In this paper, 4 types of SiGe active downconversion mixers are designed, simulated and compared with each other for non-portable S-Band applications. All mixers have single-ended RF inputs and they are designed in the same 0.35-m BiCMOS process with 5 V supply voltages. These mixers are compared in terms of conversion gain, IIP3, P1dB, DSB noise figure, and power dissipation at 2-4 GHz RF frequency. In addition to this, an LO amplifier and an IF buffer are designed to provide higher conversion gain, lower noise figure and output matching. These circuits are common for all mixers; thus, they have the same effect on all. Figure of merits of mixers are calculated and their pros and cons are explained.