Great interest is given in recent years to the small satellites as their main advantages are the low development cost and the reduced deployment time, which give attention to develop payloads that can be mounted on the platform of these satellite. the platform of small satellites imposes constraints on the sensor design to fit in the size, mass and power limitations, which leads to necessary trade-offs between the design parameters of the sensor. The selection of the operating frequency is dependent mainly on the mission requirements as each frequency band gives different information about the scene and has different penetration capabilities. However, the SAR sensors used on small satellites come with limitations, so other parameters should be considered during the design. After going through the SAR design process, a frequency analysis is presented at L, C and X bands, which is used to evaluate the effect on the size of the antenna (length and width) and the average power consumption that suit the constraints of small satellite.