Multitone power and intermodulation load-pull characterization ofmicrowave transistors suitable for linear SSPA's design

In this paper, an experimental load-pull characterization of microwave transistors operated under N-tone-excitations (2⩽N⩽32) is presented. Such characterization is very useful to investigate the linearity of high-power amplifiers via intermodulation distortion analysis. All the measurements were carried out using a newly developed multiline measurement system which uses an arbitrary waveform generator (AWG) to generate the spectrum of any N desired tones and a microwave transition analyzer (MTA) as a vector receiver. The measured intermodulation rejection (IMR) behavior, as the number of tones increases, is compared with previously published theoretical results. Constant output power contours and IMR contours in the Γ_L (f₀) plane for different number of tones are presented and discussed. The dependency of the IMR on the biasing conditions and the carriers' phase distribution is also investigated     

Analysis and modeling of low-frequency noise in resistive FET mixers

A complete analysis of the low-frequency (LF) noise is performed on resistive field-effect transistor (FET) mixers, where LF noise is created due to the self-mixing process of the local oscillator. First, a new scalable noise model for FETs in an ohmic channel bias regime (U/sub ds//spl ap/0 V) has been developed, which uses fluctuating resistances, instead of noise voltage or noise current sources. Measurements on a hybrid single-ended mixer prove a good accuracy of the proposed model and reveal a method to distinguish between the different noise sources. Further investigations discuss the LF noise in balanced mixers and explain the mechanisms of noise generation. All mixers under test operate in X-band (8, ..., 12 GHz) with IF below 1 MHz.     

Calibration techniques of active BiCMOS mixers

This paper describes calibration techniques for downconversion mixers used in integrated direct-conversion receivers. A method of achieving a high even-order intermodulation rejection is presented. Using the method presented, the receiver second-order input intercept point (IIP2) can always be improved by more than 20 dB. The minimum achieved receiver IIP2 after calibration is +38 dBm. A technique to enhance the I/Q-amplitude balance between the quadrature channels is also introduced. A single-balanced adjustable mixer is implemented as a part of a prototype direct-conversion receiver. The receiver chip consists of a low-noise amplifier, mixers and calibration circuitry, a divide-by-two circuit, local oscillator (LO) buffers for LO generation, and active baseband filters. The chip is fabricated using a 0.35-μm SiGe BiCMOS process and is characterized at 900 MHz     

Multiharmonic source-pull/load-pull active setup based on six-port reflectometers: influence of the second harmonic source impedance on RF performances of power transistors

An original measurement system for nonlinear RF power-transistor characterization is presented. This new setup enables the measurement and optimization of output power and/or power-added efficiency (PAE) using active harmonic tuning and six-port reflectometers as vector network analyzers. Two active loops are inserted at both ports of transistors in order to independently control the source and load impedances at the fundamental and at the second harmonic frequency. To the authors' knowledge, this is the only active technique that allows a complete automated multiharmonic load-pull/source-pull measurement system. Experimental results are shown for a commercial GaAs MESFET power transistor at 2 GHz.     

Analysis and design of wide-band SiGe HBT active mixers

The frequency response of SiGe HBT active mixers based on the Gilbert cell topology is analyzed theoretically. The time-varying operation of the active mixer is taken into account by applying conversion matrix analysis. The main bandwidth-limiting mechanisms experienced in SiGe HBT active mixers performing frequency conversion of wide-band signals is discussed. The analysis is verified by computer simulations using a realistic high-frequency large-signal SiGe HBT model. An active mixer design based on the Gilbert cell topology modified for wide-band operation using emitter degenerated transconductance stage and shunt feedback load stage is discussed. Experimental results are given for an active mixer implemented in a 0.8-/spl mu/m 35-GHz f/sub T/ SiGe HBT BiCMOS process.     

A symmetrical nonlinear HFET/MESFET model suitable forintermodulation analysis of amplifiers and resistive mixers

We propose a new symmetrical heterojunction FET (HFET)/MESFET model to predict intermodulation distortion in amplifiers and resistive mixers. The model is symmetric. That is, drain and source of the intrinsic FET are interchangeable. This reflects the characteristics of most microwave FET's. The model has few fitting parameters and they are simple and straightforward to extract. The model was installed into Hewlett-Packard's harmonic-balance program microwave design system and verified by measurements. The verification shows excellent results for an MESFET and an HFET in both amplifier and resistive mixer configurations     

5-6 GHz SiGe active I/Q subharmonic mixers with power supply noise effect characterization

