Ben K Sternberg

Interests

No activities entered.

Courses

Scholarly Contributions

Journals/Publications

• Dvorak, S. L., & Sternberg, B. K. (2014). Analytical studies of the vertical array-Differential Target Antenna Coupling (DTAC) method for rapid sensing and imaging of subsurface targets. Journal of Applied Geophysics, 105, 34-49.
  More info

  Abstract: In this paper we extend the Differential Target Antenna Coupling (DTAC) method to a moving vertical transmitter (TX)/receiver (RX) array. We first develop the theoretical basis for the vertical array-DTAC method and then we employ this analysis along with numerical examples to explain the physical phenomenology behind the DTAC method. In order to account for the precise orientations of the TX and RXs in the vertical DTAC array, the DTAC method uses the components of the measured magnetic field to numerically determine the null direction at a reference frequency. The measured fields are then also used to calculate the fields that exist in the reference null orientation at one or more additional frequencies. When no target is present within a layered earth, the induced conduction currents flow in simple circular patterns that are centered below the transmitter. Since the magnetic field patterns that are produced by these currents will be frequency-independent, no change in the null direction will occur and the vertical array-DTAC method effectively nulls out the combined primary and layered-earth fields. On the other hand, if either a conductive or resistive subsurface target is present that alters the flow patterns for the conduction currents in a manner that produces a frequency-dependent scattered magnetic field pattern, then the null orientation will change with frequency, and the DTAC method will pick up the small magnetic-field response associated with the buried target. In essence, the DTAC method removes the effects of the large primary field and layered-earth responses, even with misaligned RXs, thereby allowing for the accurate measurement of the much smaller target response. In addition, the vertical array-DTAC method also suppresses the responses of conductive surface clutter since the eddy currents that flow in such clutter lead to magnetic field patterns, and null directions, that are predominately frequency independent. In fact, we find that the DTAC magnitude response is reduced by 60. dB for a plate target with 10. kS conductance when it is in air compared with when the same plate is in a 10. Ω-m halfspace. Thus, the vertical-DTAC system allows for the discrimination between false targets (conductive surface clutter) and buried targets of interest. © 2014 Elsevier B.V.
• El-Kaliouby, H., Sternberg, B. K., Hoffmann, J. P., & Langenheim, V. E. (2012). Integrated geophysical surveys for mapping lati-andesite intrusive bodies, Chino Valley, Arizona. Proceedings of the Symposium on the Application of Geophyics to Engineering and Environmental Problems, SAGEEP, 483-494.
  More info

  Abstract: Three different geophysical methods (magnetic, transient electromagnetic (TEM) and gravity) were used near Chino Valley, Arizona, USA in order to map a suspected lati-andesite intrusive body (plug) previously located by interpretation of aeromagnetic data. The magnetic and TEM surveys provided the best indication of the location and depth of the plug. The north-south spatial extent of this plug was estimated to be approximately 600 meters. The depth to the top of the plug was found from the TEM survey to be approximately 350 meters near the center of the survey. The location of the plug defined by the ground magnetic data is consistent with that from the TEM data. Gravity data mostly image the basin-basement interface with a small contribution from the plug of about 0.5 mGal. Results from this investigation can be used to help define the irregular subsurface topography caused by several intrusive lati-andesite plugs that could influence groundwater flow in the area.
• Jordan, J. W., Sternberg, B. K., & Dvorak, S. L. (2011). Size, weight and power efficiency for high-power, nonlinear, geophysical-transmitter, rod-core antennas. Journal of Environmental and Engineering Geophysics, 16(1), 1-12.
  More info

  Abstract: There is a significant body of work that addresses the use of rod-core antennas as receiver coils. However, research on the use of rod-core antennas as transmitters is limited since highpermeability core materials are nonlinear at high-drive levels. This paper analyzes weight, power and volume efficiencies of rod cores constructed from six different materials: two types of ferrite toroids; black-oxide, low-carbon-steel wire; two types of Metglas foil tapes; and Nanocrystalline material foil tape. Weight efficiency is defined as the ratio of the antenna's magnetic moment to the sum of the antenna's core, wire and battery weights. Likewise, power efficiency is defined as the ratio of the antenna's magnetic moment and the antenna's resistive power losses, and volume efficiency is defined as the ratio of the antenna's magnetic moment and the antenna's volume. The magnetic moment, core-series-loss-resistance, and inductance were measured at various magnetic core flux densities. These data were then modified to simulate the effects of changing the wire gauge and number of turns to determine the optimum drive level and coil design for a specific rod core. Furthermore, we compare the results to an air-core loop whose length of one side is comparable to the length of the constructed rod antennas. It is shown that rod-core antennas possess significant advantages over air-core transmitters in weight, power and volume efficiency for the types of antennas investigated here. Specifically, at 100 Hz, the maximum weight efficiency for a 0.50-m long rod antenna made from Metglas was found to be 310% larger than a 0.50-m air-core antenna. The power efficiencies associated with the maximum weight efficiencies for these two cases differ by 420%. The volume efficiency of the Metglas rod antenna was calculated as about 500% larger than the 0.5-m air-core antenna.
• Jordan, J. W., Dvorak, S. L., & Sternberg, B. K. (2010). The use of modified scaling factors in the design of high-power, non-linear, transmitting rod-core antennas. Journal of Applied Geophysics, 72(2), 114-122.
  More info

