Robust Digital Predistortion for LTE/5G Power Amplifiers Utilizing Negative Feedback Iteration

A robust digital predistortion(DPD)technique utilizing negative feedback iteration is introduced for linearizing power amplifiers(PAs)in long term evolution(LTE)/5G systems.Different from the conventional direct learning and indirect learning structure,the proposed DPD suggests a two-step method to identify the predistortion.Firstly,a negative feedback based iteration is used to estimate the optimal DPD signal.Then the corresponding DPD parameters are extracted by forward modeling with the input signal and optimal DPD signal.The iteration can be applied to both single-band and dual-band PAs,which will achieve superior linear performance than the conventional direct learning DPD while having a relatively low computational complexity.The measurement is carried out on a broadband Doherty PA(DPA)with a 200 MHz bandwidth LTE signal at 2.1 GHz,and on a 5G DPA with two 10 MHz LTE signals at 3.4/3.6 GHz for validation in dual-band scenarios.

Alterative wire-feed system based on arc voltage negative feedback

Waveform control method was commonly adopted to reduce the spatter of CO2 arc welding and improve the weld formation. It certainly would reduce the self-regulation ability of arc due to the adoption of segmented constant current control which especially led to arc＂ blowout with the abrupt change oat＂ arc＂ length or downward welding. Therefore alterative wire-feed system based on arc voltage negative feedback was put forward to improve the .stability of arc＂ length in this paper. Double closed-loop and double fuzzy P1 regulation were adopted in this system. Fuzzy control of induced voltage was adopted in the inner-loop which improved the stability and fast response of wire-feed system. Fuzz）＂ control of arc＂ voltage negative feedback was used in the outer-loop whose output .served as the input of negative feedback regulation of inner-loop induced voltage. This method could remain arc＂ length and weld penetration unchan, ged on the basils of reducing spatter and improving formation and it was proved by downward welding tests.

Solid-state wideband GaN HEMT power amplifier with a novel negative feedback structure

The design and fabrication of an ultra-broadband power amplifier based on a GaN HEMT, which operates in the frequency range from 3 to 8 GHz, is presented in this paper. A TGF2023-02 GaN HEMT chip from Tri Quint is adopted and modeled. A novel negative feedback structure is applied in the circuit. The measured results show that the amplifier module has a wide range frequency response that is almost consistent with those of simulation at frequencies from 3 to 6.5 GHz. The measured power gain is greater than 7 dB between 3 and 6.5 GHz.The saturated output power is 38.5 dBm under DC bias of Vds =D28 V, Vgs D =-3：5 V at the frequency of 5.5 GHz.

Temporal Structures of the North Atlantic Oscillation and Its Impact on the Regional Climate Variability

In this study, the temporal structure of the variation of North Atlantic Oscillation （NAO） and its impact on regional climate variability are analyzed using various datasets. The results show that blocking formations in the Atlantic region are sensitive to the phase of the NAO. Sixty-seven percent more winter blocking days are observed during the negative phase compared to the positive phase of the NAO. The average length of blocking during the negative phase is about 11 days, which is nearly twice as long as the 6-day length observed during the positive phase of the NAO. The NAO-related differences in blocking frequency and persistence are associated with changes in the distribution of the surface air temperature anomaly, which, to a large extent, is determined by the phase of the NAO. The distribution of regional cloud amount is also sensitive to the phase of the NAO. For the negative phase, the cloud amounts are significant, positive anomalies in the convective zone in the Tropics and much less cloudiness in the mid latitudes. But for the positive phase of the NAO, the cloud amount is much higher in the mid-latitude storm track region. In the whole Atlantic region, the cloud amount shows a decrease with the increase of surface air temperature. These results suggest that there may be a negative feedback between the cloud amount and the surface air t.emperature in the Atlantic region.

A Study on the Molecular Switch of Gene Expression of the Mouse Heart Nuclear DNA Fragments

It is observed by in situ stain that LDH (1 5) ...nNAD + can probably enter the nucleopore and can be bound bound specifically with the genes that encode them. During the in vitro expression, the dilution of heart nuclear DNA fragments could enhance the expression activity of LDH/DNA and the amount of expressed LDH (1 5) is in proportion to the amount of dissociable LDH (1 5) on the LDH/DNA. With the integration of 14C Leu to the proteins, it is also observed that the addition of LDH (1 5) ...nNAD + can suppress the in vitro expression activity of LDH/DNA. AFM observation shows that the regulation sequence at the both ends of active genes may be bound with such active factors as proteins encoded by the genes which probably is the main molecular switch of gene expression and regulation we have been always searching for. Our work shows the prospective application of the combination of AFM and isotope labeling in the research of biological reaction.

