Small Signal Gain Research Articles

Novel pumping scheme of Holmium doped fiber amplifiers operating around [formula omitted] using [formula omitted] lasers exploiting cascaded fiber lasers

The optical communication window around 2μm is attracting significant research attention for future optical communication systems as an extension to the C-, L-, and U-bands. One of the research topics in the 2μm region is optical amplifiers. Holmium-doped fiber amplifier (HDFA) is a suitable candidate for amplifying signals in this region. However, the pump laser for Holmium-doped fiber (HDF) is expensive and not widely available. In this work, we propose through numerical simulations, a novel pumping scheme to pump the HDF using commercially available 1.48μm lasers by exploiting cascaded fiber lasers made up of Erbium-doped fiber (EDF) and Thulium-doped fiber (TDF). The first fiber uses a commercially available 1.48μm laser to pump a piece of EDF to generate a 1.62μm continuous wave (CW) laser. This 1.62μm CW laser is used to pump a piece of TDF in the second fiber laser to create a 1.95μm CW laser that is used to pump the HDF. The HDFA can be used to amplify modulated optical signals in the 2μm wavelength range. A small-signal gain of 52.5 dB, 46.2 dB, and 32.6 dB can be achieved for input signal powers of −30 dBm, −15 dBm, and 0 dBm, respectively, at 2.032μm using a 5 W laser diode pump at 1.48μm. A noise figure (NF) of 7.5 dB, 6.6 dB, and 5.58 dB has been observed for input signal power of −30 dBm, −15 dBm, and 0 dBm, respectively at 2.032μm.

A Compact 60GHz Power Amplifier in 65nm CMOS Technology

A compact 60GHz power amplifier chip in 65nm CMOS technology of three-stage common source structure is presented. The first two amplifiers offer sufficient gain to pre-amplify the small input power. The third stage amplifier uses two sets of differential pairs to achieve power synthesis. On-chip transformer coupling is adopted to realize inter-stage impedance matching as well as input and output matching. The compact structure of on-chip transformer can reduce the chip size and improve the integration degree. The measured small signal gain at 60GHz of 22.3dB, the saturation power of 20.2dBm, the output P-1dB of 17.3dBm, the PAE of 14%, and the core area is 0.19mm2. The power amplifier can be used in high-speed short-range wireless communication system to enhance communication data transmission capacity.

Multipass Yb : KGW disk amplifier

We have investigated a multipass Yb : KGW disk amplifier based on the White cell configuration and pumped by a laser diode with a fibre output. It is shown that the three-mirror layout of the cell is three times more efficient than the four-mirror one, since the size and position of the signal beam on the surface of the active element do not depend on the cell number of passes. For a three-mirror cell scheme, a small-signal gain G = 168 is obtained in experiments for a pump power of 360 W. The experimentally achieved gain of two such amplifiers arranged in series is 6 × 104, which exceeds G 2 approximately two-fold.

A large, high-gain, 400 mm single-aperture slab amplifier with 20 kJ laser output

This paper introduces a slab laser amplifier system of 400 mm single-aperture in the Integration Test Bed (ITB) laser facility. Based on the theoretical optimization model for parameters, the system uses flash-lamps with the diameter is 31 mm and the pump pulse width is 480 μs, the average small signal gain coefficient in the aperture of laser beam is 5.65%/cm. A uniformly distributed near-field output of laser can be achieved by adjusting the near-field of seed laser. The energy output reaches 20.4 kJ/4.5TW/1053 nm, the near-field modulation is 1.40:1, and the near-field contrast is 0.085.

A 300-GHz Low-Noise Amplifier in 130-nm SiGe SG13G3 Technology

This work presents a 300-GHz low-noise amplifier (LNA) in a SiGe:C 130-nm BiCMOS technology, featuring <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$f_{t}/f_{\text {max}}$ </tex-math></inline-formula> of 470/700 GHz. The designed amplifier uses three cascaded stages in a pseudo-differential cascode topology with input and output baluns facilitating single-ended measurements. The first stage is matched trading off noise and gain performance, while a T-type output matching network is used for broadband matching. The interstage matching is performed using center tap transformers. On-wafer measurements show that the designed LNA has a peak small-signal gain of 10.8 dB at 325 GHz, along with a 3-dB bandwidth of 68 GHz and an input 1-dB compression point of −15.6 dBm at 287.5 GHz. The simulated noise figure is better than 12.7 dB over the required band. The circuit occupies 0.26-mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> silicon area and consumes 119 mW from a 3.3-V supply.

