Separate Transmitter Research Articles

Research on indoor experimentation of range SAL imaging system

By means of advantages of both SAR and lidar, the combination of the techniques of (inverse) synthetic aperture and lidar makes it possible to obtain high resolution 2-D image. In this paper, an indoor experimental system of inverse synthetic aperture lidar imaging is given and a processing approach is presented. The given system is in the mode of lidar system with separated receiver and transmitter, which can effectively eliminate the jamming from the lens or/and the intersection between two optic fibers. Based on the reference channel techniques, a method for the compensation of nonlinear frequency in the time domain is presented, which can solve the problem of nonlinear frequency efficiently. Then, with the mature inverse synthetic aperture algorithm, an image of inverse synthetic aperture lidar can be obtained, which is the first attempt in China. Finally, experimental results confirm the validity of the presented method and the feasibility of the experimental system.

A system which uses phase and magnitude information separately enabling detection and imaging of corrosion in steel rebars located at distances of 8–9 cm

A system which enables corrosion on rebars used in reinforced concrete to be detected at distances of 8–9 cm is described. The system uses a separate transmitter and receiver which can be positioned at different locations in the transmitter field enabling an image of the bar to be generated. The receiver is positioned in an orthogonal orientation with respect to the transmitter, which generates big changes in the received signal as compared to placing the receiver in a conventional orientation. The receiver signal can be analysed using phase and amplitude information separately. The information obtained from the phase of the received signal has proven to be especially useful in detecting and generating an image which shows corrosion at deeper distances.

Omega-k Algorithm for Airborne Spatial Invariant Bistatic Spotlight SAR Imaging

Bistatic spotlight synthetic aperture radar (SAR) which uses a separated transmitter and receiver has been studied intensively due to its flexibility. To reconstruct the image for the bistatic SAR in the parallel track configuration, where the transmitter and the receiver have equal velocity, we modify the omega-k algorithm. Specifically, using the extended Taylor approximation (ETA), we convert the parallel track configuration into the single track configuration. Then, using the principle of the stationary phase, we propose an analytical method to increase the image quality of bistatic SAR systems.

New applications of transponder in focusing distributed synthetic aperture radar data

High-precision phase synchronisation or compensation techniques must be provided for distributed synthetic aperture radar (DiSAR), which operates with separate transmitters and receivers. The use of a novel transponder that was proposed for calibrating high-resolution imaging radars to compensate oscillator frequency instability is investigated here. This transponder modulates the radar pulses in a manner that the retransmitted signal shows two additional Doppler frequencies, which enables their separation from the scene echoes. In this way, DiSAR frequency synchronisation errors can be compensated. Thereafter, the DiSAR raw data is focused by using a derived image formation algorithm. The originality of this text lies in the phase compensation technique via transponder for DiSAR systems, as well as an image formation algorithm with integrated synchronisation compensation.

Distance Measurement of an Object or Obstacleby Ultrasound Sensors using P89C51RD2

Distance measurement of an object in the path of a person, equipment, or a vehicle, stationary or moving is used in a large number of applications such as robotic movement control, vehicle control, blind man's walking stick, medical applications, etc. Measurement using ultrasonic sensors is one of the cheapest among various options. In this paper distance measurement of an obstacle by using separate ultrasonic transmitter, receiver and a microcontroller is presented. The experimental setup and results are described and explained.

Ultrasonic reflectivity computed tomography with small number of transmitter/receiver transducers for carotid diagnosis

AbstractWe developed an ultrasound reflectivity computed tomography (CT) system with only a small number of transmitter/receiver transducers for carotid diagnosis. To this end, a ring array system with eight element transducers was fabricated with center frequency 10 MHz. The present CT technique assures the image with high resolution on the order of 0.1 mm over the entire imaging region. In addition, the reduction of the number of transducer element enables fast data acquisition and lower cost hardware system. With appropriate combinations of the dual and/or separate transmitter and receiver pairs, 21 backscattering projection data were observed. To comply with the ill‐posed inverse problem due to the lack of angular view data, the conjugate gradient method was applied for the solution of the matrix observation equation. Both experiment and simulation examinations were made using the cylindrical shell object as a carotid phantom. As a result, it is demonstrated that the image with greater resolution compared with the conventional B‐mode method can be obtained by using only eight element transducers. © 2008 Wiley Periodicals, Inc. Electr Eng Jpn, 163(4): 58–66, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20301

