Highest efficiency, linear X-band performance using InP DHBTs - 48%PAE at 30 dB C/IM3

InP single heterojunction bipolar transistors have previously demonstrated 5-10 dB lower third-order intermodulation products (IM3) compared to GaAs heterojunction bipolar transistors (HBTs) under low voltage (2 V) operation. This paper reports excellent single-tone and two-tone X-band operation, including high two-tone power-added efficiency (PAE), on linear InP double heterojunction bipolar transistors (DHBTs) operated at V_ce=4 V. The InP DHBT demonstrated a 30 dB carrier to third-order intermodulation product (C/IM3) output power ratio simultaneously with 48% two-tone PAE. This is the highest known efficiency of an X-band device under linear (30 dB C/IM3) operation. This is especially significant for microwave power amplifiers for satellite communication transmitters, where lower intermodulation distortion is normally accomplished by backing off in RF drive and output power, thus sacrificing PAE performance     

High linearity power X-band GaInP/GaAs heterojunction bipolartransistor

We report for the first time two-tone test results measured on a GaInP/GaAs HBT. A 2×400 μm² device delivered more than 1.3 W under one-tone testing at 7.5 GHz and output more than 1 W under two-tone. The corresponding intermodulation product is -14 dBc, and decreases to -21 and -36 dBc, respectively, at 3-dB and 10-dB back-off from the saturated two-tone output. These results demonstrate that GaInP/GaAs HBT's are suitable for microwave transmitter applications     

Influence of imbalance on distortion in optical push-pull frontends

The influence of imbalance on second-order intermodulation distortion (IMD2) in optical push-pull frontends for subcarrier multiplex CATV applications is investigated theoretically and experimentally. The investigation focuses on imbalance introduced in either the photodiode, the push-pull amplifier, or the output balun, and expressions describing the overall IMD2 cancellation efficiency are derived. The developed theory is used to predict the IMD2 cancellation behavior of an optical push-pull frontend. Commercially available PIN photodiodes for CATV purposes and ferrite core transformers are characterised for phase and amplitude balance up to 1 GHz. The overall IMD2 cancellation efficiency of an optical push-pull frontend based on the best of these devices is calculated. The theory is finally verified experimentally with an optical push-pull frontend designed with the characterised photodiode and transformer. The improvement in IMD2 suppression obtained with the push-pull structure relative to a single-ended structure is in average 29 dB across the band from 47-862 MHz. The total IMD2 suppression obtained for the frontend is between 60 dBc and 79 dBc at an average optical input power of 1 mW and with an optical modulation index (OMI) of 35 percent per carrier in a two-tone setup,     

Simultaneous load-pull of intermodulation and output power undertwo-tone excitation for accurate SSPA's design

The simultaneous measurements of the third-order intermodulation and output power under two-tone excitation have been implemented on a MESFET operated in large-signal mode for load impedances spanning quasi-entirely the Smith chart, using a six-port reflectometer with variable test port impedance. An experimental comparison between single-tone and two-tone output power and power-added efficiency was performed. The experimental results show that the load-pull of the output power capability and power-added efficiency by a two-tone test are more accurate than the single-tone characterization for multi-carrier Solid State Power Amplifiers (SSPA's) design     

Scalable visible Nd:YAG pumped Raman laser source

Experimental and analytical studies of a 60 Hz, 0.45 W, 630 nm Raman laser source with a 12 ns pulse duration have demonstrated an overall electrical to optical efficiency of 0.12 percent. This is the first demonstration of a short pulse, high repetition rate red laser at such a high average output power without the need for a visible pump laser. Additional significance arises from the fact that simple extensions of the present work will produce many wavelengths in the visible and near infrared (IR) spectral region. A 1064 nm Nd:YAG pump laser operating at 60 Hz was used to pump a methane gas Raman laser operating at 1544 nm. This wavelength was mixed with the remaining 1064 nm laser output in noncritically phase matched lithium niobate to produce 630 nm radiation. The optical energy conversion efficiencies for the three steps were 1.4, 30, and 20 percent, respectively, for output energies of 86 mJ at 1064 nm, 15 mJ at 1544 nm, and 7.5 mJ at 630 nm. rms pulse amplitude variation measured 6 percent or less. A 10.7 million pulse life test was conducted, and the average output energy did not vary more than ±10 percent from its initial value.     

