Measurement Of Characteristic Impedance Research Articles

Characterization of Parasitic Impedance in PCB Using a Flexible Test Probe Based on a Curve-Fitting Method

Switching in power semiconductors with emerging materials such as silicon carbide (SiC) leads to undesired overvoltages and oscillations that limit switching frequency, largely due to impedance in the current commutation loop. Minimizing this parasitic impedance in printed circuit boards (PCB) requires precise characterization. To this end, this work presents a new measurement method based on obtaining S-parameters with a vector network analyzer (VNA) and on using a shielded flexible probe with mobile test terminals. The flexible probe uses a metal shielding plane perpendicular to the PCB to prevent the main measurement errors resulting from the variation in the magnetic flux responsible for loop inductance during the VNA frequency sweep. The proposed curve-fitting procedure consists of measuring the characteristic impedance and propagation time of the traces, considering they form ideal transmission lines. These values are used for a nonlinear least squares adjustment for the actual line (with losses). Finally, an experimental assembly with microstrip transmission lines was developed to validate the proposed method experimentally. The experimental results were compared with those obtained by using a rigid test fixture as a reference, those calculated analytically and those obtained from partial element equivalent circuit (PEEC) simulation. The curve-fitting method yields better results than the analytical and the simulation methods and they exhibit (up to 350 MHz) precisions of 1.37% in the characteristic impedance measurement and of 0.81% in the propagation time.

Condition Assessment of I&C Cables in Nuclear Power Plants via Stepped-Frequency Waveform Reflectometry

A nuclear power plant (NPP) depends on instrumentation and control (I&C) systems to ensure its safe and efficient operation. In particular, I&C cables take on the pivotal role of measuring and controlling the critical equipment of the NPP. Thus, it is indubitable that the diagnostic technology of I&C cables for detecting faults and accurately assessing their health status is required for ensuring the safety and reliability of the NPP operation. We propose a diagnostic method that combines fault detection and evaluation algorithm for the I&C cables with stepped-frequency waveform reflectometry with signal propagation and reflection modeling. The signal modeling allows the assessment of the fault with an estimated reflection coefficient by separating the propagation and reflection effects of the measured signal. In short, cable faults are differentiated and quantified regardless of distance. The proposed algorithm is verified by characteristic impedance measurement, various fault detection/evaluation experiments, and the fault evaluation of local accelerated thermal aging cable.

Measurement of characteristic impedance of silicon fiber sheet based readout strip panel for RPC detector in INO

The India-based Neutrino Observatory (INO) is a mega science project of India, which is going to use about 30,000 Resistive Plate Chambers (RPC) as active detector elements for the study of atmoshpheric neutrino oscillations. Each RPC detector will consist of two orthogonally placed readout strip panel for picking the signals generated in the gas chamber. The area of RPC detector in INO-ICAL (Iron Calorimeter) experiment will be 2 m × 2 m, therefore the dimensions of readout strip panel should also be 2 m × 2 m. To get undistorted signals pass through the readout strip panel to front-end electronics, their characteristic impedance should be matched with each other. In the present paper, we describe the need and search of new dielectric material for the fabrication of flame resistant, waterproof and flexible readout strip panel. We will also describe the measurement of characteristic impedance of Plastic Honeycomb (PH) based readout strip panel and Silicon Fiber Sheet (SFS) based readout strip panel in a comparative way, and its variation under loading and with time. Based on this study, we found that a 5 mm thick SFS-based readout strip panel has a minimum signal reflection at 49.5 ohm characteristic impedance value. Our study shows that SFS is a good dielectric material for the purpose.

Measurement Algorithm of Clock Jitter Based on Sequential Equivalent Sampling

For the problem that general characteristic impedance measurement instrument is difficult to measure the size of clock jitter, this paper proposes a measurement algorithm to achieve clock jitter based on sequential equivalent sampling. First, according to the relationship between the equivalent sampling signal and the average signal, we count up the probability density distribution of the clock jitter and use the Tailfit jitter separation techniques to decompose total jitter (TJ) into deterministic jitter (DJ) and random jitter (RJ), then count up the peak-to-peak values of periodic jitter (PJ), cycle-to-cycle jitter (CCJ) and time interval error (TIE) to achieve a precise measurement of clock jitter. Finally we use the test results of jitter analysis software of Tektronix’s TDSJIT3 as a reference to verify the effectiveness of the algorithm. This algorithm provides quantitative analysis means for the stability of characteristic impedance measurement instrument, and provides the reference basis for self-calibration circuit design of subsequent hardware.

