Coaxial Test Fixture Research Articles

Multi-layer low frequency tissue equivalent phantoms for noninvasive test of shallow implants and evaluating antenna-body interaction.

In this work, a tissue equivalent compound phantom with dielectric properties equivalent to an average human body surface has been developed for a low frequency operating range of 30 MHz to 200 MHz. The compound phantom consists of skin, fat, and muscle layers respectively. The phantom is simple to fabricate with low cost components. A custom coaxial test fixture has been developed to characteristic phantom dielectric properties, which eliminates use of a specialized expensive dielectric measurement probe. The proposed composite phantom can be used as a noninvasive technique to evaluate shallow biomedical implants, antenna-body interaction, and specific absorption rate of tissue media.

Technique of Coaxial Frame in Reflection for the Characterization of Single and Multilayer Materials with Correction of Air Gap

Techniques based on fixture probes in reflection are used in microwave reflectometry as a novel diagnostic tool for detection of skin cancers, for complex permittivity measurements on liquid samples and oil shale, and for complex dielectric permittivity of animals’ organs and tissues measurements in microwave band for the needs of modern veterinary medicine. In this work, we have developed a technique to characterize multilayer materials in a broadband frequency range. A coaxial probe in reflection has been specially developed for microelectronic substrate. Using SMA connector, loss tangent of 10−4and relative permittivity have been measured with an error of 0.145%. The extension of the coaxial probe in reflection technique to multilayer substrates such as Delrin and Teflon permitted to measure bilayer material provided the good knowledge of electrical parameters and dimensions of one layer. In the coaxial transmission line method, a factor that greatly influences the accuracy of the results is the air gaps between the material under test and the coaxial test fixture. In this paper, we have discussed the influence of the air gaps (using samples of 0.5 mm air gaps) and the measures that can be taken to minimize that influence when material is measured. The intrinsic values thus determined have been experimentally verified. We have described the structure of the test fixture, its calibration issues, and the experimental results. Finally, electromagnetism simulations showed that the best results can be obtained.

The effects of fabric lamination angle and ply number on electromagnetic shielding effectiveness of weft knitted fabric-reinforced polypropylene composites

Abstract In this study, it was aimed to investigate the effects of fabric lamination angle and fabric ply number on electromagnetic shielding effectiveness (EMSE) of weft knitted fabric-reinforced polypropylene composites. Knitted fabric-reinforced composites are composed of aramid yarn, polypropylene yarn, and copper wire. Polypropylene is the matrix phase and the aramid yarn and copper wires are the reinforcement phase of the composite materials. It was achieved to form 1.5 to 3 mm thickness composites. The composites have nearly 20–50 dB electromagnetic shielding values. To form the knitted fabrics, 7G semiautomatic flat knitting machine was used. The composites were formed by a laboratory-type hot press. EMSE of composites were tested by using ASTM D 4935 coaxial test fixture in 27–3000 MHz frequency band. Lamination angle and ply number parameters were examined related to EMSE of structures. For this study, three different structures were knitted and named as plain knit, 1×1 rib knit, and half cardigan knit. To determine the effect of lamination angle of composites on electromagnetic shielding performance, the composites were produced in two different lamination angles as 0°/90°/0°/90° and 0°/45°/0°/45°. To determine the effect of fabric ply number of composites on electromagnetic shielding performance, the composites were produced in two and four plies. It was observed that the fabric ply number and lamination angle does not affect the EMSE of composite materials very much. It was determined that weft knitted reinforced composite structures have appropriate and high EMSE values for electromagnetic applications. This knitted fabric-reinforced polypropylene composites are flexible and suitable for other industrial applications as civil engineering, aerospace, etc.

Determination of electromagnetic shielding performance of plain knitting and 1X1 rib structures with coaxial test fixture relating to ASTM D4935

In this study, electromagnetic shielding effectiveness of some weft‐knitted structures is investigated. For this purpose, weft‐knitted structures are produced using copper wire/cotton incorporated yarns. Conductive yarns are produced by yarn‐folding machine. Four knitted constructions (plain knitting, weft in‐laid plain knitting, 1X1 rib, and weft in‐laid 1X1 rib) are formed into knitted structures with conductive yarns by using 7G flat knitting machine. Electromagnetic shielding values of test samples are determined by a coaxial test fixture relating to ASTM D4935 test standards. Measurements are made in the frequency range of 27 MHz–3 GHz. The effect of conductive content, stitch density and fabric construction parameters are investigated considering the electromagnetic shielding performance of weft‐knitted structures. Test results show that weft‐knitted structures investigated in this study have 10–40 dB shielding effectiveness under the frequency of 500 MHz.