A 5-6 GHz active subharmonic I/Q mixer pair has been designed and fabricated for use in direct conversion receivers for the Unlicensed National Information Infrastructure (U-NII) bands. The design includes I and Q subharmonic mixers and an LO conditioning chain. All circuits are fully differential and are designed to operate from a 3.3 V supply. Each mixer consumes 5 mA of current. A conversion gain of 6 dB, an IIP2 of +29 dBm and an input 1-dB compression point of -5.4 dBm were measured. The 90/spl deg/ phase balance between the I and Q mixer IF outputs was investigated in the presence of injected digital switching noise on the power supply lines; 90/spl deg/ balance was maintained over a wide range of switching waveform frequencies and amplitudes.     

Design of Lange-couplers and single-sideband mixers usingmicromachining techniques

This paper reports on the design and performance of micromachined Lange-couplers and single-sideband mixers (SSB) on thin dielectric membranes at Ku-band. The micromachined Lange-coupler results in a 3.6±0.8 dB coupling bandwidth from 6.5 to 20 GHz. The Lange-coupler and an interdigital filter are used in a 17-GHz SSB. The SSB mixer requires 1-2 mW of local oscillator (LO) power without dc bias and achieves a 30 dB upper-sideband (USB) image rejection for an IF frequency of 1 GHz and above. The micromachined membrane technology can be easily scaled to millimeter-wave monolithic microwave integrated circuits (MMIC's) to meet the low-cost requirements in automotive or portable communication systems     

Accurate analysis and design of millimeter wave mixers

The present study is based on the method introduced by B. Shuppert (1986) for nonlinear analysis of mixers, but it differs in the linear part. In particular, the circuit characterization of the mixer harmonics is emphasized, removing the usual approximation of matched terminations and employing models that effectively represent network characteristics in the microwave and millimeter wave domain. This goal is achieved through the accurate knowledge of the various components used in the mixer and the use of accurate equivalent circuits. In order to validate the model, two subharmonic mixers operating at K-band (18-26 GHz) were realized. Reasonable agreement between theoretical and experimental results is achieved     

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     

Large-signal microwave characterization of AlGaAs/GaAs HBT's basedon a physics-based electrothermal model

A physics-based multicell electrothermal equivalent circuit model is described that is applied to the large-signal microwave characterization of AlGaAs/GaAs HBT's. This highly efficient model, which incorporates a new multifinger electrothermal model, has been used to perform dc, small-signal and load-pull characterization, and investigate parameter-spreads due to fabrication process variations. An enhanced Newton algorithm is presented for solving the nonlinear system of equations for the model and associated circuit simulator, which allows a faster and more robust solution than contemporary quasi-Newton nonlinear schemes. The model has been applied to the characterization of heterojunction bipolar transistor (HBT) microwave power amplifiers     

Design and characterization of dispersion compensating fiber basedon the LP01 mode

The practical implementation of erbium-doped fiber amplifiers with gain at 1.55 μm allows long unrepeatered transmission distances. However, in order to realize high data rates over these distances with already installed standard single mode fiber, techniques must be found to overcome the pulse spreading due to the positive chromatic dispersion of the transmission fiber in this window, we review a compensation technique based on propagating the signals through a specially designed fiber with large negative dispersion for the LP₀₁ mode, thereby ending up with zero net pulse spreading. The basis of the concept are discussed and a key figure of merit for dispersion compensating devices is defined. The design and optimization of dispersion compensating (DC) fiber is described with special attention to practical concerns including packaging and manufacturability. We describe experimental fabrication results of DC fiber, results of using the fiber to make compact dispersion compensating modules, and the outcome of recent systems experiments incorporating the fiber     

X频段FET混频器的仿真设计

主要研究X频段下变频场效应管(FET)混频器的设计与仿真,利用谐波平衡法和变换矩阵法对FET漏极混频器的工作原理进行分析,根据设计要求选取合适的FET管,运用先进设计系统(ADS)软件对电路进行设计、仿真优化和加工测试。测试结果表明,在射频频率为12.3 GHz~13.2 GHz,中频频率为1.6 GHz~2.5 GHz时,变频损耗小于5 dB。     

X-parameter measurement on a GaN HEMT device: complexity reduction study of load-pull characterization test setup