Note: Practical monitoring system using characteristic impedance measurement during plasma processing

A method for characteristic impedance monitoring (CIM) is developed for anomaly detection during plasma processing. Advantages of the method include high-sensitivity and real-time monitoring, as well as structural simplicity to install the measurement system in the mass production equipment. To obtain real-time monitoring without time delay, our CIM system consists of a directional coupler and a newly developed vector processing system instead of the conventional high voltage and current probes. The system can measure the time variations of characteristic and load impedances even while the plasma is generated.

Measurement of characteristic impedance and wave number of porous material using pulse-tube and transfer-matrix methods

The time domain implementation of the transfer-matrix method developed by Song and Bolton [J. Acoust. Soc. Am. 107, 1131-1154 (2000)] for measuring the characteristic impedance and wave number of porous materials is described in this paper. The so called Butterworth impulse is generated in a standing wave tube with a flat frequency response over a wide frequency range. With only two microphone measurements, the transfer matrix of porous layers can easily be determined through the calculation of complex amplitudes of incident, reflected, and transmitted pulses. The procedure has been used to measure the acoustical properties of a fiber material, and good agreement was found between measured acoustical properties and predicted results by Delany and Bazley [Appl. Acoust. 3, 105-116 (1971)] semiempirical formulas. Although the error associated with the sample-edge constraint still remains, the new method has a better frequency response as a result of the system calibration process, and the optimal inter-microphone distance is no longer required compared to the frequency domain implementation.

Right ventricular function in scleroderma-related pulmonary hypertension

SSc-associated pulmonary arterial hypertension (PAH) has a poorer prognosis than that of other types of pulmonary hypertension. Recent echocardiographic and haemodynamic studies suggest that right ventriculer (RV) pump function and filling characteristics are altered in SSc-PAH as compared with idiopathic PAH. This could be explained by intrinsic myocardial involvement of the disease, related to abnormal collagen deposition, also observed in the left ventricle, or an increased vulnerability to ischaemia due to coronary vasculopathy, abnormal collagen cross-linking and altered myocyte function. It is also possible that a relatively more important decrease in pulmonary arterial compliance as evidenced by recently reported increased characteristic impedance measurements, would contribute to RV-arterial decoupling. More pathological, imaging and haemodynamic studies are needed for a better understanding for relatively more important vulnerability of the RV in SSc-PAH.

Technique for measurement of characteristic impedance and propagation constant for porous materials

Knowledge of acoustic properties such as characteristic impedance and complex propagation constant is useful to characterize the acoustic behaviors of porous materials. Song and Bolton’s four-microphone method [J. Acoust. Soc. Am. 107, 1131–1152 (2000)] is one of the most widely employed techniques. In this method two microphones are used to determine the complex pressure amplitudes for each side of a sample. Muehleisen and Beamer [J. Acoust. Soc. Am. 117, 536–544 (2005)] improved upon a four-microphone method by interchanging microphones to reduce errors due to uncertainties in microphone response. In this paper, a multiple microphone technique is investigated to reconstruct the pressure field inside an impedance tube. Measurements of the acoustic properties of a material having square cross-section pores is used to check the validity of the technique. The values of characteristic impedance and complex propagation constant extracted from the reconstruction agree well with predicted values. Furthermore, this technique is used in investigating the acoustic properties of reticulated vitreous carbon (RVC) in the range of 250–1100 Hz.

Characterisation and modelling of coplanar transmission lines on SiC substrates

The paper investigates the characteristics of microwave transmission in coplanar waveguides (CPWs) fabricated on various silicon carbide substrates. Propagation constant and characteristic impedance measurements were performed at frequencies from 0.1 to 10 GHz. Different propagation modes are observed as a function of frequency and substrate resistivity. In the case of the low-loss structure, a quasi-TEM equivalent circuit model was developed from the available process parameters, taking into account the effects of electromagnetic fields in CPW structures.

Characterization of broad-band transmission for coplanar waveguides on CMOS silicon substrates

This paper presents characteristics of microwave transmission in coplanar waveguides (CPW's) on silicon (Si) substrates fabricated through commercial CMOS foundries. Due to the CMOS fabrication, the metal strips of the CPW are encapsulated in thin films of Si dioxide. Many test sets were fabricated with different line dimensions, all on p-type substrates with resistivities in the range from 0.4 /spl Omega//spl middot/cm to 12.5 /spl Omega//spl middot/cm. Propagation constant and characteristic impedance measurements were performed at frequencies from 0.1 to 40 GHz, using a vector-network analyzer and the through-reflect-line (TRL) deembedding technique. A quasi-TEM equivalent circuit model was developed from the available process parameters, which accounts for the effects of the electromagnetic fields in the CPW structure over a broad frequency range. The analysis was based on the conformal mapping of the CPW multilayer dielectric cross section to obtain accurate circuit representation for the effects of the transverse fields.

