This paper reports the design methodology of wideband corrugated horn antenna (1.8:1) at C-Band (Tx: 3.7-4. 2 GHz, Rx: 5.9-6.7 GHz). This paper discusses in detail various sections of horn design. i. e. input taper, mode converter, transition section, and output flare. It brings the comparison of analyzed and measured results. The measured return loss is better than 22.9 dB over C-transmit band, better than 28 dB over C-receive band. The measured peak cross polarization is better than -34 dB in C-transmit band, better than -28.3 dB in C-receive band.