前馈线性化功率放大器设计

采用自适应结合查表控制的前馈技术,设计了用于CDMA2000的超线性功率放大器.在连续波输出功率达到45dBm时,双音IMD3低于-62dBc,用CDMA2000信号测试,其ACPR分别低于-54dB@750kHz和-71dB@1.98MHz.     

LSA relaxation oscillations in a waveguide iris circuit

Large-signal computer simulations of GaAs LSA relaxation oscillations in an X-band waveguide iris circuit are presented. The study is focused on a particular oscillator and a realistic model of an experimental circuit is used. However, the results are typical for other LSA relaxation oscillators. Basic features of the microwave circuit, characteristic voltage and current waveshapes, frequency tuning with bias voltage, and oscillator starting transients are discussed. The RF output power is shown to build up in less than ten cycles. Circuit optimization for high dc to RF conversion efficiency is discussed and circuit data for nearly 30 percent efficiency are given. Finally, efficiency degradation is discussed when doping gradients are present, and effciencies of 15 and 10 percent appear possible for doping gradients as high as 20 and 60 percent, respectively. Hence, the LSA relaxation mode is shown to be less sensitive to doping gradients than the sinusoidal LSA mode.     

A gallium-nitride push-pull microwave power amplifier

A highly efficient linear, broad-band AlGaN-GaN high electron-mobility transistor (HEMT) push-pull microwave power amplifier has been achieved using discrete devices. Instrumental was a low-loss planar three-coupled-line balun with integrated biasing. Using two 1.5-mm GaN HEMTs, a push-pull amplifier yielded 42% power-added efficiency with 28.5-dBm input power at 5.2 GHz, and a 3-dB bandwidth of 4-8.5 GHz was achieved with class-B bias. The output power at 3-dB gain compression was 36 dBm under continuous-wave operation. Along with the high efficiency, good linearity was obtained compared to single-ended operation. The second harmonic content of the amplifier was more than 30 dB down over the 4-8.5-GHz band, and a two-tone excitation measurement gave an input third-order intercept point of 31.5 dBm at 8 GHz. These experimental results and an analysis of the periodic load presented by the output balun suggest the plausibility of broad-band push-pull operation for microwave systems with frequency diversity.     

Bandpass delta-sigma class-S amplifier

A class-S amplifier with a bandpass delta-sigma modulated input is demonstrated using CMOS devices at 10 MHz. With a two-tone modulated input, third-order intermodulation products below -40 dBc were measured, with an output power of 26 dBm and a drain efficiency of 33%. This new amplifier topology demonstrates promising performance for simultaneously achieving high linearity and efficiency     

Efficient, Linear Amplification of Varying-Envelope Signals Using FET's with Parabolic Transfer Characteristics

A linear, high-efficiency mode of operation is described for FET power amplifiers of varying envelope signals (e.g., single-sideband, quadrature-amplitude-modulation, and multicarrier signals). It makes use of FET's having parabolic transfer characteristics (PTC). It is shown theoretically and experimentally that the efficiency of the PTC mode is about 2 dB higher than that of the standard class-A mode. For example, two-tone, 4-GHz measurements on a Western Electric FET model 131-L showed that, for an output power of about 1.5 W and for a relative third-order intermodulation level of -35 dB, the power-added efficiency of the PTC mode was 20 percent, while that of the class-A mode was 13 percent. Comparisons are also made with other high-efficiency modes of operation proposed elsewhere.     

