S band ranges from 2 to 4 GHz

C band ranges from 4 to 8 GHz

X band ranges from 8 to 12 GHz

Your obtained bands are within this range. Whereas, if you are focused to some specific application, you need to be concerned about the center frequency or obtain the center frequency within the achieved bandwidth.

The antenna is covering the complete bands right. So, no issue with resonant frequency. But, it should have good gain and efficiency in the bands.

The resonant frequency is the one at which the S11 and losses are less compared to other frequencies.......

Thanks Mohammad sir and Anveshkumar sir. I am getting S11 around -24 db at S and X band.

Please check gain as well.....Make sure that the complete bands are covered........

Micro-strip Antenna's performance not only depends on resonant frequency. Since you have designed the array, the bandwidth might be little wide. If your intended application lies within the band you can go for design.

If it deviates you can steer the resonant frequency towards the desired frequency by modifying the array structure or phase of the exciting signal.

Hi,

you are part of ITU region 3, so you can check by yourself in attached file (or here https://transition.fcc.gov/oet/spectrum/table/fcctable.pdf) that frequencies used are well corresponding to allowed applications.

S band : pages 38-41

C band : pages 42-45

X band : pages 48-49

Best regards.

Thank you Thirunavukkarasu sir, Anveshkumar sir and Frederic sir for your kind support. Actually my array doesnt cover the whole band but the bandwidth is more than 1 GHz. I am looking after the enhancement of bandwidth for radar application.