Experimental Study of Electrical Properties of Oil-Based Mud in the Frequency Range From 1 to 100 MHz

Summary Formation-resistivity measurements in boreholes require accurate knowledge about the electrical properties of drilling fluid to exclude any measurement misinterpretations. For many drilling applications, oil-based mud is the preferred drilling fluid because of properties that include excellent shale stability, corrosion inhibition, lubricity, reusability, resistance to contamination, and higher rate of penetration. Although the electrical resistivity of oil-based mud is generally high, it depends on many parameters. We studied electrical resistivity and dielectric permittivity of oil-based muds as a function of frequency and temperature with varying oil and salt content and varying oil/water ratio. Measurements were performed by use of a coaxial test fixture and an impedance analyzer. The accuracy of the measurement system has been determined using standard materials such as air, deionized (DI) water, methanol, n- butanol, and n-octanol. The analysis shows that published models dealing with electrical properties of rocks can be compared well with those of oil-based muds. Resistivity and relative permittivity decrease with increasing temperature and frequency. No clear relationship is revealed between resistivity and water content, but relative dielectric permittivity does depend on water content of oil-based muds. Oil and salt content are of secondary importance. The study shows that the relative dielectric permittivity is related exponentially to the oil/water ratio of oil-based muds, which provides a means of estimating dielectric permittivity of oil-based mud if the oil/water ratio is known.

40 Gbit/s differential distributed modulator driver realised in 80 GHz SiGe HBT process

A 40 Gbit/s, fully differential distributed SiGe HBT driver is presented. The IC is realised in a low-cost 80 GHz production process, and is intended to operate as a modulator driver in a 40 Gbit/s fibre-optic communication system. Resulting from the differential chip architecture, no off-chip low-frequency transmission line termination networks are required, which significantly alleviates the chip mounting process. Mounted in a coaxial test fixture, an eye opening of 2×1.25 Vpp at 40 Gbit/s operation is measured.

High-frequency input impedance characterization of dielectric films for power-ground planes

Broadband impedance characterization of high dielectric constant (high-k) films was performed using a coaxial test fixture configuration. The presented coaxial test fixture and broadband measurement methodology of impedance for high-k films minimizes systematic uncertainties by reducing the interconnection inductance and improving the calibration procedure. In the APC-7 configuration, the technique enables accurate evaluation of impedance at frequencies of 100 MHz to 10 GHz with resolution of 0.01 /spl Omega/. The electrical characteristic of high-k films was found to be consistent with a capacitive load without significant contribution from the circuit inductance that typically dominates the high-frequency response. The experimental data and numerical simulations showed that high-k organic-ceramic composite materials could considerably suppress resonant behavior of the power-ground planes. It was found that high-k organic resins filled with ferroelectric ceramic powders exhibit a high-frequency dielectric loss that increases with increasing volume fraction of the ceramic component. The dielectric dispersion and the corresponding dielectric loss of organic-ceramic hybrid materials can serve as an effective mechanism for suppressing the resonant standing waves in power-ground planes.

Control of conductivity at microwave frequenciesin a poly(aniline hydrochloride)-silver-polymer electrolyte composite material

The fabrication of a conducting polymer-silver-polymer electrolyte composite material is described. Discs of the material mounted in a coaxial test fixture exhibit changes in their microwave impedance caused by an applied DC electric field. An explanation for the observed phenomena in terms of an electrochemical cell is suggested.