Premature collection mode in IMPATT diodes

Experimental efficiencies of up to 35.5 percent have been reported for Read-type GaAs diodes, whereas theoretical calculations have predicted an upper limit of approximately 30 percent for the conversion efficiency of IMPATT diodes. The concept of a premature collection mode is shown to resolve this discrepancy by predicting maximum efficiencies close to 40 percent. Premature collection refers to large-signal conditions where the modulation of the drift width is sufficiently large to result in collection of the avalanche current pulse at drift angles smaller than the small-signal angle. It is shown that a discontinuous transition between the IMPATT and the premature collection modes takes place when the drift angle in the small-signal limit is greater than π. Designing the diode for close to punchthrough conditions in small-signal operation extends the practical frequency range for inducing premature collection by avoiding long drift angles and corresponding rapid conductance saturation in the IMPATT mode. The onset of premature collection is accompanied by a substantial increase in power output because of a more favorable drift angle, and in high noise because of the high RF levels involved. The jump in transit angle causes a discontinuous increase in negative conductance. The hysteresis in the tuning characteristic resulting from this discontinuity has been observed experimentally. Noise measures in the range 60-70 dB have been measured and calculated for the premature collection mode compared to 40-50 dB under large-signal conditions for the IMPATT mode. Therefore, the high efficiencies available with the premature collection mode are expected to be usable only in applications where high noise levels can be tolerated.     

AlGaAs/GaAs HBT linearity characteristics

Communication systems require linear power amplifiers with high efficiency and very low intermodulation distortion. AlGaAs/GaAs heterojunction bipolar transistors (HBT's) were found to have very low intermodulation distortion in power operation. Two-tone tests were carried out on both common-emitter (CE) and common-base (CB) power HBT's. At 7 GHz, the CE HBT showed -20 dBc IM₃ (third-order intermodulation ratio) and 12% power added efficiency (PAE) per tone at the 1 dB gain compression point; IM₃ dropped to -30 dBc at 1.5 dB output power backoff. The CE HBT has lower intermodulation distortion than CB HBT. Load pull data were collected to aid the understanding of the intermodulation. Parameters of the Gummel-Poon model (as used in SPICE) were derived for HBT's based on dc data and small-signal S parameters at various bias points. The accuracy and validity of the model were confirmed by comparison to experimental two-tone results. SPICE predicts that the emitter and base resistances linearize the HBT and reduce the third-order intermodulation distortion. The excellent third-order intermodulation performance of the CE HBT makes it a very attractive choice for linear power amplifiers     

Sealed-off continuous wave carbon monoxide laser at high temperature operation

The CO laser at 208-348 K operation is reported. Output power of 8.8 W, efficiency of 7.2 percent, and a lifetime of greater than 2500 h have been obtained. The laser lines were selected by a grating and showed oscillation on 63 lines in the5.1109-5.9120 mum wavelength range were obtained. The strongest line had a power output of 1.4 W at room temperature and 1.11W at 333 K operation. At 323 K there are 33 lines with a maximum power of 220 mW for one line.     

Design and performance of deflected-beam electron-bombarded semiconductor amplifiers

This paper describes the design and testing of developmental electron-bombarded semiconductor (EBS) devices as pulsed dc and pulsed RF amplifiers. These devices employ a well-focused electron beam deflected in proportion to the input signal to control the current in a semiconductor target. Both Class A and Class B amplifier configurations are described, with a prediction of their relative efficiency and distortion properties. The deflection sensitivity of simple deflection plates and traveling-wave deflection systems is considered. Experimental results are given for amplifiers with planar passivated semiconductor targets and traveling-wave deflection systems operated as video-pulsed amplifiers and Class B RF amplifiers. Performance of nanosecond-risetime videopulse amplifiers with peak output power greater than 700 W and efficiency in excess of 80 percent is described. Test data are presented from RF amplifiers with efficiency performance of 60 percent. A comparison of theoretical and experimental results is given based upon a computer simulation of semiconductor target performance. Preliminary life test data showing stabilized diode performance with negligible reverse breakdown voltage deterioration are presented.     

A highly linear and efficient differential CMOS power amplifier with harmonic control

A 2.45 GHz fully differential CMOS power amplifier (PA) with high efficiency and linearity is presented. For this work, a 0.18-/spl mu/m standard CMOS process with Cu-metal is employed and all components of the two-stage circuit except an output transformer and a few bond wires are integrated into one chip. To improve the linearity, an optimum gate bias is applied for the cancellation of the nonlinear harmonic generated by g/sub m3/ and a new harmonic termination technique at the common source node is adopted along with normal harmonic termination at the drain. The harmonic termination at the source effectively suppresses the second harmonic generated from the input and output. The amplifier delivers a 20.5dBm of P/sub 1dB/ with 17.5 dB of power gain and 37% of power-added efficiency (PAE). Linearity measurements from a two-tone test show that the power amplifier with the second harmonic termination improves the IMD3 and IMD5 over the amplifier without the harmonic termination by maximally 6 dB and 7 dB, respectively. Furthermore, the linearity improvements appear over a wide range of the power levels and the linearity is maintained under -45 dBc of IMD3 and -57dBc of IMD5 when the output power is backed off by more than 5dB from P/sub 1dB/. From the OFDM signal test, the second harmonic termination improves the error vector magnitude (EVM) by over 40% for an output power level satisfying the 4.6% EVM specification.     

