Abstract
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 f 0 ∼ 550 GHz, via radiative injection of a weak sinusoidal subharmonic signal at f 0/2. 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.
Highlights
T HERE is vital interest in compact and energy-efficient solid-state sources operating at room temperature to bridge the terahertz gap (0.3 THz < fTHz < 3 THz), especially within mobile scenarios
RTDbased oscillators operating at room temperature are currently providing the highest oscillation frequency of any solid-state electronic devices at around 2 THz [14]
We provide proof of concept for the injection locking mechanism by radiative injection of a subharmonic signal into a sub-mm wave (f0 > 550 GHz) resonant tunneling diode (RTD)-based fundamental mode oscillator
Summary
T HERE is vital interest in compact and energy-efficient solid-state sources operating at room temperature to bridge the terahertz gap (0.3 THz < fTHz < 3 THz), especially within mobile scenarios. RTDbased oscillators operating at room temperature are currently providing the highest oscillation frequency of any solid-state electronic devices at around 2 THz [14]. Alternative that is even integrated into a mobile device is signal injection locking [20], [21] This mechanism showed excellent results at microwave frequencies [16], [22], [23]. We provide proof of concept for the injection locking mechanism by radiative injection of a subharmonic signal into a sub-mm wave (f0 > 550 GHz) RTD-based fundamental mode oscillator
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