Performance Of Amplifier Research Articles

Performance Analysis of PTS PAPR Reduction Method for NOMA Waveform

Cellular systems utilize single and multicarrier waveforms for high-speed data transmission. The Fifth-Generation (5G) system proposes several techniques based on multicarrier waveforms. However, the Peak to Average Power Ratio (PAPR) is one of the significant concerns in advanced waveforms as it degrades the framework's efficiency. Non Orthogonal Multiple Access (NOMA) can provide massive connectivity, which is the crucial requirement of the Internet of Things (IoT). The 3rd generation tested NOMA applications in downlink and uplink transmission. However, NOMA uplink transmission in the power domain has performance degradation and is not considered a possible technique in 3rd generation power projects (3GPP). Presently, NOMA is not just a concept but has been introduced as a standard method in various transmission schemes. NOMA suffers from a high peak to average power ratio (PAPR), which forces the power amplifier (PA) to shift into a nonlinear region. The high value of PAPR leads the power amplifier of the multicarrier technique into a nonlinear region. As the performance of the power amplifier degrades, the overall system performance goes down. In this work, we suggest different methods to overcome the issue of PAPR in multicarrier techniques such as Selective Mapping (SLM) and Partial Transmit Sequence (PTS). The simulation results reveal that the performance of the proposed PTS is better than that of the conventional SLM and PTS.

Analytical Performance of Low Noise Amplifier Using Single-Stage Configuration for ADS-B Receiver

Automatic dependent surveillance-broadcast (ADS-B) is an equipment of a radar system to reach difficult areas. For radar applications, an ADS-B requires a low noise amplifier (LNA) with high gain, stability, and a low noise figure. In this research, to produce an LNA with good performance, an LNA was designed using a BJT transistor 2SC5006 with DC bias, VCE = 3 V, and current Ic = 10 mA, also a DC supply with VCC = 12 V, to achieve a high gain with a low noise figure. The initial LNA impedance circuit was simulated using 2 elements and then converted into 3 elements to obtain parameters according to the target specification through the tuning process, impedance matching circuit was used to reduce return loss and voltage standing wave ratio (VSWR) values. The LNA sequence obtains the working frequency of 1090 MHz, return loss of -52.103 dB, a gain of 10.382, VSWR of 1.005, a noise figure of 0.552, stability factor of 0.997, and bandwidth of 83 MHz. From the simulation results, the LNA has been successfully designed according to the ADS-B receiver specifications.

Transformer-based low frequency noise measurement system for the investigation of infrared detectors’ noise

The paper presents a noise measurement system particularly suited for the investigation of the low frequency noise in advanced infrared (IR) detectors characterized by low shunt resistance. By combining the performances of ultra-low noise amplifiers with the advantages that can be obtained by transformer input coupling and cross-correlation between two nominally identical channels, we were able to obtain excellent noise performances in the low frequency region (below 10 Hz). Indeed, the equivalent input background noise that can be obtained with the approach we propose can be as low as 1 × 10-20 V2/Hz (≈100 pV/√Hz) at 1 Hz. The system was tested using source resistances in the range from 1 to 10 Ω as well as actual advanced IR detectors to demonstrate its ability to provide information about the noise generated at very low frequencies.

Investigation Of Dual-Pump Fiber Optical Parametric Amplifier Performance Driven by Energy Transfer Between Four-Wave Mixing Process

Fiber optical parametric amplifier (FOPA) is operated based on energy transfer from pump waves to signal wave and at the end of the fiber, an idler wave is generated. This process is called four-wave mixing (FWM). Even though effects of higher-order dispersion coefficients, fiber length, fiber nonlinearity, fiber attenuation, pump powers, pump wavelength separation and distance of central pump wavelength with ZDW on gain profiles have been examined by previous researchers, but on different fiber or numerically studied using the Optisys system, analytical model or different amplitude equations. Thus, in this study, the above-mentioned parameters on the gain performance of dual pump fiber optical parametric amplifier (FOPA) using highly nonlinear shifted fiber (HNL-DSF) as a medium will be numerically investigated using ode45 function in Matlab. The gain at a certain wavelength can be obtained by solving 4 coupled amplitude equations with fiber loss and pump depletion that govern the four-wave mixing (FWM) process of pumps, signal and idler waves. Simulations results indicate positive gives poor or no gain, meanwhile, an addition of to negative widens the bandwidth, but there is no significant effect with the addition of . Besides, an increase of fiber length, nonlinearity and pump powers improve gain performance, but an increase of fiber loss decays the gain amplitude. Increment of pump separation will enhance flatness of gain at wavelength far from central wavelength but results in an increase of gain reduction at the central wavelength. Lastly, must be positive, not too small and not bigger than 1.125nm to get a high, broader and lesser ripples gain.

