Coherent power combination in highly integrated resonant tunneling diode oscillators with slot antennas

We propose highly integrated array of resonant tunneling diode oscillators and observed coherent power combination in this structure. Two InGaAs/AlAs RTD oscillators with slot antennas on the same InP wafer are arranged collinearly, and coupled with each other through a 5-mum-long metal-insulator-metal stub structure. Although the individual oscillation frequencies were 329 GHz and 332 GHz, a single peak at 321 GHz was observed when the two oscillators were driven simultaneously. The individual output powers were 1.9 muW and 2.6 muW, while 5.1 muW in simultaneous operation which was larger than the summation of individual output. These results are attributed to the mutual injection locking and coherent power combination resulting in the improvement of directivity in array antenna. From these experimental results, high-power and high-density RTD oscillators are expected by extending this structure to several elements.