Summation of Powers in Open Resonator with Slotted Coupling Elements

The paper analyzes the summation of the powers of two sources in a hemispherical open resonator (OR) during its tuning. The first higher axially asymmetric TEM10q oscillation mode is excited in the resonator. A circuit with an E- tee waveguide is proposed, which makes it possible to research the summation of the powers using a Gunn diode. Studies of the conducting part of the millimeter range have been undertaken. It is shown that the coefficient of powers summation of two sources in the OR using slot coupling elements does not exceed 72%. The use of one H- polarized diffraction grating, which is in the resonator, does not lead to a significant increase in the summation coefficient when moving it. This is due to the excitation of the first type of TEM10q oscillations in the resonator.

Study on Self-Parallel GaN-Based Terahertz Hetero-Structural Gunn Diode

In this paper, we propose a novel gallium nitride-based multi-two-dimensional-electron-gas (2DEG)-channel self-parallel Gunn diode (SPD) for the first time. In the SPD, a trench anode is etched through at least the bottommost 2DEG channels, which splits all 2DEG channels into two shorter channels with lengths of L1 and L2. Therefore, one SPD is just equal to several shorter diodes in parallel; as a result, we call it a self-parallel Gunn diode. In the symmetrical SPD, the component of fundamental frequency is nearly multiplied as compared with the regular Gunn diode. In the asymmetrical SPD (L2 = nL1, n is a positive integer), the harmonic components are greatly enhanced, specially the nth harmonic. Our work demonstrates that the GaN-based terahertz SPD not only offers an easy transfer between two different frequencies, but also realizes the simultaneous enhancement of oscillation power and frequency.

Physical-Based Simulation of the GaN-Based Grooved-Anode Planar Gunn Diode

In this paper, a novel gallium nitride (GaN)-based heterostructure Gunn diode is proposed for the first time to enhance the output characteristics of Gunn oscillation waveforms. A well-designed grooved anode contact is adopted to separate the long-channel diode into two short-channel diodes in parallel. If the grooved anode contact is positioned in the middle of the device, the output power nearly doubles in the grooved-anode diode compared with the single-channel ones, as does the output frequency. Based on the numerical results, the best output characteristics are obtained at the 2.0-µm symmetrical grooved-anode diode, which produces nearly 5.48 mW of power at the fundamental frequency of 172.81 GHz, with 3.13% efficiency of power conversion. If the grooved anode contact is not positioned in the middle of the diode, the harmonic frequency would be enhanced. The GaN heterostructure grooved-anode Gunn diode has been demonstrated to be an excellent solid-state source of terahertz oscillator.

Dynamic characteristics of frequency-locked autodynes

The results of research into the dynamic characteristics of microwave oscillators under the influence of both their own reflected radiation and external synchronising effect are presented. The basic relations for the analysis of signals during fast movement of the target are obtained, when the signal period is comparable to the autodyne response time constants. The results of numerical modelling of the characteristics are confirmed by the experimental data obtained on the example of an oscillator based on the Gunn diode of the 8-mm range.

Autodyne signal features of frequency-locked microwave oscillators

The research results on the autodyne signal formation in microwave oscillators, which are exposed under the impact of the proper reflected emission and, at the same time, of the external frequency-locked signal are presented. The basic relations are obtained for signal analysis under the condition of the quasistatic target movements. The theoretical research results are confirmed by experimental data obtained on the example of an oscillator made on the basis of the 8mm-range Gunn diode.

Isothermal measurement of current-voltage characteristics of Gunn diodes with reflection of their discontinuities and hysteresis

Requirements to the measuring setup are formulated, which make it possible obtaining isothermal current-voltage (I-V) characteristics of the Gunn diode with reflection of their discontinuities, region of negative differential resistance, and hysteresis. The influence of the inductance of the test pulses, source on the occurrence of self-excitation in the connecting transmission line is investigated. The maximum permissible values of the inductance of the test signal source are indicated. Operation of the measuring circuit without self-excitation was experimentally achieved in most of the region with negative differential resistance. The isothermal I-V characteristics of the Gunn diode were measured with a controlled systematic error due to the comparing the measurement result with the developed model of the I-V characteristic.