This article presents a 23-28-GHz digital-controlled phase-invariant and ultralow gain error variable gain amplifier (VGA) for 5G applications. The mechanisms of gain control and phase variation in ...CMOS VGA based on single-level transistor structure are analyzed in detail. According to the analysis, an active cross-coupling neutralization (ACCN) technique is proposed. The ACCN technique not only compensates for phase variation, but also makes phase compensation insensitive to the process, supply voltage, and temperature (PVT) variations. For achieving ultralow gain error, an asymmetric capacitive gain resolution improvement (ACGRI) technique is adopted, which realizes a fine gain step with low control circuit complexity. Further to reduce gain error, greatly improving the accuracy and robustness against PVT of gain control is necessary. With regard to this, a current-type digital-to-analog converter (DAC) is also integrated onto the chip. The proposed VGA is demonstrated in 65-nm CMOS technology with a core chip area of 0.14 mm 2 . Under 5-b digital gain control conditions, the presented VGA achieves a measured linear gain tunability range of 6.2 dB with a 0.2-dB fine tuning step. The measured root mean square (rms) phase error is less than 0.92° across 24-28 GHz with a minimum value of 0.63° at 27.8 GHz. The rms gain error is less than 0.13 dB, with a minimum value of only 0.03 dB at 25 GHz. At the maximum gain state, the proposed CS VGA exhibits a peak gain of 29.4 dB with 3-dB bandwidth of 23.5-27.5 GHz and the minimum noise figure is 4.8 dB at 26 GHz. Besides, the measured OP 1dB and OP 3dB are 6.3 and 9.6 dBm, respectively. The influence of VT variations on the phase compensation and gain tuning is also measured, and the proposed VGA exhibits strong robustness.
In this paper, a new nonisolated high step-up dc-dc converter is proposed. Active-passive inductor cells (APICs) are used to extend the topology. The ability to achieve high gains is the main merit ...of the proposed topology. The proposed converter operates based on parallel charging and series discharging of the inductors. The converter also achieves high step-up voltage gain with appropriate duty cycle and low voltage and current stress on the power switches and diodes. The proposed converter is analyzed in operation modes. The main parameters of the converter such as voltage gain, voltage stress of semiconductor devices are calculated to compare with other structures. Considering the output voltage ripple and filter size, the proposed converter is designed. Moreover, the losses and efficiency of the converter are calculated. The performance of the proposed converter is validated by experimental results.
In order to gain deeper insight about structureaproperty relations properties, two novel donoraacceptoradonor type monomers were studied. ...4a2-Tert-butyl-4,7-di(thiophen-2-yl)spirobenzodimidazole-2,1a2 -cyclohexane and 4,7-di(2,2a2-bithiophen-5-yl)-4a2-tert-butylspirobenzodimidazo le-2,1a2-cyclohexane were synthesized and electrochemically polymerized. Electrochemical and optical properties of the polymers were investigated via cyclic voltammetry and UVaVisaNIR spectroscopy techniques. It was found that changing donor unit from thiophene to bithiophene results in a drastic change in optical and electrochemical properties, especially in optical contrast.
In this paper, we investigate and reveal the ergodic sum-rate gain (ESG) of non-orthogonal multiple access (NOMA) over orthogonal multiple access (OMA) in uplink cellular communication systems. A ...base station equipped with a single-antenna, with multiple antennas, and with massive antenna arrays is considered both in single-cell and multi-cell deployments. In particular, in single-antenna systems, we identify two types of gains brought about by NOMA: 1) a large-scale near-far gain arising from the distance discrepancy between the base station and users; 2) a small-scale fading gain originating from the multipath channel fading. Furthermore, we reveal that the large-scale near-far gain increases with the normalized cell size, while the small-scale fading gain is a constant, given by γ = 0.57721 nat/s/Hz, in Rayleigh fading channels. When extending single-antenna NOMA to M-antenna NOMA, we prove that both the large-scale near-far gain and small-scale fading gain achieved by single-antenna NOMA can be increased by a factor of M for a large number of users. Moreover, given a massive antenna array at the base station and considering a fixed ratio between the number of antennas, M, and the number of users, K, the ESG of NOMA over OMA increases linearly with both M and K. We then further extend the analysis to a multi-cell scenario. Compared to the single-cell case, the ESG in multi-cell systems degrades as NOMA faces more severe inter-cell interference due to the non-orthogonal transmissions. Besides, we unveil that a large cell size is always beneficial to the ergodic sum-rate performance of NOMA in both single-cell and multi-cell systems. Numerical results verify the accuracy of the analytical results derived and confirm the insights revealed about the ESG of NOMA over OMA in different scenarios.
This paper presents a novel approach for time-scale modification (TSM) of speech based on temporal continuous nonnegative matrix factorisation. First, the magnitude spectrum of the speech is ...factorised to the nonnegative space and the time-varying gains. Then, the TSM problem is transformed into an interpolation problem of the time-varying gains, which leads to a better performance over the traditional methods based on waveform overlap-add. The superiority of the proposed approach is confirmed by the comparative tests against the traditional methods, including OLA, SOLA, WSOLA, and PSOLA.
