PXIE-5450 Datasheet, PDF (2/6 Pages) National Instruments Corporation – Dual-channel, differential I/Q signal generation

400 MS/s, 16-Bit I/Q Signal Generator
The NI PXIe-5450 also delivers exceptional passband flatness (Figure 2).
While the -3 dB analog bandwidth is 145 MHz, the digital flatness
correction filter provides ±0.15 dB of flatness from DC to 120 MHz.
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Flatness Correction Enabled
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Frequency (MHz)
Figure 2. Passband flatness is significantly improved with the use of digital flatness
correction in the NI PXIe-5450 FPGA.
For maximum signal purity, the phase noise of this module is
extremely low. The phase noise density of a tone generated at 10 MHz
drops from -121 dBc/Hz at a 100 Hz offset to -150 dBc/Hz at 100 kHz,
yielding an integrated system output jitter of less than 500 fs. Its highly
stable phase-locked loop (PLL) and high-resolution oscillator provide an
output sample rate resolution less than 5.7 µHz, enabling low phase
noise signal generation at any frequency with microhertz resolution.
An essential attribute for I/Q generation is tight synchronization
between channels. The NI PXIe-5450 features high-performance circuitry
that calibrates the channel skew to within 25 ps. You can achieve even
more alignment with a 10 ps resolution programmable skew, useful in
calibrating out cable length mismatches. This tight level of
synchronization minimizes the phase error between channels, especially
at high frequencies, which is essential for accurately generating high-
bandwidth I/Q signals (Figure 3).
Figure 3. Dedicated channel-alignment circuitry automatically calibrates the two channels
on the NI PXIe-5450 to within 25 ps. This particular module exhibits less than 13 ps of
skew, demonstrated on a 100 MHz sinusoid.
High-Speed Data Streaming
In addition to tight synchronization, the SMC architecture on the
NI PXIe-5450 takes advantage of the PCI Express bus to continuously
stream data from the host controller at more than 600 MB/s in dual-channel
mode or at 360 MB/s when generating a single channel. This enables the
module to continuously output I/Q waveforms at 150 MS/s or, when
upconverted, approximately 120 MHz RF bandwidth, either from host
memory or a high-speed storage solution such as the NI HDD-8264 3 TB
RAID array. With this technology, you can generate terabyte waveforms
of unique, high-bandwidth data for several hours. Applications that
benefit from this capability include RF and baseband recording and
playback for signal intelligence and communications system design,
validation, and verification.
Onboard Signal Processing
OSP significantly extends waveform playback time and shortens
waveform download times (Figure 4). A field-programmable gate array
(FPGA) on the NI PXIe-5450 implements the OSP functionality, which
enables several signal processing and I/Q-related functions. These
functions include those listed on page 3.
Waveform
Memory
Output
Engine
I/Q
Rate
Pre-Filter
Gain I
Onboard Signal Processing
Pre-Filter
Offset I
Filtering
and Interpolation I
Pre-Filter
Gain Q
Pre-Filter
Offset Q
Filtering
and Interpolation Q
Frequency
Shift
by NCO
Digital
Gain I
DAC I
Digital
Gain Q
DAC Q
Figure 4. OSP on the NI PXIe-5450 FPGA performs inline processing of waveform data
before it is sent to the digital-to-analog converter (DAC) .
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