Re: to jian
Hi, Kbmanick:
1. To convert your structure to finite ground, you just need to define the No.0 substrate to air and draw the shape of the finite ground plane there. I will e-mail you an example by assuming a finite ground plane size.
2. Your antenna is resonanting at about 5.5 GHz. You set the mesing frequency Fmax = 12. It is quite fine meshing. You can reduce the meshing frequency down to some where slightly above your highest frequency. For example, you are intersted in the frequency response from 5 to 6 GHz. You can define Fmax = 6 GHz and Cells per Wavelength Ncells = 15 to 20. You are supposed to get very similar results if the AEC parameters are set properly.
For your structure, I set Fmax = 12 and Fmax = 7, the frequency responses are very close. The dB(S11) is below - 30 dB for the Fmax = 12 and -22 dB for the Fmax = 7 GHz. As they are, the results are good. If you overlay the 2 curves together, you will see very small difference between the 2 curves.
For antenna applicaitions, if your antenna is resonanting at f0 and you are interested in the frequency range (f0-fb/2, f0+fb/2), you can set the Fmax = f0 + fb/2 with Cells per Wavelength Ncells = 15. Set the AEC Ratio from about 0.05 to 0.1. Normally, it should yield very reliable results. For GaAs IC and RFIC, we may want to increase the meshing density significantly. For IC applications, designers are more interested in the L, C and Q, those values converge much slower. Using regular meshing parameters and much refined meshing, the s-parameters may look the same while there might be siginicant difference in the L, C and Q values. There are guidelines in the manuals and the training materials, please check them. Thanks!
Best regards,