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Abstract Background The burden of malaria persists in sub-Saharan Africa and the emergence of artemisinin resistance has introduced complexity to control efforts. Monitoring the efficacy of artemisinin-based treatment for malaria is crucial to address this challenge. This study assessed treatment efficacy of artemether-lumefantrine (AL) and genetic diversity of Plasmodium falciparum isolates in a Nigerian population. Methods Participants presenting with clinical symptoms of uncomplicated malaria at a health centre in Lagos, Nigeria, were screened for P. falciparum. Enrolled participants were treated with AL and monitored through scheduled check-up visits, clinical and laboratory examinations for 28 days. Parasite clearance and genetic diversity were assessed through polymerase chain reaction (PCR) analysis of merozoite surface proteins (msp1 and msp2). The prevalence of drug resistance mutations was assessed by P. falciparum multidrug resistance gene 1 (mdr1) genotyping followed by P. falciparum ubiquitin-specific protease 1 (ubp1) gene sequencing. Results The PCR-uncorrected treatment outcome revealed 94.4% adequate clinical and parasitological response (ACPR) and 5.6% late parasitological failure (LPF) rates. After PCR correction, no suspected LPF case was detected and ACPR 67/67 (100%) was achieved in all the individuals. Moreover, a high prevalence of wild-type alleles for mdr1 N86Y (93.7%), and mdr1 D1246Y (87.5%) was observed. Genetic diversity analysis revealed predominant K1 allelic family for msp1 (90.2%) and FC27 for msp2 (64.4%). Estimated multiplicity of infection (MOI) was 1.7, with the highest MOI observed in the 5–15 years age group. ubp1 sequence analysis identified one nonsynonymous E1528D polymorphism at a low frequency (1.6%). Conclusion The study demonstrated sustained efficacy of AL for treating uncomplicated P. falciparum malaria. Genetic diversity analysis revealed various allelic types, suggesting occurrences of polyclonal infections. Nonetheless, the detection of a significant ubp1 polymorphism could have future implications for the epidemiology of anti-malarial drug resistance in the population.

Background: The burden of malaria persists in sub-Saharan Africa and the emergence of artemisinin resistance has introduced complexity to control efforts. Monitoring the efficacy of artemisinin-based treatment for malaria is crucial to address this challenge. This study assessed treatment efficacy of artemether-lumefantrine (AL) and genetic diversity of Plasmodium falciparum isolates in a Nigerian population. Methods: Participants presenting with clinical symptoms of uncomplicated malaria at a health centre in Lagos, Nigeria, were screened for P. falciparum. Enrolled participants were treated with AL and monitored through scheduled check-up visits, clinical and laboratory examinations for 28 days. Parasite clearance and genetic diversity were assessed through polymerase chain reaction (PCR) analysis of merozoite surface proteins (msp1 and msp2). The prevalence of drug resistance mutations was assessed by P. falciparum multidrug resistance gene 1 (mdr1) genotyping followed by P. falciparum ubiquitin-specific protease 1 (ubp1) gene sequencing. Results: The PCR-uncorrected treatment outcome revealed 94.4% adequate clinical and parasitological response (ACPR) and 5.6% late parasitological failure (LPF) rates. After PCR correction, no suspected LPF case was detected and ACPR 67/67 (100%) was achieved in all the individuals. Moreover, a high prevalence of wild-type alleles for mdr1 N86Y (93.7%), and mdr1 D1246Y (87.5%) was observed. Genetic diversity analysis revealed predominant K1 allelic family for msp1 (90.2%) and FC27 for msp2 (64.4%). Estimated multiplicity of infection (MOI) was 1.7, with the highest MOI observed in the 5–15 years age group. ubp1 sequence analysis identified one nonsynonymous E1528D polymorphism at a low frequency (1.6%). Conclusion: The study demonstrated sustained efficacy of AL for treating uncomplicated P. falciparum malaria. Genetic diversity analysis revealed various allelic types, suggesting occurrences of polyclonal infections. Nonetheless, the detection of a significant ubp1 polymorphism could have future implications for the epidemiology of anti-malarial drug resistance in the population. [ABSTRACT FROM AUTHOR]

