Envelope tracking active circulator

Abstract

Several embodiments of an envelope tracking active circulator is disclosed with a method to cascade them. In an active transistor based circulator (active circulator), gate (base) and drain (collector) bias voltage can be adjusted by RF or microwave input envelop signal. This is called envelop tracking active circulator. In this concept, input RF signal is detected by detection circuit, such as detection diode or coupler and converted into low frequency envelop signal by the proper filtering circuitry. The generated envelop signal controls the supply voltage of the drain and gate with the proper function of the envelop signal to improve active circulator insertion loss, isolation and power handling capability. This concept can be applied to any type of solid-state FET (Field effect transistor) transistor based active circulator, as long as they have bias dependent trans-conductance and capacitances inside. For a BJT (bipolar junction transistor) based active circulator, base bias current supply modulator will be used instead of voltage supply modulator.