Generation of 9.3-W multimode and 4-W single-mode output from 7-cm short fiber lasers

We generate 9.3-W continuous-wave 1535-nm multimode output from a 7.0-cm short-length Er-Yb codoped phosphate fiber laser. A slope efficiency of 29% is obtained at pump powers below 27 W. Very high output power per unit fiber length of 1.33 W/cm is achieved. From another 7.1-cm Er-Yb codoped fiber laser, 4.0-W single-transverse-mode output with M/sup 2//spl ap/1.1 is generated.     

Two-arm CuBr laser with a central electrode

A two-arm CuBr laser with a central electrode is reported. The laser produces maximum efficiency of 2.5% (at 42-W output power) and maximum output power of 47 W (at efficiency 2.35%). Some features of the excitation circuit and laser operation are given     

Watt-level Ka- and Q-band MMIC power amplifiers operating at lowvoltages

Ka- and Q-band watt-level monolithic power amplifiers (PAs) operating at a low drain bias of 3.6 V are presented in this paper. Design considerations for low-voltage operation have been carefully studied, with an emphasis on the effect of device models. The deficiency of conventional table-based models for low-voltage operation is identified. A new nonlinear device model, which combines the advantages of conventional analytical models and table-based models, has been developed to circumvent the numerical problems and, thus, to predict optimum load impedance accurately. The model was verified with load-pull measurements at 39 GHz. To implement a low-voltage 1-W monolithic-microwave integrated-circuit amplifier, careful circuit design has been performed using this model. A Q-band two-stage amplifier showed 1-W output power with a high power gain of 15 dB at 3.6-V drain bias. The peak power-added efficiency (PAE) was 28.5% and 1-dB compression power (P_{1 dB}) was 29.7 dBm. A Ka-band two-stage amplifier showed a P_{1 dB} of 30 dBm with 24.5-dB associated gain and 32.5% PAE. Under very low dc power conditions (P_dc<2 W, V_ds=3.4 V), the amplifiers showed 29-dBm output power and PAE close to 36%, demonstrating ultimate low-power operation capability. To the best of our knowledge, this is the first demonstration of watt-level PA's under 3.6-V operation at 26 and 40 GHz. Compared with the published data, this work also represents state-of-the-art performance in terms of power gain, efficiency, and chip size     

A 60-W Multicarrier WCDMA Power Amplifier Using an RF Predistorter

In this brief, we present a 60-W power amplifier that is linearized using an RF predistorter for multicarrier wideband code-division multiple-access (WCDMA) applications. The proposed RF predistorter is fully composed of RF or analog circuits, and it has a moderate memory effect compensation capability using a delayed third-order intermodulation (IM3) component path. It also includes the IM5 generation circuits and a compact IM3 generator that is capable of autocanceling for the fundamental component. The proposed RF predistorter was implemented and applied to a 60-W high-power WCDMA amplifier. For a four-carrier downlink WCDMA signal, the RF predistorter improved the adjacent channel leakage power ratio at a 5-MHz offset by 6.19 dB at an average output power of 48 dBm. The total efficiency of the system is as high as 13.6% at the same output power level. At an output power level of 60 W, the linearized power amplifier complies with the linearity specification of the WCDMA system.     

InP depletion-mode microwave MISFET's

Depletion-mode aligned-gate InP MISFET's with gate lengths of 1.5-1 µm have given output power of 1.26-W/mm gate width and power-added efficiencies of up to 40 percent at 4 GHz. At 12 GHz, 0.75-W/mm gate width with 22-percent power-added efficiency was obtained. At 18 GHz, a power output of 331 mW (0.59 W/mm) with 3.1 dB of gain and 15.7-percent power-added efficiency was measured. An output power of 245 mW (0.44 W/mm) with 3-dB gain and 10.7-percent efficiency was obtained at 20 GHz.     