Influence of higher-order nonlinear effects on optical solitons of the complex Swift-Hohenberg model in the mode-locked fiber laser

The complex Swift-Hohenberg equation (CSHE) has been widely studied in recent years. It is a more real model in the mode-locked fiber laser with the saturable absorber due to the addition of the diffraction term compared with the complex Ginzburg-Landau equation. In this work, the dynamics process of the traditional soliton and M−type soliton pulses in the mode-locked fiber laser is demonstrated based on the CSHE model with higher-order nonlinear effects. The results show that with the increase of the small signal gain coefficient, the number of soliton molecules adds gradually. Under the same transmission conditions, the transmission of M−type solitons in the laser are more stable than that of single solitons. By adding the self-steepening effect, it can be found that the time-domain shift due to higher-order dispersion effects is compensated. The self-frequency shift effect caused by the Raman scattering can produce not only time domain shift, but also frequency domain shift. Moreover, the addition of higher-order diffraction term can describe the spectral response of multiple peaks, and makes the pulse spectrum show the asymmetric propagation in the transmission process. Finally, the increase of the length of the single-mode fiber on the right side of the gain fiber in the optical circuit will not only shift the center position of the output pulse backward, but also make the pulse energy show a ladder type downward trend.

Diode-end-pumped all-liquid-cooled square rod Nd: Glass amplifier with sub-joule energy extraction and ultralow thermal induced wavefront

A diode-end-pumped all-liquid-cooled square rod Nd: glass eight-pass amplifier is reported. Amplification energy of 700 mJ under a single-pass small signal gain of 2.36 and input energy of 6.5 mJ at a 1 Hz repetition rate and at 9 J pump energy is achieved, corresponding to an effective energy-extraction efficiency of 25.6%. The total single-pass thermally induced wavefront is measured to be 0.57 μm (peak to valley). To the best of our knowledge, this is the first demonstration of an all-liquid-cooled sub-joule-level square rod Nd: glass amplifier. By optimizing the flowing fluid, the near-field spatial intensity modulation at the maximum energy is 1.38 and 91.6% of the far-field energy is concentrated at three times the diffraction limit.

670-GHz Cascode Circuits Based on InGaAs Metamorphic High-Electron-Mobility Transistors

This article reports the development of high-gain cascode amplifier circuits in the frequency range around 670 GHz. The cascode circuits are based on a 35-nm metamorphic high-electron-mobility transistor (HEMT) technology. Till date, only common-source transistors have been used in HEMT-based amplifier circuits above 600 GHz. For this reason, prospects and design considerations of cascode devices operating at this terahertz frequency band are evaluated. The design and implementation of high-gain six-stage cascode amplifier circuits is described, achieving up to 30 dB of measured gain at 670 GHz and a small-signal gain of at least 25 dB over the frequency range from 630 to 690 GHz. The gain benefit of cascode devices is demonstrated with up to 5 dB of gain per cascode stage at 670 GHz. This corresponds to the highest reported gain per stage for HEMT-based WR-1.5 circuits.

A 5.5/12.5‐GHz concurrent dual‐band power amplifier MMIC in 0.25 μm GaAs technology

A concurrent 5.5/12.5-GHz dual-band power amplifier (PA) is designed and implemented in a 0.25 μm GaAs pseudomorphic high electron mobility transistor process. The PA is composed of two stages and adopts LC parallel and series networks for dual-band matching. The efficiency of the PA is improved by lowering the drain voltage of the driver stage. Measurement results show that the proposed PA features the maximum small-signal gain of 17.1 and 15.6 dB, the maximum output power of 24.9 and 24.5 dBm, and peak power-added efficiency (PAE) of 35.5% and 35% at 5.5 and 12.5 GHz, respectively. The PA consumes a total DC of 73 mA, and its power consumption is 503 mW. The chip size of the PA is 1.4 × 1.3 mm2 including all testing pads.