  Abstract: In this paper, we develop a technique for designing high-power, non-linear, transmitting rod-core antennas by using simple modified scale factors rather than running labor-intensive numerical models. By using modified scale factors, a designer can predict changes in magnetic moment, inductance, core series loss resistance, etc. We define modified scale factors as the case when all physical dimensions of the rod antenna are scaled by p, except for the cross-sectional area of the individual wires or strips that are used to construct the core. This allows one to make measurements on a scaled-down version of the rod antenna using the same core material that will be used in the final antenna design. The modified scale factors were derived from prolate spheroidal analytical expressions for a finite-length rod antenna and were verified with experimental results. The modified scaling factors can only be used if the magnetic flux densities within the two scaled cores are the same. With the magnetic flux density constant, the two scaled cores will operate with the same complex permeability, thus changing the non-linear problem to a quasi-linear problem. We also demonstrate that by holding the number of turns times the drive current constant, while changing the number of turns, the inductance and core series loss resistance change by the number of turns squared. Experimental measurements were made on rod cores made from varying diameters of black oxide, low carbon steel wires and different widths of Metglas foil. Furthermore, we demonstrate that the modified scale factors work even in the presence of eddy currents within the core material. © 2010 Elsevier B.V.
• Sternberg, B. K. (2010). The variability of naturally occurring magnetic field levels: 10 Hz to 8 kHz. Geophysics, 75(6), F187-F197.
  More info

  Abstract: The variability of naturally occurring magnetic fields in the frequency range from 10 Hz to 8 kHz over a period of one year was studied. Contour plots for the Hx, Hy, and Hz components and for frequencies of 10, 100, 1000, 2000, and 8000 Hz were produced. Average, minimum, maximum, and the standard deviations of these fields were also calculated for 12 distinctive time intervals. In the 1- to 8-kHz frequency range, the noise levels are typically higher at night. In the 10- to 100-Hz frequency range, the noise levels are typically higher during the day. During mid- to late-summer, there is frequent thunderstorm activity, known in the southwest United States as the monsoon season. The magnetic field levels are often very high during this time period. These variability ranges can be used to estimate the lowest levels of noise that may be encountered during field surveys, which iswhat the authors are looking for when running controlled-source electrical method surveys. These variability ranges can also be used to estimate the highest levels that may be encountered, which is what the authors are looking for when running natural-source electrical methods surveys, such as audio frequency magnetotelluric (AMT) surveys. These measurements of magnetic field strength variability show that better data for controlled-source electrical measurements can be obtained using the minimum noise level measurements, as opposed to using signal integration or signal averaging with all of the data. The minimum noise level is found by using frequency bins adjacent to the signal-frequency bin. Likewise, if one is interested in measuring the naturally occurring magnetic field data, using the maximum values during each time interval makes AMT measurements possible when the natural signal level is very low, particularly in the AMT dead zone around 1-5 kHz. © 2010 Society of Exploration Geophysicists.
• Dvorak, S. L., & Sternberg, B. K. (2009). Development of a new method for making high dynamic range, vector mixer characterisations. IET Science, Measurement and Technology, 3(6), 365-376.
  More info

  Abstract: Vector network analysers (VNAs) employ static error models that allow for the removal of static instrumentation errors, thereby enabling the accurate measurement of vector scattering parameters for devices under test (DUTs). Since standard VNA error models are inherently based on relative measurements (i.e. either the reflected or transmitted signal is measured relative to the incident signal at the same frequency), they typically do not provide information about the magnitude and phase of the signal that is input into the DUT, or the signal that is transmitted through the DUT into the second receiver. Such information is crucial for VNA measurements of frequency-offsetting DUTs like mixers. In previous papers, the authors demonstrated how the inclusion of an additional bidirectional signal path allows for the absolute vector error correction (AVEC) of a one-port transmitter/receiver module, thereby allowing for the accurate vector measurement of the signals that are flowing into and/or out of the test port. The authors show how the AVEC method can be used to calibrate multi-port systems, thereby allowing for vector measurements of mixer DUTs (MUTs). © 2009 The Institution of Engineering and Technology.
• Dvorak, S. L., & Sternberg, B. K. (2009). Extension of an absolute vector error correction technique to wideband, high-frequency measurements. IET Science, Measurement and Technology, 3(1), 59-71.
  More info