Dynamic characteristics of high speed p-substrate GaInAsP buriedcrescent lasers

A detailed behavior of 1.3-μm GaInAsP p-substrate buried-crescent lasers emitting maximum output powers of more than 30 mW/facet is discussed. A 3-dB modulation bandwidth of 11.5 GHz, and relative intensity noise level of ~-145 dB/Hz were observed at 5 I _th. The two-tone intermodulation distortion was more than 30 dB below the 9-GHz subcarriers for a current modulation index of ~40%     

Obtaining high efficiency at low power using a quantum-dotmicrocavity light-emitting diode

Efficiencies are calculated for quantum-dot apertured-microcavity light-emitting diodes. Although the maximum efficiency depends strongly on the quantum-dot inhomogeneous broadening, greater than 20% efficiency is calculated for a small-sized apertured microcavity, even for an inhomogeneous linewidth as large as 30 meV. The efficiency can be increased to 40% if the inhomogeneous linewidth is reduced to 10 meV and to more than 60% if the inhomogeneous linewidth is eliminated to leave a homogeneous linewidth of 6.6 meV. The maximum output powers are ~40 nW, although a microarray can increase this value. For the case of a single quantum dot, an efficiency >80% is estimated for a submicron apertured-microcavity, with a maximum output power of ~3 nW     

Optimal adaptation methods and class of operation: keys to improving feedforward amplifier power efficiency

This paper studies the influences of two new adaptation methods and the class of main amplifier operation on the achievable power efficiency of the feedforward amplifier under typical design constraints. These two influences are weak for a two-tone driving signal, but they interact powerfully for a real-life high-stress signal, leading to optimal designs involving Class AB or even Class B main amplifiers, depending on the required output linearity. Assuming a code-division multiple-access signal, typical MESFETs, and an output linearity commonly used in mobile systems design, the new adaptation methods allowed relative efficiency improvements of 21% and 36% using main amplifiers biased near Class B and at Class B, respectively.     

A Novel Quasi-Optical Frequency Multiplier Design for Millimeter and Submillimeter Wavelengths

This paper describes a novel design for millimeter and sub-millimeter wavelength varactor frequency triplers and quadruplers. The varactor diode is coupled to the pump source via waveguide and stripline impedance matching and filtering structures. Output power at the various harmonics of the pump frequency is fed to quasi-optical filtering and tuning elements. The low-loss quasi-optical structures enable near-optimum control of the impedances seen by the varactor diode at the idler and output frequencies, resulting in efficient high-order harmonic conversion. A minimum efficiency of 4 percent with 30-mW input power has been obtained for a tripler operating between 200 and 280 GHz, with a peak efficiency of 8 percent between 250 and 280 GHz. Another tripler, designed for the 260-350-GHz band, gave a minimum conversion efficiency of 3 percent with 30-mW input power, with a peak efficiency of 5 percent at 340 GHz.     

InP-In1-xGaxAsyP1-yembedded mesa stripe lasers

A laser structure was fabricated using two-step liquid-phase epitaxy, employing the melt-back technique. The fabrication and properties of this structure are described in detail. Good linearity of the power output up to power levels of 20 mW was obtained. The threshold current density at 300 K is 9-12 kA/cm². This high value is mainly due to Zn-diffusion from the third to the buffer layer during the second growth step of the fabrication process. The external differential quantum efficiency is 30-35 percent under pulsed operation at 25°C. The pulsed threshold current has an exponential behavior with temperature whereT_{0} = 60degC. The far-field beam divergences in the directions parallel and perpendicular to the junction plane are12-15degand35-40deg, respectively. Transverse mode stabilization was improved with this laser structure.