Radiation Pattern of a planar array on finite circular ground Plane

Hello,

I have designed a simple probe fed microstrip patch antenna in FEKO, which produces a 43.1% 2:1 VSWR bandwidth (638.2-990.6 MHz). The .cfx file for the antenna is attached. This antenna is now used as each element in a uniformly excited 11x11 array on a finite circular ground plane. The array was simulated (using supercomputer) to calculate the  radiation pattern at 3 different frequencies (638.2, 814.4, and 990.6 MHz). Results could be obtained at the two lower frequencies of 638.2 MHz and 814.4 MHz, but it returned an empty matrix for 990.6 MHz. Why is this so? What can be done to resolve this issue?

Thanks in advance.

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