In this paper, LNB(low noise block) downconverter MMIC is designed for Ku-band satellite communication system using InGaP/GaAs HBT high linear process. Designed MMIC consists of low noise amplifier, double balanced mixer, and IF amplifier with a total chip area of 2.6${ imes}$1.1 $ extrm{mm}^2$. Designed MMIC has the characteristics of over 37.5 ㏈ conversion gain, 14 ㏈ noise figure, ripple of 3 ㏈, and output-referred <TEX>$P_{1dB}$TEX>(1 ㏈ compression power) of 2.5 ㏈m with total power dissipation of 3 V, 50 mA.