Broadband Class-J GaN Doherty Power Amplifier

This paper presents a broadband 3–3.7 GHz class-J Doherty power amplifier exploiting second harmonic tuning in the output network. Furthermore, the output impedance inverter is eliminated and its effect is embedded in the main device’s output matching network, thus trading off among bandwidth, efficiency, and gain. The proposed amplifier adopts two 10 W packaged GaN transistors, and it achieves in measurement 60–74%, and 46–50% drain efficiency at saturation and 6 dB output back-off, respectively, with a saturated output power of 43–44.2 dBm and a small-signal gain of 10–13 dB. The proposed DPA exhibits a simulated adjacent channel power ratio less than −30 dBc at 36 dBm average output power, when a 16-QAM modulation with 5 MHz bandwidth is applied to the 3.5 GHz carrier.

Design of a Broadband MMIC Driver Amplifier with Enhanced Feedback and Temperature Compensation Technique

This paper presents a broadband GaN pseudo high-electron-mobility transistor (pHEMT) two-stage driver amplifier based on an enhanced feedback technique for a wideband system. Through well-designed parameter values of the feedback and the matching structure of the circuit, a relatively flat frequency response was obtained over a wide frequency band. Simultaneously, in order to reduce the fluctuation of current caused by the environmental temperature, a bias circuit with quiescent current temperature compensation was designed. The driver power amplifier, which was implemented in the form of a monolithic microwave integrated circuit (MMIC), was designed to drive a broadband high-power amplifier. The designed broadband driver amplifier for the 6 GHz to 20 GHz frequency band had a very small die size of 1.5 × 1.2 mm2 due to the use of an optimized impedance matching structure. It exhibited a small-signal gain of 12.5 dB and output power of 26 dBm. The flatness of this driver amplifier for gain and output power was achieved as ±2.5 dB and ±1 dB over the entire frequency band, respectively. The experimental results showed up to 35 dBm in the OIP3, and the current variation range was ±5 mA after using the temperature compensation bias circuit.

High Gain Broadband Power Amplifier Design Based on Integrated Diplexing Networks

This letter presents an enhanced gain broadband power amplifier (PA) design approach that is based on using an integrated diplexer with a phase compensation network to combine PAs of narrower bandwidths (BWs) over a wider overall bandwidth PA. The input and output matching networks of each amplifier are individually synthesized using a wideband matching network. The diplexer is designed using a lowpass/highpass topology approach. The separate amplifiers are integrated with the proposed diplexer, resulting in extended bandwidth and enhanced gain. For verification purposes, a broadband PA is designed and implemented over the frequency range of 2–4 GHz. Measurements demonstrate that the output power varies between 40.1 and 41.2 dBm with a drain efficiency (DE) of 61%–75%. The proposed design achieves a high small-signal gain of 12.5–15.3 dB. The reported saturated power gain is 10.1–11.2 dB.

A 37-GHz Asymmetric Doherty Power Amplifier With 28-dBm P sat and 32% Back-Off PAE in 0.1-μm GaAs Process

