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Radio Science Conference, 1996. NRSC '96., Thirteenth National

Date 19-21 March 1996

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  • Thirteenth National Radio Science Conference. NRSC '96

    Publication Year: 1996
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    Freely Available from IEEE
  • Multi-user chirp modulation signals (M-CM) for efficient multiple-access communication systems

    Publication Year: 1996 , Page(s): 289 - 297
    Cited by:  Papers (2)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (400 KB)  

    We present a novel technique for a multi-user communication system utilizing binary chirp modulated (CM) signals. This suggested technique is motivated by the inherent interference rejection capability of such spread-spectrum type system, specially in circumstances where immunity against Doppler shift and fading due to multipath propagation are important. The chirp signals used are selected such that they all have the same power as well as the same bandwidth. Closed form expressions, as well as approximate analytical expressions, for the cross-coherence functions between the different forms of considered chirp signals are derived. The performance of a suggested coherent receiver structure is investigated and the corresponding error rates are presented. The results show that the proposed multi-user chirp signaling technique is efficient and promising as a multiple-access technique View full abstract»

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  • Channel sharing policies for a mobile radio network providing wireless telephone and dispatch services

    Publication Year: 1996 , Page(s): 299 - 308
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    Channel sharing policies are proposed for a mobile radio network that provides telephone and dispatch services. The two services have different features and different service fields. The salient features and operational principles of both services are described. Based on these features, channel sharing policies are proposed. Analytical models are established for the policies in order to gauge the performance of the network. Results are provided and discussed for nominal network parameters View full abstract»

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  • A non-destructive assay system for the verification of uranium fuel rods

    Publication Year: 1996 , Page(s): 609 - 616
    Cited by:  Papers (1)
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    This paper describes a Non-Destructive Assay System for the verification of uranium fuel rods used in nuclear reactors. The system is based on gamma-ray spectroscopy technique. It employs a NaI(Tl) Detector, a Photo-multiplier tube, a Multi-channel Pulse-height Analyzer, associated electronics and a lead collimator. Two segments of well-known enrichments are used as “Standards”. By selecting certain gamma-rays peaks in the uranium spectra, the U-235 enrichment can be measured. Measurements performed on the verification of fuel rods of a gave U-235 enrichment with relative accuracy of about ±5%. The obtained results showed that the system can be very useful for the physical inventory verification, accountability and control, of uranium fuel rods at nuclear reactors and at the fuel fabrication stage as well View full abstract»

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  • A novel target identification and discrimination scheme using matched spread-spectrum techniques

    Publication Year: 1996 , Page(s): 309 - 320
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    This paper presents a method of accurate identification using a radar sensor incorporating the matched frequency-hopping spread-spectrum (MFH/SS) technique. Our work is based on the fact that targets of different shapes have different frequency signatures. This means that each target is characterized by a special frequency dependence of the scattering cross-section. Our approach to identifying objects is based on matching the radar receiver circuit to the selected hopping frequencies which give maximum backscattering contribution for different identified targets at different look directions. Also, we suggest a single radar sensor incorporating modified techniques, MFH combined with angle diversity (AD) and cumulative matched frequency hopping (CMFH) for three-dimensional target identification. The results of a simulation study are presented showing the effectiveness of incorporating the MFH/SS technique in the radar sensor for enhancing target identification and provide the redundancy and complementarity provided by multiple sensors View full abstract»

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  • Linear and quadratic objective function effects on force directed method based analog placement

    Publication Year: 1996 , Page(s): 617 - 627
    Cited by:  Papers (5)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (552 KB)  

    This paper advocates the use of linear objective function in analytic analog placement. The role of linear and quadratic objective functions in the behavior and results of an analog placement algorithm based on the force directed method is discussed. Experimental results for a MCNC benchmark circuit and another one from text books are shown to demonstrate the effect of a linear and quadratic objective function on the analog constraints satisfaction and CPU time. By introducing linear objective function to the algorithm, we obtain better placements in terms of analog constraint satisfaction and computation cost than in case of conventional quadratic objective function View full abstract»

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  • Preliminary results of a broad beam RF ion source with electron plasma interaction

    Publication Year: 1996 , Page(s): 629 - 636
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    A new design of a broad beam RF ion source is made to deliver currents of 100 μA up to 30 mA with extraction voltages 200 V up to 2 kV. Its plasma intensifying system is made with both addition of electrons from an immersed filament in the discharge and axial magnetic field of 70 up to 300 G. Uniform beam density distribution is made with a planner graphite cathode which has a number of holes of varying diameter arranged to produce perveance matching with the normal Gaussian distribution of the beam density variation of the output current is studied with the variation of extraction magnetic field intensity, discharge pressure and electron injection into the plasma. The influence of electron injection into the plasma is found to have a great effect on increasing the extracted current to about four times its value without electron injection. The increase of extraction voltage is limited with the use of electron injection at Vex>2kV due to the presence of breakdown inside the discharge tube View full abstract»

