AWR Software for the Design of MIMO and Phased Array Antenna Systems
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Modeling Impairments and Yield Analysis
RF hardware impairments of the array will affect the resulting side-lobe levels and beam patterns and will ultimately reduce
system-level performance. For transmitter arrays, side-lobe levels from imperfectly formed beams may interfere with
external devices or make the transmitter visible to countermeasures. In radar systems, side lobes may also cause a form of
self-induced multipath, where multiple copies of the same radar signal arrive from different side lobe directions, which can
exaggerate ground clutter and require expensive signal processing to remove. Therefore, it is critical to identify the source of
such impairments, observe their impact on the array performance, and take steps to reduce or eliminate them.
The AWR VSS phased array configuration file allows engineers to simulate array imperfections due to manufacturing flaws or
element failure. All gain/phase calculations are performed internally and yield analysis can be applied to the block in order to
evaluate sensitivity to variances of any of the defining phased array parameters. As an example, the AWR VSS software was
used to perform an element failure analysis on a 64-element (16 x 4) array, producing the plots in Figure 12, which illustrates
the side-lobe response degradation.
Figure 12: Side-lobe degradation to element failures 2 percent and 5 percent
RF impairments also can be caused by any number of items relating to the feed network design and related components.
Systematic errors that may be compensated include inter-chain variations caused by asymmetrical routing (layout),
frequency dependencies, noise, temperature, and varied mismatching due to changing antenna impedance with steer
angle, which also impacts amplifier compression. Therefore, it is imperative to be able to simulate the interactions between
the antenna array and the individual RF links in the feed network.
