Digital predistortion is one of the most widely used techniques to linearize a power amplifier (PA) to
reduce the error vector magnitude (EVM) distortion and spectral regrowth. By far, the lookup table (LUT) predistorters are most frequently used scheme to mitigate the effects of non-linear power amplifier. In this paper, a new algorithm of joint-polynominal LUT predistorter which attains the best linearization performance is proposed. The algorithm employs the hermite interpolation LUT, which has a higher accuracy of interpolation. Simulation results show that the proposed method provides a better rejection of EVM distortion and an improvement of 30-40% of adjacent channel leakage ratio (ACLR) for the wideband code division multiple access at a minimal memory usage.
In this paper a study on the wideband double-pass Raman fibre amplifier with mirror as the pump reflector is reported. The pump lights at 1435 nm and 1455 nm were launched in a co-directional manner with respect to the input signal. The double-pass direction of the signal was achieved through a fibre loop mirror constructed using an optical circulator. It was shown that multiple signal amplification was achieved without any disturbance of stimulated Brillouin scattering.
A four-stage erbium-doped fibre amplifier with the gain bandwidth of 35 nm is demonstrated. The amplifier was designed to include a dispersion compensating module to compensate the accumulated dispersion by signals. The amplifier design permited some dynamic features such as the amplifier’s gain could be adjusted from 15 dB to 30 dB by varying the input signal power from –26 dBm to 8 dBm. The maximum output power of 23 dBm was obtained with a maximum allowable gain flatness of 1.5 dB.
We demonstrate an enhanced architecture of Brillouin-Erbium fiber laser utilizing the reverse-S-shaped fiber section as the coupling mechanism. The enhancement is made by locating a common section of Erbium-doped fiber next to the single-mode fiber to amplify the Brillouin pumps and the oscillating Stokes lines. The requirement of having two Erbium gain sections to enhance the multiple Brillouin Stokes lines generation is neglected by the proposed fiber laser structure. The mode competitions arise from the self-lasing cavity modes of the fiber laser are efficiently suppressed by the stronger pre-amplified Brillouin pump power before entering the single mode fiber section. The maximum output power of 20 mW is obtained from the proposed fiber laser with 10 laser lines that equally separated by 0.089 nm spacing.
We demonstrate an opto-optical gain-clamped L-band erbium-doped fiber amplifier by manipulating the C-band lasing wavelength as the control signal. The L-band gain-clamped value is achieved by tuning the control laser in the C-band wavelength range that propagates in the opposite direction to the L-band signal. Within the wavelength range of 1538 nm and 1560 nm, the L-band gain decreases linearly with the increment of the C-band lasing wavelength. The L-band gain dynamic range decreases with the increment of the cavity loss. By combining two different levels of cavity loss, the gain dynamic range of 10 dB from 11 dB to 21 dB is achieved with an average noise figure of less than 5.9 dB. The whole gain spectrum of the L-band can be used for multiple-channel amplification because the laser is created outside its signal band.
This paper presents the temperature characteristics of silicon nanowire transistors (SiNWTs) and examines the effect of temperature on transfer characteristics, threshold voltage, I(ON)/I(OFF) ratio, drain-induced barrier lowering (DIBL), and sub-threshold swing (SS). The (MuGFET) simulation tool was used to investigate the temperature characteristics of a transistor. The findings reveal the negative effect of higher working temperature on the use of SiNWTs in electronic circuits, such as digital circuits and amplifiers circuits, because of the lower I(ON)/I(OFF) ratio, higher DIBL, and higher SS at higher temperature. Moreover, the ON state is the optimum condition for using a transistor as a temperature nano-sensor.
We demonstrate a multi-wavelength light source using a semiconductor optical amplifier (SOA) in conjunction with an array waveguide grating (AWG). The experimental results showed more than 20 channels with a wavelength separation of 0.8 nm and an optical signal-to-noise ratio of more than 10 dB under room temperature. The channels operated at the wavelength region from 1530.4 nm to 1548.6 nm, which corresponded to AWG filtering wavelengths with SOA drive current of 350 mA. The proposed light source had the advantages of a simple and compact structure, multi-wavelength operation and the system could be upgraded to generate more wavelengths.