High-power high-efficiency quasi-CW Sb-based mid-IR lasers using1.9-μm laser diode pumping

Power efficiency is a critical issue for mid-infrared (mid-IR) semiconductor lasers. Previously, the highest power and efficiency 4-μm laser was pumped with 0.98-μm laser diode. This letter used 1.9-μm diode pumping for better quantum defect ratio and heat flow geometry. A 3.7-μm InAsSb-AlAsSb laser yielded a pump-power-limited 1.25-W single-ended output in 1-ms-long pulse with 6.5% net optical-to-optical efficiency, in contrast with a 0.67-W thermally limited output and 2.7% efficiency with 0.98-μm diode pumping, at 70 K. The results are believed to represent the highest quasi-continuous-wave power from a single device, highest efficiency, and, scaled to the emitting aperture, highest power density for any 3-4-μm semiconductor laser for 1-ms pulse and ⩾70 K     

Development of high-power Ka-band and Q-band helix-TWTs

Recent advancements made in millimeter-wave helix-traveling wave tubes (TWTs) at L-3 Communications Electron Technologies (L-3 ETI), Inc. (formerly Electron Dynamic Devices, Inc. and originally Hughes Electron Dynamics Division), in continuous-wave (CW) output power capability and the overall efficiency of Ka-band and Q-band devices are presented. The 8921HP, L-3 ETI's latest high-power communications Ka-band TWT model, demonstrates 250-300-W CW output power and 47% minimum overall efficiency with a two-stage collector over 27.5-31 GHz. Another Ka-band device, the 8922HP, developed for pulsed radar applications over 33.4-36 GHz, produces 230-W minimum output power over the bandwidth with 49% minimum overall efficiency. This device was developed for pulsed operations but has demonstrated CW power-handling capability up to 270 W. In Q-band, the 8925HP, derived from the current production 120-W Q-band helix-TWT (8905HP), significantly extends the CW output power capability, demonstrating 230-W minimum over 43.5-45.5 GHz. The beam focusing is improved in both the Ka-band and the Q-band TWT models, with saturated radio-frequency beam interception well below 1% of the nominal beam current of 95 mA. The devices can be operated in pulsed mode by using the focus electrode to cut off the beam. The electron gun typically requires a focus electrode voltage of -800 to -900 V with respect to cathode for beam cutoff.     

New control scheme for class DE inverter by varying driving signals

A new control scheme for the class DE inverter is presented. This method generates the output voltage and power by varying driving signals which turn switches on and off. The advantages of the proposed scheme are the improvement of the power conversion efficiency for low output voltage, the operation at fixed operating frequency, unneccessity of enlargement of the circuit scale, and suitability for controlling the wide output range. An exact analysis and circuit experiments are carried out. It is shown that the experimental results are very similar to the theoretical predictions qualitatively. Measured efficiency is over 93% with 1.0-MHz 1.8-W output.     

A Single Supply, High Linearity 2-W PA MMIC for WLAN Applications Using Quasi-Enhancement Mode PHEMTs

A fully matched, 2-W high linearity amplifier monolithic microwave integrated circuit, by using quasi-enhancement mode technology of AlGaAs/InGaAs/ GaAs pseudomorphic high electron mobility transistors, is demonstrated for wireless local area network applications. At Vgs= 0 V, V_ds= 5 V, this power amplifier has achieved 14-dB small-signal gain, 33-dBm output power at 1-dB gain compression point, and 34.5-dBm saturated output power with 35% power added efficiency at 5.8 GHz. Moreover, high-linearity with 45.2-dBm third-order intercept point is also achieved     