Measurement of sound propagation in glass wool

A new acoustic method for directly measuring the flow resistance, and the compressibility of fibrous materials such as glass wool, is given. Measured results for monochromatic sound in glass wool are presented and compared with theoretically calculated results. The agreement between experimental results and theory is good. Results of measurements of characteristic impedance, attenuation, and phase shift for plane monochromatic traveling waves are presented and compared with theoretically calculated ones. Good agreement between experimental and theoretical results was found.

Measurements of the characteristic impedance of coaxial air line standards

A method for electrically measuring the characteristic impedance of coaxial air line standards is described. This method, called the gamma method, determines the characteristic impedance of a coaxial air line from measurements of its propagation constant and capacitance per unit length. The propagation constant is measured on a network analyzer, and the capacitance per unit length is measured on a capacitance bridge at 1 kHz. The measurements of characteristic impedance with the gamma method are independent of any dimensional measurements. Measurements of the characteristic impedance using the gamma method are compared to theoretical predictions from dimensional measurements. Test results are shown for 14 mm, 7 mm, and 3.5 mm coaxial air lines.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Measurement of the characteristic impedance and propagation constant of materials having high flow resistivity

A technique for the measurement of characteristic acoustical impedance and propagation constant of porous materials is presented. Samples are mounted in an impedance tube and both the surface impedance and a transfer function along the sample length are determined; characteristic impedance and propagation constant may be calculated using these quantities. For this implementation, a classical standing wave procedure is used for the determination of surface impedance. Measurements are obtained for frequencies between 100 and 4000 Hz. A special procedure that makes use of extension tubes, between sample and the fixed part of the impedance tube, is used to achieve the low-frequency results. The new technique yields results that are comparable in accuracy to the ‘‘two-cavity’’ technique described by Utsuno et al. [J. Acoust. Soc. Am. 86, 637–643 (1989)] for samples of low flow resistivity (17.2 and 43.6 cgs-rayl cm−1 ), but substantially better for a sample of higher flow resistivity (380 cgs-rayl cm−1 ).

An analysis of coplanar waveguides with finite conductor thickness-computation and measurement of characteristic impedance

An analysis of coplanar waveguides with finite conductor thickness-computation and measurement of characteristic impedance

An analysis of coplanar waveguides with finite conductor thickness‐computation and measurement of characteristic impedance

AbstractComputer analysis is performed for coplanar waveguides with finite conductor thickness. Such line parameters as the characteristic impedance and effective filling fraction are obtained. Experimental verification is given for the characteristic impedance.Assuming that the line cross section is approximately symmetrical, Laplace's equation is solved by a successive over‐relaxation method for one quarter of the cross section. The characteristic impedance obtained by this approximate method is compared with that obtained by analysis of one half of the cross section with rigorous symmetry and the difference is found to be less than 0.27%. Experimental verification of the characteristic impedance is conducted by correcting the discontinuity between the measurement setup and the line to be measured. The difference between the analytical and experimental results is less than 10%. Approximate analysis by the present method is thus sufficiently accurate. The size of the storage locations in the computer is reduced and the processing time is shortened.

Impedance tube measurement of propagation constant and characteristic impedance of porous acoustical material

In this paper an impedance tube technique is described and evaluated for the measurement of the characteristic impedance and propagation constant of porous acoustical materials. In this method, data are determined under dynamic conditions through the investigation of the standing wave patterns existing in a tube driven at one end by a sound source and terminated at the other end by (1) a sample backed by a rigid wall; (2) a sample backed by an air space, a quarter-wave long, itself terminated in a rigid wall. The validity of the method is assessed by comparing values of characteristic impedance and propagation constant for Owens Corning Fiberglas, type 705, density 6 lb/ft3, obtained in this way to values obtained by two other well-known techniques: Beranek's method and Scott's method. Data were obtained at 800, 1200, and 1600 Hz. The analysis performed on the data obtained by the impedance tube technique and Beranek's method are in agreement at all frequencies. Comparable analyses on the data obtained by Scott's method show agreement with data obtained by the other two techniques only for values of the propagation constant at 1200 Hz and 1600 Hz. The discrepancies observed are attributed to experimental difficulties inherent in Scott's method.

Characteristic impedance measurements of a coplanar waveguide

A coplanar waveguide which consists of a strip of metallic thin film on the surface of a dielectric slab with two ground electrodes running adjacent and parallel to the strip is easily accessible for shunt connections of semiconductor devices. This letter presents experimental data, and a theoretical equation including correction factors, for an effective relative permittivity concerning characteristic impedance. The measurements have been made by the t.d.r. method.