Many modern electronic warfare systems utilize a multichannel phase-coherent system for tasks such as direction finding in passive radar systems, or providing multipath redundancy in jamming-resistant communications. In practical MIMO test systems, the radio hardware should be capable of acquiring and generating phase-coherent and phase aligned signals across the multiple channels. After achieving phase coherence, the constant phase difference between the coherent signals can be compensated for by using phase alignment methods 1.įigure 3 8 × 8 MIMO configuration with NI PXI VST. Figure 2 shows the coherency for two channels with different frequencies, where the signals are at a specified phase relationship at every N cycles.
1 Figure 1 shows conceptual diagrams of phase coherency of two channels with same frequency. Phase coherency is an attribute of two or more waves where the relative phase is constant during the resolving time of the observer. Finally, an example of a next-generation multichannel phase-coherent test system including tests performed to validate that the system meets the requirements will be studied. Additionally, the article will look at the actual steps needed to develop a multichannel phase-coherent test system from commercially available software-defined modular instruments, and discuss the details of a real-time calibration process for fine-alignment in phase and amplitude. This article will provide an overview of the challenges and requirements for testing a multichannel phase-coherent measurement and generation system and review how these requirements map to test instrument design specifications. To efficiently test these systems, it is mandatory for test and measurement equipment to provide equal or better precision in signal coherence, and complete control over phase, time, frequency and amplitude.įigure 2 Phase coherency at different frequencies.
PHASE COHERENCE METER VERIFICATION
The precise phase and amplitude synchronization of each channel poses serious challenges to testing and verification of multichannel phase-coherent systems. However, such MIMO systems must overcome key technical challenges related to channel-to-channel phase and amplitude synchronization to coherently receive and process the data acquired or generated from each input/output. Engineers are employing MIMO systems in a wide range of electronic warfare and radar applications ranging from phased array radars to beamforming and direction finding systems. With rapid advancements in the areas of RF components and subsystems, and high-density digital signal processing electronics, multiple input multiple output (MIMO) technologies are receiving high attention for their capabilities to increase the data rates through multiplexing, or to improve the system performance by an order of magnitude or more through spatial diversity. Figure 1 Phase coherency at the same frequency.
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