PXIE-5450 Datasheet, PDF (3/6 Pages) National Instruments Corporation – Dual-channel, differential I/Q signal generation

400 MS/s, 16-Bit I/Q Signal Generator
• Independent I and Q prefilter gain and offset – Adds gain and
offset imbalance impairments and I and Q prefilter gain. You can adjust
the offset before or during the generation of an output signal (Figures 5, 6).
Figure 5. LO leakage and poor image rejection of a quadrature modulator cause
undesired RF emissions.
• Baseband interpolation – Generates smooth baseband signals.
You can use the NI PXIe-5450 OSP block to interpolate low-sample
rate waveforms to a much higher sample rate, thereby improving the
output frequency spectrum by relocating zero-order sample-and-hold
reconstruction images to higher frequencies. With the images at
higher frequencies, the device’s image suppression filter greatly
suppresses them without disturbing the signal’s amplitude response
or phase information.
Waveform Sequencing and Triggering
You also can program the NI PXIe-5450 to sequence and loop a set of
waveforms. You can choose from several methods to step through the
sequence of waveforms. In cases when you know the duration of each
waveform in advance, you can program the generator to loop them a
specified number of times. When you do not know the duration before
the start of generation, you can use a hardware or software trigger to
advance the generator to the next waveform in the sequence. The
NI PXIe-5450 implements advanced triggering behavior with four trigger
modes: single, continuous, burst, and stepped. In addition, scripting
provides the ability to link and loop multiple waveforms together, managing
triggers and markers. For a detailed discussion of these modes, consult
the NI Signal Generators Help guide available at ni.com/manuals.
NI SMC-based generators have the unique capability of storing
multiple sequences and their associated waveforms in the generator’s
onboard memory (see Figure 7). In automated test applications involving
multiple tests, each requiring a different waveform sequence, you can
download all of the sequences and waveforms once at the beginning
of the test cycle and store them in the generator’s memory for the entire
session. By downloading all required waveforms and sequences once to
an SMC-based generator instead of repeatedly reloading them for each
test, you save time and improve throughput.
Waveform Waveform
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Figure 6. On-the-fly-adjustable parameters on the NI PXIe-5450 correct for the
quadrature modulator impairments seen in Figure 5.
• Pulse-shaping finite impulse response (FIR) filter – Shapes and
interpolates the waveform data. FIR filter types include flat, raised
cosine, and root raised cosine, with a programmable α parameter.
Digital interpolation factors range from 2 to 32,768 times.
• Numerically controlled oscillator (NCO) – Produces sinusoidal
waveform data for complex (I/Q) frequency shifts before or during
generation with up to a ±86 MHz shift and 710 nHz resolution.
NCO tuning time is 250 µs.
Figure 7. NI SMC-based arbitrary waveform generators increase test throughput by
storing all the waveforms and sequences required for a set of tests in onboard memory.
Timing and Synchronization
Using NI T-Clock (TClk) synchronization technology, you can synchronize
multiple NI PXIe-5450 modules for applications requiring a greater
number of channels, such as I/Q signal generation for MIMO systems.
Because it is built into the SMC, TClk can synchronize the NI PXIe-5450
with SMC-based vector signal analyzers and generators, high-speed
digitizers, and digital waveform generators and analyzers for tight
correlation of analog and digital stimulus and response. Using onboard
calibration measurements and compensation, TClk can automatically
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