A 2.4 GHz variable-gain low noise amplifier (VGLNA) intended for use in a Wide-band Code Division
Multiple Access receiver was designed in 0.18 um CMOS process for low voltage and low power applications. Rivaling classical designs using voltage mode approach, this design used the current mode approach, utilizing the current mirror principle to obtain a controllable gain range from 8.26 dB to 16.95 dB with good input and output return losses. By varying the current through the widths of transistors and a bias resistor, the VGLNA was capable of exhibiting 8 dB gain tuning range without degrading the noise figure. Therefore, higher gain was possible at lower current and thus at lower power consumption. Total power consumption simulated was 4.63 mW from a 1 V supply and this gave a gain/power quotient of 3.66 dB/mW. Comparing this with available published data, it was observed that this work demonstrated a good gain tuning range and the lowest noise figure with such power consumption.
Pulse Shaping Amplifier (PSA) is an essential component in nuclear spectroscopy system. This
amplifier has two functions; to shape the output pulse and performs noise filtering. In this paper,
we describe the procedure for the design and development of a pulse shaping amplifier which can
be used in a nuclear spectroscopy system. This prototype was developed using high performance
electronics devices and assembled on a FR4 type printed circuit board. Performance of this
prototype was tested by comparing it with an equivalent commercial spectroscopy amplifier (Model
Silena 7611). The test results showed that the performance of this prototype was comparable
to the commercial spectroscopic amplifier.
The purpose of this research is to enhance the gain signal amplification by using dual
pump double pass configuration in comparative with single pump double pass that are
commonly used as conventional optical amplifier configuration in optical
communication system nowadays. Two input signals power have been implemented
which are -30 and 0 decibel (dB). The input signal defined as low and high input signals
power by using a pump power of 1480 nm. The amplification of EDFA in this study have
been taken place in conventional band (C) band and long wavelength band (L) band of
EDFA within the range of 1515 to 1615 nm. Therefore, to understand the performance
of the gain amplification, the OptiSystem software simulator version 13 has been used
for simulation and the values of fiber length and pump power has been varied for both
configurations. It has been found that the, dual pump double pass configuration has
shown better gain performance at lower input signal power compared to the single
pump double pass configuration.
This paper presents a modified design of low power recovery circuit in micro-system implanted device to stimulate the human nerve and muscle. The amplitude shift keying ASK was used to modulate data by using operating frequency 6.78MHz ISM industrial scientific medical band to be less invasive to tissue. The proposed system consists of an external part which has ASK modulator and class-E power amplifier with 94.5% efficiency. The internal part has half wave rectifier and voltage regulator to generate very stable 1.8VDC using 0.35um CMOS technology. The Orcad pspice 16.6 and MULTISIM 11 software were used to simulate the design of power recovery and class-E power amplifier respectively. The regulated voltage utilised to power the sub-electronic device implanted inside human body with very stable voltage even change implanted load resistance. The proposed system has 12.5%modulation index and low power consumption.
Wireless communication is a technology that plays an important role in current technology transformation. wireless communication is a method of telecommunication that are available for transmitting large amounts of data, voice and video over long distance using different frequencies. Specifically, Low Noise Amplifier which is located at the first block of receiver system, makes it one of the important element in improving signal transmission. This study was aimed to design a microwave Low Noise Amplifier for Long Term Evolution (LTE) application that will work at 5.8 GHz using high-performance low noise superHEMT transistor FHX76LP manufactured by Eudyna Technologies. The low noise amplifier (LNA) produced gain of 17.2 dB and noise figure (NF) of 0.914 dB. The input reflection (S11) and output return loss (S22) are -17.8 dB and -19.6 dB respectively. The bandwidth of the amplifier recorded is 1.2 GHz. The input sensitivity is compliant with the Long Term Evolution (LTE) standards.