  Abstract: The authors have previously demonstrated how a transmitter (Tx), a reciprocal transmitter/receiver (Tx/Rx) signal path and two unidirectional receiver (Rx) paths can be used together with short, open and load standards for the absolute vector error correction (AVEC) of a Tx/Rx module. Once calibrated, this Tx/Rx module can then provide accurate vector measurements of the signals that are flowing into and/or out of the test port. In order to simplify the analysis, the AVEC technique was applied to a simplified baseband circuit that did not include frequency conversion mixers in a previous paper. Now, in this paper the authors first show how the AVEC technique can be extended to the vector calibration of high-frequency receivers that involve frequency conversion mixers. The authors then show how to calibrate a system that allows for wideband absolute phase relationship measurements of periodic modulated signals, provided that the same local oscillator is employed for the two down-conversion receivers, and different radio frequencies and intermediate frequencies are employed in these receivers. This novel AVEC technique is one of the key concepts in the design of a wideband absolute vector signal measurement system, which overcomes the limitations of traditional measurement instruments by combining the features of vector signal analysers, spectrum analysers and vector network analysers. © 2008 The Institution of Engineering and Technology.
• Krichenko, O., Dvorak, S. L., & Sternberg, B. K. (2009). A new dual-tone, signal-normalisation method for the measurement and prediction of small-signal distortion. International Journal of Electronics, 96(1), 11-27.
  More info

  Abstract: A new method for characterising small-signal distortion is introduced. This novel gain-compression measurement approach employs a ratio of high- and low-level tones, closely spaced in frequency, which are simultaneously measured. A theoretical analysis of two tones passing through a weakly nonlinear device under test is used to demonstrate this new procedure for recovering the gain-distortion (i.e. power series) coefficients from the dual-tone measurement data. The signal normalisation procedure is also shown to effectively remove the time-varying errors associated with the linear receiver circuitry, thereby providing a high level of measurement accuracy. Test results for two amplifiers show that the gain-distortion coefficients can be used to accurately predict the amplifier's weakly nonlinear behaviour at low input power levels for different amplitude offsets between the high- and low-level tones. Although this new technique is demonstrated by using a power-series representation to estimate the small-signal gain compression at the fundamental frequency for memoryless devices, the general techniques that are developed here for this relatively simple problem can be extended to more complex problems where a Volterra series representation is required.
• Dvorak, S. L., & Sternberg, B. K. (2008). New absolute vector error correction technique for a transmitter/receiver module. IET Science, Measurement and Technology, 2(5), 359-366.
  More info

  Abstract: The authors demonstrate how a transmitter (Tx), a reciprocal transmitter/receiver (Tx/Rx) signal path and two unidirectional receiver (Rx) paths can be used together with short, open, and load standards for the absolute vector error correction (AVEC) of a Tx/Rx module. Once calibrated, this Tx/Rx module can then provide accurate vector measurements of the signals that are flowing into and/or out of the test port. This novel AVEC technique is one of the key concepts in the design of a wideband absolute vector signal measurement system, which overcomes the limitations of traditional measurement instruments by combining the features of vector signal analysers, spectrum analysers, and vector network analysers. The AVEC method is validated using numerical simulation data for a simplified baseband test circuit. The AVEC technique is then extended to the calibration of wideband, high-frequency Tx/Rx modules that involve frequency up/down conversion mixers in a follow-on paper. © 2008 The Institution of Engineering and Technology.
• Krichenko, O., Sternberg, B. K., & Dvorak, S. L. (2008). A new high-sensitivity subsurface electromagnetic sensing system: Part II - Measurement results. Journal of Environmental and Engineering Geophysics, 13(3), 263-275.
  More info

  Abstract: In a previous paper, we discussed the design of a new electromagnetic measurement system that employed an Alternating Target Antenna Coupling (ATAC) method to greatly improve the sensitivity and stability of the measurement system. In this paper, we demonstrate this new measurement system by applying it to the detection of various targets, including unexploded ordnance (UXO). First we demonstrate that this new measurement method increases survey efficiency because a richer data set is acquired at each measurement location. Our measurement results show that our current system will detect a standard pipe target at a 2.0-m depth below the earth's surface, which is 0.5-m deeper than the 1.5-m detection depth achieved by current state-of-the-art systems. When the full potential of the ATAC system is realized, we estimate that the projected depth of detection may increase to as much as 9 m. We also show that the measured responses of UXO are different based on the UXO's shape and material composition. The measurement results obtained with our current prototype show that the maximum range for detection of an 81-mm mortar and an 84-mm cannon projectile MK31 to be up to 1.25 m. When the full potential of the ATAC system is realized, we estimate that the projected depth of detection for these targets may increase to as much as 5 m.
• Sternberg, B. K., & Dvorak, S. L. (2008). New vector signal measuring system, featuring wide bandwidth, large dynamic range and high accuracy. IET Science, Measurement and Technology, 2(4), 219-232.
  More info