In this paper, we propose a new robust joint digital pre-distorter (DPD) for the linearization of RF power amplifier and compensation of the direct conversion transmitter imbalances based on an Augmented Parallel Hammerstein model (APH). Due to the numerical instability in the conventional polynomial modeling, Complex Hermite polynomial basis functions are proposed and designed to be orthogonal for all real and complex values of the input signal and making the DPD robust to the input signal statistics and numerical instability. The simulation results show the promising performance of the proposed structure and approve its numerical stability in a fixed point calculation environment. It is shown that the ACPR of the transmitted signal is improved by more than 16 dB for the WCDMA and LTE-16 QAM excitation signals. The conditional number of the observation matrix is less than 30 dB, i.e. significantly higher than the performance of the reference models. Various computations have been introduced to analyze and evaluate the proposed pre-distortion structure with LTE-16QAM exciting signal. [ABSTRACT FROM AUTHOR]

Radio over fiber (RoF) is a promising solution for the next-generation wireless networks including fifth-generation Cloud/Centralized Radio Access Network (C-RAN). There exists a possibility to use Sigma Delta Modulated RoF (S-DRoF) that combines the advantages of analog RoF and digital RoF by means of sigma delta modulation (SDM) at the transmitter side subsequently replacing the employment of expensive and high-speed digital-to-analog converters. In this paper, we demonstrate the usage of second-order SDM for LTE 20 MHz signal having 64 QAM modulation on a central carrier frequency of 1.14 GHz for the implementation of S-DRoF for 20 km of standard single mode fiber with baud rate from 25 to 100 Mbaud. Furthermore, a comprehensive analysis of the design of SDM is explained followed by the experimental setup. The performance is reported in terms of error vector magnitude, constellations and adjacent channel power ratio. The results show that the proposed architecture performance is in with accordance to the limitations set by the 3GPP (Third Generation Partnership Project) standards and is a reasonable choice either for upgrading installed systems as well as for the new deployments. [ABSTRACT FROM AUTHOR]

A holistic and effective experimental method of optimum static gate bias identification is presented here for a modern wireless Radio Frequency (RF) power amplifier operating in 1900 MHz band. The amplifier is targeted for low complexity, high efficiency and low power Base Station (BS) having RF conducted power of less than 1 watt at its output load. Through the measured results, it is shown that out of various other static gate bias points obtained, the optimum gate bias condition is achieved at 2.4 volts. At this bias point setting, the PA delivers a modulated output power of +24 dBm in a standalone mode and with external RF linearization circuits added, the channel power enhanced upto +26 dBm and the Adjacent Channel Power Ratio (ACPR) is improved by 5.3 dB. At linear back-off power level, the achieved efficiency is 13.2%. [ABSTRACT FROM AUTHOR]

This paper introduces the measurement/modeling of a nonlinear RF power amplifier (PA) model extraction of spectral overlaps and peak-to-average power ratio (PAPR). The modeling consists of a weighted cubic-spline basis approach that preserves a relationship by its generic asymptotic properties under adequate PAPR regime to estimate signaling conditions. To jointly provide a data-driven model a field-programmable gate array (FPGA) testbed is proposed, in which a precomputed approach with deterministic signals is used to perform: (i) parameter estimation; (ii) adequate PAPR levels; (iii) reinforcement of sparsity data with extrapolation fitting; and (iv) FPGA implementation. Moreover, a technique for parameter identification is introduced to provide insights of a digital predistortion (DPD) PA model extraction with cubic-spline to efficiently improve the linearization performance. A theoretical analysis that states on the benefits from coefficients precomputation to preserve multiple-input multiple-output (MIMO) relationship with antenna selection technique estimation, is also proposed. Also, a Cholesky FPGA algorithm implementation to matrix inversion is validated, which aims to show the good numerical and computational complexity for up to $64\times 64$ MIMO arrays. Experimental results prove a good accuracy and close agreement between the modeling and estimation yielding a reliable model with a little overfitting.

