Wansheng Su

Design and evaluation of a coaxial transmission line fixture to characterize portland cement concrete

Abstract Electrical characterization of portland cement concrete (PCC) is necessary for reliable operation of many electromagnetic nondestructive evaluation (NDE) techniques. Examples of such techniques include ground penetration radar (GPR). For that purpose, PCC specimens were cast, and their complex permittivity and magnetic permeability were measured over a wideband of frequencies (1 MHz to 10 GHz) using both time domain and frequency domain measurement techniques. As part of an ongoing research project, three set-ups to measure the dielectric properties of PCC were designed. The measurements are carried out over a frequency range of 0.1 MHz to 10 GHz. The three different set-ups are parallel plate capacitor (0.1 MHz–40 MHz), coaxial transmission line (0.1 GHz–1 GHz), and TEM horn antenna (0.5 GHz– 10 GHz). This paper discusses the development of the coaxial transmission line fixture. It was designed to allow the evaluation of large PCC specimens and obtain an average effect of PCC components. A time domain reflectometry (TDR) setup was used in the design of the fixture and in testing its performance. A calibration scheme was developed and used to calibrate the fixture. Using a two-port S-parameter model, the complex permittivity and magnetic permeability of the PCC specimens were evaluated by frequency domain measurement. Time domain measurement techniques were based on one-port S-parameter model. Evaluation of the set-up using especially molded PCC specimens showed that curing status can be detected at a lower frequency using the imaginary component of the relative permittivity.

Velocity of an RF pulse signal propagating in a waveguide

An RF pulse signal has been used to investigate the velocity of a wave propagating in a waveguide. Contrary to a recent report, the measurements demonstrate that an RF pulse signal cannot travel faster than light. The energy of the signal is transported at the subluminal group speed that can be measured.<<ETX>>

Supplement to "Velocity of an RF pulse signal propagating in a waveguide"

An experiment was conducted in order to investigate the possible differences between velocity measurements based on the leading edge and falling edge of an RF pulse propagating in an air-filled waveguide. The experiment was performed using a test setup identical to that previously used by the authors (see ibid., vol. 2, p. 255-6, June 1992), except that two PSPL Model 5810 pulse amplifiers were used to enhance the signal amplitude. The experimental observations demonstrate that there are no significant propagation velocity differences between leading edge and falling edge measurements.<<ETX>>

Plastic packaging modeling and characterization at RF/microwave frequencies

Summary form only given. At high frequencies, material properties and properties of signal lines/interconnects are equally important. Thus, the present study deals with material (molding compound) characterization and modeling and characterization of lead frames and bond wires. While the microwave characterization of molding compounds can be utilized in a variety of plastic package structures, the objective of the modeling was to develop an electrical model of the 16 lead SOIC plastic package, which is popular for packaging wireless RFICs. The developed models have been successfully used by ITT GTC in developing a new generation of power amplifier RFICs. Measurement results, error analysis, and time domain package modeling techniques are presented.

Detecting flaws in Portland cement concrete using TEM horn antennae

To understand the dielectric properties of PCC and better correlate them with type and severity of PCC internal defects, a study was conducted to evaluate PCC complex permittivity and magnetic permeability over a wideband of frequencies using both time domain and frequency domain techniques. Three measuring devices were designed and fabricated: a parallel plate capacitor, a coaxial transmission line, and transverse electromagnetic (TEM) horn antennae. The TEM horn antenna covers the microwave frequencies. The measurement technique involves a time domain setup that was verified by a frequency domain measurement. Portland cement concrete slabs, 60 by 75 by 14 cm, were cast; defects include delamination, delamination filled with water, segregation, and chloride contamination. In this paper, measurements using the TEM horn antennae and the feasibility of detecting flaws at microwave frequency are presented.

Wideband electrical characterization and modeling of plastic packaging materials

Summary form only given. The paper presents the efforts performed in the areas of package modeling, and package and material (molding compound) characterization at RF/microwave frequencies. At high frequencies, material properties and properties of signal lines/interconnects are equally important. As such, the presented efforts dealt with material (molding compound) characterization of lead frames and bond wire. While the microwave characterization of the molding compounds performed in this study over a wideband of frequencies can be utilized in a variety of the plastic package structures, the objective of the model development was to develop an electrical model of 16 lead SOIC plastic packages, that gained lately a great popularity for packaging wireless RFICs. The models developed and used will be discussed along with experimental results. In this work, discussion of the techniques validation, the accuracy, the repeatability, and the variability will be conducted. For dielectric materials, such as plastic molding compounds used in RF/microwave packages, their electrical properties can be described by their relative dielectric constant and loss tangent. To measure these properties at microwave frequencies, the two most commonly used techniques are the resonant technique and the transmission line technique. In this paper, both techniques are used to characterize the dielectric properties of the plastic molding compounds. Two measurements techniques, the HP coaxial probe and the stripline resonator were used to characterize the material properties. Several issues related to these techniques will be described.

A time-domain approach for wideband modeling of electronic packages: Research Articles

Low-frequency parameters have important effects on the nonlinear performances of power amplifiers. Injection at the output of a low-frequency-voltage device, following the signal envelope, is proposed. Two-tone simulations, measurements using the principle of a low-frequency active load-pull system, and implementation of the technique are presented.

Application of Time Domain Measurement and Characterization to the Modeling of Leadframes of Plastic Packages for RFIC Devices

This paper presents a time domain measurements and simulation technique for Characterization and modeling of wideband and microwave electronic structures. The technique is successfully applied to the Leadframes of plastic packages for RFIC devices. The modeling process leads to the development of spice-models for the leadframe and wirebonds used in the package and hence enable the designer to improve the circuit performance by considering the packaging effects. Electrical modeling was performed on a 16 lead SOIC plastic package using time domain approach. The developed models have been successfully used by ITT GTC in developing a new generation of power amplifier RFICs.