  Abstract: A new measurement system, with two receiver channels per measurement port, has been developed that provides absolute magnitude and absolute phase relationship measurements over wide bandwidths. Gain ranging is used at radio frequency to provide optimum noise performance and a swept yttrium iron garnet (YIG) preselector filter is used to avoid spurious signals. A new absolute vector error correction method is used to calibrate the measurement system in order to allow for absolute vector measurements, and it also removes the time-varying responses caused by the swept YIG preselector filters. A quasi-reciprocal mixer with a characterised non-reciprocal ratio is used to provide the absolute calibration standard. The two receiver channels can be adapted to a wide variety of applications, including wide bandwidth vector signal analyser measurements, mixer measurements and harmonic measurements. The two channels can also be used as an absolute calibrated transmitter/ reflectometer. © The Institution of Engineering and Technology 2008.
• Sternberg, B. K., & Dvorak, S. L. (2008). Quasi-reciprocal mixer as an absolute vector signal standard at microwave frequencies. IET Science, Measurement and Technology, 2(4), 258-267.
  More info

  Abstract: A reciprocal mixer has the potential to extend an absolute calibration of magnitude and phase relationships at baseband to an absolute calibration at microwave frequencies. Unfortunately, recent publications have shown that mixers are not in general reciprocal devices. The authors' tests have shown that the up- and down-conversion transmission responses for a mixer change with time and temperature. The ratio of the up- and down-conversion transmission responses, however, can be remarkably constant with time and temperature for some mixers. The authors refer to this ratio as the characterised non-reciprocal ratio (CNR) for the mixer. By using a new calibration circuit, they are able to utilise this CNR for a quasi-reciprocal mixer and provide an effective absolute vector calibration standard at microwave frequencies. © The Institution of Engineering and Technology 2008.
• Sternberg, B. K., Krichenko, O., & Dvorak, S. L. (2008). A new high-sensitivity subsurface electromagnetic sensing system: Part I - System design. Journal of Environmental and Engineering Geophysics, 13(3), 247-261.
  More info

  Abstract: We have developed a prototype frequency-domain electromagnetic geophysical system that currently has a usable dynamic range of 134 dB. In order to achieve this large dynamic range, we substantially reduced the measurement errors that are common limiting factors in achieving high measurement sensitivity. First, we reduced the measurement error caused by mechanical deformations of the measurement apparatus from 70 ppm to the order of 0.1 ppm. Second, as a result of developing a novel Alternating Target Antenna Coupling (ATAC) measurement method, we reduced the temporal drift from 400 ppm to the order of 0.1 ppm over a 50 min time period. Finally, as a result of using transmitter and receiver monitoring and dynamic calibration, we reduced the percentage error in the Real and Imaginary components of the target response, measured over a 105-minute period of time, from 5% and 80% to 0.5% and 2%, respectively. By increasing the TX moment, further increasing the TX/RX stability, and reducing the RX noise level, we estimate that the full potential of the ATAC system can achieve a usable dynamic range of the order of 200 dB.
• Sternberg, B. K., Sternberg, B. K., Levitskaya, T. M., & Levitskaya, T. M. (2005). Measurement of sheet-material electrical properties: Extending lumped-element methods to 10 GHz. IEE Proceedings: Science, Measurement and Technology, 152(3), 123-128.
  More info

  Abstract: A procedure for measuring the complex dielectric permittivity ε̂ of sheet materials, which uses a lumped-element approach for calculating ε̂ is described. Air is used as a standard material to determine the stray capacitance, inductance, and resistance of the sample holder. With a careful determination of these stray parameters, the frequency limit for these measurements can be extended up to 10 GHz. The residual scatter in the data, after the data have been corrected for stray capacitance, resistance, and inductance effects, is typically below 1% for ε′ and is of the order of 0.001 for tan δ. The procedure uses a low-cost sample holder and a conventional network analyser. © IEE, 2005.
• Dvorak, S. L., & Sternberg, B. K. (2002). Suppression of phase-noise interference due to closely spaced data and calibration signals. IEEE Transactions on Instrumentation and Measurement, 51(6), 1157-1162.
  More info

  Abstract: At high frequencies, phase noise, which occurs at frequencies surrounding a data frequency, may seriously interfere with the measurement of nearby signals. Our motivation for removing phase noise was based on our use of simultaneous data and calibration signals, which were closely spaced in frequency. We found that by measuring the source phase noise, we are able to effectively remove phase-noise interference from the measured data and calibration signals. In order to accomplish this phase-noise suppression, a normalization procedure has been developed so that signals on differing measurement channels can be compared. Using this phase-noise suppression procedure and a prototype measurement system, we were able to improve magnitude mesurements by 36 dB. We were able to improve phase measurements by a factor of 70. We propose that this procedure can significantly improve measurement accuracy in many situations where two closely spaced signals, which have a common source, must be measured with high accuracy. This procedure can also be used to monitor, and thereby remove, other types of interference besides just phase noise. © 2002 IEEE.
• Dvorak, S. L., Dvorak, S. L., Sternberg, B. K., & Sternberg, B. K. (2002). Removal of time-varying errors in network-analyser measurements: Signal normalisation and test results. IEE Proceedings: Science, Measurement and Technology, 149(1), 31-36.
  More info

