Bogdan Galwas

Planar resonator sensor for moisture measurements

In the paper a model of microwave planar resonator sensor has been presented. The structure of resonator sensor is described. A dielectric material is placed above microstrip ring resonator. As a consequence, the parameters of resonator: resonance frequency, quality factor, and resonance transmission change in relation to the permittivity of the material. The first results of measurements are presented. The sensor may be used for nondestructive measurements of the moisture content of dielectric materials like grain or sand.

Photovaractor for remote optical control of microwave circuits

A photovaractor for the remote optical control of microwave circuits was studied. The photovaractor was fabricated as a p-i-n photodiode placed in a pigtailed fiber optical module. The study of the impedance in the frequency range up to 3 GHz in darkness and under illumination has shown that the photovaractor capacitance strongly depends on the incident optical power. The capacitance variation of the photovaractor diode under illumination is discussed.

Measurement of Reflection Coefficient by Means of Slotted Line and Homodyne Detection System

A new method for measuring the complex reflection coefficient in a measurement system with a slotted line and homodyne detector is presented. The measurement involves the investigation of the change of phase angle of wave voltage along the waveguide terminated with the element under test. The principle of measurement and X-band measurement system consisting of waveguide elements are described. The signal fed to the homodyne detector is subject to the rectangular phase modulation which facilitates the construction of the modulator and increases the accuracy of phase determination. The phase shifter used in the system includes a slotted line. The reduction of the influence of residual reflections on the phase shift determination is described. Even with standard waveguide elements the measuring accuracy of amplitude reflection coefficient is found to be approximately 10-3.

Study of frequency conversion process of two optically transmitted signals to p-i-n photodiodes

Three planar InGaAsP/InGaAs/InP p-i-n photodiodes have been fabricated and used in a frequency conversion process of two optically transmitted signals. Nonlinear properties of the photodiodes have been measured. The differences between photodiode characteristics and obtained frequency conversion product level are discussed.

Analysis of photovaractors for microwave photonic application

The photovaractors for microwave photonic application were studied. The photovaractors were fabricated as a planar p-i-n or metal-semiconductor-metal (MSM) photodiodes placed in a pigtailed fiber optical module. The study of S11 parameters in the frequency range up to 3 GHz under illumination has shown that capacitances of p-i-n and MSM photodiodes strongly depend on the optical power. The capacitance variation of the photo-varactor diode under illumination is discussed.

Investigation of optical-microwave frequency conversion processes for PIN photodiode

Investigations of optical-microwave mixing process performed on a PIN photodetector are reported in the paper. The planar InGaAsP/InGaAs/InP heterostructure PIN photodiode operating at 1.3 /spl mu/m has been used in an optoelectronic mixer configuration. The nonlinear model of the PIN photodiode has been assumed. The parameters of nonlinear equivalent circuit of the device have been extracted from the measured data. The influence of nonlinear responsivity has been considered. The short mathematical analysis, and measurement results are presented.

Idea of six-port vector-voltmeter with homodyne phase-sensitive detectors

A broadband six-port vector-voltmeter concept is presented. Homodyne detection with rectangular phase modulation is used in the measurement system. A mathematical model of the system, which takes into account all the imperfections of system components, is discussed in detail. The principles of the system calibration procedure are described, and the solutions for a six-port structure are given. The concept of homodyne detection with rectangular phase modulation, which is equivalent to double-sideband suppressed-carrier modulation, is presented. The combination of systematic error elimination with high dynamics offered by homodyne detection makes high-accuracy measurements possible.<<ETX>>

Broadband Homodyne Sixport Reflectometer

The paper presents a new concept of the broadband homodyne sixport reflectometer. Homodyne detection with rectangular phase modulation, which is equivalent of DSBSC modulation is used in the measurement system. The mathematical approach of the reflectometer bases on the mathematical analysis of the sixport reflectometer with power meters. Eight real calibration coefficients describe every kind of imperfections of the measurement system. They join output voltages of homodyne detectors with real and imaginary part of a measured reflection coefficient by the linear equations. It affords possibilities for calibrating the measurement system using various calibrating procedures. The principle of operation, the exact mathematical analysis of the sixport homodyne reflectometer, its idea of calibration and measurement results are presented in the paper.

Fiber Bragg Gratings Based Tuning of an Optoelectronic Oscillator

In this paper, we present an opportunity to use fiber Bragg gratings (FBGs) in tuning process of optoelectronic oscillators. The concept involves an optoelectronic oscillator with a set of two FBGs and an optical circulator inserted into its optical path. Presented research results show the influence of the FBG-based tuning solution on the oscillators spectrum for different optical path lengths.

Optically-Switched Microwave Filter with the Use of Photovaractors in Self-Bias Mode

A new type of semiconductor optoelectronic device, which is called as photovaractor, was used in a self-bias mode of operation to obtain an optically-variable impedance. This approach allowed designing an optically-switched microwave band-pass filter. The use of the photovaractor in the microwave structure was investigated. The measurements of the photovaractor, the idea of the self-bias mode, and the simulations of the filter have been presented.