Search

This letter presents a novel harmonic impedance matching technique by using a parallel LC resonate block after the combining point to design a fully integrated high-efficiency Doherty power amplifier (DPA). The second harmonic impedances of both carrier and peaking amplifiers can be matched to the optimal area with only one harmonic tuner easily. The insertion loss and size of the output matching network (OMN) can be reduced. For verification, a 4.6–5.2-GHz monolithic microwave integrated circuit DPA was designed and fabricated using a 0.25- $\mu \text{m}$ gallium nitride (GaN)-HEMT process. Experimental results show that a saturated power of 41.8–42.1 dBm, a saturated drain efficiency (DE) of 63.8%–68.4%, and a 6-dB back-off DE of 53.3%–57.4% are achieved from 4.6 to 5.2 GHz. For a 160-MHz modulated signal, a high DE of 54% with good linearity after linearization is obtained at an average output power of 35.6 dBm.

Insomnia has become one of the common clinical diseases. In recent years, it has been found that patients with insomnia of Yang deficiency type are more and more common, and the trend of rejuvenation gradually appears, which seriously affects the normal progress of people's life, work and study. Clinical treatment through syndrome differentiation, mainly from the heart, spleen, kidney three viscera yang deficiency, on the basis of the warm yang method to add Qianzhen tranquilizing products, and pay attention to multiple organs as diseases, add moisture, blood The qi thing, while not forgetting the psychological counseling, adjusting the body and mind, and achieving a certain clinical effect, can provide ideas for the treatment of this disease.

A modified load‐modulation network to design a fully integrated wideband Doherty power amplifier (DPA) from 4.6 to 5.5 GHz is presented in this letter. The modified load‐modulation network uses only two π‐type high‐pass equivalent quarter wavelength transmission lines (QWTLs). Unlike the existing methods, the bandwidth of the load‐modulation network composed of two merged π‐type equivalent QWTLs is broadened. Furthermore, a drain bypass capacitor compensation method is proposed to reduce the leakage of RF power after the drain supply inductors are merged. For verification, a wideband monolithic microwave integrated circuit DPA was designed and fabricated using a 0.25‐μm gallium nitride based high‐electron‐mobility transistor process. Measurement results show that a saturated power of 41.6–42.4 dBm, a saturated drain efficiency (DE) of 65.3–72%, and a 6‐dB back‐off DE of 45–55.4% are achieved from 4.6 to 5.5 GHz. Using a 160‐MHz orthogonal frequency‐division multiplexing signal with a peak‐to‐average power ratio of 6.2 dB, the high average efficiency of 49% with an adjacent channel leakage ratio of –47.2 dBc after linearisation was obtained at an average output power of 35 dBm at 4.9 GHz.

This paper presents a dual-band and wideband switchable Doherty power amplifier (DPA) with back-off efficiency reconfiguration. It can be operated in wideband mode and dual-band mode with higher back-off efficiency through switching the carrier and peaking amplifier roles directly. The phase relationship required for dual-mode operation is first given. Meanwhile, the efficiency reconfigurable feature is realized by utilizing the integrated compensating reactance (ICR) technology. To verify the proposed circuits, a back-off efficiency reconfigurable dual-mode Doherty power amplifier (DM-DPA) which can be operated in wideband mode from 3 GHz to 3.8 GHz and dual-band mode at 2.4 GHz and 4.4 GHz was designed and fabricated. The implemented efficiency reaches 35% and 40% for wideband mode and dual-band mode respectively at 6-dB back-off power. When excited by a 100-MHz long-term evolution-advanced modulated signal with 6.5-dB peak-to-average power ratio, the DM-DPA can achieve an average efficiency of more than 37.3% in both wideband and dual-band modes. To the best of authors’ knowledge, this is the first kind of operation mode switchable DPA with back-off efficiency reconfiguration.

Background: To study the impact of acupuncture treatment on structural brain network for patients with different courses of migraine without aura based on fMRI. Methods: A total of ten patients with a long course (>5 years) of migraine without aura (MWoA), ten patients with a short course (Results: 1) The small-world property on the group with a long course was decreased significantly (pConclusions: The two unequal ways of acupuncture on the structural brain network of migraineurs with different disease courses were revealed. Acupuncture could regulate the central sensitization of chronic migraines, differently with the early stage. The nodal efficiency of the left posterior limb of the internal capsule and right tapetum would be symbols to discriminate against the process of MWoA.

A novel broadband balun of owning bandwidth of more than a decade octaves is proposed, which is comprised of two parallel stacked spiral transformers with slightly different dimensions. The equivalent coupled line model reveals that the amplitude imbalance of the balun with symmetric structure equals to the coupling coefficient of the coupled line in decibel. Therefore, with higher coupling degree comes smaller amplitude imbalance. Furthermore, combined with the high coupling degree of stacked spiral transformers, the balun of owning optimal amplitude balance can be realised by slightly adjusting the size of one side transformer. Finally, the balun is designed and fabricated in Sanan's integrated passive device (IPD) process and its core size occupies an area of 690 μ m × 240 μ m . The simulation and measurement agree well in general, exhibiting a bandwidth covering from 1.34 up to 16.37 GHz with good return loss, flat insertion loss and high stability of 180° phase difference.

Smart design of advanced substrates for surface-enhanced Raman scattering (SERS) activity is challenging but vital. Herein, we synthesized a new kind of AgNPs/MnO2@Al flexible substrate as a SERS substrate for the detection of the analyte rhodamine 6G (R6G). The fabrication of porous MnO2 nanoflakes on Al foil was conducted via a facile hydrothermal strategy. Owing to the large active surface area of the MnO2 nanoflakes, the Ag nanoparticles were immobilized and displayed superior SERS performance with a low detection concentration of 1 × 10−6 M for R6G. In addition, the SERS performance was found to be strongly related to the morphology of the MnO2@Al substrate material. Our smart design may provide a new method of construction for other advanced SERS substrates for the detection of R6G.