  Abstract: A new approach to network-analyser measurements has been developed, which uses a dynamic-error suppression technique to remove time-varying component-drift errors (such as amplifier- and filter-response changes) and physical-device errors (such as response changes due to cable flexure). This dynamic-error suppression technique is combined with a conventional static-error suppression technique, such as 'short/open/load/thru' (SOLT) or 'thru/reflection/line' (TRL), to remove all types of errors. This procedure is referred to as the accurate real-time total-error-suppression technique (ARTTEST). Special signal flow models and normalisation equations are developed for the suppression of both static and time-varying errors in the transmitter, receiver, reference, and link circuitry. In order to test the prototype system, time-varying reflection and transmission errors are introduced in the various paths in the ARTTEST network analyser. Based on these tests, it is found that the ARTTEST network analyser's dynamic-error suppression technique provides an improvement, when compared with conventional network analyser measurements, of greater than 50 dB for reflection and greater than 40 dB for transmission measurements. Corresponding improvements of greater than a factor of 300 for reflection phase and greater than a factor of 100 improvement for measurements of transmission phase are also achieved.
• Sternberg, B. K., Sternberg, B. K., Dvorak, S. L., & Dvorak, S. L. (2002). Removal of time-varying errors in network analyser measurements: System design. IEE Proceedings: Science, Measurement and Technology, 149(1), 22-30.
  More info

  Abstract: A new approach to network-analyser measurements has been developed, which uses a dynamic-error suppression technique to remove time-varying component-drift errors (such as amplifier- and filter-response changes) and physical-device errors (such as response changes due to cable flexure). This dynamic-error suppression technique is combined with a conventional static-error suppression technique, such as 'short/open/load/thru' (SOLT) or 'thru/reflection/line' (TRL), to remove all types of errors. This procedure is referred to as the accurate real-time total-error-suppression technique (ARTTEST). Frequency-offsetting mixers are used to produce the normalisation signals that are required for the dynamic-error supression. The ARTTEST method allows for the simultaneous measurement of data and normalisation signals that reside at unique, but closely spaced frequencies. These simultaneous normalisation signals are used to greatly improve the measurement accuracy of the system. The ARTTEST method is applicable to a wide variety of measurement problems where high-accuracy results are required. The application of this method to a network-analyser application is demonstrated.
• Sternberg, B. K., & Levitskaya, T. M. (2001). Electrical parameters of soils in the frequency range from 1 kHz to 1 GHz, using lumped-circuit methods. Radio Science, 36(4), 709-719.
  More info

  Abstract: A lumped circuit approach was applied to study electrical properties of soil samples with various compositions and water contents. The extension of this method was made possible by using a coaxial sample holder. Electrical parameters of soils such as the conductivity, resistivity and permittivity were obtained by measuring magnitude and phase of sample impedance. Third degree polynomial equations, relating the relative permittivity to the volumetric soil moisture were different for various frequencies.
• Levitskaya, T. M., & Sternberg, B. K. (2000). Laboratory measurement of material electrical properties: extending the application of lumped-circuit equivalent models to 1 GHz. Radio Science, 35(2), 371-383.
  More info

  Abstract: For measurements of material electrical properties in a frequency range from 1 kHz to 1 GHz, we used a laboratory method based on the concept of lumped R, L, and C circuit elements. While this method has typically been used at frequencies of less than 100 MHz, we have extended its application up to 1 GHz. The complex electrical parameters of a material, such as resistivity, conductivity, and dielectric permittivity were obtained by measuring magnitude Z and phase φ of the sample impedance Z. We relate the material electrical parameters to either series or parallel lumped-circuit equivalent models. Depending on the frequency range, two different designs of the sample holder can be used: (1) a parallel-plate capacitor with disk electrodes, for low frequencies (from 1 kHz to 100 MHz), and (2) a coaxial capacitor, for a broad band up to higher frequencies (from 1 kHz to 1 GHz). Measured values of the sample impedance usually include errors due to effects from the sample holder and its connections to the instrument. These effects, caused by the inductance, resistance, and stray capacitance of the measuring system, are taken into account. Our measurements of several standard materials, including air, Teflon, octanol, butanol, and methanol, showed that the relative standard deviation from the mean for the dielectric permittivity (in the range where it is frequency independent) is typically less than 1%. The difference between our mean values and previously published values for these standard materials is also less than 1%.
• Levitskaya, T. M., & Sternberg, B. K. (1996). Polarization processes in rocks 1. Complex Dielectric Permittivity method. Radio Science, 31(4), 755-779.
  More info