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  • A novel built-in-self test structure for analog circuits with application to filters

    Publication Year: 1996 , Page(s): 363 - 370
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    The aim of built-in-self test (BIST) is to increase the number of test points. But there is a tradeoff between the chip area and pin overhead. An alternative novel BIST for fault diagnosis and testing of analog circuits is presented to enhance the testability of the circuit under test. This novel technique minimizes the required test points to only input/output pins. Moreover, the technique consumes less chip area and monitors the obtained data with high speed View full abstract»

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  • Design and implementation of MW balanced amplifier using branch-line couplers

    Publication Year: 1996 , Page(s): 385 - 394
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    The design and implementation of MW balanced amplifier operating at 3.5 GHz have been performed using microstrip technology. A duroid substrate of relative permittivity 2.2, and Motorola MRF-9411, L packaged MW transistors are used. A network computer analysis program has been developed to asses the amplifier performance, and its results are compared to the practical measurements of the implemented schematic. The amplifier provides a power gain of 9 dB with input and output VSWR of 1.65, and 1.35 respectively. Such an amplifier can be used in satellite communication, electronic support measure (ESM) receivers, and airborne radar View full abstract»

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  • The wavelet transform: a review and application to enhanced data storage reduction in mismatched filter receivers

    Publication Year: 1996 , Page(s): 1 - 22
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1288 KB)  

    The wavelet transform (WT) is an efficient time-frequency signal processing tool. In the first part of this paper, a general review of the characteristics of some of the popular time-frequency representations (TFRs) is given. In particular we review the short-time Fourier transform (STFT) and the Wigner distribution (WD). The WT is then reviewed in detail as well as the discrete (orthogonal) wavelet transform (DWT). It is shown that the WT overcomes the main drawbacks of the STFT and the WD w.r.t. simultaneous time and frequency resolution. In the second part of the paper, we present a contribution dealing with a new application of the DWT. In particular, we show that by using orthogonal wavelet basis functions, we achieve a considerable reduction in the data storage needed for the matched receiver of chirp signals. Linear and nonlinear chirp signals with Gaussian envelopes are considered. The simulation results show that with more than 80% reduction, the performance of the matched filter (mismatched in this case) is very close to that of the classical MF receiver without data compression. The results are very important for chirp pulse compression radar systems as well as for digital communication and multiple-access systems based on the use of chirp signals View full abstract»

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  • Smith chart based analytical design of lumped transistor amplifiers

    Publication Year: 1996 , Page(s): 395 - 407
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (468 KB)  

    The design of a radio-frequency or a microwave amplifier, for any load and source impedance, using an analytical design method based on the Smith chart equations is presented. Five different cases are considered namely; (i) maximum gain, (ii) minimum noise figure at both the input and output, (iii) minimum noise figure at the input and maximum gain at the output, (iv) minimum noise figure at the input and a certain gain for the whole network, and (v) broadband output network amplifier design. These designs use the scattering parameters of the transistor and the Smith chart equations and are limited to lossless L-sections only. It is observed that the obtained circuit parameters are accurate compared to those obtained manually working with a Smith chart. Also the broadband design is exact and do not follow the trial and error method used by other authors View full abstract»

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  • Effect of shunt resistance and reverse saturation current on the performance of solar cells

    Publication Year: 1996 , Page(s): 537 - 545
    Cited by:  Papers (1)
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    A study of the solar cell model concerning the effect of shunt resistance (Rsh) and the reverse saturation current (IO ) on the performance of solar cells is presented. It is found that an upper bound for the fill factor determines the maximum attainable efficiency. Also, there is a shunt value after which the model behaves independently of the value of the shunt resistance. The effect of the product of Rsh and IO on the maximum efficiency was further studied. This resulted in detecting a region of improved performance for both Rsh and IO View full abstract»

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  • Penetration of the nuclear electromagnetic pulse (EMP) in lossy dielectric media

    Publication Year: 1996 , Page(s): 193 - 198
    Cited by:  Papers (1)
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    The nuclear electromagnetic pulse (EMP) presents a dangerous threat to electronic systems. We investigate the penetration capabilities of the EMP through a lossy dielectric. A transient solution is presented that takes into consideration the special time function of EMP pulses and the dispersion of the medium. The spectrum and time domain responses of the induced pulses at different depths are computed for different degrees of medium conductivity. The results are of importance in determining the EMP shielding capabilities of different media and to get a measure of the EMP leakage through buildings, antenna radomes and shelters View full abstract»