Two-pump parametric amplification in the presence of fiber dispersion fluctuations: a comparative study.

Fiber optical parametric amplifiers (FOPAs) operating based on four-wave mixing (FWM) are versatile devices with increasing applications in optical communication systems. In this paper, the effects of dispersion fluctuations on the performance of bandwidth, ripple, parametric gain, and saturation power of a two-pump FOPA based on four-wave and six-wave models are studied and compared. Coupled-amplitude equations representing the non-degenerate FWM process in optical fiber are solved numerically to compute the parametric gain over the communication wavelengths. The behaviors of the performance parameters are critically analyzed and compared with different types of fluctuation strengths (or amplitudes) specified by the combinations of correlation length (Lc) and fluctuation amplitude (σ). Based on the results, it was found that the flat gain bandwidth for the four-wave model remains unchanged and is insensitive to the strengths of fluctuations. The gain ripples, however, get higher as the fluctuation strengths increase. On the other hand, the flat gain bandwidths of the six-wave model are hardly identified due to the tremendous and continuous ripples within the pump wavelengths. In addition, the minimum parametric gain values for both four-wave and six-wave models reduce as the fluctuation strengths increase. Also, the lowest value of parametric gain leads to the highest saturation power and vice versa. The dispersion fluctuations affect the FWM process's efficiency and deteriorate the overall amplifier performance, particularly for the six-wave model. The numerical analysis obtained via the six-wave model is especially useful since this model closely matches with practical circumstances.

The effects of pump pulse fluence on the output energy and amplified spontaneous emission of a femtosecond regenerative amplifier

In this paper, the effects of pump pulse fluence on the output energy and amplified spontaneous emission (ASE) of a femtosecond regenerative amplifier are investigated. One can easily enhance the output energy of laser amplifiers by increasing their pump fluence. This in turn can increase the ASE and reduce the performance of amplifiers in terms of output beam quality, beam stability, etc. This effect would eventually lead to what is called ‘temporal intensity contrast deterioration’. In this work, it is shown that an optimum state of the pump pulse fluence can indeed optimize the amount of the output energy from a regenerative amplifier without much reducing the performance of the amplifier due to the higher ASE. Temporal gain characteristics were employed to achieve this optimum value for a better design, performance, and maintenance of femtosecond laser amplifiers. The results of the current study can be effectively used in designing a wide range of regenerative amplifiers for femtosecond pulses.

Drive-Induced Backward-Wave Oscillations in Helix Traveling-Wave Tubes—A Case Study

The output section of helix traveling-wave tubes (TWTs) usually features a tapered delay line to enhance the amplifier performance. This alters the phase velocity of the circuit waves, which, in particular, disturbs the narrowband synchronism between the backward wave (BW) and the electron beam. As a result, the excitation threshold of BW oscillations (BWOs) increases. Large-signal operation significantly alters beam-wave synchronism, as the electrons loose kinetic energy during the amplification process, i.e., toward the TWT output. As a result, beam and BW may interact over a larger distance, thus lowering the threshold for the onset of BWOs. These would thus be drive-induced in contrast to the zero-drive BWOs mentioned above. The following investigates the occurrence of such drive-induced BWOs as a case study of several different TWT models and proposes a theory for the large-signal instability. As the simulation process is quite involved and time-consuming, a heuristic approach for the fast prediction of the oscillation is presented as well.

A high-bandwidth low current transimpedance amplification circuit

A measuring circuit is designed based on the transimpedance amplifier. The methods of reducing parasitic capacitance and improving amplifier performance are introduced in detail. The influence of the parasitic capacitance generated by the feedback resistors on the bandwidth in the transimpedance amplification circuit is discussed. The circuit can measure the wide-dynamic-range low current ranging from 10-13 A to 10-5 A in four ranges. The circuit's bandwidth is up to 500 Hz when the circuit can normally work to measure a wide-range low current. The peak-to-peak amplitude of circuit noise is less than 0.22 pA. The current drift is less than 1.06 fA/∘C over a temperature range of 0∘C to 85∘C, and the integral nonlinearity is less than 0.25%.

