Instrument Innovations for mmWave Test
Implementing a validation or production test strategy for new wireless standards is difficult. It is made even harder by the constant increase in complexity in new wireless standards and technologies like 5G New Radio (NR). This includes wider and more complex waveforms, an exponential increase in test points, and restrictive link budgets that require technologies like beamforming and phased-array antennas. To help you address these challenges, NI introduced the PXIe-5831 millimeter wave (mmWave) vector signal transceiver (VST), which delivers high-speed, high-quality measurements in an architecture that can adapt to the needs of the device under test (DUT) even as those needs are changing. This PXI Vector Signal Transceiver (VST) shortens the time you need to bring up new test assets by simplifying complex measurement requirements and the instrumentation you need to test them.
At its core, the VST combines a high-bandwidth vector signal generator, vector signal analyzer, high-speed digital interface, and a user-programmable FPGA into a single PXI instrument. The mmWave VST (PXIe-5831) extends the VST architecture with innovations focused on addressing the increasing complexity—and uncertainty—of wireless standards, protocols, and technologies.
Frequency conversion to and from mmWave is performed in a radio head that is cabled to the PXI-based IF subsystem, extending frequency coverage up to 44 GHz for the PXIe-5831 mmWave VST. Each mmWave VST IF subsystem can support up to two radio heads, which come in three configurations—2-, 9-, and 16-port—to adapt to the needs of the DUT. The additional ports are created with a switch network that is integrated into the calibration routines of the instrument, so performance specifications are accurate all the way to the test ports. The following is an example test configuration that shows how the mmWave radio heads can map to potentially high-port requirements for a multiband TX/TX RF front-end module:
Performing the final conversion stage in a remote head provides additional flexibility in the physical configuration of a tester or test cell as well. You can position the radio heads nearer to the DUTs and alleviate long high-frequency cable runs and the associated losses in power and signal quality. Losses at intermediate frequencies (IFs) can be significantly less than those at mmWave, so shifting power delivery requirements to the lower frequencies means more power where it matters: at the mmWave test ports. Consider the following example comparing a three-meter cable run for a +23 dBm instrument versus a one-meter IF and two-meter mmWave cable .run for a +17 dBm instrument like the mmWave VST.
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