Length Of Coaxial Cable Research Articles

Direct‐Current Circuit Analysis of Time Domain Reflectometry with Variable Coaxial Cable Length for Electrical Conductivity Measurements

Core Ideas Formula of soil EC was simply derived from a multi‐section transmission line at zero frequency. A multi‐section transmission line at zero frequency acted as a direct‐current circuit. The Kirchhoff's voltage law rather than reflection scatter functions was used in the derivation. Formula of soil EC derived from zero frequency was identical to that when frequency approached zero. The improved formula of time domain reflectometry (TDR) with variable coaxial cable length for electrical conductivity (EC) measurements was derived based on the theory of multi‐section transmission line when the frequency was approaching zero. The derivation procedure was quite complicated. The goal of this study was to derive the formula when the multi‐section transmission line was at zero frequency. At zero frequency, the multi‐section transmission line became a direct‐current circuit which consisted of the resistance of the soil sample, the series resistance and shunt conductance of the coaxial cable, and the characteristic impedence of the cable tester. Kirchhoff's voltage law was used to formulate the ratio of the voltage at the interface between the coaxial cable and the cable tester to the voltage of the cable tester. The formula for soil EC measurement derived from zero frequency was identical to that derived from the procedure when the frequency was approaching zero.

Characteristics of high‐gain ESPAR antenna using collinear dipole array

AbstractIn this study, a high‐gain electrically steerable parasitic array radiator (ESPAR) antenna using a collinear dipole array as a feed element is proposed, and its radiation characteristic is discussed. The feed element of the proposed antenna has a higher gain than existing ESPAR antennas, and it makes impedance matching easier via a length of coaxial cable between the arrayed feed elements and the thickness of the dielectric, using a collinear dipole array of circular dipole antennas. The proposed antenna is structured with feed elements of two‐layer collinear circular dipole arrays surrounded by four parasitic elements with an array radius of λ/16. The variable directional radiation pattern and high‐gain characteristic can be achieved through changes in reactance between the parasitic elements. The gain of the proposed antenna is 7.2 dBi approximately at the center frequency, and the return loss is less than −15 dB at the used frequencies of 2.4–2.5 GHz.

Improved Theory of Time Domain Reflectometry with Variable Coaxial Cable Length for Electrical Conductivity Measurements

Improved Theory of Time Domain Reflectometry with Variable Coaxial Cable Length for Electrical Conductivity Measurements

Computational characterization of cutoff probe system for the measurement of electron density

The wave cutoff probe, a precise measurement method for measuring the electron density, was recently proposed. To characterize the cutoff probe system, in this paper, the microwave simulations of a cutoff probe system were performed at various configurations of the cutoff probe system. The influence of the cutoff probe spectrum stemming from numerous parametric elements such as the probe tip length, probe tip distance, probe tip plane orientation, chamber volume/geometry, and coaxial cable length is presented and discussed. This article is expected to provide qualitative and quantitative insight into cutoff probe systems and its optimization process.

Improved rejection of transmitter noise: a convenient scheme with resonant crossed diodes

A method is presented for improved rejection of transmitter noise in the duplexer (transmit–receive switch). The capacitance of a set of crossed diodes forms a resonant circuit with a length of coaxial cable. The rejection of our resonant design is 60 dB, compared with only 12–15 dB for the usual method, all measured at 175 MHz. Tuning the entire duplexer to different frequencies is convenient, requiring only two new lengths of cable. The scheme is most useful with ungated linear rf power amplifiers at very high frequencies (above 100 MHz), where transmitter noise can be a severe problem.

Neutron/ γ-ray pulse-shape discriminator

We present a neutron/ γ-ray pulse-shape discriminator that is inexpensive and highly stable. Both of these favorable attributes come from the fact that the basic element of the device is a length of co-axial cable. The quality of discrimination is similar to that obtained with other modern devices.

