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Multi-channel phase coherent systems are highly considered in several applications, such as Active Electronically Scanned Arrays for Radar, EW, GNSS and 5G networks, typically for beam steering, multipath signal propagation, estimating channel parameters and testing antenna arrays. For successful beam shaping and scanning in array systems, it is essential to precisely set the amplitude and phase differences between the element channels.
However, considerable amplitude and phase differences among those channels can occur due to the RF instrumentation connected to each element.
In this example code we will show how to setup a multi-channel phase coherent system using the PXIe-5830/1 the multi generation/Analysis channels, by building a phase coherent system, based on Vector Signal Transceivers (VST) PXIe 5830/1, covering C/X/K/Ku band, where we will go through the physical system setup and the Software Configuration to run this example.
The PXIe-583x module is a 4-slot module, so you can fit up to 4 devices in a single 18-Slot PXI chassis such as PXIe-1095, which is equivalent to 4x4 MIMO system. This can be expanded to Multi-Chassis synchronous system by sharing the Reference Clock and triggers from one chassis to another using Timing and Synchronization Module.
For a single chassis setup, follow the below steps to setup your phase coherent configuration:
This example is compatible with LabVIEW 2019 and above. To run this example, download the attached code and follow these instructions:
To run the multichannel RFSG Synchronization VI, follow these steps:
This example calculates the phase/amplitude skew of the analysis channels. To use the same setup for calculating skew of transmission channels, first you need to equalize the skew on the analysis side by reading the skew values and adjusting the Initial Phase Offset of the acquired signal. Then you perform the previously described steps to measure the Tx channel to channel skew.How-Separate-2
The steps described in this document are the foundations of multi-channel phase coherent system. You can then generate complex scenarios and stream them to the VST for generation to stimulate your device under test (DUT) such as multi-channel TRM or beamformer, then use the phase coherent acquisition to capture the DUT response and analyze it onboard on the FPGA or stream it to RAID for offline analysis.
Certain applications i.e. measuring antenna array elements coupling, require not only phase coherent acquisition and generation but also phase alignment between all channels including the Leader device. Such applications require certain level of System Level Calibration to compensate for irregulaties introduced by external components, impedance mismatch, cabling, etc... And also require Flatness correction and compensation for phase linearity errors on the Leader device, so not only we mimic the behavior of the Leder on the followers but also we correct the behavior of the Leader with respect to the specific signal parameters to be used such as central frequency, bandwidth and power levels.
Example code from the Example Code Exchange in the NI Community is licensed with the MIT license.