A 9.1–10.7 GHz 10-W, 40-dB Gain Four-Stage PHEMT MMIC Power Amplifier

This letter presents a compact X-band high gain and high power four-stage AlGaAs/InGaAs/GaAs pseudomorphic high electron mobility transistor (PHEMT) monolithic microwave integrated circuit (MMIC) high power amplifier (PA). This amplifier is designed to fully match a 50-Omega input and output impedance. Based on 0.35-mum gate-length power PHEMT technology, this PA MMIC is fabricated on a 3-mil thick wafer. While operating under 8 V and 2700-mA dc bias condition, the characteristics of 40-dB small-signal gain, a 10-W continuous-wave saturation output power, and 33% power added efficiency at 9.7GHz can be achieved     

A single-supply Ku-band 1-W power amplifier MMIC with compact self-bias PHEMTs

In this letter, the design of a self-bias 1.8-mm AlGaAs/InGaAs/GaAs pseudomorphic high electron mobility transistor with a compact source capacitor for operation in Ku-band frequency is described. Based on the proposed device, a self-bias Ku-band 1-W two-stage power amplifier monolithic microwave integrated circuit (MMIC) is also demonstrated. Under a single bias condition of 8 V and 630 mA, the self-bias MMIC possesses 14.2-dB small-signal gain, 30.2-dBm output power at 1-dB gain compression point with 19.2% power added efficiency and 31.3-dBm saturated output power with 22.5% power added efficiency at 14GHz. With the performance comparable to the dual-bias MMIC counterpart, the proposed self-bias MMIC is more attractive to system designers on very small aperture terminal applications.     

A common-gate switched 0.9-W class-E power amplifier with 41% PAEin 0.25-μm CMOS

A power amplifier for wireless applications has been implemented in a standard 0.25-μm CMOS technology. The power amplifier employs class-E topology to exploit its soft-switching property for high efficiency. The finite dc-feed inductance in the class-E load network allows the load resistance to be larger for the same output power and supply voltage than that for an RF choke. The common-gate switching scheme increases the maximum allowable supply voltage by almost twice from the value for a simple switching scheme. By employing these design techniques, the power amplifier can deliver 0.9-W output power to 50-Ω load at 900 MHz with 41% power-added efficiency (PAE) from a 1.8-V supply without stressing the active devices     

Power Flexible Ka-band Traveling Wave Tube Amplifiers of Up to 250-W RF for Space Communications

The latest model Ka-band helix traveling wave tube (TWT) amplifier designed and manufactured for onboard space satellite-communications systems at L-3 Communications Electron Technologies, Inc. is significantly improved over previous generations. This present-generation (model 999HA) TWT has demonstrated over 250-W RF output power over the 31.8- to 32.3-GHz deep-space frequency band with an overall efficiency exceeding 61% Robbins (Proc. IEEE Int. Vacuum Electron, 2006). In addition, the 999HA has low distortion and has demonstrated over 100-W RF output with 9-GHz instantaneous bandwidth. This TWT is expected to have application as a single unit or in power-combined systems so that deep-space missions can achieve a total RF output power of as much as 1 kW Wintucky (Proc. IEEE Int. Vacuum Electron, 2006). The 999HA can be mated to either 7-kV electronic power conditioners (EPCs) for low-power applications or to a recently developed 14-kV EPC (model 1693HC) to support higher power applications     

An asymmetric broad waveguide structure for a 0.98-μm high-conversion-efficiency diode laser

A novel asymmetric broad waveguide diode laser structure was designed for high power conversion efficiency (PCE). The internal quantum efficiency, the series resistance, and the thermal resistance were theoretically optimized. The series resistance and the thermal resistance were greatly decreased by optimizing the thickness of the P-waveguide and the P-cladding layers. The internal quantum efficiency was increased by introducing a novel strain-compensated GaAs0.9P0.1/InGaAs quantum well. Experimentally, a single 1-cm bar with 20% fill factor and 900 μm cavity length was mounted P-side down on a microchannel-cooled heatsink, and a peak PCE of 60% is obtained at 26.3-W continuous wave output power. The results prove that this novel asymmetric waveguide structure design is an efficient approach to improve the PCE.     

