A double layer microstrip spatial amplifier with increased active device density

A new quasi-optical amplifier consisting of four HEMTs coupled to a single receiving and a single transmitting microstrip patch antenna is presented. This circuit can be used as a unit cell for the construction of a power combining amplifier array at millimeter-wave frequencies. The advantage of this circuit is its high active device density which is desirable in the construction of monolithic integrated circuits. The amplifier was constructed on double layer back to back microstrip circuits with a shared ground plane which provides an effective isolation between the receiving antenna and the transmitting antenna. The coupling between the two stages is accomplished through microstrip to slot transitions, which facilitates monolithic fabrication of such amplifiers. The measured gain at 10.1 GHz is 10 dB.