Graphene has become a type of important material for the construction of new nanoelectronic devices due to its high mobility, high thermal conductivity, good flexibility as well as mechanical strength. When graphene materials and their electronic devices are placed in a scene containing irradiation factors, the lattice structure can be changed. The charges then are accumulated due to interactions with high-energy photons and charged particles, resulting in changes in the performance of graphene materials and electronic devices. This paper mainly reviews the main effects of typical irradiation factors on graphene and its devices and the research progress, aiming to summarize the physical effects induced by irradiations on graphene and its electronic devices. This work deepens the understanding of the irradiation effect on graphene materials and devices, and lays a foundation for promoting its practical application in the irradiation scene.
Silicon-Germanium Heterojunction Bipolar Transistors(SiGe HBTs) is a strong contender for space applications in extreme environment on account of its superior temperature characteristics, which can bear extreme temperatures from -180 ℃ to 200 ℃ owing to the bandgap grading of heterojunction. Because of new features in material, structure and process, the radiation effects of SiGe HBTs present complex characteristics which are different from those of bulk-Si devices. In this work, the research dynamics and trends of space radiation effects in SiGe HBTs are introduced, and the radiation effects of domestic SiGe HBTs include Single Event Effects(SEE), Total Ionizing Dose(TID) effect, Enhanced Low Dose Rate Sensitivity(ELDRS) and synergistic effect are highlighted. The research shows that SiGe HBT naturally presents favorable build-in TID and displacement damage hardness without any radiation hardening, but the high sensitivity to SEE is a main drawback. Due to the different manufacturing processes, the domestic SiGe HBTs experience significant low dose rate sensitivity and are vulnerable to combined effect of ionizing dose/displacement damage and total ionizing dose on single event effect.
GaN High Electron Mobility Transistor(HEMT) devices have superior advantages in high-frequency, high-power, high-temperature and high-pressure applications, and due to the excellent radiation resistance characteristics of gallium nitride materials, the devices are useful in radiation environments such as satellites, space exploration, and nuclear reactors. Although the theory and some existing experimental results have shown that GaN materials have excellent radiation resistance properties, in actual situations, the radiation resistance properties of GaN HEMT devices are greatly affected and challenged due to the influence of the device manufacturing process and structure. The major radiation effects of GaN HEMT devices are discussed, and the radiation research of GaN HEMT devices is reviewed.
The irradiation effect of fast neutrons(1.2 MeV) on Gallium Nitride(GaN) white Light-Emitting Diodes(LEDs) with fluence of 1×1014 cm -2 is reported. The Electroluminescence(EL) spectrum, output power-current(L-I) and current-voltage(I-U) characteristics of the device are measured and analyzed. It is found that the optical output power decreasing after irradiation, while the shape of the EL spectrum almost remains unchanged, indicating that the neutron irradiation mainly causes damage to the blue LED chip. Further analysis shows that neutron irradiation leads to the generation of a large number of nonradiative recombination centers in the quantum well, which increases the leakage current and decreases the carrier density, thus reducing the output power of LED. In addition, the influencing factors caused by neutron irradiation are added to the original equivalent circuit model of GaN-based LEDs. This model not only helps to understand the mechanism of the degradation of the neutron irradiation on the LED output power, but also provides a feasible method to predict the change of the output power after irradiation.
The total dose damage to the Double buried oxide layer Silicon-On-Insulator silicon Metal Oxide Semiconductor Field Effect Transistor(DSOI MOSFET) is studied as well as the regulation of the back gate bias by the total dose radiation. The mechanism of the degradation of the electrical parameters of the transistor caused by the radiation is analyzed, and DSOI transistor total dose effect Simulation Program with Integrated Circuit Emphasis(SPICE) model is established. The model simulates the transistor threshold voltage, the simulated and measured results are below 6 mV. The corresponding back gate bias compensation model is given according to the total dose effect model. The SPICE model simulation output of the total dose effect is regulated by the transistor back bias. Comparing the compensation voltage with the experimental test results, the error of the back-bias control model of NMOSFET is 9.65%, and that of PMOSFET is 5.24%.
In order to explore the problem of the difference of dose response of P-channel Metal Oxide Semiconductor(PMOS) dosimeter to photons of 60Co and 10 keV photons, comparative irradiation tests of 60Co Gamma ray and 10 keV X-ray on 400 nm-PMOS dosimeter with different gate voltages are carried out. The effect of oxide trap charge and interface state trap charge are separated by the mid gap technique and charge pumping method. It is found that the response of PMOS to 10 keV X-ray is significantly lower than that to 60Co gamma rays. The main difference is from oxides-trap charge. The difference of annealing indicates that the trap charge competition mechanism is different between gamma and X-rays, and different analysis methods also bring some discrepancy. By using dose factor and charge yield correction, the difference of dose response is reduced, and the microphysical mechanism of the response is explained. The dose response difference between gamma and 10 keV X-rays can be greatly reduced by effective dose correction and charge yield correction, which provides reference for the application of PMOS in low energy photon radiation environment.