Characterization of power transistors is an indispensable step in the design of radio frequency and microwave power amplifiers. A full harmonic load-pull measurement setup is normally required for the accurate and comprehensive characterization of RF power transistors. The setup is usually highly complex, leading to a relatively high hardware cost and low measurement throughput. This paper presents X-parameter measurement on a gallium nitride(GaN) high-electron-mobility transistor and studies the potential of utilizing an X-parameter-based modeling technique to highly reduce the complexity of the harmonic load-pull measurement setup for transistor characterization. During the X-parameter measurement and characterization, load impedance of the device is tuned and controlled only at the fundamental frequency and is left uncontrolled at other higher harmonics. However,it proves preliminarily that the extracted X-parameters can still predict the behavior of the device with moderate to high accuracy, when the load impedance is tuned up to the third-order harmonic frequency. It means that a fundamental-only load-pull test setup is already enough even though the device is to be characterized under load tuning up to the third-order harmonic frequency, by utilizing X-parameters.     

Electrical and reliability characterization of metal-gate/HfO2/Ge FET’s with Si passivation

Field-effect transistors with metal gate and HfO₂ gate dielectric on silicon-passivated germanium substrate are studied. Capacitance-Voltage characteristics show lower gate capacitance at negative gate voltages, irrespective of the device channel polarity. Possible mechanisms for this asymmetry are discussed. Reliability of the metal/high-k gate stack on sub-micron p-channel transistors is evaluated. Time-dependent dielectric breakdown analysis indicates comparable gate-stack quality on germanium and silicon substrates.     

Millimeter-wave generation and characterization of a GaAs FET byoptical mixing

Coherent mixing of optical radiation from a tunable continuous-wave dye laser and a stabilized He-Ne laser was used to generate millimeter-wave signals in GaAs FETs attached to printed-circuit millimeter-wave antennas. The generated signal was further down-converted to a 2-GHz IF by an antenna-coupled millimeter-wave local oscillator at 62 GHz. Detailed characterizations of power and S/N under different bias conditions have been performed. This technique is expected to allow signal generation and frequency-response evaluation of millimeter-wave devices at frequencies as high as 100 GHz     

Offset averaging in flash and folding A/D converters using second-order active resistive networks

A novel approach to average the random offsets in flash and folding A/D converters is introduced. The proposed method uses second-order active resistive networks and, compared to previously reported methods employing passive resistive grids, a better offset reduction is achieved without sacrificing the signal gain. Both behavioural and transistor-level simulation results confirm the performance of the proposed technique.     

Performance characterization of polarimetric active radarcalibrators and a new single antenna design

Several topics associated with the use of a polarimetric active radar calibrator (PARC), which is a high radar-cross-section transponder with a known scattering matrix, are addressed. The first involves experimental measurements of the magnitudes and phases of the scattering-matrix elements of a pair of PARCs that operate at 1.25 GHz and 5.3 GHz. The measurements were conducted over a wide range of incidence angles (relative to the boresight direction) in the azimuth, elevation, 45°, and 135° planes. The 5.3-GHz PARC, which consisted of two antennas placed several wavelengths apart, exhibited symmetrical patterns with no ripples and excellent isolation between orthogonal polarization channels. The 1.25-GHz PARC, whose antennas were in very close proximity to one another, exhibited unsymmetrical patterns as well as ripples in the phase patterns, thereby introducing errors in the elements of the scattering matrix. To avoid this problem, a single-antenna PARC is designed,, using an orthomode transducer. The single-target calibration technique is extended so that it applies to the use of a PARC as well as reciprocal passive calibration devices such as spheres and trihedral corner reflectors     

Large-signal computer-aided analysis and design of silicon bipolarMMIC oscillators and self-oscillating mixers

A large-signal analysis and design of silicon bipolar monolithic microwave integrated circuit (MMIC) feedback oscillators and self-oscillating mixers are discussed. Emphasis is placed on the modeling of the active and passive devices and the large-signal analysis and design of nonlinear circuits using SPICE. Measured and simulated data of a C-band self-oscillating mixer are presented     

Ge APD/GaAs FET/op-amp transimpedance optical receiver design having minimum noise and intersymbol interference characteristics

The recent commercial availability of broadband linear-phase operational amplifiers has allowed a new high-bit-rate transimpedance optical receiver design to be realised. This design allows the convenient optimisation of the receiver frequency response for minimum noise and intersymbol interference. Practical sensitivities of ?49.3 dBm (70% QE) at 140 Mbit/s and 1.52 ?m have been routinely achieved using packaged components and 30 ?m-diameter Ge p+n APDs.