Paradigms and Paradox in the Ethylene Signaling Pathway and Interaction Network

Phytohormone ethylene plays pivotal roles in plant response to developmental and environmental signals. During the past few years, the emerging evidence has led us to a new understanding of the signaling mechanisms and regulatory networks of the ethylene action. In this review, we focus on the major advances made in the past three years, particularly the findings leading to new paradigms and the observations under debate. With the recent demonstration of the regulation of the protein stability of numerous key signaling components including EIN3, ELL1, EIN2, ETR2, EBFI/EBF2, and ETPI/ETP2, we highlight proteasome-dependent protein degradation as an essential regulatory mechanism that is widely adopted in the ethylene signaling pathway. We also discuss the implication of the negative feedback mechanism in the ethylene signaling pathway in light of ethylene-induced ETR2 and EBF2 gene expression. Meanwhile, we summarize the controversy on the involvement of MKK9-MPK3/6 cascade in the ethylene signaling versus biosynthesis pathway, and discuss the possible role of this MAPK module in the ethylene action. Finally, we describe the complex interactions between ethylene and other signaling pathways including auxin, light, and plant innate immunity, and propose that EIN3/ EIL1 act as a convergence point in the ethylene-initiated signaling network.

Rapamycin in fibrotic diseases： beneficial or detrimental agent？

apamvcin was first isolated from a strain of Sreptomyces hygroscopicus in the early 1970s froma soil sample taken on Easter Island. Because the antiproliferative effects of rapamycin on yeast cell, as well as B and T lymphocytes, it was first identified as an antimicrobial agent with potent immunosuppressive activity and has been used in antirejection therapy.

Mutual regulation between Hippo signaling and actin cytoskeleton

Hippo signaling plays a crucial role in growth control and tumor suppression by regulating cell proliferation,apoptosis,and differentiation.How Hippo signaling is regulated has been under extensive investigation.Over the past three years,an increasing amount of data have supported a model of actin cytoskeleton blocking Hippo signaling activity to allow nuclear accumulation of a downstream effector,Yki/Yap/Taz.On the other hand,Hippo signaling negatively regulates actin cytoskeleton organization.This review p rovides insight on the mutual regulatory mechanisms between Hippo signaling and actin cytoskeleton for a tight control of cell behaviors during animal development,and points out outstanding questions for further investigations.

A 2.5-V 56-mW baseband chain in a multistandard TV tuner for mobile and multimedia applications

This paper presents post-layout simulated results of an analog baseband chain for mobile and multimedia applications in a 0.13-μm SiGe BiCMOS process.A programmable 7th-order Chebyshev low pass filter with a calibration circuit is used in the analog baseband chain,and the programmable bandwidth is 1.8/2.5/3/3.5/4 MHz with an attenuation of 26/62 dB at offsets of 1.25/4 MHz.The baseband programmable gain amplifier can achieve a linear 40-dB gain range with 0.5-dB steps.Design trade-offs are carefully considered in designing the baseband circuit,and an automatic calibration circuit is used to achieve the bandwidth accuracy of 2%.A DC offset cancellation loop is also introduced to remove the offset from the layout and self-mixing,and the remaining offset voltage is only 1.87 mV.Implemented in a 0.13-μm SiGe technology with a 0.6-mm2 die size,this baseband achieves IIP3 of 23.16 dBm and dissipates 22.4 mA under a 2.5-V supply.

Mixed-integrator-based bi-quad cell for designing a continuous time filter

A new mixed-integrator-based bi-quad cell is proposed. An alternative synthesis mechanism of complex poles is proposed compared with source-follower-based bi-quad cells which is designed applying the positive feedback technique. Using the negative feedback technique to combine different integrators, the proposed bi-quad cell synthesizes complex poles for designing a continuous time filter. It exhibits various advantages including compact topology, high gain, no parasitic pole, no CMFB circuit, and high capability. The fourth-order Butterworth lowpass filter using the proposed cells has been fabricated in 0.18μm CMOS technology. The active area occupied by the filter with test buffer is only 200 × 170 μm^2. The proposed filter consumes a low power of 201 μW and achieves a 68.5 dB dynamic range.