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  • Adaptive system identification based on adaptation with data discarding

    Publication Year: 1996 , Page(s): 441 - 449
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    At high data rates, the adaptation processor of the adaptive filter may be unable to perform the multiplications required by the adaptation algorithm each baud interval. A direct, but expensive, solution of this problem is to use parallel processing. The present paper presents a simple alternative solution that is suitable for the case of adaptive system identification. The idea of the proposed method is to make one iteration for each several baud intervals. The idea is implemented as follows. With N being the number of adaptive filter coefficients, N successive input samples and the corresponding sample of the system output are injected to the adaptation processor to perform one iteration. Input and output samples that come before the termination of this iteration are discarded by the adaptation processor. After termination of the iteration, new N input samples and the corresponding output sample are injected to the adaptation processor and the procedure is repeated. The above idea is applied to both the LMS algorithm and the sign algorithm. The effect of data discarding on the transient performance of the identification procedure is studied by computer simulations for both white and correlated inputs of the system View full abstract»

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  • Partially coherent detection of continuous phase chirp (CPCM) signals

    Publication Year: 1996 , Page(s): 485 - 495
    Cited by:  Papers (1)
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    This paper treats the partially coherent detection of continuous phase chirp modulation (CPCM) signals. The optimum partially coherent receiver structures are described. Suboptimum receivers are also described and the corresponding bounds on error rate are calculated for optimum signal parameters. The optimum signal parameters are obtained for each degree of channel coherency by using a search program for the error probability versus the signal parameters View full abstract»

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  • Solution of the three-dimensional corner reflector antenna problems using the method of moments

    Publication Year: 1996 , Page(s): 141 - 148
    Cited by:  Papers (1)
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    A reflector antenna utilizing three planar reflectors and a 3/4λ-unipole radiator has been used to increase the gain of the two-dimensional corner reflector antenna. The calculation of the antenna parameters were based on the image and electromotive force (EMF) methods. The method of moments is used for calculating the input impedance, gain and radiation patterns for two cases. In the first case continuous grounded conducting plane reflectors were used with the method of images. In the second case grided type plane reflectors consisting of parallel wires of suitable radii separation and length are used directly without the method of images. A good agreement between the results is indicated View full abstract»

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  • Wideband VHF monopole antenna loaded with optimized resistivity loading

    Publication Year: 1996 , Page(s): 199 - 207
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    An optimization process is carried out for determining the optimal continuous resistive load of the monopole antenna to establish the wideband performance over the operating frequency range of 30-90 MHz. The optimization process depends upon the modification. A non-adaptive tuning circuit was synthesized to promote a good impedance match for the entire frequency range View full abstract»

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  • Principles of low PIM hardware design

    Publication Year: 1996 , Page(s): 355 - 362
    Cited by:  Papers (3)  |  Patents (7)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (356 KB)  

    In space RF communications payloads, it is increasingly required that high-power multi-channel transmitters and broadband receivers have shared, or closely adjacent RF feeds. Because of the large power level difference between the transmit and receive signals and the limitation of frequency allocation, passive intermodulation (PIM) interference due to passive non-linearities in the high-power transmission path can be serious problem. One of the main sources of PIM in RF microwave systems is the metal-to-metal contact. A contact model regardless of the suspected non-linear mechanisms, i.e. semiconductor, electron tunnelling and microdischarge, has been used to explain the non-linear effect at metallic contacts. The model requires that the non-linear effect is current dependent and the PIM level is proportional to the current density at the contacts. Because metal-to-metal contact in an RF coaxial connector is unavoidable, an alternative has to be developed. The work reported represents some of our efforts toward developing a demountable RF coaxial connector which does not involve metal-to-metal contact in any electrically significant part, i.e. a “contactless connector”. The novel design of the coaxial contactless connector and the theoretical analysis are described View full abstract»

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  • Objective methods for radar systems evaluation

    Publication Year: 1996 , Page(s): 497 - 505
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    In view of lack of a simple and generalized procedure to technically compare between a group of radars, a set of theoretical criteria have been adopted, and mathematical relations are derived for radar system evaluation. These radars may have different structures and technologies but they are utilized in the same application. In order to utilize the derived equations, the technical parameters of the radar modules (transmitter, receiver, antenna, signal processing, displays, ECCM techniques, and other radar system control functions) are required in advance. If some of the major radar parameters are not available default values are assigned for these parameters. These values are either known to the radar specialists or derived from other radar parameters based on mathematical expressions. Examples are given and the application of the calculated results to radar system analysis and design are discussed View full abstract»