We demonstrate a simplified algorithm to manifest the contribution of amplified spontaneous emission in variable gain-flattened Erbium-doped fiber amplifier (EDFA). The detected signal power at the input and output ports of EDFA comprises of both signal and noise. The generated amplified spontaneous emission from EDFA cannot be differentiated by photodetector which leads to underestimation of the targeted gain value. This gain penalty must be taken into consideration in order to obtain the accurate gain level. By taking the average gain penalty within the dynamic gain range, the targeted output power is set higher than the desired level. Thus, the errors are significantly reduced to less than 0.15 dB from 15 dB to 30 dB desired gain values.
The front-end electronics (FEE) of the Compact Muon Solenoid (CMS) is needed very low power consumption and higher readout bandwidth to match the low power requirement of its Short Strip application-specific integrated circuits (ASIC) (SSA) and to handle a large number of pileup events in the High-Luminosity Large Hadron Collider (LHC). A low-noise, wide bandwidth, and ultra-low power FEE for the pixel-strip sensor of the CMS has been designed and simulated in a 0.35 µm Complementary Metal Oxide Semiconductor (CMOS) process. The design comprises a Charge Sensitive Amplifier (CSA) and a fast Capacitor-Resistor-Resistor-Capacitor (CR-RC) pulse shaper (PS). A compact structure of the CSA circuit has been analyzed and designed for high throughput purposes. Analytical calculations were performed to achieve at least 998 MHz gain bandwidth, and then overcome pileup issue in the High-Luminosity LHC. The spice simulations prove that the circuit can achieve 88 dB dc-gain while exhibiting up to 1 GHz gain-bandwidth product (GBP). The stability of the design was guaranteed with an 82-degree phase margin while 214 ns optimal shaping time was extracted for low-power purposes. The robustness of the design against radiations was performed and the amplitude resolution of the proposed front-end was controlled at 1.87% FWHM (full width half maximum). The circuit has been designed to handle up to 280 fC input charge pulses with 2 pF maximum sensor capacitance. In good agreement with the analytical calculations, simulations outcomes were validated by post-layout simulations results, which provided a baseline gain of 546.56 mV/MeV and 920.66 mV/MeV, respectively, for the CSA and the shaping module while the ENC (Equivalent Noise Charge) of the device was controlled at 37.6 e- at 0 pF with a noise slope of 16.32 e-/pF. Moreover, the proposed circuit dissipates very low power which is only 8.72 µW from a 3.3 V supply and the compact layout occupied just 0.0205 mm2 die area.
An efficient erbium/ytterbium co-doped fibre amplifier was demonstrated by using a dual-stage partial doublepass structure with a band-pass filter (BPF). The amplifier achieved the maximum small signal gain of 56 dB and the corresponding noise figure of 4.66 dB at 1536 nm with an input signal power and total pump power of –50 dBm and 140 mW, respectively. Compared with a conventional single-stage amplifier, the maximum gain enhancement of 16.99 dB was obtained at 1544 nm with the corresponding noise figure was improved by 2 dB. The proposed amplifier structure only used a single pump source with a partial double pass scheme to provide a high gain and dual-stage structure to provide the low noise figure.
Detection and quantification of DNA is critical to many areas of life sciences and health care, from
disease diagnosis to drug screening. The transduction of DNA through electrochemical methods have a fast response rate and with a conductometric device like the silicon nanowire which can be fabricated to have a similar diameter of the DNA molecule being targeted, detection is real-time. Critical to this is the interfacing of a current-source and an amplifier capable of achieving a maximum of 10 pico ampere input bias. In this project, we fabricated a silicon nanowire using the top down approach and built a circuit that can mimic the output signal as low as 12 nA and achieved a gain of 1 million to be interfaced with the nanowire for real-time DNA detection.
A multi-wavelength laser comb is demonstrated using a nonlinear effect in a backward pumped Bismuth-based Erbium-doped fiber (Bi-EDF) for the first time. It uses a ring cavity resonator scheme containing a 215 cm long highly nonlinear Bi-EDF, optical isolators, polarisation controller and 10 dB output coupler. The laser generates more than 10 lines of optical comb with a line spacing of approximately 0.41 nm at 1615.5 nm region using 146 mW of 1480 nm pump power.
