Presentation Information
[ED5-03-INV]Expanding superposition bandwidth with frequency-modulated terahertz radiation from superconducting Josephson plasma emitter
*Itsuhiro Kakeya1, Ryota Kobayashi1, Rintaro Mori1, Keitaro Sugimoto1, Manabu Tsujimoto2 (1. Kyoto University (Japan), 2. AIST (Japan))
Keywords:
Josephson effect,cuprate superconductor,terahertz radiation,signal transmission
[Purpose]
Communication using terahertz (~1012 Hz) electromagnetic waves is critical for developing 6th-generation wireless network infrastructures. Conflictions between stable radiation and the modulation frequency of terahertz sources impede the superposing of transmitting signals on carrier waves. The Josephson junctions included in a cuprate superconductor radiate terahertz waves1) with frequencies proportional to the bias voltages2) . Thus, the modulation of the bias voltage leads to the modulation of the Josephson plasma emission (JPE) frequency. We achieved to demonstrate sinusoidal signal at 3 GHz superimposed on sub-terahertz carrier waves in a JPE device radiating at 840–890 GHz with the maximum FM bandwidth of 40 GHz
[Method and results]
To achieve higher transmission rate of wireless communications, expanding bandwidth of superimposed signals and increasing in radiation power resulting in increased signal-to-noise ratio are indispensable. When the superimposed signal frequency was increased up to 10 GHz, FM comb spectrum was found up to 7.5 GHz and the spectrum bandwidth given by the actual modulation amplitude applied to the JPE showed complicated superimposed frequency dependence. This is the result of complicated frequency dependence of impedance of bias-applied circuit of the JPE. We discuss the loss and the reflection of the circuit and suggest the method to expand the bandwidth of the superimposed signal. We also continue to increase radiation efficiency of JPE with implementing numerical simulations to actual device fabrications. The development of reproducing radiation properties of JPE by circuit simulations using a SPICE simulator4) and three-dimensional finite-difference time-domain simulations.
Communication using terahertz (~1012 Hz) electromagnetic waves is critical for developing 6th-generation wireless network infrastructures. Conflictions between stable radiation and the modulation frequency of terahertz sources impede the superposing of transmitting signals on carrier waves. The Josephson junctions included in a cuprate superconductor radiate terahertz waves1) with frequencies proportional to the bias voltages2) . Thus, the modulation of the bias voltage leads to the modulation of the Josephson plasma emission (JPE) frequency. We achieved to demonstrate sinusoidal signal at 3 GHz superimposed on sub-terahertz carrier waves in a JPE device radiating at 840–890 GHz with the maximum FM bandwidth of 40 GHz
[Method and results]
To achieve higher transmission rate of wireless communications, expanding bandwidth of superimposed signals and increasing in radiation power resulting in increased signal-to-noise ratio are indispensable. When the superimposed signal frequency was increased up to 10 GHz, FM comb spectrum was found up to 7.5 GHz and the spectrum bandwidth given by the actual modulation amplitude applied to the JPE showed complicated superimposed frequency dependence. This is the result of complicated frequency dependence of impedance of bias-applied circuit of the JPE. We discuss the loss and the reflection of the circuit and suggest the method to expand the bandwidth of the superimposed signal. We also continue to increase radiation efficiency of JPE with implementing numerical simulations to actual device fabrications. The development of reproducing radiation properties of JPE by circuit simulations using a SPICE simulator4) and three-dimensional finite-difference time-domain simulations.