Hybrid inductor modeling for successful filter design

A method for deriving accurate L-band inductor models using I-port fixtured S-parameter measurements is presented, along with examples of successful filter designs using the models. Models were developed for a number of surface-mount and leaded devices with values ranging from 4.7 nH to 470 nH. The devices were measured in a coaxial test fixture on an HP8510B network analyzer, with fixture de-embedding performed using CAD software. The models are seen to fit measured data over a broadband, from low RF through resonance. To further validate the models, several filter circuits were developed and fabricated. The results of 5th- and 9th-order lowpass filter designs are presented here. The 9th-order filter was optimized for the desired performance using the parasitic inductor models. Measurements confirm that the use of the models led to a successful design on the "first pass." Finally, simulations show that this success would not have been achieved without the developed inductor models.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Diode characterization in a coaxial mount

AbstractA previously presented technique for experimentally characterizing packaged microwave diodes mounted in a coaxial test fixture is investigated. It is demonstrated that the fields surrounding the diode and the calibration packages are adequately developed to provide an accurate diode equivalent circuit model for use in computer‐aided design. © 1993 John Wiley &amp; Sons, Inc.

A coaxial test fixture for characterizing low‐impedance microwave two‐terminal devices

AbstractA technique using a coaxial diode test fixture for the mount‐independent characterization of potentially unstable two‐terminal devices is presented. A standard three‐terminal calibration procedure using reference packages is used to calibrate to the surface of the packaged device. The test fixture is designed to present a low, nonresonant impedance to the device so that measurement resolution is enhanced. The characterization of an IMPATT diode is presented as an example. © 1993 John Wiley &amp; sons, Inc.

Simulating the Effects of Plasma Disruption with A 1 MA Current Pulse in a Coaxial Test Fixture

A test fixture for simulating plasma disruptions, comprising two coaxial cylinders, has been designed for use with Argonne's electromagnetic test facility FELIX. A pulsed power supply drives a half cycle sine wave current of 106 A through the test fixture generating fields of ≤ 2 T and field changes of Ḃ ≤ 1250 T s−1. The coaxial structure is 140 cm long, has an outer cylinder with an OD of 78 cm and an inner cylinder with an OD of 8.3 cm. It is surrounded by the FELIX solenoid field of 1 T. This proposed upgrade of the FELIX facility should be useful for testing the effect of plasma disruption on First Wall-Blanket-Shield (FWBS) structures; a future upgrade of the solenoid field to 4 T will allow to simulate reactor conditions even better.

Coaxial Test Fixture and Pulsed Power Supply for Contact Material Screening Testsa

A coaxial test fixture and a pulsed power supply have been built to conduct high-current screening tests on candidate materials for contacts to be used in first wall connectors on fusion devices, particularly tokamaks. The fixture was operated with half-sine-wave pulses of less than or equal to 300 kA; it is designed for carrying currents of up to 600 kA for approximately 300 ms at a repetition rate of 1 pulse every 5 minutes. The fixture is built as a vacuum vessel and capable of testing specimens in an ambient temperature of 300/sup 0/C. Instrumentation is provided to measure the current pulse, contact voltage drop, contact pressure, the strain caused by contact pressure, and the operating temperature. The test fixture, its power supply and possible future upgrades are described.

Wide-Bandwidth Test Fixture for Electromagnetic Beam Sensors

The Fusion Materials Irradiation Test (FMIT) accelerator will provide an intense deuteron beam at 35 MeV (ß = 0.19). The beam, following a stripping reaction on a lithium target, will supply the neutron flux required for studying materials that may be used in a fusion environment. The diagnostic measurement instrumentation, which will characterize the accelerator beam, must be noninterceptive because of the beam's power density. Instrumentation also must be fully functional for start up of the FMIT accelerator. To this end, a test facility was needed to examine signals from diagnostic probes that sense electromagnetic fields emanating from the charged particle beam. The test facility also will help evaluate the probes' corresponding measurement systems before final assembly into the beamline. Three types of test facility were proposed: (1) a low-energy electron accelerator, (2) a large "electron-gun assembly," and (3) a coaxial structure that produces electromagnetic fields similar to that of the proposed FMIT accelerator. The third type was chosen because the design and fabrication could be done at Los Alamos and Types (1) and (2) would be more costly. The coaxial structure can carry the impulse currents required but cannot model the FMIT accelerator charged-particle bunch velocities accurately. However, one may introduce a highly resistive dielectric material into the coaxial test fixture so that its electromagnetic-wave velocities match those of the accelerator's particle-bunch velocities. This paper describes the design and some experimental results of the coaxial test fixture.