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  • Neural matched filter detection in synchronous code-division multiple-access (CDMA) systems

    Publication Year: 1996 , Page(s): 259 - 271
    Cited by:  Papers (1)
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    In communication networks employing spread-spectrum (SS) code-division multiple-access (CDMA), the performance of single user matched filter receivers are highly degraded when the relative powers of the interfering signals are large (the near-far problem). Optimum multiuser (maximum likelihood) receivers have been suggested to overcome the near-far problem, but they are too complex to implement, specially when the number of users is high. In addition, such multiuser detectors lacks security, which is one of the main advantages of SS techniques, as all of the users messages are detected simultaneously. We introduce a new technique for separately demodulating the packets belonging to different users using feedforward artificial neural networks. A special neural network, the neural matched filter (NMF), is trained not only to detect the spreading code of the assigned user but also to suppress the multiple-access interference caused by the waveforms of other users. This technique is shown to be highly resistant to near-far effects. A comparative performance analysis of conventional, optimum multiuser and NMF single user receivers is carried out via Monte Carlo simulation. It is shown that the proposed single user NMF detectors have a better performance than the optimum receiver in severe near-far cases. This exalted performance is due to the implicit cancellation of cross-correlation between different users codes. The suggested technique is also not sensitive to the code selection and does not necessitates the use of sophisticated optimized code families. Our suggested NMF technique solves most of the security, complexity and near-field problems associated with CDMA systems View full abstract»

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  • Radioholographic antenna measurements with extraterrestrial sources

    Publication Year: 1996 , Page(s): 53 - 60
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    The interferometric (correlational) radioastronomical antenna measurements with terrestrial sources is a variant of the radioholographic method. This method, which is illustrated, requires a special two-channel correlational receiver and an additional tracking receiver. The radio source is combined with the tested source in an interferometer. As a signal source, one may use a variety of radio sources and satellites. The article presents some experimental results obtained from different antennas. The peculiarities of the measurements, using natural radio sources and satellites, are discussed View full abstract»

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  • Performance analysis of adaptive DFE-RLS in mobile fading channels

    Publication Year: 1996 , Page(s): 563 - 569
    Cited by:  Papers (1)
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    An extensive analysis of using the decision feedback equalizer (DFE) that uses a recursive least squares (RLS) adaptation algorithm to equalize multipath fading radio channels in general and digital cellular radio (DCR) channels in particular is performed. Throughout this analysis, the effect of the fade rate, multipath spread, equalizer size, and tracking speed on convergence rate and steady state behavior of a DFE-RLS is examined. Also, for a given fade rate, a compromise between fast adaptation (necessary to track variations in the input statistic) and slow adaptation (necessary to contain noise in the adaptive process) is performed. In addition, for a proposed mobile communication system for North America, recommendations are also documented for some system parameters to ensure an acceptable performance View full abstract»

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  • A proposed ATE for digital systems

    Publication Year: 1996 , Page(s): 209 - 220
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    An ATE-system that can perform digital system testing to localize the faulty part is developed. The test system strategy is based on system and/or board partitioning and hierarchical testing. Testing takes place automatically by software programs within complete test packages including test models, test simulation, fault detection and fault diagnosis View full abstract»

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  • Effect of power change from interferer sources on the CDF probability in a mobile radio cellular system

    Publication Year: 1996 , Page(s): 409 - 416
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    Most cellular radio systems provide for the use of transmitter power control to reduce co-channel interference for a given channel allocation. Efficient interference management aims at achieving acceptable carrier to interference ratios (CIR) in all active communication links within the system. This paper is a study of the effect of decreasing the power from interferer sources in a frequency-reuse system on the co-channel interference and cellular channel capacity. It also provides a comparative cumulative distribution function (CDF) probability performance study for the AMPS (Advanced Mobile Phone System) and GSM (Global System for Mobile Communications) systems at the pertaining CIR levels of 18 dB and 11 dB respectively. A 7 cell cluster is used throughout the simulations, in line with the AMPS system. However a 3 cell cluster is used for the GSM frequency-reuse model View full abstract»

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  • Comparing the dynamic behavior between LFSRs and counting techniques

    Publication Year: 1996 , Page(s): 231 - 237
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    Transition counting is one of the schemes which is used for testing digital circuits. A relation for the aliasing error probability has been deduced which depends on the length of the input pattern. Previously, we have proved that the final value for aliasing error probability for both linear and counting techniques are similar. However, the practical results indicate that the linear technique has a better performance than the counting technique. We study the dynamic behavior for the counting technique. The results are discussed and compared with the results obtained from the linear technique which supports the empirical and practical conclusions for the superiority of the LFSR View full abstract»

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