A Comprehensive Harmonic Analysis of Current-Mode Power Amplifiers

This work presents a comprehensive theoretical analysis of current-mode power amplifiers as a function of input power for different biasing classes under the common simplifying assumption of constant transconductance and hard current cut-off/saturation. Typically, the theoretical analysis of power amplifier performance and behavior are carried out only at maximum output power. However, to achieve high data-rates, modern telecommunication systems adopt signals characterized by a very high peak-to-average power ratio, thus it is useful to analyze the power amplifier behavior as a function of power back-off. Moreover, in many cases, to enhance the efficiency and/or to apply harmonic shaping techniques, a clipped drain-source current, which approaches a square wave, is required. The classical analysis can be extended to low power levels only under the assumption of power-independent conduction angle, which is true only for class-A and class-B amplifiers, and does not take into account possible waveform clipping at maximum current. This work presents a complete theoretical Fourier analysis of FET-based power amplifiers as a function of quiescent drain-source current at any input power level and accounting for the clipped current case, up to the square-wave limit, reorganizing and completing the material that can be found in classical textbooks in the field.

Heat transfer in microwave transistors at cryogenic temperatures

Heat transfer in transistors at cryogenic temperatures occurs by radiation of atomic vibrations and limits the noise performance of modern microwave amplifiers.

CW and Modulated Input Second Harmonic Injection for Efficiency Enhancement in Broadband Power Amplifiers

The second-harmonic input impedance plays a critical role on the performance of GaN power amplifiers. In a recent paper, a drain efficiency enhancement for a continuous-mode power amplifiers was reported to be achieved using active broadband second-harmonic injection at the PA input. In this paper, the strategy for selecting the second-harmonic input impedance and the necessity for using active injection in such broadband PAs are discussed in detail. Additionally, the methodology for designing an embedded broadband diplexer in the input matching network is reported. Finally, the importance of the phase of the second-harmonic signal injected is demonstrated for both CW and modulated signals using both simulation and measurement, respectively. The effectiveness of the CW and modulated active second-harmonic injection methodology presented here are validated by previously reported measurements that demonstrated an average drain efficiency improvement of 9.4% from 1.3 to 2.4 GHz for CW signals and of 9.7% at 2 GHz for a frequency-modulated 30 MHz chirp radar signal.

Yb-ASE Suppression in Single-Frequency Hybrid Double Cladding Erbium–Ytterbium Co-Doped Fiber Amplifier with SMS Structure

A hybrid double cladding erbium–ytterbium co-doped fiber (EYDF) amplifier with a single-mode-multimode-single-mode (SMS) active fiber is demonstrated in this study. The hybrid gain fiber with an SMS structure is composed of two kinds of EYDFs with 6 and 12 μm core diameters. The transmission spectra of the SMS fiber structure were theoretically analyzed and the simulation results indicated that the maximum loss in the 1~1.1 μm band where the Yb-band amplified spontaneous emission (Yb-ASE) located, was much larger than that of the 1.5-μm band because of the wavelength difference. The power performance and spectra properties of the hybrid fiber amplifier were theoretically and experimentally analyzed and compared with a typical uniform fiber amplifier under the same conditions. The experimental results demonstrated that this hybrid fiber amplifier can suppress the Yb-ASE by over 12 dB and increase the slope efficiency by more than 2%, but the ASE in the 1.5-μm band increases by 2~3 dB. This work provides a possible method to enable EYDF amplifiers to suppress the Yb-ASE and overcome the pump bottleneck effect.

Evaluating the impact of doping concentration on the performance of in-band pumped thulium-doped fiber amplifiers

Abstract This study is to investigate the impact of thulium concentration on the performance of in-band pumped thulium-doped silica fiber amplifiers with considering ion–ion interactions. Due to the fluorescence quenching in silica glass, the fluorescence lifetimes are required to compute at every Tm concentration. The theoretical model of fluorescence decay curves at in-band pumped thulium-doped silica fiber is used to determine the fluorescence lifetimes of the 3F4 and 3H4 levels. The calculated lifetimes of the commercially available thulium-doped silica fiber are 650 µs for 3F4 level and 14 µs for 3H4 level and these results are consentient well with the experimental reported results. The theoretical evaluating of the amplifier performance shows that the gain amplifier reduces with concentration increase because of the impact of both fluorescence quenching and the reverse cross-relaxation process. Thus, in contrast to pumping wavelength at 790 nm, there are negative effects of the high doping concentration of Tm ions on the amplifier performance at the in-band pumping scheme.