In this article, the analysis, design, and development of a 37-GHz asymmetric Doherty power amplifier (DPA) are presented. In a practical DPA, the main power amplifier (PA) shows nonideal characteristic, which varies the effect of the load modulation. Based on the theoretical analysis, we derive the relationship among the efficiency, power back-off (PBO) level, and the corresponding load impedance in a nonideal load modulation. The result suggests that a Class-AB main PA shows a decreased PBO efficiency during the load modulation. To achieve a good compromise between PBO level and PBO efficiency of the main PA, the load modulation scheme is redesigned in this work. A 2-dB PBO of the main PA is chosen to maintain the high efficiency during the load modulation. An asymmetric DPA topology is employed to compensate the inadequate PBO of the main PA so that a desired 6-dB PBO is achieved. Generally, the RF leakage at the DPA output degrades its performance. To solve this issue, we propose a modified low characteristic impedance DPA output network. The output matching network of the auxiliary PA is particularly designed to enlarge its output impedance. Through these design techniques, the leakage loss is significantly reduced to 0.2 dB, which improves the gain and power-added efficiency (PAE) at PBO. To validate the proposed techniques, a DPA chip is designed and fabricated in a D-mode 0.1- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{m}$ </tex-math></inline-formula> GaAs pHEMT process. At 37 GHz, the 1.6 mm <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times1.8$ </tex-math></inline-formula> mm integrated chip exhibits a measured small-signal gain of 15.6 dB and a saturated power ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$P_{\mathrm{sat}}$ </tex-math></inline-formula> ) of 28.0 dBm, with an associated 33.2% peak PAE and a 32.0% PAE at 6-dB PBO. To the best of our knowledge, the proposed chip exhibits the state-of-the-art overall performance among DPAs operating around 37 GHz for 5G n260 millimeter-wave (mm-wave) band.

Study of gain and trajectories in elliptical electron beam considering a planar wiggler and self fields and ion-channel in free electron laser

In this study, the relativistic electron beam with an elliptical cross-section is introduced instead of the relativistic electron beam with a circular cross-section in free-electron laser (FEL). Influences of ion-channel guiding, axial magnetic field, Planar Wiggler Magnetic Field (PWMF) and self-fields on trajectories of the elliptical relativistic electron beam have also been investigated. At first, it was assumed that the PWMF is applied along the minor axis of the beam cross-section ellipse. In the second case, the PWMF was applied along the major axis of beam cross-section ellipse, the results of which were compared for the two cases. Effects of elliptical cross-section demotions and elliptical electron beam density on electron trajectory have been studied. The results were compared in the limit that the elliptical electron beam is converted to a circular electron beam, which has also been graphically presented. Moreover, a limit case in which the elliptical beam is converted into a sheet beam was studied. Furthermore, a formula was obtained for the small signal gain in a FEL with elliptical electron beam. The obtained gain for a FEL, together with a relativistic electron beam with an elliptical cross section was compared to the maximum gain for a FEL together with a relativistic electron beam with a circular cross section. It is shown that increasing the ratio of the semi-major to semi-minor axes of the beam cross-section causes the gain rate of the FEL to increases. We investigated a study of electron trajectories and dispersion equation in relativistic electron beam with elliptical cross section under the influence of electromagnetic wave wiggler and axial magnetic field considering ion-channel guiding and self fields in Appendix A.

Performance Enhancement of Praseodymium Doped Fiber Amplifiers

In this paper, we report a simulation study on the performance enhancement of Praseodymium doped silica fiber amplifiers (PDFAs) in O-band (1270–1350 nm) in terms of small signal gain, power conversion efficiency (PCE), and output optical power by employing bidirectional pumping. The PDFA performance is examined by optimizing the length of Praseodymium doped silica fiber (PDF), its mode-field diameter (MFD) and the concentration of Pr3+. A small-signal peak gain of 56.4 dB, power conversion efficiency (PCE) of 47%, and output optical power of around 1.6 W (32 dBm) is observed at optimized parameters for input signal wavelength of 1310 nm. Minimum noise figure (NF) of 4.1 dB is observed at input signal wavelength of 1310 nm. Moreover, the effect of varying the pump wavelength and pump power on output optical power of the amplifier and amplified spontaneous emission (ASE) noise is also investigated, respectively. Finally, the impact of ion-ion interaction (up-conversion effect) on small-signal gain of the amplifier is also studied by considering different values of up-conversion coefficient.

Analysis of nonlinear distortions of DpHEMT structures based on the GaAs/InGaAs compound with double-sided delta-doping

Computational and experimental studies of the characteristics of a high-power AlGaAs/InGaAs/GaAs DpHEMT were performed. A self-consistent numerical solution of the Schrodinger and Poisson equations was used to calculate the band diagram and the electron concentration in the channel of the transistor under study. The electron mobility in the transistor channel was estimated experimentally at 9300 cm2/V·s. The obtained transfer current--voltage characteristic of the transistor was used to calculate the parameters of a model differential amplifier (small-signal gain and third-order non-linear distortion factor). Keywords: AlGaAs/InGaAs/GaAs DpHEMT, nonlinear distortion, spacer layers.