Effect of Cable Length on Time Domain Reflectometry Calibration for High Surface Area Soils

Time domain reflectometry (TDR) has been used by soil scientists to determine soil water content (θ). A waveform analysis determines an apparent dielectric number (ϵa) which can often be empirically related to ϵ. “Bound water” near colloid surfaces has different properties than free water. At the gigahertz frequencies used for TDR, free water has a negative temperature effect but bound water has a positive temperature effect on dielectric number. Long coaxial cables reduce the higher frequencies of the TDR equipment, which can influence the frequency dependent ϵa of bound water. The objective of this study was to determine the effect of coaxial cable length and temperature on apparent dielectric properties for samples with and without large amounts of bound water. Two undisturbed columns of Okoboji mucky silty clay loam (fine, smectitic, mesic cumulic Endoaquoll) with a specific surface area of 286 m2 g−1 and two packed sand samples with calculated surface areas of 0.01 m2 g−1 were used for the experiment. The ϵa was determined at four cable length combinations, three temperatures, and a range of θ. The temperature correction factors for Okoboji ranged from 0.008 to 0.012 θ/°C, depending on cable length. Long cables increased the rise time 41%, which decreased the frequency bandwidth. The Okoboji samples had a bulk electrical conductivity as high as 0.14 S m−1, which hampered determination of the final part of the waveform. In summary for Okoboji, cable length and temperature had a greater effect on ϵa than did θ. High surface area samples should be calibrated using the same cable length used for measurements, and the temperature effect should be incorporated.

Quartz crystal resonator g sensitivity measurement methods and recent results

A technique for accurate measurements of quartz crystal resonator vibration sensitivity is described. The technique utilizes a crystal oscillator circuit in which a prescribed length of coaxial cable is used to connect the resonator to the oscillator sustaining stage. A method is provided for determination and removal of measurement errors normally introduced as a result of cable vibration. In addition to oscillator-type measurements, it is also possible to perform similar vibration sensitivity measurements using a synthesized signal generator with the resonator installed in a passive phase bridge. Test results are reported for 40 and 50 MHz, fifth overtone AT-cut, and third overtone SC-cut crystals. Acceleration sensitivity (gamma vector) values for the SC-cut resonators were typically four times smaller (5x10(-10) per g) than for the AT-cut units. However, smaller unit-to-unit gamma vector magnitude variation was exhibited by the AT-cut resonators. Oscillator sustaining stage vibration sensitivity was characterized by an equivalent open-loop phase modulation of 10(-6) rad/g.

Fast recovery with a conventional probe

A relatively simple scheme is proposed for reducing, without loss of sensitivity, the ringdown time of a conventional, 50 Ω matched probe by about an order of magnitude. It is shown that the ringing properties following a pulse are grossly influenced by the impedance into which the probe operates, and that, while optimal damping may only be achieved under special circumstances, in general, considerable reductions may be obtained by selecting correctly the preamplifier input impedance and the length of coaxial cable between the probe and the preamplifier. Suggestions are made for damping the high-voltage voltion of the ringdown, and a practical circuit (used in imaging studies at 5 MHz with a probe of quality factor 1000) is given by way of example.

Simple nonlinear equalisers for binary baseband signals

Some very recent work on equalisers has led to a simple development of a conventional nonlinear (decision-feedback) equaliser, that involves only changes to the equalisation process itself and can, under certain conditions, give a useful improvement in tolerance to additive white Gaussian noise. The technique is particularly effective when binary data symbols are transmitted, at a high signal/noise ratio, and there is severe amplitude distortion in the received data signal. The paper is concerned with a further development of the technique, suitable for applications where a binary data signal is transmitted at a high rate over a linear baseband channel and where the channel introduces severe amplitude distortion. The channel may be either minimum phase or linear phase, or else it may approximate to some compromise between these two. It is shown that, under the given conditions, the linear feedforward transversal filter that forms the first part of a conventional nonlinear equaliser can often be replaced by a simple two-tap feedforward transversal filter, with either an improvement in performance or, at least, no serious degradation in performance. The paper describes both the new equaliser and a further development of this for the case where the received data signal is sampled at twice the data symbol rate. Finally, results of computer-simulation tests are presented, comparing the tolerances to additive white Gaussian noise of the two new equalisers with those of more conventional detectors, for models of various channels. Three quite different applications have been considered, one of which involves the transmission of digital data at 140 Mbit/s over a length of coaxial cable.

