With the exponential growth of the data traffic in wireless communication systems, terahertz(THz) frequency band is envisioned as a promising candidate to support ultra-broadband for future beyond fifth generation(5G)...With the exponential growth of the data traffic in wireless communication systems, terahertz(THz) frequency band is envisioned as a promising candidate to support ultra-broadband for future beyond fifth generation(5G), bridging the gap between millimeter wave(mmWave) and optical frequency ranges. The purpose of this paper is to provide a comprehensive literature review on the development towards THz communications and presents some key technologies faced in THz wireless communication systems. Firstly, despite the substantial hardware problems that have to be developed in terms of the THz solid state superheterodyne receiver, high speed THz modulators and THz antennas, the practical THz channel model and the efficient THz beamforming are also described to compensate for the severe path attenuation. Moreover, two different kinds of lab-level THz communication systems are introduced minutely, named a solid state THz communication system and a spatial direct modulation THz communication system, respectively. The solid state THz system converts intermediate frequency(IF) modulated signal to THz frequency while the direct modulation THz system allows the high power THz sources to input for approving the relatively long distance communications. Finally, we discuss several potential application scenarios as well as some vital technical challenges that will be encountered in the future THz communications.展开更多
研究设计基于CBB(Common Building Block)架构的宽带通信雷达一体超外差接收机,旨在提供一种快速、高效的多用途接收整机设计方法。该方法设计7种共用基础模块,各自实现接收整机中的一部分技术与功能指标;对7种共用基础模块按照各自特...研究设计基于CBB(Common Building Block)架构的宽带通信雷达一体超外差接收机,旨在提供一种快速、高效的多用途接收整机设计方法。该方法设计7种共用基础模块,各自实现接收整机中的一部分技术与功能指标;对7种共用基础模块按照各自特点进行系列化研制、生产,形成各自的产品库;在通信雷达一体超外差接收机的设计中,结合技术指标要求,选用相应的共用基础模块进行组合,即可完成相应的整机设计工作。此方法的优点是:简化整机设计难度、减少重复开发、缩短研制周期、提高产品成熟度,以及便于设备的测试、维修等。展开更多
We propose an absolute distance measurement method that employs heterodyne and superheterodyne combined interferometers to achieve synchronous detection and demodulation of multiwavelengths.Coarse and fine synthetic w...We propose an absolute distance measurement method that employs heterodyne and superheterodyne combined interferometers to achieve synchronous detection and demodulation of multiwavelengths.Coarse and fine synthetic wavelengths are generated by a dual-longitudinal-mode He-Ne laser and four acoustic optical frequency shifters.Further,to improve phase synchronization measurement for multiwavelengths,we analyze the demodulation characteristics of coarse and fine measurement signals and adopt a demodulation method suitable for both signals.Experimental results demonstrate that the proposed method can achieve high-precision synchronous demodulation of multiwavelengths,and standard deviation is 1.7×10^(-5)m in a range of 2 m.展开更多
The amplification of microwaves in n-GaAs films has been widely studied. On the other hand, using nonlinear parametric effects in microwave, millimeter, and THz ranges has a large potential. In this paper the resonant...The amplification of microwaves in n-GaAs films has been widely studied. On the other hand, using nonlinear parametric effects in microwave, millimeter, and THz ranges has a large potential. In this paper the resonant nonlinear phenomena are investigated in active n-GaAs semiconductor and in films on its base. The phenomena are the nonlinear interactions of space charge waves, including the frequency multiplication and mixing, and the three-wave interaction between two THz electromagnetic waves and a single space charge wave. This three-wave interaction results in the superheterodyne amplification of THz waves. The electron velocity in GaAs is the nonlinear function of an external electric field. If the bias electric field is more E0>Ecrit ≈3KV/cm , it is possible to obtain a negative differential mobility (NDM and space charge waves). The space charge waves have phase velocity of electrons equal to v0=v(E0), E0=V0/Lz , where V0 is the voltage, producing the bias electric field E0?in GaAs film. The superheterodyne amplification and the multiplication of microwaves are very promising for building active sensors in telecommunications system, radiometers, and radio telescopes. The superheterodyne mechanism has an advantage related to decreasing noise because of increasing of frequency in the process of amplification. It is used in the process of amplification of longitudinal space charge waves that in turn causes the transfer of energy from longitudinal wave into transverse one with increasing frequency. This is realized due to parametric coupling of two transverse waves and a single space charge wave in GaAs.展开更多
The superheterodyne amplification of electromagnetic waves is investigated when the resonant three-wave interaction of two electromagnetic waves with the space charge wave occurs in the waveguides nitride <em>n&...The superheterodyne amplification of electromagnetic waves is investigated when the resonant three-wave interaction of two electromagnetic waves with the space charge wave occurs in the waveguides nitride <em>n</em>-GaN, <em>n</em>-InN films-dielectric. The amplification of SCW waves due to the negative differential conductivity is investigated in nitride <em>n</em>-GaN, <em>n</em>-InN films at the frequencies <em>f</em> ≤ 400 GHz in the lower part of the terahertz (THz) range. The electromagnetic waves are either in the upper part of THz range or in the optical range. The superheterodyne amplification is considered in two geometries, the collinear one in which the three interacting waves travel in the same direction and the anti-collinear geometry where the second electromagnetic wave propagates in the opposite direction. The preferences and drawbacks of each geometry are pointed out. The finite width of space charge waves leads to decrease of increments of amplification.展开更多
基金supported by the National High Technology Research and Development Program of China (863 program) of China under Grant No.2011AA010200 supported by the National Natural Science Foundation of China (NSFC) under Grant No.61771116 and No.91738102
文摘With the exponential growth of the data traffic in wireless communication systems, terahertz(THz) frequency band is envisioned as a promising candidate to support ultra-broadband for future beyond fifth generation(5G), bridging the gap between millimeter wave(mmWave) and optical frequency ranges. The purpose of this paper is to provide a comprehensive literature review on the development towards THz communications and presents some key technologies faced in THz wireless communication systems. Firstly, despite the substantial hardware problems that have to be developed in terms of the THz solid state superheterodyne receiver, high speed THz modulators and THz antennas, the practical THz channel model and the efficient THz beamforming are also described to compensate for the severe path attenuation. Moreover, two different kinds of lab-level THz communication systems are introduced minutely, named a solid state THz communication system and a spatial direct modulation THz communication system, respectively. The solid state THz system converts intermediate frequency(IF) modulated signal to THz frequency while the direct modulation THz system allows the high power THz sources to input for approving the relatively long distance communications. Finally, we discuss several potential application scenarios as well as some vital technical challenges that will be encountered in the future THz communications.