In this paper, the magnetic and thermodynamic behaviors of a mixed-spin ferrimagnetic cubic nanoisland, consisting of a core with spin-1 atoms surrounded by shell with spin-1 and spin-3/2 atoms in the external magnetic field have been investigated. We have used the Monte Carlo simulation to examine the effects of the crystal-field, the exchange coupling and the external magnetic field on the magnetization, susceptibility, internal energy and blocking temperature of the nanoisland. Depending on different values of the magnetic parameters, we have found various types of magnetization curves. In particular, multiple hysteresis loop behaviors such as double and triple hysteresis loops have been discovered for certain parameters.

The Monte Carlo simulation has been applied to discuss the step effect on a zigzag graphene nanoribbon structure in a longitudinal magnetic field. The effects of the singe-ion anisotropies, longitudinal magnetic fields and temperature on the magnetization plateaus have been investigated in detail. Our results show that the number of magnetization plateaus for the system dissatisfy 2 S + 1 criterion at low temperatures, originating from not only the competition between the anisotropy and the external magnetic field, but also the contributions of edge effects. It has been found that the single-ion anisotropy plays a significant role in modulating the spin configurations of the zigzag graphene nanoribbon structure. In addition, the effects of single-ion anisotropies and external magnetic fields on the magnetization, the susceptibility, the internal energy and the blocking temperature have been examined.

Monte Carlo simulation has been used to study magnetic and thermodynamic properties of a ferrimagnetic mixed-spin (1, 3/2) Ising nanowire with hexagonal core-shell structure. The ground phase diagrams are obtained for different exchange couplings. The critical values of the exchange couplings have been found, determining whether the compensation points appear in the present system. In particular, the effects of the exchange couplings and the temperature on the magnetization, the internal energy, the specific heat, the compensation points and hysteresis loops are discussed in detail. Under certain physical parameters, multiple cycle hysteresis loops such as triple and quintuple hysteresis loop patterns have been observed in the system. It is found that the exchange coupling and the temperature strongly affect the coercivity and the remanence of the system. Compared our results with other theoretical and experimental studies, a good agreement has been obtained qualitatively.

A novel broadband balun based on centrosymmetric spiral transformers is proposed. Two parallel circular spiral transformers comprise the proposed balun, which is different from the Marchand structure. The equivalent coupled line model demonstrates that asymmetric structure is helpful to realise the appropriate balun with good amplitude balance and low return loss. Finally, combined with the structural characteristics of the spiral transformer in monolithic microwave integrated circuit designs, a centrosymmetric structure with compact size is adopted. The balun is designed and fabricated in WIN's IP2M process and its core size occupies an area of 700 μ m × 300 μ m . The simulation and measurement agree well, exhibiting a bandwidth covering from 2 to 18 GHz with good return loss, flat insertion loss and high stability of 180° phase difference.

This paper presents the simulation result of a 4.9-GHz GaN MMIC Doherty Power Amplifier for 5G Application using a 0.25-μm gallium nitride (GaN)-HEMT process. According to the simulation results, a saturated power of 40 dBm-40.3 dBm, a saturated drain efficiency (DE) of 60%-63%, and a 6-dB back-off DE of 51%-53% are achieved from 4.8 GHz to 5 GHz. When driven by a 100MHz orthogonal frequency division multiplexing (OFDM) signal with 6.1 dB peak-to-average power ratio (PAPR), an adjacent channel leakage ratio (ACLR) of -29 dBc with a DE of 50% was achieved at an average power of 34 dBm. After a digital predistortion process, the ACLR was improved to -46 dBc.

Monte Carlo simulation has been performed in detail to study magnetic and thermodynamic properties of a ferrimagnetic mixed-spin (1, 3/2) cylindrical Ising nanowire with core-shell structure. The ground phase diagrams are obtained for different single-ion anisotropies. The system can display rich phase transitions such as the second- and first-order phase transitions, the tricritical points and the compensation points. Especially, emphasis has been given to the effects of the single-ion anisotropy and the temperate on the magnetization, the internal energy, the specific heat, the compensation points and hysteresis loops of the system as well as two sublattices. A number of characteristic phenomena such as such as various types of magnetization curves and triple, duadruple as well as quintuple hysteresis loops behaviors have been observed for certain physical parameters, originating from the competitions among the anisotropies, temperature and the longitudinal magnetic field. It is found that the single-ion anisotropy and the temperature strongly affect the coercivity and the remanence of the system. A satisfactory agreement can be achieved from comparisons between our results and previous theoretical and experimental works.

Monte Carlo simulation has been used to study the magnetic properties of a nano-graphene bilayer which consists of the upper layer A with spin-3/2 and the bottom layer B with spin-5/2. The effects of the single-ion anisotropy, the intralayer exchange coupling and the longitudinal magnetic field on the magnetization, the susceptibility, the blocking temperature and hysteresis loops of the mixed-spin nano-graphene bilayer system have been examined detailedly. In particular, the variations of the blocking temperature with different intralayer exchange couplings, single-ion anisotropies, and the longitudinal magnetic field are obtained for the present system. Many multiple hysteresis loop behaviors have also been found, depending on the combinations of both the upper and bottom layer magnetizations in the longitudinal magnetic field. Through a comparison, our results obtained are according well with other theoretical researches and experimental results.

Smart design of advanced substrates for surface-enhanced Raman scattering (SERS) activity is challenging but vital. Herein, we synthesized a new kind of AgNPs/MnO