  Abstract: This is the first part of a review of research performed in the former USSR. Experimental data were used from several regions of the USSR, including Russia, Ukraine, and Georgia. Many of the publications are available in U.S. libraries. Some of them are translated into English. This part contains results from applying the Complex Dielectric Permittivity method (Dielectric Spectroscopy) for studying the electrical response of rocks in alternating fields with frequencies from 100 Hz to 100 MHz. Data on dielectric properties of sedimentary rocks of different lithology and with various porosities, salinities of saturating solution, and hydrocarbon content are reviewed here. Measurement methods, including means for avoiding or reducing the electrode polarization, are also considered. It is shown that wet rocks exhibit a Maxwell-Wagner polarization process at frequencies 105-107 Hz, caused by charge accumulation on the pore boundaries.
• Levitskaya, T. M., & Sternberg, B. K. (1996). Polarization processes in rocks 2. Complex Dielectric Permittivity method. Radio Science, 31(4), 781-802.
  More info

  Abstract: This is the second part of a review of research performed in the former USSR. Experimental data were used from several regions of the USSR, including Russia, Ukraine, and Georgia. Many of the publications are available in U.S. libraries. Some of them are translated into English. This part considers results of studying rocks with the Complex Electrical Resistivity method, primarily in the frequency range from 0.01 Hz to 50 MHz. Results of studying polarization processes in sedimentary rocks of different lithology and porosity with different types of saturation (salt solutions of various salinity and hydrocarbons) are described. Laboratory studies of ore-mineral containing rocks are also considered. Describing the measurement methods, we have placed primary emphasis on means for avoiding or reducing the electrode polarization effects. It is shown that wet rocks may have two polarization processes: one at low frequencies, below 1 Hz, and one at high frequencies, above 10 kHz. The mechanisms of these processes are discussed based on experimental results.
• Sternberg, B. K., & McGill, J. W. (1995). Archaeology studies in southern Arizona using ground penetrating radar. Journal of Applied Geophysics, 33(1-3), 209-225.
  More info

  Abstract: Conventional ground penetrating radar (GPR) surveys typically have a maximum depth of penetration of 1 2 to 1 m in the basin-fill sediments of the southwestern United States. Although this depth of penetration is too limited for many engineering and environmental surveys, it is often suitable for archaeological investigations in this region. We have found a center frequency of 500 MHz to be optimum. Radar signals having a center frequency of about 80 MHz produce records with much lower resolution and only slightly greater maximum depth of penetration. Successful GPR surveys have imaged buried plaster and adobe walls, roasting pits, canals, trash pits, plastered floors, and artifacts such as pot sherds and knives. We have found that GPR is a valuable tool for archaeological studies in this area. GPR can provide some of the detailed survey information that has been provided in the past by extensive excavation, but without the high cost of excavation, without the dangers of vandalism when artifacts are exposed, and without disturbing sensitive areas. © 1995.
• Ward, S. H., Sternberg, B. K., LaBrecque, D. J., & Poulton, M. M. (1995). Recommendations for IP research. Leading Edge (Tulsa, OK), 14(4), 243-247.
  More info

  Abstract: The John S. Summer Memorial International Workshop on Induced Polarization in Mining and the Environment was organized to get recommendations for geologic, geochemical, and geophysical research from IP users and practitioners for IP applications to mining and environmental problems. Conventional IP, as well as IP effects in EM and GPR, were considered. During the program, research recommendations came from 'break-out' sessions and round table discussions. As to be expected, uniform reports were not received from the break-out groups. Thus, the report was homogenized into a common format. Considerable condensation of the material has resulted in a more readable document without any significant loss of information content.
• Bak, N. H., Sternberg, B. K., Dvorak, S. L., & Thomas, S. J. (1993). Rapid, high-accuracy electromagnetic soundings using a novel four-axis coil to measure magnetic field ellipticity. Journal of Applied Geophysics, 30(3), 235-245.
  More info

  Abstract: A unique high-resolution electromagnetic sounding system, utilizing a four-axis coil and a new calibration technique, has been designed, constructed, and tested. The resulting measurements have an accuracy of approximately ±0.1%. The four-axis coil, which includes three approximately orthogonal coils and a calibration coil, is designed to automatically collect ellipticity data at 20 discrete frequencies in the range 30 Hz-30 kHz. The approximately orthogonal coils detect three components of the magnetic field and the calibration coil injects a calibration signal into the receiving system at the same time that the data are being recorded. A three-dimensional mathematical rotation program was developed to calculate ellipticity, removing the need to know the absolute coil orientation. Equations were formulated for the angular relationships between the approximately orthogonal coils. The actual intercoil angles were computed using a nonlinear optimization analysis applied to the measured data. The system was tested by measuring the ellipticity at one point on the earth's surface for various orientations of the coil. In addition, a close match between calculated and measured ellipticity profiles was obtained in a field test over a known target. © 1993.
• Poulton, M. M., Sternberg, B. K., & Glass, C. E. (1992). Location of subsurface targets in geophysical data using neural networks. Geophysics, 57(12), 1534-1544.
  More info