In this paper, a novel buck-boost dc-dc converter with continuous input current is proposed. The voltage gain of the presented converter is higher than conventional converters, such as buck-boost, ...single-ended primary-inductance converter, Cuk, and Zeta converters. This converter works only by one switch and voltage stress across the switch is low. Input current of the proposed converter is continuous so a large filter at the input is not needed. Furthermore, continuous input current has made this converter suitable for renewable energy and fuel cell applications. In this converter, noninverting output voltage is obtained and high gain of voltage is achieved as well. So it can operate at wide output voltage range only by changing the duty cycle of the power switch pulse. The presented converter can easily controlled in continuous conduction mode operation, because of using only one power switch. In the following, the principle of operation and the mathematical analyses of the proposed converter are explained, finally, validity of the proposed dc-dc converter is verified by the experimental results.
For the fixed-gain inertial control of wind power plants (WPPs), a large gain setting provides a large contribution to supporting system frequency control, but it may cause over-deceleration for a ...wind turbine generator that has a small amount of kinetic energy (KE). Further, if the wind speed decreases during inertial control, even a small gain may cause over-deceleration. This paper proposes a stable inertial control scheme using adaptive gains for a doubly fed induction generator (DFIG)-based WPP. The scheme aims to improve the frequency nadir (FN) while ensuring stable operation of all DFIGs, particularly when the wind speed decreases during inertial control. In this scheme, adaptive gains are set to be proportional to the KE stored in DFIGs, which is spatially and temporally dependent. To improve the FN, upon detecting an event, large gains are set to be proportional to the KE of DFIGs; to ensure stable operation, the gains decrease with the declining KE. The simulation results demonstrate that the scheme improves the FN while ensuring stable operation of all DFIGs in various wind and system conditions. Further, it prevents over-deceleration even when the wind speed decreases during inertial control.
DC microgrids are popular due to the integration of renewable energy sources such as solar photovoltaics and fuel cells. Owing to the low output voltage of these dc power generators, high efficient ...high gain dc-dc converters are in need to connect the dc microgrid. In this paper, a nonisolated high gain dc-dc converter is proposed without using the voltage multiplier cell and/or hybrid switched-capacitor technique. The proposed topology utilizes two nonisolated inductors that are connected in series/parallel during discharging/charging mode. The operation of switches with two different duty ratios is the main advantage of the converter to achieve high voltage gain without using extreme duty ratio. The steady-state analysis of the proposed converter using two different duty ratios is discussed in detail. In addition, a 100 W, 20/200 V prototype circuit of the high gain dc-dc converter is developed, and the performance is validated using experimental results.
A novel theory of stability for two-port networks is developed. Using this theory, a new method of designing amplifiers with a high-power gain working close to the maximum frequency of oscillation (f ...max ) is proposed. Contrary to the existing amplifier design methodologies, in this method, the transistor capability of power amplification is fully utilized. This becomes more important at frequencies close to the f max where having a high-power gain is challenging due to the degraded activity of the employed device. The proposed method considers the modeling errors and process-voltage-temperature variations of the employed components in the design stage to ensure that the fabricated amplifier will be stable with a decent power gain even if the worst case variations and modeling errors happen. To show the feasibility of the proposed approach, a three-stage amplifier at 173 GHz, using bipolar junction transistors from a 130 nm SiGe process, is designed. The fabricated amplifier has a maximum measured power gain of 18.5 dB at 173 GHz. A similar three-stage amplifier using the same transistors with the same bias would give a maximum gain of 6.8 dB in simulation, assuming perfect lossless conjugate matching at input, output, and between stages. So it is clear that the fabricated amplifier achieves a significant improvement over the power gain.
This letter presents a 39-GHz phase-inverting variable gain power amplifier (VGPA) for 5G communication. Adopting a Gilbert structure-based variable gain amplifier (VGA) stage, the VGPA realized the ...dB-linear gain control characteristic as well as 180° phase inversion. At 0°/180° phase states, the 39-GHz VGPA achieves the maximum gain of 38.7/38.9 dB with gain tuning range of 5.6/5.2 dB, respectively. Over 38-43 GHz, the phase inversion error is limited within 5.9°, and the rms phase error is less than 3.6°/2.2°. Meanwhile, with the metal interleaving coplanar transformer matching network, this VGPA achieves 17.7/17.6-dBm Psat and 13.2/13.36-dBm OP1 dB, with the power added efficiency (PAE) of 35%/34.5% and 13.6%/14.4% at the saturation and 1-dB compression points, respectively. Over the gain control states, the OP1 dB fluctuation is less than 0.3 dB. Implemented in a 65-nm CMOS process, the proposed VGPA consumes 150 mW with a chip area of 0.3 mm2.
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