Device for correcting the frequency response of an electromechanical transducer

A device for correcting the frequency response of an electromechanical transducer, thus allowing said transducer to be used over a wide frequency band and set at or near its resonance frequency. The device includes a delay element having substantially the inverse transfer function of said transducer. An amplifier may be connected between said transducer and said delay element. Said delay element may comprise a variable delay line such as an adjustable length of coaxial cable, and may also include an integrated delay line.

Ultrasound spectroscopy applied to blood coagulation studies

Two frequency scanning ultrasonic spectrographs utilizing time-delay signal processing techniques have been developed. These permit measurement of time delays (and hence velocity changes) in a sample in the order of 10 −8 s. The present instruments allow such measurements to be made continuously over a frequency range of 1–10 MHz. These instruments have been used to monitor changes in velocity as a function of frequency during coagulation in purified human fibrinogen solution and human plasma. It was found that velocity dispersion occurred at discrete frequencies during the coagulation process. The frequency dependent data is reproducible, although this depends to some extent upon the samples used. The instruments which were calibrated using a fixed length of coaxial cable, exhibit a high degree of reproducibility.

Evaluation of Aftereffects in Impatt Oscillators with Transient Ionizing Radiation

Aftereffects in IMPATT oscillators under transient ionizing radiation were evaluated using half watt Si and GaAs X-band IMPATT diodes in a resonant cap waveguide cavity. During the radiation testing, the RF impedance was varied by changing the length of a sliding short behind the diode and the bias impedance was varied independently by inserting lengths of coaxial cable between a fixed R-C bias network and the diode. From the experimental. results we conclude that: 1. the aftereffects are clearly related to a device-circuit interaction, which occurs in the resonant cap waveguide circuit only if the sliding short is one guide wavelength, rather than one-half guide wavelength, from the resonant cap diode structure; 2. the principal cause of the aftereffects is not improper bias circuit impedance resulting in bias circuit oscillations, although bias circuit oscillations can cause diode failure if they are allowed to occur; and 3. the GaAs Schottky diode is more prone to the aftereffects, occurring at power levels above 200 mW and dose rates above 2 x 109 rads/sec for the diode tested. The aftereffects appear to be triggered by a looping RF circuit impedance locus combined with the change in large signal IMPATT impedance with enhanced leakage current.

A Method for Remote Use of Hot Wire Anemometer

Hot-wire anemometer remote operation, discussing coaxial cable length, terminal connection and bridge current

A Tunnel Diode Time Mark Generator

A recycling time mark generator has been developed in which the only active element is a shunt connected tunnel diode. The diode is mounted at the junction of a 50/g=W/ stripline T. Two legs of the T are joined with a length of coaxial cable; the third leg proceeds 2.5 cms to a five port mis-match. The mis-match provides five input-output ports, and its distance from the diode determines the pulse width. Pulse width is about 0.8 ns and recycling periods as short as 3 ns and as long as 160 ns have been used. With a selected diode, up to two hundred pulses can be simultaneously recirculated in a 160 ns RG-8 transmission line indefinitely. Short term instability of circulation period as measured by beating the radiated signal with a quartz crystal is less than .05 ps. Bias coefficient of circulation period is 8 ps per mv at 90 mv with a General Electric TD-103 diode, and the tuning range which can be obtained by varying bias is 150 ps. The temperature coefficient of circulation period is 1.5 ps per °C. These measurements were made with a circulation period of 100 ns.

Transient Analysis of Coaxial Cables Considering Skin Effect

A transient analysis of coaxial cables is made by considering the skin effect of the center conductor as the distorting element. Generalized curves are presented by which the response of any length of coaxial cable can be predicted if one point on the attenuation vs frequency curve is known. An experimental check on the analysis is made by comparing measurements and prediction of the responses of several different coaxial cables.

Crosstalk in Coaxial Cables-Analysis Based on Short-Circuited and Open Tertiaries

The problem considered herein is that of estimating, from measurements on short lengths of coaxial cable, the crosstalk to be expected in long lengths of the same cable. The method developed, which is particularly applicable to cases in which the effect of tertiary circuits on the crosstalk is large, is based on measurements of crosstalk in a short length, with the tertiaries first short-circuited and then open. The application of this method to the cable described in the companion paper by Messrs. Booth and Odarenko gave crosstalk values in good agreement with their experimental results.