microstrip antenna with air gap design

Pls, forum members i recently came across a paper online on how to optimize rectangular microstrip antenna using air gap technique. I have tried for more than two weeks without ant success, the design is in two phases. the first one is without air gap which i have uploaded the HFSS design here while i have no idea on how to design the second phase (ie with air gap).Iam very excited for your help.

See Pozar's "Microwave Engineering" textbook. It has at least one detailed design example.

hi terrycool,
please state your specific question in order others to help. your question is too general.

i dont have experience in HFSS. i have only dealt with ADS and CST before.

thanks very much sir for your concern, i have read the book and it added my knowledge greatly. my main concern is the use of the software. this are my parameters; W=42mm, L=40mm, h=1.6mm, mt=0.07, feed position = 21,8.93,0 edge impedance = 120.11.