A TEG Efficiency Booster with Buck–Boost Conversion

A thermoelectric generator (TEG) efficiency booster with buck–boost conversion and power management is proposed as a TEG battery power conditioner suitable for a wide TEG output voltage range. An inverse-coupled inductor is employed in the buck–boost converter, which is used to achieve smooth current with low ripple on both the TEG and battery sides. Furthermore, benefiting from the magnetic flux counteraction of the two windings on the coupled inductor, the core size and power losses of the filter inductor are reduced, which can achieve both high efficiency and high power density. A power management strategy is proposed for this power conditioning system, which involves maximum power point tracking (MPPT), battery voltage control, and battery current control. A control method is employed to ensure smooth switching among different working modes. A modified MPPT control algorithm with improved dynamic and steady-state characteristics is presented and applied to the TEG battery power conditioning system to maximize energy harvesting. A 500-W prototype has been built, and experimental tests carried out on it. The power efficiency of the prototype at full load is higher than 96%, and peak efficiency of 99% is attained.     

A fully matched high linearity 2-W PHEMT MMIC power amplifier for 3.5 GHz applications

A 2-W monolithic microwave integrated circuit power amplifier, operating between 3.3 and 3.8GHz by implementing AlGaAs/InGaAs/GaAs pseudomorphic high electronic mobility transistor for the applications of wideband code division multiple access, wireless local loop, and multichannel multipoint distribution service, is demonstrated. This two-stage amplifier is designed to fully match 50/spl Omega/ input and output impedances. With a dual-bias configuration, the amplifier possesses the characteristics of 30.4dB small-signal gain and 34dBm 1-dB gain compression power with 37.1% power added efficiency. Moreover, with a single carrier output power level of 24dBm, high linearity with a 43.5-dBm third-order intercept point operating at 3.5GHz is also achieved.     

A 6-GHz Four-Stage GaAs MESFET Power Amplifier (Short Papers)

A 6-GHz GaAs MESFET power amplifier with 1-W output power, 26dB gain, and 8-dB noise figure is described. It is a fully integrated four-stage amplifier with an efficiency of 22 percent. The third-order intermodulation product is 31.5 dB below the carrier at an output power of 1 W.     

A 25-W 5-GHz GaAs FET Amplifier for a Microwave Landing System

A 25-W 29-dB gain 5-GHz GaAs FET amplifier has been developed which can be used for a transmitter in the Microwave Landing System. By using 10-W class practical internally matched GaAs FET's hermetically sealed in ceramic packages, the four-stage amplifier has been constructed simply. The amplifier provides 30-W power output with 18.5 percent power efficiency at 17-dBm power input level. It also exhibited an exceffent AM/PM conversion of approximately 1°/dB, compared to 6°/dB for TWT amplifiers.     

A High-Efficiency 100-W GaN Three-Way Doherty Amplifier for Base-Station Applications

A three-way Doherty 100-W GaN base-station power amplifier at 2.14 GHz is presented. Simple, but accurate design equations for the output power combiner of the amplifier are introduced. Mixed-signal techniques are utilized for uncompromised control of the amplifier stages to optimize efficiency, as well as linearity. The combination of the above techniques resulted in an unprecedented high efficiency over a 12-dB power backoff range, facilitating a record high power-added efficiency for a wideband code division multiple access test signal with high crest factor, while meeting all the spectral requirements for Universal Mobile Telecommunications System base stations.      

300-W cryogenically cooled Yb:YAG laser

Thermooptic effects often limit the power and beam quality of bulk-solid-state lasers. Cryogenically cooled (/spl sim/100 K) Yb:YAG lasers have been previously demonstrated to have relatively low thermooptic effects and high efficiency due to improved material properties at low temperatures. In this work, >300-W average power with M/sup 2//spl sim/1.2 and 64% optical-optical efficiency has been demonstrated from an end-pumped-rod geometry power oscillator. To our knowledge, this is the highest average power to date from a cryogenically cooled Yb:YAG laser.