The resonance features of traditional metamaterial are fixed and unable to be tuned dynamically. A hybrid fishscale metamaterial combined with integrated photoconductive silicon is proposed to realize a tunable THz Fano response. The hybrid metamaterial is composed of a metallic fishscale structure, silicon layer and polymide substrate. The tunable Fano resonance is investigated by changing the incident angle and the conductivity of silicon layer in the proposed hybrid fishscale metamaterial without or with split in the metallic arc. When the conductivity of silicon layer reaches 1×103 S/m, the modulation depth reaches 1 at multiple THz frequencies. The proposed hybrid metamaterial offers an opportunity to achieve tunability of Fano resonance, and is of importance for active tuning, sensing in THz applications.
The fabrication of a terahertz filter with -40 dB attenuation depth at the resonant frequency of 130 GHz is presented, while some technical details during the procedures of evaporation, lithography, development etching introduced. filter sample is<±3μm,whichisacceptabandlebwetytheinvestiaregationoftheeffeThectofmerroracofhininthegerrorsonfabricatedtransmission characteristics. The measured transmission response of the fabricated sample by employing free space measurement setup is in good agreement with the design, which demonstrates the reliability and robustness of the fabrication technology. Finally, the feasibility and improvements of the presented fabrication technology applied to higher frequency devices are discussed. The presented technology based on silicon substrate is helpful in integration development of electronics devices and photonic devices.
To explore the effect of Terahertz(THz) on neurogenesis in the Subgranular Zone(SGZ) of the hippocampal dentate gyrus of adult mouse and the cognitive ability of elderly mouse, the heads of mice in THz group are irradiated with THz radiation for 10 min/time, 2 times/d, for 21 days. The mice in the control group are anesthetized for the same time. 5-Bromodeoxyuridine(BrdU) staining is utilized to evaluate the survival of newborn cells. BrdU/Neuron nucleus(NeuN) staining is adopted to evaluate cell differentiation. The Morris Water Maze(MWM) experiment is employed to analyze the changes in cognitive ability. Results indicate that 0.14 THz radiation for 10 min/time, twice/d, for 21 days can effectively promote SGZ neurogenesis in adult mouse without affecting the differentiation of newborn cells into neurons compared with the control group, and the survival of SGZ newborn cells in adult mouse is significantly improved(P<0.05), while the differentiation of newborn cells into neurons is not significantly changed. There are no significant changes in the escape latency and the locus of movement in the elderly mouse. It is concluded that THz irradiation does not affect the spatial cognitive ability of old mouse.
With the wide application of radar seeker on missile, the anti-jamming capability of the seeker is a key technology. The radar frequency synthesizer is the core part of radar system. The quality of local oscillator signal generated by radar frequency synthesizer shows a critical impact on the radar system’s ability of confrontation and anti-confrontation. Therefore, it proposes higher requests on the parameters of the local oscillator signal including wideband hopping, phase noise, clutter suppression, flatness and so on. Based on Direct Digital Synthesizer(DDS) technology and Advanced Design System (ADS) simulation technology, broadband impedance matching is performed. The effective signal crosstalk isolation technology is adopted to improve the indexes of X-band local oscillator signal of the radar frequency synthesizer. Through experimental testing, the local oscillator signal can achieve fast frequency hopping, and the frequency hopping bandwidth reaches 500 MHz, which improves the anti-interference capability of the radar; the phase noise is better than -98 dBc/Hz@1 kHz, which effectively improves the receiving sensitivity of the radar seeker.
The traditional frequency-domain anti-interference technology of satellite navigation signals is processed in the frequency domain of the received signal, and the spectrum of the interference signal is suppressed to achieve anti-interference. This method suppresses the interference while suppressing part of the signal, resulting in the loss of signal energy. Aiming at this problem, a frequency domain anti-interference algorithm using the spectrum symmetry of satellite navigation signals is proposed. This method utilizes the spectrum redundancy of satellite navigation signals and uses it in the process of interference spectrum suppression. A complete signal spectrum can be obtained by recovering the symmetrical undisturbed lines. The simulation data of Beidou B3 frequency point code shows that when the spectrum of the interference signal appears on one side of the center frequency, the proposed method is not sensitive to the bandwidth of the interference signal, even if the spectrum of the interference signal accounts for half of the signal spectrum, the energy of the output signal remains stable; the loss of signal energy is reduced during the interference line rejection compared to that in conventional methods.Simulation experiments show that in typical scenarios, the proposed method can improve the carrier-to-noise ratio by about 1 dB compared with the traditional zero-setting method.