A 50 W dual‐band high‐efficiency gallium nitride high electron mobility transistor power amplifier with three‐stage L‐type DC bias circuit at 1.8 and 2.6 GHz

AbstractA 50 W dual‐band high‐efficiency gallium nitride (GaN) high electron mobility transistor (HEMT) power amplifier with a three‐stage L‐type DC bias circuit capable of individually adjusting second‐harmonic impedances is proposed for 1.8 and 2.6 GHz frequencies. The output network of this power amplifier is composed of an output matching network comprising five‐stage transmission lines and a three‐stage L‐type DC bias circuit with three L‐type circuits and one transmission line. The one‐stage L‐type circuit comprises a series transmission line and a quarter‐wavelength open‐ended shunt stub. For the high‐efficiency performance of the power amplifier, the output matching network is matched to the optimum impedances of the fundamental frequencies, and the DC bias circuit optimizes the impedances individually at the second‐harmonic frequencies without affecting the matched fundamental frequency impedances in the output matching network. Measured results show that the proposed dual‐band GaN HEMT power amplifier achieved gains of 15.6 and 13.8 dB as well as maximum power‐added efficiencies of 70.5% and 66.3% with 47 dBm output power at 1.8 and 2.6 GHz, respectively.

Comparison of 1480 nm and 980 nm-pumped Gallium-Erbium fiber amplifier.

Background: One way to reduce the length of the gain medium in Erbium-Doped Fiber Amplifier (EDFA) is by doping the fiber core with a high concentration of Erbium. However, this method caused ion clustering effects, which limits the EDFA's efficiency. In this research, the use of Gallium as a new co-dopant in erbium-doped silica fiber is explored. Methods: The new fiber, namely Gallium co-doped Erbium fiber (Ga-EDF), is used as a gain medium in an optical fiber amplifier setup. A 2-meter length of the Ga-EDF fiber was used in a single pass configuration with a forward pumping scheme at 150 mW pump power. The Ga-EDF amplifier's gain and noise figure while pumping at 980 nm and 1480 nm were compared. The amplifier's performance was evaluated as the input signal power varied between -30 dBm to 3 dBm, over the wavelength range of 1520 nm to 1580 nm. Results: The 980 nm-pumped Ga-EDF amplifier achieved the maximum small-signal gain of 22.45 dB and the corresponding noise figure of 5.71 dB at the input signal wavelength of 1535 nm. Meanwhile, the 1480 nm-pumped Ga-EDF amplifier attained the maximum small-signal gain of 20.83 dB and the corresponding noise figure of 5.09 dB at the input signal wavelength of 1550 nm. At the input signal power below -20 dBm and the wavelength range 1520 nm to 1547 nm, the Ga-EDF performs better when pumped at 980 nm. Their performance is comparable at the input signal wavelength range between 1547 nm to 1580 nm. At the input signal power above -20 dBm, the 1480 nm-pumped Ga-EDF outperformed the 980 nm-pumped amplifier. Conclusions: The overall performance indicates that the gain saturation point of the 1480 nm-pumped amplifier is higher than the 980 nm-pumped.

A Novel OTA Architecture Exploiting Current Gain Stages to Boost Bandwidth and Slew-Rate

A novel architecture and design approach which make it possible to boost the bandwidth and slew-rate performance of operational transconductance amplifiers (OTAs) are proposed and employed to design a low-power OTA with top-of-class small-signal and large-signal figures of merit (FOMs). The proposed approach makes it possible to enhance the gain, bandwidth and slew-rate for a given power consumption and capacitive load, achieving more than an order of magnitude better performance than a comparable conventional folded cascode amplifier. Current mirrors with gain and a push–pull topology are exploited to achieve symmetrical sinking and sourcing output currents, and hence class-AB behavior. The resulting OTA was implemented using the 130 nm STMicroelectronics process, with a supply voltage of 1 V and a power consumption of only 1 µW. Simulations with a 200 pF load capacitance showed a gain of 92 dB, a unity-gain frequency of 141 kHz, and a peak slew-rate of 30 V/ms, with a phase margin of 80°, and good noise, PSRR and CMRR performance. The small-signal and large-signal current and power FOMs are the highest reported in the literature for comparable amplifiers. Extensive parametric and Monte Carlo simulations show that the OTA is robust against process, supply voltage and temperature (PVT) variations, as well as against mismatches.

