Microwave and Millimeter Wave Techniques

Contains reports on three research projects.Joint Services Electronics Program (Contract DAAB07-71-C-0300)National Science Foundation (Grant GP-40485X

Portable automated radio-frequency scanner for non-destructive testing of carbon-fibre-reinforced polymer composites

A portable automated scanner for non-destructive testing of carbon-fibre-reinforced polymer (CFRP) composites has been developed. Measurement head has been equipped with an array of newly developed radio-frequency (RF) inductive sensors mounted on a flexible arm, which allows the measurement of curved CFRP samples. The scanner is also equipped with vacuum sucks providing mechanical stability. RF sensors operate in a frequency range spanning from 10 up to 300 MHz, where the largest sensitivity to defects buried below the front CFRP surface is expected. Unlike to ultrasonic testing, which will be used for reference, the proposed technique does not require additional couplants. Moreover, negligible cost and high repeatability of inductive sensors allows developing large scanning arrays, thus, substantially speeding up the measurements of large surfaces. The objective will be to present the results of an extensive measurement campaign undertaken for both planar and curved large CFRP samples, pointing out major achievements and potential challenges that still have to be addressed

A Dual Reflector Antenna for Point-to-Point System Applications

In this paper design and realization of a dual reflector antenna for receiving internet signal in the point-to-point system is presented. Three different configurations of dual reflector antenna have been considered to obtain the antenna operating in 5.2-5.8 GHz band and having small dimensions. The results of computer simulations and measurements are shown. The design was based on electromagnetic simulations using QW-V2D package (an axisymmetrical version of finite-difference time-domain software). In measurements the method with a reference antenna was used. Additional discussion about using the main reflector of smaller diameter and decreasing spillover radiation was performed

FDTD analysis of magnetized plasma using an equivalent lumped circuit

The paper describes a new approach to electromagnetic analysis of magnetized plasma using finite difference time domain (FDTD) method. An equivalent lumped circuit describing an FDTD cell filled with plasma is developed and applied in the analysis. Such a method is proved more effective than previously reported methods. The new approach is verified on a canonical example of known analytical solution

A Computer-controlled System of High-power Microwave Sources

The paper presents the design and hardware implementation of a computer controlled system composed of up to four high-power microwave sources. Each source provides up to 200 W of continuous wave power. Frequency of each source is stabilized within ±0.5 ppm of the nominal frequency adjustable within 2.35÷2.6 GHz range. All four sources can be synchronized to the same frequency with computer-controlled phase shift between the signals generated by each of them. The paper concentrates on the choice of components for such a system and the properties of the realized hardware implementation

A 100 W ISM 2.45 GHz-band power test system

This paper describes development of solid-state microwave power test system (MPTS) operating over 2.3 to 2.6 GHz with the output power level of 100 W for industrial applications in material processing, and for designing of microwave power industrial equipment. The MPTS unit consists of four major parts: PLL synthesizer, high power solid-state amplifier, detector probes for return losses and leakage measurement and microcontroller. The MPTS system is able to operate in either single fixed-frequency regime, or in swept mode with self-tuning for minimum reflection of a heated load

Analysis and optimization of outputs of high power microwave tubes

The subject of this work is optimization of outputs of L-band high power microwave tubes. These outputs are constructed as coaxial-to-waveguide transitions with a vacuum barrier in a form of glass or ceramic cup. The goal of optimization is to obtain sufficiently low reflection loss in the predefined frequency band and to avoid so called hot spots caused by excessive dissipation of microwave power in parts of the cup. Electromagnetic simulator has been applied to model the behavior of the optimized transition and to propose its optimum shape. The proposed solutions were verified by Z.E. Lamina SA in prototypes of high power (pulsed 600 kW) amplitrons and are to be used in manufacturing practice

Experimental studies of planar metamaterials with a tunable cylindrical TE(01)n mode cavity

Abstract not availableJerzy Krupka, Wojciech Gwarek and John G. Hartnet

Measurements of planar metal-dielectric structures using split-post dielectric resonators

Split-post dielectric resonators were used for the measurement of the complex permittivity and the complex permeability of planar, uniaxialy anisotropic, low- and medium-loss metamaterials at microwave frequencies. Several metamaterials with different metal patterns deposited on dielectric substrates by plasma deposition were investigated, including edge-coupled and broadside-coupled split-rings and circles. It has been shown that, depending on the type of metal pattern and their surface resistance, the metamaterials may exhibit various magnetic and dielectric properties. Several small metamaterial samples were scanned in the cavity electromagnetic field by moving them inside the split-post dielectric resonator. This allowed us to identify loss mechanisms in the samples and to distinguish between their electric and magnetic properties. Our measurements were confirmed by modeling the transmission/reflection characteristics of virtual waveguides containing real metamaterial samples and homogenous samples with the same effective electromagnetic properties as those obtained from the split-post dielectric resonator method using a finite-difference time-domain electromagnetic simulator software package.Jerzy Krupka, Wojciech Gwarek, Norbert Kwietniewski, and John G. Hartnet