  Abstract: Neural networks were used to estimate the offset, depth, and conductivity-area product of a conductive target given an electromagnetic ellipticity image of the target. Five different neural network paradigms and five different representations of the ellipticity image were compared. For input patterns with less than 100 elements, the directed random search and functional line networks gave the best results. For patterns with more than 100 elements, self-organizing map to back propagation was most accurate. Using the whole ellipticity image gave the most accurate results for all the network paradigms. -from Authors
• Poulton, M. M., Sternberg, B. K., & Glass, C. E. (1992). Neural network pattern recognition of subsurface EM images. Journal of Applied Geophysics, 29(1), 21-36.
  More info

  Abstract: Neural networks are computer simulations of the brain's neural functions; as such they perform well on the same types of problems on which humans perform well, namely pattern recognition. Neural networks have shown the capability to learn human speech, read handwritten signatures and recpgnize human faces. Applied to geophysical data, neural networks offer the ability to estimate model parameters in near realtime. A backpropagation neural network was trained to estimate the spatial location (offset and depth) of a target given an image of the electromegnetic ellipticity. Three components of the magnetic field were measured from which the ellipticity was calculated. Theoretical ellipticity images were used for training the neural network; field data were used to test it. The input data representation was important in obtaining results with 10% error or less from the neural network; generally, smaller input vectors yielded more accurate results. Five different representations were examined: the whole image, the subsampled image, trough-peak-trough, peak amplitude and frequency domain. The frequency-domain representation estimated the target locations in the field data with the least error, 0.4% for the offset and 1.5% for the depth. The network was examined for its ability to generalize, to extrapolate beyond the spatial limits of the training set and to ignore discrepancies between synthetic and field data. The generalization from synthetic training data to synthetic test data had errors near 5% for most offset estimates and near 2% for most depth estimates. We considered extrapolation errors satisfactory (10%) up to 1.5 model spacings beyond the limits of the training set. © 1992.
• Poulton, M. M., Sternberg, B. K., & Farmer, I. W. (1991). In situ strength measurements of weak rocks. Journal of geotechnical engineering, 117(9), 1424-1429.
  More info

  Abstract: The need to obtain more reliable data arose during investigations for the Arizona superconducting super collider proposal. Estimates of strength for tunnel and cut design obtained from disturbed and reconstituted samples were obviously too low, as were previous estimates from back analysis. Estimates based on refraction seismology, while intuitively sound, involved many assumptions and required validation from field or laboratory strength measurements. This note discusses the application of plate load tests. Because of the high strength of the fanglomerates, large reaction loads were required to induce failure. Interpretation of the results of these tests provides an interesting example of the different failure models needed in rock and soils mechanics as welll as the necessary data to correlate with seismic measurements.
• Sternberg, B. K., Poulton, M. M., & Sully, M. J. (1991). Introduction. Geoexploration, 28(3-4), 179-182.
• Sternberg, D. K. (1991). Review of some experience with the induced-polarization/resistivity method for hydrocarbon surveys. Successes and limitations. Geophysics, 56(10), 1522-1532.
  More info

  Abstract: Our experience with the induced polarization (IP) and resistivity method for hydrocarbon exploration has shown both successful surveys and limitations of the method. Four examples demonstrate a close correlation between shallow IP and resistivity anomalies and deeper hydrocarbon production. In each of these examples, anomalies occurred over the producing fields which have significantly greater amplitudes than the variations in the surrounding background response. Another important result of our research is the development of a geological/geochemical model for the formation of IP and resistivity anomalies over hydrocarbon reservoirs. The two main requirements for formation of IP and resistivity anomalies, according to this model, are: (1) absence of any thick impermeable seals, such as evaporites, above the reservoir and (2) presence of porous, iron-rich, near-surface host rocks, such as clastic rock sequences. The IP and resistivity method can be more successfully applied by selecting those areas for surveys in which these two requirements hold. We have also found that the IP/resistivity method for hydrocarbon exploration has significant limitations. Many areas do not appear to have the required geological and geochemical conditions for the formation of IP or resistivity anomalies. IP and resistivity anomalies may also need to be tested with shallow drill holes to separate anomalies caused by hydrocarbon seepage from false anomalies due to other causes.
• Poulton, M. M., Sternberg, B. K., & Glass, C. E. (1990). Continuous-output neural networks for EM ellipticity pattern recognition. Digest - International Geoscience and Remote Sensing Symposium (IGARSS), 2, 1297-1300.
  More info

