Contactless Characterization Method Research Articles

Contactless Method to Estimate Antenna Efficiency in a Reverberation Chamber

Measuring the efficiency of electrically small antennas and integrated antennas is challenging, since for electrically small antennas, the probe may significantly affect the results and for integrated antennas, establishing a connection with the integrated antenna is in many cases not possible. Therefore, a contactless method to estimate the efficiency of electrically small antennas and integrated antennas is necessary. This paper proposes a novel method to estimate antenna efficiency contactlessly using a reverberation chamber: the contactless efficiency method. In the contactless efficiency method, we combine the two-antenna method with the contactless characterization method, to estimate the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">S</i> -parameters contactlessly. To validate the results, the contactless efficiency method measurements are compared to the measurements of the widely-used two-antenna method and for both methods an uncertainty analysis is performed. Results show a good agreement in the 95% confidence interval between the contactless efficiency method and the existing connectorized method for both the total antenna efficiency and the radiation antenna efficiency. The uncertainty of the contactless efficiency method with a 95% confidence level is below 6% for the whole 0.55 GHz to 1.05 GHz frequency band.

Zinc sulfate hydrates characterization by terahertz time domain spectroscopy

Hydrates, which commonly appear in drugs, are undesirable because they may affect the stability and even efficacy of drugs to some extent. To efficiently identify the hydrates, we demonstrate a contact-less characterization method of Zinc sulfate hydrates with different water contents based on the all-fiber terahertz time-domain spectroscopy (THz-TDS). By using the continuously varying THz spectra with high resolution, the thermal dehydration process of hydrates has been accurately monitored. The THz spectra of anhydrous and different crystalline hydrates exhibit significant differences. A series of experiments on hydrate characterization confirm the unique advantages of the THz-TDS in quality control of drug.

Determining the input reflection coefficient of integrated antennas using over-the-air measurements under near-field conditions

AbstractOne of the current trends in the integrated circuit (IC) development is the integration of antennas on-chip or in the package of the IC. This poses challenges in the production testing process of the packaged IC, as the antenna functionality has to be included and at least one of the signal ports cannot be accessed at a conducted manner. In order to measure the reflection coefficient of an integrated antenna, a contactless characterization method (CCM) can be used. In this paper, the practicality of a CCM is assessed, having the application of a cost-effective high-volume testing procedure for integrated antennas in mind. It is shown that the CCM yields accurate results for different imperfections in the measurement setup. Moreover, measurement results around 33 GHz using a connectorized patch antenna are shown, which experimentally verify the validity of using the CCM under near-field conditions.

Verification of a Contactless Characterization Method for Millimeter-Wave Integrated Antennas

The characterization of integrated antennas is challenging as they usually do not provide a suitable direct interface for the measurement equipment. Adding a connector or using on-wafer probes to interconnect to the measurement system often results in a change in antenna characteristics and requires a separate prototype resulting in additional complexity and associated costs. In order to measure the input impedance and realized gain of an integrated antenna, a contactless characterization method (CCM) can be used. In this article, the CCM is applied to an open-ended waveguide (OEWG). The OEWG operates in the $K_{a}$ -band and has a gain similar to typical integrated antennas. A good match between the reference measurements and the CCM is achieved, making this method potentially useful for the characterization of integrated mm-wave antennas.

Measurement-Based Thermal Modeling Using Laser Thermography

There have been several studies in using infrared thermography for nondestructive evaluation and testing of materials. Some studies have explored the potential of using thermography for classification of materials based on their thermal response. However, the modeling behind these efforts is rather simplistic, and in some ways not corresponding well with practical applications. This paper presents a realistic model-based approach for characterizing unknown materials using laser thermography. The process being modeled is laser excitation step thermography with finite but not infinitesimal excitation length and uniform distribution over a finite radius. A mathematical model, based on the heat equation that governs the flow of heat in materials, is introduced to characterize objects based on their response to thermal excitation. Experimental results consistently demonstrated the ability of the proposed approach to classify different materials based on their thermal properties. This contactless characterization method might prove to be suitable for a range of applications including teleoperation, haptic mapping and multimodal human computer interaction.

Graphene Characterization by Hilbert-Huang Transform-Based Terahertz Spectroscopy

We demonstrate a contact-less characterization method of monolayer graphene (MG) with all-fiber terahertz time-domain spectroscopy (THz-TDS) based on the Hilbert–Huang transform (HHT). The MG was grown on a Cu foil by chemical vapor deposition and then transferred to the poly (ethylene terephthalate) substrate by polymethyl methacrylate-assisted wet transfer. In our THz-TDS system, the time-domain pulse signal through MG is decomposed into eight components called the intrinsic mode functions (IMFs). It is found that the decomposed low-order modes are related to the original MG signal oscillations, whereas the other high-order modes correspond to the noise. The first IMF component can be used to extract the apparent graphene absorption peak near 0.7 THz, which could be more obvious with superposition of the second IMF due to the increasing spectral amplitude in the lower frequency range. The proposed HHT-based THz-TDS provides a more efficient way for graphene characterization.

Contactless characterization of metastable defects in Cu(In,Ga)Se2 solar cells using time-resolved photoluminescence

The authors present a contactless optical characterization method for the study of metastable defects in Cu(In,Ga)Se2 solar cells. A methodology for the analysis of time-resolved photoluminescence (TRPL) signals is presented. It leads to the observation of a hysteresis phenomenon regarding the minority carrier dynamics following the activation of the metastable defects. The amplitude of the hysteresis phenomena was compared between CIGS solar cells with different absorber/buffer layer interface properties. It is in these particular spatial regions where the metastable defects can be mostly found. The developed contactless characterization method was compared with classical current–voltage measurements. TRPL leads to a more complete understanding of the physics of metastable defects in terms of quantifying the shift in minority charge carriers dynamics that it induces.

Theoretical study of time-resolved luminescence in semiconductors. I. Decay from the steady state

Time-resolved luminescence (TRL) is a non-destructive, non-invasive, and contactless characterization method. We studied TRL decay on semiconductor layers and thin film homostructures after a steady state illumination by simulation with Synopsys TCAD® and by analytical approximate solution of the appropriate equations. First, we show that the luminescence decay time in general equals the minority carrier lifetime only for a homogeneous and time-independent carrier lifetime. Then, we investigate the influence of photon recycling, injection level, charge carrier diffusion, defects in the bulk and at the surfaces, as well as space charge on the TRL decay separately by quasi one-dimensional simulations of semiconductor layers and semiconductor homostructures. We further study the influence of sample non-homogeneity as may be found in polycrystalline semiconductors. We show how carrier lifetime can be extracted from the TRL transients and how the samples can be characterized by excitation dependent measurements in the open circuit case. We can explain some effects found in luminescence experiments, like a decrease of the decay time with an increasing excitation, a maximum in the decay time due to saturated bulk-defects and curved luminescence transients due to high injections or sample inhomogeneities. Furthermore, we are focussing on the question, how single layers within a semiconductor stack can be characterized.