RF Input Subsystem
- Updated2025-04-22
- 2 minute(s) read
The PXIe-5841 has two configurable RF paths comprised of an independent vector signal analyzer (RF input) path and vector signal generator (RF output) path. The following high-level block diagram represents the PXIe-5841 RF input path.
The PXIe-5841 RF input path is AC coupled and covers a frequency range of 9 kHz to 6,000 MHz center frequency. For frequencies below 120 MHz (low frequency), RF input signals are directly sampled via analog-to-digital conversion. Frequencies greater than 120 MHz (high frequency) are translated to baseband via a single stage direct conversion (I/Q) downconverter, allowing for wide instantaneous bandwidth.
High Frequency RF Input Path
The high frequency subsystem of the RF input path consists of a programmable and filtered front end that feeds into a direct conversion downconverter. Once at baseband frequencies, the signal is sampled with an analog-to-digital converter (ADC) capable of up to 1,000 MHz of complex equalized bandwidth.
RF attenuation greater than 70 dB can be nominally configured through the combination of switchable attenuation and programmable step attenuators. RF attenuation is automatically chosen in conjunction with amplification stages to provide optimal reference levels over the support range of the device.
A switchable pre-amplifier is also configurable in the front end of the device to further optimize the signal path for noise figure. This pre-amplifier can be configured for bypass, forced inline, or automatically configured based on application needs. The configurable range of reference levels may vary based on which option is selected for the pre-amplifier.
Low Frequency RF Input Path
The low frequency subsystem of the RF input path is used to directly sample RF input signals below 120 MHz. The RF input signal is provided via a frequency selective diplexer to programmable gain components before being filtered and sampled with an analog-to-digital converter.
The programmable gain elements at low frequency consist of a switchable amplifier and a programmable attenuator. When disabled, the switched amplifier is bypassed by a 10 dB attenuator. The programmable attenuator is capable of 31 dB attenuation in 1 dB steps.
Refer to the RF Path Transitions topic for more information on using the low frequency RF input path.
Cal In Path
- NI-RFSA Self-Calibrate VI or niRFSA_SelfCalibrate
- NI-RFSG Self-Calibrate VI or niRFSG_SelfCal
- NI-RFSA Self-Calibrate Range VI or niRFSA_SelfCalibrateRange
- NI-RFSG Self-Calibrate Range VI or niRFSG_SelfCalibrateRange
Related Information
- RF Path Transitions
The PXIe-5841 supports acquisition and generation of RF signals from 9 kHZ to 6 GHz. For both the RF Input and RF Output channels, the transition from low frequency to high frequency is implemented with a passive diplexer scheme. This passes RF energy below 120 MHz to the low frequency path and RF energy above 120 MHz to the high frequency path. Because the diplexer has a frequency response of its own, it is possible to extend RF frequency coverage above or below 120 MHz in both paths.