This paper presents a new high-efficiency two-way Doherty Power Amplifier (DPA) with a modified output matching structure for Wideband Code Division Multiple Access (W-CDMA) low-to-medium power base station applications. A blended design is proposed using the symmetrical topology of equal rated power amplifying devices with unequal output impedances for the carrier and peaking amplifier to achieve enhanced efficiency and desired linearity in 1900 MHz band. The proposed output circuit modifications encompass the usage of parasitic capacitor compensation technique for the carrier amplifier, optimum offset line along with the Doherty combiner to achieve high efficiency over 6 to 10 dB extended range of back-off operation. The measured results of the DPA demonstrate a Power Added Efficiency (PAE) of more than 49.9% at +34 dBm W-CDMA signal power, which is between 8 and 8.5 dB back-off from the peak power level of 42.2 dBm. The DPA has a large signal power gain of 13 dB at 1960 MHz. Further, the PAE is 39.5% and linearised Adjacent Channel Power Ratio (ACPR) is −46.2 dBc, both at 10 dB back-off from peak power. In these back-off power levels, this implementation provides significant efficiency improvement using symmetrical devices and with excellent linearity. [ABSTRACT FROM AUTHOR]

We characterize the nonlinearities of our previously designed 10 W class-J power amplifier with a carrier at 1.5 GHz. We employ numerical simulations and real time adjacent channel power ratio (ACPR) measurements on the fabricated prototype. The measurements are performed for a wideband code division multiple access (WCDMA) signal with 10.5 dB peak-to-average power ratio (PAPR) and 3.84 MHz bandwidth.

In this work, a frequency reconfigurable broadband radio frequency‐predistorter (BB RF‐PD) is proposed that can effectively suppress the power amplifier (PA) intermodulation distortion from 200 MHz to 2.5 GHz. It is an attractive lineariser solution for radio repeaters in long distance communication, where baseband information is not readily available. For broadband signals, existing linearisation techniques become intractable due to high cost and power consumption. The proposed BB RF‐PD eliminates the use of data converters, field programmable gate arrays, but still provides the well‐intentioned linearisation using the passive components. Three application scenarios have been investigated – (i) and (ii) intra‐band: 160 MHz long‐term evolution (LTE) signal and 100 MHz two‐tone signal, and (iii) inter‐/multi‐band: two‐component carrier LTE signal with frequency spacing of 1 GHz. For verification, the proposed BB RF‐PD is implemented with a 10 W HMC8500 PA and tested using 160 MHz signal at 1.8 GHz. It delivers an adjacent channel power ratio (ACPR) of −45.65 dBc with an improvement of 16.87 dB, while for inter‐band scenario a new technique has been devised for multiband communication, which is known as BB multipath RF‐predistorter. It delivers an ACPR of −50 and −47 dBc for lower and upper CC, respectively. [ABSTRACT FROM AUTHOR]

In the design of the single board of mobile communication, isolator is often used in between the amplifier stage and the drive stage to enhance the interaction between circuits and to improve the adjacent channel power ratio (ACPR) of power amplifier channel and other wireless performance indexes. In this paper, the one way analysis of variance (ANOVA) was used to study whether there is indicator difference in single board when using different isolatorfirstly. Then, the regression analysis method was employed to verify the correlation between y (ACPR of the single board of radio frequency power amplifier) and x (parameters S11 or S12 of isolator). Finally, it concluded that the ACPR values may be affected by different types of isolators, and there is no significant univariate linear fitting relationship between the parameters S11/S12 of isolators and the ACPR of single boards. [ABSTRACT FROM AUTHOR]

This paper proposes a new measurement method for the effective measurement of the 99% occupied bandwidth (OBW) at monitoring stations. Although the OBW measurement of radio signal is recommended by the International Telecommunication Union Radio (ITU-R) with several methods, there still does not exist a clear measurement recommendation or standard for terrestrial DTV signal on-air environment. Modified adjacent channel power ratio (MACPR), which can be applied to 8-VSB (Vestigial Side Band) DTV (Digital Television) signal, is herein defined to verify the results of measurements obtained using the proposed measurement method. MACPR is a proper measuring parameter for determining the measuring area of a monitoring station. From measurement results obtained in real field environment, it has been found that the OBW of 8-VSB DTV signal can be effectively measured in areas where the MACPR value is over 35 dB and when the measurements are repeated more than 600 times in the same reception site. It also has been verified that measured results are within an error range of +/-0.1% compared to results directly obtained at a transmission station. It is expected that the proposed method is able to be employed in order to determine the proper location of monitoring station and provide a reliable OBW measurement procedure for 8-VSB DTV signal on-air environment. [ABSTRACT FROM AUTHOR]

