HBT optoelectronic mixer at microwave frequencies: modeling andexperimental characterization

A heterojunction bipolar transistor (HBT) optoelectronic mixer was studied experimentally and theoretically. A detailed large signal π-model and a small signal analysis are described. The frequency dependence of down and up conversion has been analyzed and measured. In terms of conversion gain, the advantage of the down conversion process is clearly demonstrated. The values of parameters employed in the mixing process are also discussed for both large and small signal regimes     

Transmission through abrupt heterojunction potential barriers

A new expression is derived for the transmission coefficient of incident electrons scattered by a varying potential with discontinuities. The expression is applicable above, below, and near the potential peak. As an example, electron transmission across the energy barrier in the emitter of an InP/InGaAs heterojunction bipolar transistor is calculated. Excellent agreement with a numerical calculation is obtained, even for electron energies close to the potential peak, where other expressions fail. It is shown how this new approach reduces to other expressions in limiting cases, and its validity in comparison to other approximations is discussed     

An 18-GHz continuous-time Σ-Δ analog-digital converterimplemented in InP-transferred substrate HBT technology

We report an 18-GHz clock-rate second-order continuous-time Σ-Δ analog-digital converter (ADC) implemented using InP-transferred substrate HBTs. Under two-tone test conditions, the ADC achieved 43 dB and 33 dB SNR at signal frequencies of 500 MHz and 990 MHz, respectively. The IC occupied 1.95 mm² die area and dissipated ~1.5 W     

On solving the Lyapunov and Stein equations for a companion matrix

When the matrix A is in companion form, the essential step in solving the Lyapunov equation PA + A^TP = −Q involves a linear n × n system for the first column of the solution matrix P. The complex dependence on the data matrices A and Q renders this system unsuitable for actual computation. In this paper we derive an equivalent system which exhibits simpler dependence on A and Q as well as improved complexity and robustness characteristics. A similar results is obtained also for the Stein equation P − A^TPA = Q.     

Electron transport in heavily doped bases of InP/GaInAs HBT'sprobed by magneto transport experiments

Magneto transport experiments were carried out to study electron transport in the p-type base of InP/GaInAs heterojunction bipolar transistors (HBT's). Electron minority carrier mobility was measured in the °K for two dopant concentrations in the base. The experimentally obtained mobility is compared to the theoretically predicted one. The scattering mechanisms considered in the calculations are screened ionized impurity scattering, alloy scattering, and coupled plasmon polar optical phonon scattering. The latter is calculated in the random phase approximation. The Boltzman transport equation (BTE) is solved to obtain the ratio between the measured mobility and the drift mobility. Good agreement was obtained between the measured results and the calculated ones for temperatures above 100 °K. At lower temperatures the calculated results differ from the experimental ones, probably due to hot electron effects     

Submicron scaling of HBTs

The variation of heterojunction bipolar transistor (HBT) bandwidth with scaling is reviewed. High bandwidths are obtained by thinning the base and collector layers, increasing emitter current density, decreasing emitter contact resistivity, and reducing the emitter and collector junction widths. In mesa HBTs, minimum dimensions required for the base contact impose a minimum width for the collector junction, frustrating device scaling. Narrow collector junctions can be obtained by using substrate transfer or collector-undercut processes or, if contact resistivity is greatly reduced, by reducing the width of the base ohmic contacts in a mesa structure. HBTs with submicron collector junctions exhibit extremely high f_max and high gains in mm-wave ICs. Transferred-substrate HBTs have obtained 21 dB unilateral power gain at 100 GHz. If extrapolated at -20 dB/decade, the power gain cutoff frequency f_max is 1.1 THz. f_max will be less than 1 THz if unmodeled electron transport physics produce a >20 dB/decade variation in power gain at frequencies above 110 GHz. Transferred-substrate HBTs have obtained 295 GHz f_T. The substrate transfer process provides microstrip interconnects on a low-ϵ_r polymer dielectric with a electroplated gold ground plane. Important wiring parasitics, including wiring capacitance, and ground via inductance are substantially reduced. Demonstrated ICs include lumped and distributed amplifiers with bandwidths to 85 GHz and per-stage gain-bandwidth products over 400 GHz, and master-slave latches operating at 75 GHz     

Estimation of Frequency for AM/FM Models Using the Phase Vocoder Framework

This paper proposes an extension of the applicability of phase-vocoder-based frequency estimators for generalized sinusoidal models, which include phase and amplitude modulations. A first approach, called phase corrected vocoder (PCV), takes into account the modification of the Fourier phases resulting from these modulations. Another approach is based on an adaptation of the principles of the time-frequency reassignment and is referred to as the reassigned vocoder (RV). The robustness of the estimation against noise is studied, both theoretically and experimentally, and the performance is assessed in comparison with two state-of-the-art algorithms: an unmodified version of the reassignment method and a quadratically interpolated fast Fourier transform method (QIFFT).     

Reduced order IIR approximation to FIR digital filters

An algorithm for designing an infinite-impulse-response (IIR) stable filter using a finite-impulse-response (FIR) given filter, with the objective of reducing the delay and order, is described. The design is in the time domain using the least-squares-inverse algorithm, which is briefly described. In this method, the numerator of the approximated filter is part of the FIR filter itself and no calculations and minimization are needed to find the numerator coefficients (except finding the FIR roots). An error analysis between the given FIR and approximated IIR filters is provided. This error analysis enables the designer to fix a design parameter, often unnoted, keeping the energies of the approximated and original filters equal. Results and two illustrative examples are presented     

Modified output error identification-elimination of the SPRcondition

In this note, we present a modified adaptive output error algorithm for identification. We refer to both the continuous time and the discrete time cases. In the standard algorithm, stability requires that a certain transfer function should be strictly positive real (SPR); however, in the present algorithm, the SPR condition, which is difficult to satisfy, is eliminated. This is achieved by adding a fixed feedback gain. When there exists an a priori partial knowledge about the parameters of the plant, we provide a simple procedure to design that gain. An illustrative example comparing the modified algorithm to the standard one is provided