A novel Coplanar Waveguide(CPW) airbridge-free power divider based on CPW-slotline transition is proposed in order to solve the problem of narrow bandwidth and large size of traditional circularly polarized microstrip array antenna. By using the power divider, a compact CPW-fed circularly-polarized array antenna with high directivity is designed. Compared with traditional CPW power divider, the proposed power divider has realized energy distribution by utilizing odd mode of CPW rather than suppressing this mode, which means the power divider needs no airbridge structure. Meanwhile, since there is no need to use 1/4 wavelength matching line, the antenna size is more compact and the structure is simpler. The designed circularly-polarized antenna array is only 1 mm in thickness, the measured axial ratio bandwidth and impedance bandwidth is 4.14% and 7.03% respectively. In addition, the measured gain is 8.412 dBi at 5.8 GHz. Therefore, the proposed array antenna can simultaneously provide adequate working bandwidth and gain while ensuring low profile and small size.
The use of antenna selection algorithms in massive Multiple Input Multiple Output(massive MIMO) systems can improve energy efficiency and system throughput. However, antenna selection algorithms suitable for traditional MIMO systems have high complexity and are difficult to be applied to massive MIMO systems. In order to optimize the antenna selection algorithm in two aspects: the algorithm complexity and system capacity, a joint threshold antenna selection algorithm for transmitting and receiving is proposed. The algorithm uses the maximum norm bidirectional antenna selection algorithm at the transmitting side, and the grouped maxvol antenna selection algorithm with an optimum preset threshold at the receiving side. The optimum threshold is obtained by simulation results. Results show that the joint threshold antenna selection algorithm can increase the system capacity while reducing the complexity. Compared with the incremental antenna selection algorithm, the system capacity can be increased up to 52.2 bit/s/Hz. The joint threshold antenna selection algorithm proposed in this paper can meet the transmission environment of different antenna correlation coefficients and SNR.
The Lubich coefficient is investigated from the point of view of signal processing, and the frequency characteristics of Lubich coefficient are analyzed. A fast algorithm based on Inverse Fast Fourier Transform (IFFT) for computing Lubich coefficient is designed. The Lubich coefficient directly solved by IFFT algorithm is not accurate. The Gibbs effect exists in the frequency domain with low order operations, and the new algorithm can reduce this effect effectively by zero-frequency assignment. The numerical simulation results show that, compared with Lubich accuracy coefficient, the Lubich approximation coefficients computed by the new algorithm have better performance in constructing the digital fractional differentiator with a certain proper fraction operation order range, and the new algorithm has low computational complexity and high efficiency.
In order to effectively improve the accuracy and real-time performance of target tracking, a dual-model adaptive correlation filtering tracking algorithm based on multi-template matching is designed in this study. The parameters of the multi-template matching model and the kernel-related filtering tracking model are initialized firstly. Among them, the multi-template matching model takes the score function as the matching criterion between the template and the candidate sample, obtains the best target through the candidate sample score, and realizes the multi-template matching through the deformation and diversity similarity after updating the multi-template. The kernel correlation filter tracking model uses the collected target sample data to establish a circulant matrix, obtains the kernel correlation filter and the response confidence map by training the core ridge regression classifier. Then the target position of the next frame of image is obtained by using the response confidence map. An adaptive fusion strategy is adopted to obtain the estimated target position of the two models, and then the pyramid scale estimation strategy is employed to estimate the target scale change. Accurate target tracking is achieved by continuously updating each model parameter. The experimental results show that the center tracking error of the algorithm is lower than 15 dpi, the average tracking accuracy is higher than 98%, and the target positioning time is less than 100 ms in complex environments such as target occlusion or rotation and illumination changes. The above results indicate that the algorithm bears obvious application advantages in tracking accuracy and real-time performance.
In multilayer integrated circuit, the parasitic mode problem is caused by Defect Ground Structure(DGS). By comparing the effects of window shielding form and various back hole arrays in suppressing the propagation of parasitic modes, it is found that the window shielding form can effectively suppress the propagation of parasitic modes but greatly increase the circuit loss. The existence of the simplest back hole array can achieve parasitic suppression. Without changing the process structure, the double-back-hole form and the four-back-hole form can meet the suppression requirements of dielectric films below 200 GHz and 300 GHz respectively. In these cases, the back holes occupy the smallest area. It can effectively reduce the back hole arrangement density and increase the circuit integration.