Knowledge-Base
22xx low range option
The option (M4i.22xx-ir40m) for the high-speed 22xx series of digitizer products increases their input sensitivity and therefore absolute resolution for low amplitude signals in the 40 mV up to 0.5 V range.
Matching the digitizer's range to the signal under test is important as it ensures maximum dynamic range as well as better measurement accuracy and resolution. For example, if a signal only covers half of a digitizer's selected full scale range then only half of the digitizer's available analog-to-digital converter (ADC) resolution can used. Smaller, or lower level, signals will use even less of the ADC's capabilities and further reduce the digitizer's overall signal-to-noise performance. This option lets users select more sensitive, full scale ranges so that, even for low amplitude signals, the ADC's complete dynamic range is available.
Comparison
The following table gives a comparison of standard input range option and low voltage input range option
| Standard ranges | low voltage ranges | |
|---|---|---|
| Input Ranges | ±200 mV | ±40 mV |
| ±500 mV | ±100 mV | |
| ±1 V | ±200 mV | |
| ±2.5 V | ±500 mV | |
| Bandwidth 1.25 GS/s models | 500 MHz | 500 MHz |
| Bandwidth 2.5 GS/s models | 1.5 GHz | 700 MHz |
| Bandwidth 5 GS/s models | 1.5 GHz | 700 MHz |
| ENOB example HF path | 7.5 bit | 7.0 to 7.2 bit |
Comparison with 10 bit Digitizers
The Spectrum 22xx series of 8 bit digitizers can often overpower other vendors 10 bit digitizers in terms of SNR and ENOB. The new option gives even more advantages. As an example, a 10-bit digitizer with a lowest 50 Ω range at 0.5 V full scale input range that has to acquire a signal with an amplitude of around 50 mV. The 10-bit ADC offers 1024 (2^10) levels of resolution each of about 1 mV (1V/1024). The signal would therefore only cover about 50 levels of the 10-bit ADC's available range. Spectrum's 22xx series digitizers use 8-bit ADCs that give 256 (2^8) levels of resolution. So, by using this new low range option, the digitizer becomes more sensitive with around 0.3 mV (80mV/256) of resolution capturing the 50 mV signal with around three times more resolution than the more expensive 10-bit unit.
Lower Amplitude Signals
For extremely low amplitude signals, the 22xx series digitizers can also be used with Spectrum's high bandwidth (up to 2 GHz) external SPA series amplifiers. These free-standing units offer additional x10 (20 dB) or x100 (40 dB) gain making it possible to capture and analyze signals that go down into the low mV ranges.
Product Range
The option is available for all digitizer products based on the 22xx plattform:
- M4i.22xx-x8, PCIe card with up to 4 channels
- M4x.22xx-x4, PXIe card with up to 4 channels
- DN2.22x-xx, mobile digitizerNETBOX Ethernet/LXI system with up to 8 channels
- DN6.22x-xx, 19 digitizerNETBOX Ethernet/LXI system with up to 24 channels
Please note that the option for digitizerNETBOX devices is an individual per internal digitizer.
Order and Upgrade
The alternative front-end option has to be ordered with the card. Later upgrade may be possible if the PCB version of the module is equal or greater than version 1.3. Please use the Spectrum Control Center to examine the version of your product.