A MMIC demodulator has been designed and characterized over the [0.79 – 0.97] GHz RF band. It consists of an RF differential amplifier and an LO 4-way phase splitter affording the 0°, 90°, 180° and 270° relative phase shift and equal amplitude signals. Both RF and LO channels drive a double double balanced quad FET mixer which provides the four quadrature phase shift voltage baseband IF signals on high outputs impedances. This chip (4 x 3.1 mm²) has been fabricated using a GaAs 0.5µm MESFET process and reaches a high performance as far as IF signals balance accuracy is pursued