We demonstrate an enhanced multiwavelength L-band Brillouin-erbium fiber laser (BEFL), in which the Brillouin pump is pre-amplified before entering the single-mode fiber. The Brillouin pump pre-amplification provided by the Erbium-doped fiber has created higher intensity of Brillouin Stokes line generated in the single-mode fiber that leads to the homogenous gain saturation. Thus the built-up of self-lasing cavity modes is suppressed in a wider wavelength range. In contrary to the conventional linear-cavity BEFL, the number of output channels is enhanced within the same tuning range.
For the first time, a new circuit to extend the linear operation bandwidth of a LTE (Long Term Evolution) power amplifier, while delivering a high efficiency is implemented in less than 1 mm2 chip area. The 950 µm × 900 µm monolithic microwave integrated circuit (MMIC) power amplifier (PA) is fabricated in a 2 µm InGaP/GaAs process. An on-chip analog pre-distorter (APD) is designed to improve the linearity of the PA, up to 20 MHz channel bandwidth. Intended for 1.95 GHz Band 1 LTE application, the PA satisfies adjacent channel leakage ratio (ACLR) and error vector magnitude (EVM) specifications for a wide LTE channel bandwidth of 20 MHz at a linear output power of 28 dBm with corresponding power added efficiency (PAE) of 52.3%. With a respective input and output return loss of 30 dB and 14 dB, the PA's power gain is measured to be 32.5 dB while exhibiting an unconditional stability characteristic from DC up to 5 GHz. The proposed APD technique serves to be a good solution to improve linearity of a PA without sacrificing other critical performance metrics.
The structural, thermal, linear, and femtosecond third-order nonlinear optical (NLO) properties of two pyridine-based anthracene chalcones, (2E)-1-(anthracen-9-yl)-3-(pyridin-2-yl)prop-2-en-1-one (2PANC) and (2E)-1-(anthracen-9-yl)-3-(pyridin-3-yl)prop-2-en-1-one (3PANC), were investigated. These two chalcones were synthesized following the Claisen-Schmidt condensation method. Optically transparent single crystals were achieved using a slow evaporation solution growth technique. The presence of functional groups in these molecules was established by Fourier transform infrared and NMR spectroscopic data. The detailed solid-state structure of both chalcones was determined from the single-crystal X-ray diffraction data. Both crystals crystallized in the centrosymmetric triclinic space group P1̅ with the nuance of unit cell parameters. The crystals (labeled as 2PANC and 3PANC) have been found to be transparent optically [in the entire visible spectral region] and were found to be thermally stable up to 169 and 194 °C, respectively. The intermolecular interactions were investigated using the Hirshfeld surface analysis, and the band structures (highest occupied molecular orbital-lowest unoccupied molecular orbital, excited-state energies, global chemical reactivity descriptors, and molecular electrostatic potentials) were studied using density functional theory (DFT) techniques. The ultrafast third-order NLO properties were investigated using (a) Z-scan and (b) degenerate four-wave mixing (DFWM) techniques using ∼50 fs pulses at 800 nm (1 kHz, ∼4 mJ) from a Ti:sapphire laser amplifier. Two-photon-assisted reverse saturable absorption, self-focusing nonlinear refraction, optical limiting, and optical switching behaviors were witnessed from the Z-scan data. 3PANC demonstrated a stronger two-photon absorption coefficient, while 2PANC depicted a stronger nonlinear refractive index among the two. The time-resolved DFWM data demonstrated that the decay times of 2PANC and 3PANC were ∼162 and ∼180 fs, respectively. The second hyperpolarizability (γ) values determined by DFT, Z-scan, and DFWM were found to be in good correlation (with a magnitude of ∼10-34 esu). The ultrafast third-order NLO response, significant NLO properties, and thermal stability of these chalcones brands them as potential candidates for optical power limiting and switching applications.