G.V. Kopcsay

Broad-band microwave measurements with transient radiation from optoelectronically pulsed antennas

A broadband microwave measurement technique based on picosecond transient radiation from optoelectronically pulsed antennas is described. It is performed with exponentially tapered coplanar stripline antennas which are integrated with the photoconductive devices used for ultrafast pulse generation and sampling. The signal analysis required for deriving the desired physical properties from the measured time-domain waveforms is discussed. This is a coherent technique that independently determines both the real and the imaginary parts of the dielectric constants of materials, from 10 to 130 GHz, in a single experiment. Some representative results are presented. >

Coherent broadband microwave spectroscopy using picosecond optoelectronic antennas

We describe coherent microwave transient spectroscopy experiments using picosecond optoelectronic integrated antennas. The effectiveness of the experimental setup for the measurement of the loss and dispersion properties of materials in the 10–125 GHz range is characterized using microwave filters of predictable behavior. We also present measurements of the absorption coefficient and refractive index of fused silica over this frequency band.

Dielectric properties of uniaxial crystals measured with optoelectronically generated microwave transient radiation

Absorption and dispersion properties of sapphire and crystal quartz between 15 and 130 GHz were measured using the freely propagating transient radiation from optoelectronically pulsed integrated antennas. The polarization sensitivity of the experimental apparatus was characterized and used to obtain the absorption coefficients and refractive indices in the above frequency range for both ordinary and extraordinary beam propagation. We also studied the frequency‐dependent transmission (amplitude and phase) of these two materials as a function of the angle between the electric field and the optic axis.

Anisotropic conductivity in stretch‐oriented polymers measured with coherent microwave transient spectroscopy

Stretch‐oriented and doped polyacetylene and polyaniline are characterized using the coherent microwave transient spectroscopy technique. Conductivities parallel and perpendicular to the direction of elongation are determined. The measured orientation dependence of the sample transmissions are observed to follow the predictions of theory.

Picosecond time-domain electromagnetic scattering from conducting cylinders

The microwave scattering properties of conducting cylinders are characterized by measuring their response to picosecond-duration electromagnetic pulses. The ultrafast electromagnetic transients are generated and detected with optoelectronically pulsed antennas. The time-domain response gives physical insight into the scattering process. In addition, Fourier analysis is used to obtain the frequency dependence of the scattered amplitude and phase from 15 to 140 GHz.<<ETX>>

Microwave diffraction and interference in reflection using transient radiation from optoelectronically pulsed antennas

Broadband (15–130 GHz) microwave interference and diffraction are demonstrated in a reflection configuration using transient radiation from optoelectronically pulsed antennas. The measured complex reflection function of Fabry–Perot interferometers and diffraction from amplitude gratings are presented. The effectiveness of the technique for quantifying the scattering from general three‐dimensional objects is discussed.

Microwave reflection measurements on doped semiconductors with picosecond transient radiation

Broadband microwave reflection spectroscopy using the COMITS (coherent microwave transient spectroscopy) method is described. COMITS is particularly suited to reflection studies because the picosecond transient radiation emitted from planar antennas is strongly linearly polarized. The validity of the technique is verified by reflection measurements on isotropic and anisotropic dielectrics. Reflection studies on a series of doped silicon samples demonstrate that the carrier dynamics in the 15-140-GHz frequency range are well described by a simple Drude model.<<ETX>>

Characterization Of An Experimental Thin-Film Interconnection Structure.

Measurements and simulation of high-speed pulse propagation and cross-talk on an experimental thin-film transmission line structure are presented. The measurements are carried out using both an optoelectronic pulse generation and detection technique, and a recently developed non-contact high-speed sampling method based on a picosecond electron beam. We find through simulation that a quasi-static coupled transmission line model with frequency dependent skin-effect loss accurately predicts the pulse delay and distortion characteristics of our sample.

Picosecond Optoelectronic Study of a Thin Film Transmission Line Structure

In several laboratories high-speed logic circuits which are capable of generating electrical pulses with risetimes in the order of ten picosecond have been demonstrated [1]. Consequently it is now important to be able to transmit these pulses without significant distortion and to be able to characterize the transmission line structures used for this purpose with picosecond time resolution. In addition to the delay and distortion of the pulses as they propagate between generating and receiving points, knowledge of the noise coupled onto adjacent lines is of critical importance to the workings of computers and communication systems. Here we present measurements of high-speed pulse propagation and coupling on an experimental thin film transmission line structure. Photoconductive switches are used for generating and sampling the ultrashort electrical pulses used in this study [2].

Microwave Properties of Anisotropic Materials Characterized with Picosecond Transient Radiation

The anisotropic microwave dielectric properties of uniaxial crystals and stretch-oriented conducting polymers are characterized using the coherent microwave transient spectroscopy technique.