Array GPR investigation of the cathedral of Uppsala

We present an example of a so‐called array GPR investigation outside the Cathedral of Uppsala, Sweden. The aim of the investigation was to reveal historically interesting features in surroundings where excavations are not allowed. In the investigation, 17 different GPR antennae of the same frequency were used to obtain measurements in 16 parallel profiles simultaneously. When several separate transmitter and receiver antennae are combined into one single antenna array unit, exactly positioned parallel profiles are obtained, resulting in a seamless high‐resolution 3D picture of the subsurface. Processing the radar data into the resulting images involves several steps, such as aligning traces, removing static shifts and matching the mean response. Radar data are merged with geometry data from a total station (used to track the position of the antenna array) and then gridded and migrated. In the Uppsala case presented here, the resulting pictures in the form of time slices gave archaeologists very valuable help in understanding the subsurface and mapping historical anomalies. The findings indicate former paths and early medieval streets, among other features.

Bistatic SAR Processing and Experiments

Bistatic synthetic aperture radar (SAR) uses a separated transmitter and receiver flying on different platforms to achieve benefits like exploitation of additional information contained in the bistatic reflectivity of targets, reduced vulnerability for military applications, forward-looking SAR imaging, or increased radar cross section. Besides technical problems such as synchronization of the oscillators, involved adjustment of transmit pulse versus receive gate timing, antenna pointing, flight coordination, and motion compensation, the development of a bistatic focusing algorithm is still in progress and not sufficiently solved. As a step to a numerically efficient processor, this paper presents a bistatic range migration algorithm for the translationally invariant case, where transmitter and receiver have equal velocity vectors. In this paper, the algorithm was successfully applied to simulated and real bistatic data. The real bistatic data have been acquired with the Forschungsgesellschaft fur Angewandte Naturwissenschaften (FGAN)'s X-band SAR systems, namely the Airborne Experimental Radar II and the Phased Array Multifunctional Imaging Radar, in October 2003

LWD for Imaging, Wellbore Placement, and Formation Evaluation

This article, written by Technology Editor Dennis Denney, contains highlights of paper OTC 17646, "LWD for Imaging, Wellbore Placement, and Formation Evaluation," by J.C. Rasmus, SPE, C. Esmersoy, SPE, J. Seydoux, and A. Hawthorn, Schlumberger, prepared for the 2005 Offshore Technology Conference, Houston, 2-5 May. Logging-while-drilling (LWD) measurements are widely available for a variety of applications. Many of the first generation LWD measurements are similar to those obtained traditionally with wireline methods. However, there are measurements available now that are either complementary or are entirely unique compared with traditional wireline measurements. Introduction LWD borehole-seismic measurements can enable placing the bit on the seismic map or producing a seismic-impedance map ahead of the bit while drilling the well. These measurements provide accurate depth determination of drilling targets and identification of pore-pressure transgressions. LWD ultradeep-resistivity (UDR) measurement technology meets the requirements for geosteering at the reservoir level by use of subseismic resolution. Its major applications include delineation of the oil/water contact (OWC) and distance to reservoir caprock and bottom shale. Well Placement Since the emergence of LWD in the 1980s, the industry wanted a reliable while-drilling borehole-seismic measurement. However, several technical roadblocks prohibited its realization until recently. These difficulties included the nature of and required accuracy of the measurement, timing issues, sensors, automation, and the lack of an electrical connection between the downhole tools and the surface in a while-drilling configuration. Technological solutions to these road-blocks have since been found. Seismic-while-drilling data are delivered in real time to make critical decisions while a well is being drilled. They also replace intermediate wireline check-shot surveys, eliminating the need to stop the drilling process and pull drilling equipment out of the hole for the duration of a survey. Real-time accurate positioning of a horizontal borehole within a reservoir can be performed with standard LWD tools. However, a limitation of these measurements is the relatively small volume of investigation with traditional LWD sensors, which typically probe no deeper than 1 m into the formation. Therefore, unpredictable geological events are, in many cases, detected too late to allow proactive geosteering decisions. A prototype LWD resistivity tool was developed with a much larger radial response that allows detection of lithology features and fluid contacts that are tens of meters away from the borehole. The tool has a modular design with separate transmitter and receiver subassemblies that can be placed a large distance away, anywhere in the bottomhole assembly (BHA). The main output is estimated distance to boundaries indicated by resistivity contrasts. These distances are computed through inversion of a formation model in real time. On the basis of tool measurements, determining the optimum formation model and its related parameters allows proactive geosteering decisions and pro-vides significant geological insight into the reservoir structure.

