FEKO simulation warnings

When i simulated a Microstrip Grid Array Antenna by using FEKO, i've got these annoying warnings :

1- WARNING 594: Due to rounding errors the solution may be totally invalid.
I've changed to double precision but it was with no result.

2- WARNING 1681: Matrix is numerically singular, solution very critical.

3- WARNING 3843: Directivity is not defined because the radiated power is equal to the power loss.

I can't figure out what are the causes of these problems and how to solve in FEKO?

I attached my project in order if someone can help.

May I know which version of FEKO you are using so i can see if i can run in my system

Hi MrElec

Warning 594 : This may be due to small electrical size of your design and/or your frequency is too low.

Thank you for response.

I'm using Altair CadFeko 14.0. I'm trying to get the results of this article :"Analysis And Synthesis of Millimeter-Wave Microstrip Grid-Array Antennas". The radiator works at 60 GHz.

Width of all the strips is small 0.1 mm and the length is 2.84 mm.

Hi Mr. Elec,

You said the model is designed to work at 60GHz but in your model you have given the working range as 50 - 70Hz. change the freq min and max to 50e9 and 70e9 respectively.
and then you are working in mm dimensions so your lambda value should be c0/freqmax*1e3

Try this out.