  Abstract: The interpretation of images of magnetic field polarization (ellipticity) acquired with a geophysics electromagnetic (EM) imaging system is treated as a pattern-recognition problem. A continuous-output backpropagation network is presented with images from a target in various locations and is taught to associate the spatial location of the target with the pattern in the image. Five different data representations were examined for training speed, accuracy, and generalization capabilities. The results are shown to be relatively insensitive to network design, but the overall errors decrease as the the size of the input vector decreases. The network located the target in the field data within 3% of the horizontal location and 1.2% of the depth.
• Sternberg, B. K., & Nopper Jr., R. W. (1990). High-accuracy, simultaneous calibration of signal measuring systems. Measurement Science and Technology, 1(3), 225-230.
  More info

  Abstract: We describe a new calibration method that makes possible a very accurate calibration of a signal measuring system. We inject a precisely known calibration signal into the measuring system while we acquire the data signal. The calibration signal is designed to have a discrete frequency spectrum that interweaves with, but does not contaminate, the spectrum of the data signal. Since the calibration is performed simulataneously with data acquisition, there is no danger that the equipment response will change between the time when the data are collected and when the instrument is recalibrated. Further, this procedure may be automated so experiments are much more efficient than with separate and frequent calibrations. This calibration technique should be applicable in a wide variety of scientific and engineering problems. To illustrate the power of this technique, we use an example from the field of exploration geophysics.
• Sternberg, B. K., Washburne, J. C., & Pellerin, L. (1988). Correction for the static shift in magnetotellurics using transient electromagnetic soundings. Geophysics, 53(11), 1459-1468.
  More info

  Abstract: Shallow inhomogeneities can lead to severe problems in the interpretation of magnetotelluric (MT) data by shifting the MT apparent resistivity sounding curve by a scale factor, which is independent of frequency on the standard log-apparent-resistivity versus log-frequency display. The amount of parallel shift, commonly referred to as the MT static shift, cannot be determined directly from conventionally recorded MT data at a single site. One method for measuring the static shift is a controlled-source measurement of the magnetic field. Inversions of the static shift-corrected MT data provide a much closer match to well-log resistivities than do inversions of the uncorrected data. Central-induction TEM measurements were made adjacent to over 100 MT sites in central Oregon. The complete data base of over 100 sites showed an average static shift between 0 and 0.2 decade. However, in the rougher topography and more complex structure of the Cascade Mountain Range, the majority of the sites had static shifts of the order of 0.3 to 0.4 decade. The static shifts in this area are probably due to a combination of topography and surficial inhomogeneities. -from Authors
• Oehler, D. Z., & Sternberg, B. K. (1984). SEEPAGE-INDUCED ANOMALIES, 'FALSE' ANOMALIES, AND IMPLICATIONS FOR ELECTRICAL PROSPECTING.. American Association of Petroleum Geologists Bulletin, 68(9), 1121-1145.
  More info

  Abstract: Two detailed case studies have been made of shallow electrical anomalies. In one study (Ashland field, Oklahoma), the anomalies are shown to be related to vertical seepage from a hydrocarbon reservoir; in the other (Salt Draw prospect, Texas), the anomalies are shown to be 'false' anomalies and unrelated to any deeper hydrocarbons. The results also suggest that seepage-induced pyrite and marcasite are likely to form only over hydrocarbon reservoirs where at least two geologic conditions are met: some hydrocarbons from the reservoir can seep to the near surface, and the near-surface section contains porous, iron-bearing host rocks. Study conclusions are combined with those drawn from 40 other electrical surveys to develop a strategy for using shallow-investigation electrical techniques in the search for petroleum which is discussed in the paper. Refs.
• Sternberg, B. K. (1979). ELECTRICAL RESISTIVITY STRUCTURE OF THE CRUST IN THE SOUTHERN EXTENSION OF THE CANADIAN SHIELD - LAYERED EARTH MODELS.. J Geophys Res, 84(B1), 212-228.
  More info

  Abstract: A combination of electrical sounding methods has been used to study the vertical resistivity structure of the crust on the southern extension of the Canadian Shield in northern Wisconsin. The soundings were made in a region where the gross subsurface structure is laterally uniform, so horizontal, plane-layered models were used to interpret the data. Layered earth models were randomly generated and tested against the observed data to determine the range of models that fit the data: surface layer, comprised mainly of glacial till, has a few hundred ohm meters resistivity down to depths of a few tens of meters; a bedrock layer has a resistivity in the range of 3000 to 7000 ohm m down to depths of 4. 5 to 11 km; a deeper, high-resistivity layer has resistivities of greater than 100,000 ohm m down to depths of 14 to 22 km; a lower layer has resistivities of from 50 to 1500 ohm m. The paper discusses interpretations of these resistivities. Refs.