Telemetric recording of neuronal activity

A telemetric system is described which allows the wireless registration of extracellular neuronal activity and vocalization-associated skull vibrations in freely moving, socially living squirrel monkeys ( Saimiri sciureus). The system consists of a carrier platform with numerous guiding tubes implanted on the skull. Custom-made microdrives are mounted on the platform, allowing the exploration of two electrode tracks at the same time. Commercially available quartz-insulated platinum–tungsten microelectrodes are used. The electrodes can be moved over a distance of 8–10 mm by turning a screw on the microdrive. Vocalization-associated skull vibrations are recorded with a piezo-ceramic element. Skull vibration signal and the signals from the two microelectrodes are fed into separate transmitters having different carrier frequencies. The signals are picked up by an antenna in the animal cage and are sent to three receivers in the central laboratory. Here, the signals are transferred via an analog/digital interface to a personal computer for data analysis and to a video recorder for long-term storage. The total weight of the head mount including carrier platform, microdrive, electrodes, skull vibration sensor, three transmitters, and protection cap is 32 g. The transmitters are powered with two rechargeable lithium batteries, allowing about 8 h of continuous recording. Reliable signal transmission is obtained over a distance of about 2 m. Recording stability allows to follow the activity of specific neurons up to several hours, with no movement artefacts during locomotion.

Bistatic SAR – translational invariant processing and experimental results

Bistatic synthetic aperture radar (SAR) uses a separated transmitter and receiver, flying on different platforms, which enables the exploitation of additional information contained in the bistatic reflectivity of targets. The feasibility of the bistatic concept has already been demonstrated although technical problems such as the synchronisation of the oscillators still persist. The processing of bistatic raw data has still not been resolved sufficiently, either. The omega-k (or range migration) processor has proven popular in the monostatic case because of its relatively simple implementation, its close-to-optimum performance and its numerical efficiency, but has not been generalised for the bistatic case. A method to eliminate the deviation of the bistatic range history from the monostatic hyperbolic shape in the omega-k domain making subsequent omega-k processing possible has been recently proposed, and generalisations of the omega-k algorithm to the bistatic case can also be found. Adding to the literature, an omega-k-type processor for the special case of equal-velocity vectors of transmitter and receiver, the so-called ‘spatial invariant’ case, is introduced. This processor is not optimum in the sense of the monostatic omega-k processor but degradation for wide ranges of geometrical parameters proved negligible. During flight testing in November 2003, different spatially invariant flight geometries were tested and high resolution bistatic SAR images were generated successfully.

Magnetic resonance soundings with separated transmitter and receiver loops

ABSTRACTTriggered by an extended mathematical formulation of the response signal for magnetic resonance soundings (MRS), which allows the treatment of individual transmitter and receiver loops, we make a comprehensive evaluation and assessment of the emerging new possibilities of the technique. Based on a reformulation of the basic equation, we indicate and interpret the evolving effects. The influence of loop separation on MRS sounding curves in terms of offset and direction is also assessed as is the corresponding sensitivity to depth and lateral spin variation. Interpretation of field data measured with separated loops using the extended formulation is found to fit the predicted response extremely well. From the encouraging results, we derive new aspects of two‐dimensional investigation of groundwater resources. Furthermore, new perspectives of future developments of the MRS technique, with individual loops for optimized field measurements and hydrological applications, are discussed.