Fibre optic parametric amplifier for high capacity burst-mode access networks.

We compare performance of a polarization insensitive fiber optic parametric amplifier (PI-FOPA), a commercial erbium doped fiber amplifier (EDFA) and a discrete Raman amplifier (DRA) in a 50 km long-reach optical access network transmitting bursts of 10 Gbps signal with traffic density ranged from 5% to 97%. We demonstrate that for the same power budget the PI-FOPA allows for transmission of bursty traffic with density up to 97% while DRA and EDFA are limited to 30% and 15%, respectively. Alternatively, we demonstrate PI-FOPA to allow for 3 dB and 5 dB higher power budget than the DRA and EDFA, respectively, for the worst case scenario of 75% traffic density.

Evaluation of Switching Power Amplifier Topology for Active Magnetic Bearings

Active magnetic bearings (AMBs) have led to great progress in the field of rotating machinery due to their many advantages, such as their non-contact and non-lubrication properties. As the key component of an AMB actuator, the switching power amplifier has an important impact on the performance of magnetic bearings and rotating machinery. In this paper, the topologies of switching power amplifiers for AMBs are introduced. The traditional half-bridge topology and two newly proposed topologies—the three-phase-half-bridge and neutralized-sharing-bridge topology—are analyzed and discussed. The volume, current output performance and cost of the power amplifier with different topologies are comprehensively evaluated, providing a theoretical basis and guidance for the selection and design of the topology of switching power amplifiers for AMBs under different conditions.

Organic Electrochemical Transistor Common‐Source Amplifier for Electrophysiological Measurements

AbstractThe portability of physiological monitoring has necessitated the biocompatibility of components used in circuitry local to biological environments. A key component in processing circuitry is the linear amplifier. Amplifier circuit topologies utilize transistors, and recent advances in bioelectronics have focused on organic electrochemical transistors (OECTs). OECTs have shown the capability to transduce physiological signals at high signal‐to‐noise ratios. In this study high‐performance interdigitated electrode OECTs are implemented in a common source linear amplifier topology. Under the constraints of OECT operation, stable circuit component parameters are found, and OECT geometries are varied to determine the best amplifier performance. An equation is formulated which approximates transistor behavior in the linear, nonlinear, and saturation regimes. This equation is used to simulate the amplifier response of the circuits with the best performing OECT geometries. The amplifier figures of merit, including distortion characterizations, are then calculated using physical and simulation measurements. Based on the figures of merit, prerecorded electrophysiological signals from spreading depolarizations, electrocorticography, and electromyography fasciculations are inputted into an OECT linear amplifier. Using frequency filtering, the primary features of events in the bioelectric signals are resolved and amplified, demonstrating the capability of OECT amplifiers in bioelectronics.

Enhanced seismic base isolation using inertial amplifiers

Harnessing the concept of inertial amplification, an inertial amplifier coupled base isolator (IABI) is proposed in this paper. The seismic performance, in terms of story drift, base shear reduction, of this proposed inertial amplifier coupled base isolator has been compared with that of the classical base isolator (CBI) and inerter-based isolation system (Inerter-BI). A thorough analytical study, implementing rationals of random vibration for harmonic and Gaussian white noise is conducted to identify the performance of the inertial amplifier coupled base isolator (IABI) in the frequency domain. Further, a numerical study is conducted to determine the story drift, base shear response in time-domain for the inertial amplifier based base-isolated structure and classical base-isolated structure for twenty-two real earthquake ground motions. The results elucidate the histogram of base shear and story drift reduction percentage shifts towards higher values for inertial amplifier coupled isolator compared to CBI and Inerter-BI. From both analytical and numerical study, it is observed that the seismic performance and response reduction capacity of proposed IABI is significantly 89.38% and 72% superior to the classical base isolator and inerter-based isolation system, respectively. This finding evidenced towards the supremacy of the inertial amplifier base isolator over the classical base isolator and inerter coupled base isolator in terms of seismic vibration control.