This work presents the design and implementation of a stand-alone linear power amplifier at 2.4 GHz with high output power. A GaN HEMT transistor is selected for the design and implementation of the power amplifier. The device exhibits a gain of 11.7 dB and a drain efficiency of 39% for an output power of 36.7 dBm at 2.4 GHz for an input power of 25dBm. The carrier to intermodulation ratio is better than 25 dB for a two tone input signal of 25 dBm of total power and a spacing of 5 MHz. The fabricated device is also tested with LTE input signals of different bandwidths (5MHz to 20MHz).

This paper introduces a direct-conversion CMOS RF transmitter for the IEEE 802.15.4 standard with a low-power high-gain up-conversion mixer designed in 0.18 μm process. The designed RF DCT(Direct Conversion Transmitter) is composed of differential DAC(Digital to Analog Converter), passive low-pass filter, quadrature active mixer and drive amplifier. The most important characteristic in designing RF DCT is to satisfy the 2.4 GHz Zigbee standard in low power. The quadrature active mixer inside the proposed RF DCT provides enough high gain as well as sufficient linearity using a gain boosting technique. The measurement results for the proposed transmitter show very low power consumption of 7.8 mA, output power more than 0 dBm and ACPR (Adjacent Channel Power Ratio) of —30 dBc. [ABSTRACT FROM AUTHOR]

In this paper, we are comparative study of performance analysis of polynomial based predistorter technique with three different architectures viz. memory polynomial, envelope memory polynomial and hybrid envelope memory polynomial models for high order of nonlinearity (K = 7) and large memory length (Q = 3). The nonlinear distortion is a critical issue for radio over fiber link. The predistorter is one of the most important approaches to overcome the nonlinear distortion. In this paper the performance analysis of the two most prevailing predistorters (memory polynomial and envelope memory polynomial) have been compared with the performance of the model (hybrid envelop memory polynomial) developed by the author. The performance of different predistorter model are analyzed for input laser power ranging from −4dBm to 4dBm, input frequency for ∼0.55 GHz to ∼3.00 GHz and for different type of input signal like m-QAM, orthogonal frequency division multiplex, WiMax and LTE ( long term evolution ) . The performance metrics are adjacent power ratio, error vector magnitude and normalized mean square error. The model have been tested for fiber length up to ∼50 km. Whole of the simulation work to compare the performance analysis has been carried out on OptiSystem v13.0 and MATLAB R20013a. [ABSTRACT FROM AUTHOR]

Introduction The aim of this study was to assess the efficacy of artesunate-amodiaquine (AS + AQ) which is the first-line treatment for uncomplicated falciparum malaria in Eritrea. Materials and methods The study was conducted from December 2014 to March 2015 in Ghindae Zonal Referral Hospital in Northern Red Sea Zone. Out of 481 patients screened, 103 were enrolled in the study. The therapeutic efficacy test was done as per the WHO protocol for a period of 28 days of follow-up. Results The PCR-uncorrected treatment outcome was classified as adequate clinical and parasitological response (ACPR) in 95 patients, which meant the cure rate was 96.0 (95% CI: 89.7%–98.5%) after survival analysis. Conclusions Therapeutic efficacy of AS + AQ still meets the WHO efficacy criteria for its continued use in the study area as the first-line drug against uncomplicated falciparum malaria. However, further studies are needed using correction with molecular markers to monitor therapeutic efficacy of antimalarial drugs in this area. [ABSTRACT FROM AUTHOR]

At present, most of digital predistortion (DPD) systems theory verification and algorithm simulation are based on i-deal conditions. Simulation results under ideal conditions are difficult to reproduce in the real system due to the many error components exist in the system. This paper analyzed Several common errors in the DPD system and built the baseband error model according to the expression of error in digital domain. Through a mass of simulation data, the error sensitivity in DPD system was analyzed and concluded. Finally, it proposed the design specifications of main system components and reduced the workload of debug by the simulation. [ABSTRACT FROM AUTHOR]

