Gallium arsenide antenna switch

Abstract

An electronic switch uses GaAs transistors to switch signals that have peak-to-peak voltage swings that exceed the breakdown voltage of the transistors. A two port impedance transformer (Z1) has a high input impedance and a low output impedance to transform a high voltage input signal (at T1) to a corresponding output signal having lower voltage, but higher current. This transformed signal is coupled to the second port of a three port impedance transformer (Z2) through a first GaAs transistor switch (Q1). A half wave rectifier circuit (D1, R7, R8 and C3) generates a negative DC voltage from the input signal (at T1), thereby eliminating the requirement for a separate bias voltage supply. A bipolar transistor switch selectively couples this negative bias voltage to the gate of the first GaAs transistor (Q1). The second port of the three port impedance transformer (Z2) has a lower impedance than either the first or third ports. A second GaAs transistor switch (Q2) is coupled between the third port of the three port impedance transformer (Z2) and ground, and a third GaAs transistor switch (Q3) couples the third port to a output terminal (T6) of the switch. The first port of the three port impedance transformer (Z2) is coupled to an input/output terminal (T2) of the switch.