Range error detection caused by occlusion in non-coaxial LADARs for scene interpretation

When processing laser detection and ranging (LADAR) sensor data for scene interpretation, for example, for the purposes of feature extraction and/or data association in mobile robotics, most previous work models such devices as processing range data which follows a normal distribution. In this paper, it is demonstrated that commonly used LADARs suffer from incorrect range readings at changes in surface reflectivity and/or range discontinuities, which can have a much more detrimental effect on such algorithms than random noise. Most LADARs fall into two categories: coaxial and separated transmitter and receiver configurations. The latter offer the advantage that optical crosstalk is eliminated, since it can be guaranteed that all of the transmitted light leaves the LADAR and is not in any way partially reflected within it due to the beam-splitting techniques necessary in coaxial LADARs. However, they can introduce a significant disparity effect, as the reflected laser energy from the target can be partially occluded from the receiver. As well as demonstrating that false range values can result due to this occlusion effect from scanned LADARs, the main contribution of this paper is that the occurrence of these values can be reliably predicted by monitoring the received signal strength and a quantity we refer to as the “transceiver separation angle” of the rotating mirror. This paper will demonstrate that a correct understanding of such systematic errors is essential for the correct further processing of the data. A useful design criterion for the optical separation of the receiver and transmitter is also derived for noncoaxial LADARs, based on the minimum detectable signal amplitude of a LADAR and environmental edge constraints. By investigating the effects of various sensor and environmental parameters on occlusion, some advice is given on how to make use of noncoaxial LADARs correctly so as to avoid range errors when scanning environmental discontinuities. © 2005 Wiley Periodicals, Inc.

少数の送受信素子で構成した頸動脈診断用超音波反射率CT

We developed an ultrasound reflectivity computed tomography(CT) system with only small number of transmitter/receiver transducers for the carotid diagnosis. To this end, a ring array system with 8 element transducers was fabricated with center frequency 10MHz. The present CT technique assures the image with high resolution in the order of 0.1mm over the entire imaging region. In addition to that, the reduction of the number of transducer element enables the fast data acquisition and the lower cost hardware system. With appropriate combinations of the dual and/or separate transmitter and receiver pairs, 21 backscattering projection data were observed. To comply with the ill-posed inverse problem due to the lack of the angular view data, conjugate gradient method was applied for the solution of the matrix observation equation. Both experiment and simulation examinations were made using the cylindrical shell object as a carotid phantom. As a result, it is demonstrated that the image with greater resolution compared with the conventional B-mode method can be obtained by using only 8 element transducers.

Inspection of CFRP components by ultrasonic imaging with air-coupling

This paper reports the investigations of air coupled ultrasonic imaging techniques which are part of the German research project MaTech. Project partners are Airbus, Bremen, Ingenieurburo Dr. Hillger, Braunschweig, and intelligeNDT, Erlangen, with DLR, Braunschweig, as subcontractor. One task is the development and the construction of a non-contact ultrasonic imaging system („Demonstrator III“) for basic researches. This system provides fast scanning with a single-shot data acquisition (without signal averaging). The dynamic range in one shot reaches up to 50 dB. The demonstrator allows the application of different types of air coupled transducers and therefore it allows the comparison of their performances. The modular design of the system provides further developments and adaptations to special inspection tasks. A power transmitter with burst-signals ( peak power of 1.2 kW) and a free programmable transmitter can be used for the excitation of the transducers. The user-friendly software records C-scans and full wave scans and provides C-scan evaluations. The development and construction of special transducers for air coupling and the development of a system for echo-technique are further research tasks of the MaTech project. Usually, the air coupled ultrasound is used in through-transmission technique with separate receiver and transmitter transducers on opposite sides of the component under test. In order to get a high acoustic power and a low noise in the receiver amplifier usually the bandwidth of the system is smaller than 10% of the centre (test) frequency. Therefore, the effects of (*/2)-resonances in the components are investigated. Also the application of broadband transducers will be investigated.