This article presents the design and evaluation of a linear 3.3 V SiGe power amplifier for 3 G and 4 G femtocells with 18 dBm modulated output power at 2140 MHz. Different biasing schemes to achieve high linearity with low standby current were studied. The adjacent channel power ratio linearity performance with wide-band code division multiple access (3 G) and long term evolution (4 G) downlink signals were compared and differences analysed and explained. [ABSTRACT FROM PUBLISHER]

A real-time adaptive digital predistortion system (RT-ADPD) for power amplifier linearization is described in this paper, featuring fast closed-loop adaptation to provide robust linearity across quickly shifting power amplifier (PA) operating conditions. The RT-ADPD system requirements, architecture, and its design methodology are analyzed in detail, with particular emphasis on the optimization of the feedback loop convergence speed and stability. A novel, compact algorithm to achieve rapid adaptation of the predistortion lookup tables, without any prior knowledge of the PA distortion characteristics, is introduced. A prototype of the RT-ADPD system is implemented using a field-programmable gate array (FPGA), and it is experimentally exploited to linearize a handset WCDMA PA module. Due to the linearization action, the PA maximum modulated output power is increased by 1.9 dB, to 30.9 dBm, and its power-added efficiency by 9%, to 48.5%, still maintaining a -40-dB ACPR at a 5-MHz offset. In addition, a true closed-loop adaptation ensures excellent PA linearity under load mismatch and other environmental variations. Indeed, ACPR is improved by up to 15 dB, below -47 dB, under 2:1 VSWR at 28 dBm. Remarkably fast adaptation speed is also demonstrated, as adequate signal fidelity is achieved within a \sim\!\! \50-\mu\s time frame. [ABSTRACT FROM AUTHOR]

A millimeter-wave Power Amplifier (PA) based on a 65nm CMOS technology from STMicroelectronics has been designed. The targeted feature is the unlicensed band around 60 GHz suitable for wireless personal area network application (WPAN). To optimize the linearity, the PA is designed under class A biasing to have an output compression point (OCP) close to its saturated Power ( P). S-parameters and large signal measurement results are demonstrated and compared with electromagnetic simulations. The PA offers a P of 8.3 dBm, an OCP of 6 dBm and a gain of 6.7 dB. The die area is 0.29 mm with pads. Considering those results, one-tone simulations are not sufficient to characterize the linearity performances of the PA in its real conditions of use. Consequently, two-tone simulations are firstly performed. After, linearity figures of merit (FoM) are discussed applying an orthogonal frequency-division multiplexing (OFDM) modulated signal. The PA offers an adjacent channel power ratio (ACPR) of 15 dB and an error vector magnitude (EVM) of 20% at PA compression operating mode. [ABSTRACT FROM AUTHOR]

Abstract: Simulation results of a 863–870MHz frequency-hopped spread-spectrum (FHSS) transceiver with binary frequency shift keying (BFSK) modulation at 20kb/s for wireless sensor applications is presented. The transmit/receive RF front end contains a BFSK modulator, an upconversion mixer, a power amplifier (PA), and an 863–870MHz band pass filter (BPF) at the transmitter side and a low-noise amplifier with down conversion mixer to zero-IF, a low-pass channel-select filter, a limiter and a BFSK demodulator at the receiver side. The various block parameters of the transmit/receive RF front end like noise figure (NF), gain, 1dB compression point (P-1dB), and IIP3 are simulated and optimized to meet low power and low cost transceiver specifications. The transmitter simulations show an output ACPR (adjacent channel power ratio) of −22dBc, 3.3dBm P-1dB of PA, and transmitted power of 0dBm. The receiver simulations show 51.1dB conversion gain, −7dBm IIP3, −15dB return loss (S11), and 10dB NF. Low power arctangent-differentiated BFSK demodulator has been chosen and the BER performance has been co simulated with the analog receiver. The complete receiver achieves a BER of 10−3 at 10.5dB of EbtoNo. The transceiver simulations show an RMS frequency error of 1.45kHz. [ABSTRACT FROM AUTHOR]