A 68-GHz Loss Compensated Distributed Amplifier Using Frequency Interleaved Technique in 65-nm CMOS Technology

This article presents a frequency interleaved technique (FIT) that can be applied to add resonant peaks in the response of distributed amplifier (DA) for loss compensation and then a frequency-interleaved distributed amplifier (FIDA) that can achieve a high-gain and wide-bandwidth frequency response by summing multiple overlapping distinct-band frequency responses through a distributed configuration. A detailed discussion was introduced to verify the FIDA and a DA was implemented using the FIT. The reported 65-nm CMOS FIDA chip occupies an area of 0.9 x 0.95 mm² and achieves a 17.2 dB small-signal power gain, 2-68 GHz -3-dB bandwidth, gain bandwidth product (GBW) of 478 GHz, and gain ripple of less than 2 dB, while consuming 120 mW under 1.2 V.

Dual-Band Power Amplifier Design at 28/38 GHz for 5G New Radio Applications

This paper presents the design of a dual-band power amplifier (PA) featuring similar performance at 28 GHz and 38 GHz. In the new radio (NR) of the fifth generation (5G) communication system, the inter-band carrier aggregation technique is commonly adopted for data rate enhancement. In such configuration, operation at both bands of the 5G frequency range 2 (FR2) spectrum is often necessary. The stacked-FET topology was adopted for mitigation of the gain roll-off with frequency to achieve similar performance at both frequency bands. Implemented in the commercial 0.15-&#x03BC;m gallium arsenide (GaAs) pseudomorphic high electron mobility transistor (pHEMT) technology, the PA delivered a small signal gain of 18.5/18 dB, an output power at saturation (P_sat) of 28.5/28.2 dBm, and a peak power-added efficiency (PAE) of 39%/36% at 28/38 GHz, respectively. The measurement results have demonstrated great potential of the proposed PA for 5G NR applications.

A GaAs Low Noise Amplifier for 2.4 GHz ISM band Applications

In this paper, a Low Noise Amplifier (LNA) operating in the Industrial Scientific and Medical (ISM) band of 2.45 GHz is proposed. The designed LNA is based on GaAs ATF21170 active device. To improve gain and matching parameters, a hybrid matching technique based on smith chart and optimization is used. The proposed biasing network as well as the stabilization circuit allow achieving a minimum noise figure with an unconditionally stability over the whole operating frequency ranging from 2.25 GHz to 2.55 GHz. Finally, some tradeoffs were done to obtain the minimum noise figure with the greatest available power gain. In terms of performances, the proposed structure shows an excellent noise figure of ~1Db.The simulated results show an excellent input/output return loss under -15 dB over the operation frequency band with an excellent small signal gain ranging between 17 dB and 15 dB. In terms of large signal performance, the proposed LNA achieves an output power of 17 dBm (52 mW) with a PAE of 22% and an output intercept IP3 around 27 dBm.

A W-Band Amplifier With a New Wide-Band Interstage Matching Technique Using Self-Resonance of a Microstrip-Coupled Line

A new interstage matching technique is presented for design of a wide-band multi-stage amplifier using commercial 60- <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n</i> m GaN-on-silicon technology in the W-band. The proposed interstage matching network is designed as a two-pole conjugated impedance matching approach for wideband characteristics using low-characteristic impedance transmission lines and an optimized microstrip-coupled line. In particular, the microstrip-coupled line provides strong resonance at the desired frequency, enabling optimal conjugate impedance matching of both edge and intermediate frequencies simultaneously. The implemented W-band three-stage amplifier using the proposed interstage matching technique exhibited a small-signal gain above 14.1 dB from 75 to 103 GHz. Also, the output power between 92-100 GHz was greater than 25 dBm, and the maximum output power at 96 GHz was 25.8 dBm. The W-band amplifier was designed with an area of 2 mm × 1.2 mm.