External Feedback Effect in Terahertz Resonant Tunneling Diode Oscillators

The external feedback effect of a resonant tunneling diode oscillator in terahertz (THz) proximity wireless transmission is modeled and analyzed. The model is based on the circuit modeling of the resonant tunneling diode and the passive structures. We investigate important system parameters such as the reflectivities at the transmitter and the receiver and the power coupling. It is found that the frequency change, the frequency change rate, and the direct-current change are mainly dependent on the reflectivity at the receiver. The received power change is mainly caused by the reflectivity at the transmitter. The simulations agree well with the experimental results. In addition, we demonstrate the high accuracy of our models by clarifying origins of the bit-error-rate change with distance. This demonstrates that the proposed model can be used for the design of a stable THz proximity wireless communication system. The model is also considered to be potentially applicable in other promising THz applications including sensing and radar.