select within WaveForms as well.

I imagine this leads to the question of "Why list frequency ranges that don't match the bandwidth values"? The are multiple reasons for this:

- It's commonly done in industry. Check out the analyzers and/or oscilloscopes from big name players in the industry and you'll see that the maximum frequency / sample rate is notably higher than the bandwidth. If the bandwidth is higher than the frequency, be sure to double check if it is only applicable to periodic waveforms.
- Listing frequency ranges looks better. The "bigger number must be better" mentality is everywhere, not just in the electronics industry.
- Arbitrarily limiting the selectable frequency range in software to some other value is not the philosphy adopted by WaveForms. The end user knows their setup best and what extra steps they have taken (BNC, external signals, twisted wires, etc) to get the best signal that they can, so the software will happily analyze whatever frequency range you configure the hardware to do. Whether or not the data from the environment is accurate is not something that the software can or should decide for the user.

Please let me know if you have any questions.

Thanks,
JColvin

[Satian Anantapanyakul]

So specifications of AD3 with BNC Adapter

Spectrum Analyzer Frequency Range: 0 Hz to 62.5 MHz.

Network Analyzer Frequency Range: 20 uHz to 31.25 MHz.

Impedance Analyzer Frequency Range: 20 uHz to 31.25 MHz.

 

and specifications of AD2 with BNC Adapter

Spectrum Analyzer Frequency Range: 0 Hz to 62.5 MHz.

Network Analyzer Frequency Range: 20 uHz to 25 MHz.

Impedance Analyzer Frequency Range: 20 uHz to 25 MHz.

 

Please correct me if there's anything wrong.

[JColvin]

Hi @Satian Anantapanyakul,

The information you have listed is almost correct. I have underlined the changes that I made.
 

Analog Discovery 3 with or without BNC Adapter:

Spectrum Analyzer Frequency Range: 0 Hz to 62.5 MHz
Network Analyzer Frequency Range: 20 uHz to 31.25 MHz
Impedance Analyzer Frequency Range: 20 uHz to 31.25 MHz

-----

Analog Discovery 2 with or without BNC Adapter:

Spectrum Analyzer Frequency Range: 0 Hz to 50 MHz
Network Analyzer Frequency Range: 20 uHz to 25 MHz
Impedance Analyzer Frequency Range: 20 uHz to 25 MHz

 

Please let me know if you have any questions.

Thanks,
JColvin