Theory of Operation

The RF vector signal generator hardware consists of two parts: the PXI-5421/5441 or PXIe-5442 Wavefrom Generator and the PXI-5610 RF Signal Upconverter. The PXI-5421/5441 and PXIe-5442 generates a signal centered at an intermediate frequency (IF) between 15 MHz and 35 MHz. The IF signal is sent to the PXI-5610, which frequency-translates it to center between 250 kHz and 2.7 GHz.

The NI-RFSG instrument driver operates both hardware modules as a single instrument by handling all module programming and interaction. When you specify a carrier frequency and power for the RF output signal, NI-RFSG selects the appropriate IF frequency and power level settings for the PXI-5421/5441 or PXIe-5442 AWG module, and the frequency shift, gain, and attenuation settings for the PXI-5610.

The power and carrier frequency of the IF signal generated by the PXI-5421/5441 or PXIe-5442 are determined by NI-RFSG. To optimize dynamic range, NI-RFSG attempts to use the full scale of the PXI-5421/5441 or PXIe-5442 digital-to-analog converter (DAC) and adjusts output signal power by means of the PXI-5610 attenuators.

The PXI-5610 contains a stable and accurate 10 MHz frequency reference. A coaxial cable feeds the frequency reference from the PXI-5610 10 MHzOUT (TO AWG CLK IN) front panel connectors to the PXI-5421/5441 or PXIe-5442 CLK IN front panel connectors. The PXI-5421/5441 or PXIe-5442 locks its internal Reference Clock to this reference.

Note RF signal generator operation requires that the PXI-5610 module front panel connector labeled 10 MHzOUT (TO AWG CLK IN) be connected to the PXI-5421/5441 or PXIe-5442 module front panel connector labeled CLK IN. Most timing configurations generate an error if this interconnection is not in place.

The PXI-5610 reference can also be locked to an external 10 MHz frequency reference. The source of this external reference can be either the REF IN connector on the PXI-5610 module front panel or the PXI_CLK10 backplane signal.

The PXI-5610 accomplishes frequency shifting by mixing the IF signal with local oscillators in the PXI-5610 signal chain circuit. One of these local oscillator (LO) signals can be tuned from 3.2 GHz to 5.9 GHz. A separate output connector on the PXI-5610 module front panel, LOCAL OSC OUT 0, allows you to export this LO signal if you have enabled the oscillator output.