文摘研究设计基于CBB(Common Building Block)架构的宽带通信雷达一体超外差接收机,旨在提供一种快速、高效的多用途接收整机设计方法。该方法设计7种共用基础模块,各自实现接收整机中的一部分技术与功能指标;对7种共用基础模块按照各自特点进行系列化研制、生产,形成各自的产品库;在通信雷达一体超外差接收机的设计中,结合技术指标要求,选用相应的共用基础模块进行组合,即可完成相应的整机设计工作。此方法的优点是:简化整机设计难度、减少重复开发、缩短研制周期、提高产品成熟度,以及便于设备的测试、维修等。
基金supported by the National Natural Science Foundation of China(No.52175500)the National Key Research and Development Program of China(No.2022YFF0605102)the Natural Science Foundation of Heilongjiang Province(No.LH2019E048)。
文摘We propose an absolute distance measurement method that employs heterodyne and superheterodyne combined interferometers to achieve synchronous detection and demodulation of multiwavelengths.Coarse and fine synthetic wavelengths are generated by a dual-longitudinal-mode He-Ne laser and four acoustic optical frequency shifters.Further,to improve phase synchronization measurement for multiwavelengths,we analyze the demodulation characteristics of coarse and fine measurement signals and adopt a demodulation method suitable for both signals.Experimental results demonstrate that the proposed method can achieve high-precision synchronous demodulation of multiwavelengths,and standard deviation is 1.7×10^(-5)m in a range of 2 m.
文摘The amplification of microwaves in n-GaAs films has been widely studied. On the other hand, using nonlinear parametric effects in microwave, millimeter, and THz ranges has a large potential. In this paper the resonant nonlinear phenomena are investigated in active n-GaAs semiconductor and in films on its base. The phenomena are the nonlinear interactions of space charge waves, including the frequency multiplication and mixing, and the three-wave interaction between two THz electromagnetic waves and a single space charge wave. This three-wave interaction results in the superheterodyne amplification of THz waves. The electron velocity in GaAs is the nonlinear function of an external electric field. If the bias electric field is more E0>Ecrit ≈3KV/cm , it is possible to obtain a negative differential mobility (NDM and space charge waves). The space charge waves have phase velocity of electrons equal to v0=v(E0), E0=V0/Lz , where V0 is the voltage, producing the bias electric field E0?in GaAs film. The superheterodyne amplification and the multiplication of microwaves are very promising for building active sensors in telecommunications system, radiometers, and radio telescopes. The superheterodyne mechanism has an advantage related to decreasing noise because of increasing of frequency in the process of amplification. It is used in the process of amplification of longitudinal space charge waves that in turn causes the transfer of energy from longitudinal wave into transverse one with increasing frequency. This is realized due to parametric coupling of two transverse waves and a single space charge wave in GaAs.
文摘The superheterodyne amplification of electromagnetic waves is investigated when the resonant three-wave interaction of two electromagnetic waves with the space charge wave occurs in the waveguides nitride <em>n</em>-GaN, <em>n</em>-InN films-dielectric. The amplification of SCW waves due to the negative differential conductivity is investigated in nitride <em>n</em>-GaN, <em>n</em>-InN films at the frequencies <em>f</em> ≤ 400 GHz in the lower part of the terahertz (THz) range. The electromagnetic waves are either in the upper part of THz range or in the optical range. The superheterodyne amplification is considered in two geometries, the collinear one in which the three interacting waves travel in the same direction and the anti-collinear geometry where the second electromagnetic wave propagates in the opposite direction. The preferences and drawbacks of each geometry are pointed out. The finite width of space charge waves leads to decrease of increments of amplification.