Transmission of waves near the lower oblique resonance using dipoles in the ionosphere

The observations in the OEDIPUS‐C experiment of bistatic propagation along the lower oblique resonance cone between a separated transmitter and receiver in the ionosphere are explained through detailed calculations of the radiated field of the V‐dipole antenna used in the experiment and by a novel theory of the receiving antenna under resonance conditions. Unexpectedly high values of 25 kHz signal observed at the resonance and its structure agree well with calculations of the transmission between the exciter and receiver, when antenna layout and dispersive properties of the plasma at resonance are taken into account.

Multiple-input - multiple-output measurements and modeling in Manhattan

Narrowband multiple-input-multiple-output (MIMO) measurements using 16 transmitters and 16 receivers at 2.11 GHz were carried out in Manhattan. High capacities were found for full, as well as smaller array configurations, all within 80% of the fully scattering channel capacity. Correlation model parameters are derived from data. Spatial MIMO channel capacity statistics are found to be well represented by the separate transmitter and receiver correlation matrices, with a median relative error in capacity of 3%, in contrast with the 18% median relative error observed by assuming the antennas to be uncorrelated. A reduced parameter model, consisting of 4 parameters, has been developed to statistically represent the channel correlation matrices. These correlation matrices are, in turn, used to generate H matrices with capacities that are consistent within a few percent of those measured in New York. The spatial channel model reported allows simulations of H matrices for arbitrary antenna configurations. These channel matrices may be used to test receiver algorithms in system performance studies. These results may also be used for antenna array design, as the decay of mobile antenna correlation with antenna separation has been reported here. An important finding for the base transmitter array was that the antennas were largely uncorrelated even at antenna separations as small as two wavelengths.

Combining digital and analog signals for US IBOC FM broadcasting

IBOC DAB (In-Band On-Channel Digital Audio Broadcasting) requires the simultaneous broadcast of an analog and a digital signal within one channel of the FM band. Because broadcasters are adding IBOC to their existing systems, it is vital that they achieve maximum power efficiency while working within their existing space and power limitations. There are currently three different strategies proposed for accomplishing this goal, each having its own advantages and disadvantages. One strategy is to establish a separate, second antenna for the digital service. The other two strategies involve combining the analog and digital signals, either in a single hybrid transmitter or at the output of separate analog and digital transmitters. This paper discusses the equipment required for accomplishing this last strategy.

Increasing Control and Accuracy in the Separation Process by Density Profiling

Three-phase, horizontal, gravity separation vessels are the principal method of extracting oil and gas from unwanted produced water and solids prior to transportation. Traditionally, oil production separators have used separate single-point transmitters for interface and bulk level measurement. This paper shows how a profile of the different layers as opposed to single-point measurement can enable oil production and chemical usage to be optimised.

Practical Application of Electromyogram Radiotelemetry: The Suitability of Applying Laboratory-Acquired Calibration Data to Field Data

Abstract One of the practical problems with quantifying the amount of energy used by fish implanted with electromyogram (EMG) radio transmitters is that the signals emitted by the transmitters provide only a relative index of activity unless they are calibrated to the swimming speed of the fish. Ideally, calibration would be conducted for each fish before it is released, but this is often not possible. Consequently, calibration curves derived from more than one fish are used to interpret EMG signals from individuals that have not been calibrated. We tested the validity of this approach by comparing EMG data within three groups of three wild juvenile white sturgeon Acipenser transmontanus implanted with the same EMG radio transmitter. We also tested an additional six fish that were implanted with separate EMG transmitters. Within each group, a single EMG radio transmitter usually did not produce similar results in different fish. Grouping EMG signals among fish produced less accurate results than having in...