When a CDMA signal is passed through an RF transmitter, nonlinear elements cause spectral regrowth which result in reduction of spectral efficiency. CDMA signal has a pseudo noise nature; hence its mathematical treatment is too complex to analysis. In this paper, first it will be shown how to simplify the complex mathematics of CDMA signal. Then, a deterministic signal replaces the CDMA signal and the system response to both of them is calculated. In this paper, for the first time, ACPR is explicitly calculated for both the CDMA and deterministic signals. ACPR is calculated in terms of the nonlinear system coefficients and input power, and therefore, can be used in design objectives. In addition, it will be shown that if input power of the deterministic signal is multiplied by $\sqrt{20}$ (i.e., correction factor), ACPR error of these kinds of signals in -55 dBc is less than 2.2% for the system nonlinearity orders up to 13. This correction factor is obtained by both theoretical and simulation methods. [ABSTRACT FROM AUTHOR]

This paper demonstrates a two-stage 1.95-GHz WCDMA handset RFIC power amplifier (PA) implemented in a 0.25-μm SiGe BiCMOS process. With an integrated dual dynamic bias control of the collector current and collector voltage, the average power efficiency of the two-stage PA is improved from 1.9% to 5.0%. The measured power gain is 18.5 dB. The gain variation with dynamic biasing is less than 1.8 dB. An off-chip memoryless digital predistortion linearizer is also adopted, satisfying the 3GPP wideband code division multiple access (WCDMA) linearity specification by a 10 dB improvement of adjacent channel power ratio (ACPR) at +26 dBm average channel output power. [ABSTRACT FROM AUTHOR]

A scalable rf large-signal model of quasi-enhancement-mode AlGaAs/InGaAs pHEMTs has been purposed to make a well prediction of the device non-linear characteristics. Besides the fundamental requirements of the well-matched dc, small signal characteristics and power performance provided by this model, a strict and accurate estimation of microwave non-linear power behavior especially under a digital modulation operation is also included. In this report, not only device microwave load-pull test has been described, the output spectra of the device under a digitally modulated scheme can be also predicted by this model, including the spectra regrowth and adjacent-channel power ratio. [Copyright &y& Elsevier]

A new third-order transconductance (gm3) cancellation technique is proposed and applied to a conventional radio frequency (RF) mixer for improving circuit linearity. The bulk-to- source voltage is applied to adjust the peak value position of gms. The cancellation of gm3 is utilized by a negative peak gm3 transistor combined in parallel with a positive peak gm3 transistor. For a single device, the measured adjacent channel power ratio (ACPR) and third-order intermodulation (IMD3) distortion are both improved over 15 dB. A Gilbert-cell mixer in commercial 0.18-mum CMOS process was designed using the proposed method to further evaluate the linearity. The compensated gm3 device is placed in the input RF gm-stage and then reducing the principle nonlinearity source of the mixer. From the experiment results, the ACPR and IMD3 of the mixer are improved about 10 and 15 dB, respectively. [ABSTRACT FROM PUBLISHER]

A highly efficient code division multiple access power amplifier of parallel amplification architecture exhibits power added efficiency of 17% and adjacent channel power ratio less than -51 dBc at an output power of 16 dBm. The output impedances of the low/high-power amplifier chains are very low because the collector impedances of the "OFF-state" power heterojunction bipolar transistors are low and the low impedances are transformed into even lower ones by low-pass output matching circuits. The low impedances are boosted up using a compact lumped λ/4 transmission line and the chains are operated independently without producing any significant performance degradation. [ABSTRACT FROM PUBLISHER]

A 2.4-GHz CMOS power amplifier (PA) with an output power 20 dBm using 0.25-μm 1P5M standard CMOS process is presented. The PA uses an integrated diode connected NMOS transistor as a diode linearizer. It is believed that this is the first reported use of the diode linearization technique in CMOS PA design. It shows effective improvement in linearity from gain compression and ACPR measured results. Measurements are performed by using an FR-4 PCB test fixture. The fabricated power amplifier exhibits an output power of 20 dBm and a power-added efficiency as high as 28%. The obtained PA performances demonstrate the standard CMOS process potential for medium power RF amplification at 2.4 GHz wireless communication band. [ABSTRACT FROM PUBLISHER]

This letter presents the initial results of a study on a diode-based power amplifier (PA) linearization technique. The optimization of a diode's parameters to match a MESFET PA is discussed. The relevance of AM-AM and AM-PM curves to linearity requirements and modulation format is also discussed. As much as a 6.7-dB improvement in ACPR is made in the upper channel using a series diode linearizer [ABSTRACT FROM PUBLISHER]