Phase and frequency control of resonant tunneling diode (RTD) based terahertz oscillators are major challenges in realizing coherent signal sources for arrayed applications, such as spatial power combining, beam steering, or multi-in multi-out systems. In this letter, we demonstrate frequency locking and control of an RTD oscillating at f0 ∼ 550 GHz, via radiative injection of a weak sinusoidal subharmonic signal at f0/2. Precise frequency control, within the locking range of around 2 GHz, is demonstrated. A peak output power enhancement of 14 dB in the whole locking range, compared to the free running oscillator, is achieved. Furthermore, occurrence of phase locking is identified by the spectral linewidth reduction, quantifiable in the full-width at half-maximum parameter. A signal linewidth of 490 Hz was achieved in locked operation.

中文翻译：

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基于RTD的太赫兹振荡器相位和频率控制的次谐波注入锁定

基于谐振隧道二极管 (RTD) 的太赫兹振荡器的相位和频率控制是实现阵列应用（例如空间功率组合、波束控制或多入多出系统）的相干信号源的主要挑战。在这封信中，我们展示了通过在 f0/2 处辐射注入弱正弦次谐波信号，对在 f0 ∼ 550 GHz 处振荡的 RTD 进行频率锁定和控制。展示了在 2 GHz 左右锁定范围内的精确频率控制。与自由运行的振荡器相比，在整个锁定范围内实现了 14 dB 的峰值输出功率增强。此外，锁相的发生通过光谱线宽的减少来识别，可在半高全宽参数中量化。在锁定操作中实现了 490 Hz 的信号线宽。