Small-signal modeling of HBTs using a hybridoptimization/statistical technique

A new formulation for extracting the elements of the small-signal equivalent-circuit model of heterojunction bipolar transistors (HBTs) is proposed in this paper. This approach avoids the main problem of the conventional extraction methods which, in most cases, is the use of brute-force optimization techniques to extract a large number of parameters. At the beginning, this technique first uses the extraction procedure of a low-frequency HBT model. An analytical formulation that allows the reduction of the number of the unknowns of the low-frequency model to only two, which have to be calculated using a suitable optimization technique, is described. This makes the optimization problem much easier to handle and increases the probability for converging to the actual elements of the model, thus avoiding the converging to spurious solutions. Secondly, in order to extend the model to higher frequencies, a statistical approach is proposed to extract parasitic extrinsic elements. An experimental validation is carried out on three HBT devices and satisfactory results are obtained up to 30 GHz     

A CAD-suitable approach for the analysis of nonuniform MMIC andMHMIC transmission lines

A new method of moment-based formulation for the solution of the telegraphist's equations in nonuniform transmission lines is presented. Entire domain basis functions that build in a frequency variation are used to cover wider frequency and physical dimension ranges. The results obtained using the proposed formulation are validated by comparison to those obtained by a CAD package and to measured data. Different nonuniform lines in microstrip and coplanar technologies on monolithic microwave/millimeter wave integrated circuit (MMIC) and miniaturized hybrid microwave integrated circuit (MHMIC) substrates are investigated with an application to the design a matched taper transition in a MMIC coplanar line     

Source-pull/load-pull oscillator measurements at microwave/MM wavefrequencies

A six-port reflectometer with variable test port impedance over 2-6 GHz was designed, built, and tested. The potential use of this reflectometer is in large signal characterization of negative resistance devices and oscillators. Experimental source-pull/load-pull measurements on a commercial oscillator (Rieke diagram) were performed using this reflectometer over the entire Smith chart     

A new DC model of HBT's including self-heating effect suitable forcircuit simulators

This paper presents a new empirical DC model which includes self-heating effects. The expression of the collector current does not explicitly incorporate the junction temperature of the device to aid convergence process and to simplify the equations involved. A comparison of simulated and experimental DC-IV characteristics over the ohmic and active regions demonstrates the accuracy of the model. This model is suitable for optimization purposes and has been implemented in nonlinear circuit simulators, HSPICE and HP-MDS     

A calibration and measurement method of a tri-six-port networkanalyzer suitable for on-wafer characterization of three-port devices

A calibration and measurement method using a wideband tri-six-port network and analyzer (TSPNA) is proposed. The scattering parameters of a three-port device under test are found to be the unknowns of a set of nine simultaneous complex linear equations. These equations are established via a group of three calibrated linearly independent excitations. No isolators are required for calibration and measurement procedures. Three unknown reciprocal two-port standards are needed for the calibration of the TSPNA. The proposed method is rigorous, explicit, and suitable for wideband on-wafer three-port device S-parameter measurements. It can easily be adapted for heterodyne automated network analyzers equipped with three reflection test-set units     

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     

The treatment of ureteroceles complicated by calculi

In a series of 13 adults with calculi in ureteroceles, 10 cases underwent endoscopic meatotomy associated with endoscopic lithotripsy. In 2 bulky ureteroceles with calculi, the authors performed excision of the ureterocele and reimplantation of the ureter. In one case, the authors successfully performed extracorporeal lithotripsy. The authors obtained good results in all cases. Endoscopic meatotomy with lithotripsy is a very useful procedure for treatment of small or medium sized ureteroceles with calculi in adults.     

A Data-Based Nested LUT Model for RF Power Amplifiers Exhibiting Memory Effects

In this letter, a new model is proposed for radio frequency power amplifiers exhibiting memory effects. The model is based on nested look-up tables that compute the estimated amplifier output signal, based on the current input sample and the preceding ones. The model is validated experimentally, using input and output waveforms of a high-power LDMOS based amplifier driven by a multicarrier WCDMA signal. It is shown that the performance of the proposed model is comparable to that of the conventional memory polynomial model. However, the nested look-up table based model significantly reduces the complexity of the identification of the model's parameters, as well as the computational complexity in calculating the estimated output signal.     

Fast and low complexity frequency domain analysis of nonuniform substrate integrated waveguide‐based structures

A novel, low complexity approach for the analysis of nonuniform lossy substrate‐integrated waveguide transmission lines based on the method of moments is proposed. The approach uses frequency‐dependent basis functions derived from the structure's propagation characteristics. Two tapered structures are analyzed, fabricated, and measured to validate the proposed approach. The analytical results of the proposed approach for both structures are compared to those obtained by measurement and by three‐dimensional field simulation. Excellent agreement is observed between the three sets of results with simulation time savings on more than 98% and memory requirement reduction of more than 97%.