Showing papers on "Wideband published in 1977"

Transmitting signals over alternating current power networks

Abstract: This invention relates to communication systems of the type particularly useful in power line communications. Signals to be transmitted, which can be in the form of short, fixed frequency signals, are expanded in time and/or bandwidth to provide a longer signal with a variable frequency. At the receiver, power line noise, which is typically either short wideband noise or long narrowband noise, is removed and the remaining expanded signal is detected. The expanded signal can then be compressed in time and/or bandwidth to reproduce the original signal.

New Application of Evanescent Mode Waveguide to Filter Design

Abstract: Evanescent waveguide (rectangular or round) sections are used in conjunction with an admittance inverter synthesis technique incorporating frequency variable turns ratios to realize wideband microwave (up to 1 octave) and low frequency (60 MHz) low-loss bandpass filters. This work extends and corrects previous published information.

Beamformer for wideband signals

Abstract: A beamformer for wideband signals wherein the elemental signals available the sensors of a receiving array are subjected to Fast Fourier Transformations which decompose them into a plurality of narrowband signals. The narrowband signals, which consist of signals having the same Fourier coefficients, are subjected to appropriate phase shifts to form a plurality of narrowband beams having the directional characteristics desired. Reconstruction of the wideband signal is accomplished by subjecting the narrowband beams to an inverse Fast Fourier Transform. The beamforming is thus performed with narrowband signals, and only phase shift circuits are required.

Microstrip antennas and arrays. Part 2: New array-design technique

Abstract: Open-circuit terminations on half-wavelength stubs form the radiating elements in a new design technique for linear microstrip microwave arrays. Measured results, on computer-designed resonant and wideband travelling-wave arrays with broadisde beams, demonstrate the technique; the effects of corporate feeds and radomes are also considered. The computer design of medium gain arrays, with H-plane sidelobe levels below about -21 dB, demands characterisation of the microstrip T-junction with an accuracy that is currently unavailabe, and the dimensional precision has to be obtained by experimental means. It is concluded, to date, that the known extraneous sources of radiation do not inhibit the control of H-plane sidelobes to a level of at least -25 dB and the new design technique makes microstrip arrays highly competitive with their conventional waveguide counterparts.

Efficient wideband guided-wave acoustooptic Bragg diffraction using phased surface acoustic wave array in LiNbO(3) waveguides.

Abstract: Efficient wideband guided-wave acoustooptic Bragg diffraction has been demonstrated using a phased surface acoustic wave array in Y-cut LiNbO3 waveguides. The results of measurement made on the devices which employ the first-order acoustic beam steering from six-element phased-SAWs of relatively small total acoustic aperture, at the center frequency of 325 MHz, have shown that accurate tracking of the Bragg condition is achievable for a frequency band of more than 250 MHz. In one of the deflectors that employ a larger total acoustic aperture, only 68 mW of electric drive power or 3.5 mW of acoustic power was required to diffract 50% of the light over a bandwidth of 112 MHz. This bandwidth is a nearly sixfold increase over that of the deflector that employs a single SAW of identical aperture. The quality of both deflected and undeflected light beams was very good.

Detection of Digital FSK and PSK Using a First-Order Phase-Locked Loop

Abstract: A classical problem in digital frequency-shifted keyed (FSK) demodulation is the evaluation of the bit error probability performance when an estimator-correlator that incorporates a phaselocked loop (PLL) is employed. Although some attention has been devoted to this problem in the past, an accurate account of the mechanism which produces decision errors has not yet been advanced. This paper examines a special case, viz., a first-order PLL preceded by a wideband IF filter, of the above problem using a new approach which is based upon the renewal Markov process theory and the Meyr distribution. In particular, the ad hoc approach of invoking the Gaussian assumption on the decision variable and patching it with a correction term based on Rice's click theory is not used. Rather, the effective noise is properly characterized by unfolding the renewal Markov process associated with the loop phase error. As a slight extension of the results, the performance of the above PLL detector operating on low data rate PSK is given and demonstrated to be approximately 3 dB superior to that of FSK reception. The theory and analysis presented herein apply to the special case where the bandwidth of the IF filter preceding the first-order PLL is required to be several times the data rate because of frequency uncertainties due to channel Doppler and oscillator instabilities, but the frequency deviation to data rate ratio may be chosen small (if desired) to optimize system error probability performance. In addition to presenting results for the case where the oscillator instabilities are assumed absent and channel Doppler is prefectly tuned out at the receiver oscillator, the effects of small residual Doppler on bit error probability performance is considered. In all cases tested, excellent agreement was obtained between theory and computer simulation results.

Wideband optical isolator

Abstract: A linear voltage controlled current sink is used to power a linear LED with fast optical rise time. The signal is transmitted through a small aperture in a grounded shield plate. The receiver is a PIN photodiode with fast optical rise time.

Microwave wideband open resonator of large aperture

Abstract: A method of constructing a large Fabry-Perot type resonator for operation in the microwave region is described. Simple and moderately inexpensive techniques are used to fabricate the mirrors which are 1 m in diameter and have a radius of curvature of 10 m. Tests show that Q-factors in excess of 105 may be observed at 10 GHz. The system is found to support resonances at frequencies over a wide bandwidth, namely 2-26 GHz.

Optimum pulse shaping application of binary transversal filters used in satellite communications

Abstract: The implementation of binary transversal filters (b.t.f.) is gaining wide acceptance, due to their operational adaptability to variable bit rates, their achievable high out-of-band attenuation and linear phase performance and to the recent availability of medium-scale integrated components such as charged-coupled devices.The design and evaluation results of a b.t.f. meeting the single channel per carrier Intelsat satellite communications specifications are presented, which are based on Mueller's synthesis method. The performance evaluation problems of these type of filters are also described and, in particular, emphasis is given to the following: out-of-band to in-band power ratio inaccuracies when wideband measurement techniques are employed, and the evaluation of the r.m.s. jitter of b.t.f. based on the jitter probability density function.

Guided-Wave Acousto-Optic Signal Processors For Wideband Radar Systems

Abstract: Through the supports of the ONR and NSF we have recently developed several schemes which utilize multiple surface acoustic waves for wideband efficient guided-wave acoustooptic (AO) Bragg diffraction The development of these wideband schemes has made it possible to design and fabricate very wideband guided-wave (thin-film) AO devices, and has thus paved the way for the realization of wideband AO processors in thin-film form In this paper a review of the more recent developments on wideband (up to 500 MHz bandwidth) guided-wave AO signal processors, emphasizing those being carried out at the authors' institution, is given The processors to be discussed include spectrum analyzers, convolvers and pulse compressors Typical performance characteristics that have been obtained are presented The guided-wave processors, in comparison to their bulk-wave counterparts, possess inherent advantages of requiring less RF drive power, being smaller, lighter weight, less susceptible to environmental effects, and more integratable and thus potentially less costly Consequently, the guided-wave versions, when fully developed, should complement the existing bulk-wave processors© (1977) COPYRIGHT SPIE--The International Society for Optical Engineering Downloading of the abstract is permitted for personal use only

Optical coupling modulation in traveling‐wave cavities

Abstract: Efficient very wideband coupling modulation of the CO2 laser has been achieved in a traveling‐wave cavity configuration termed ’’ring modulator’’ that avoids the usual transit‐time‐limited bandwidth of conventional coupling modulation. A 10.6‐μm modulation experiment demonstrates flat frequency response from 10 MHz to 1 GHz.

Tandem connections of wideband and narrowband speech communications systems: Part 1–narrowband-to-wideband link

Abstract: The performance of a tandem connection of narrowband and wideband speech communication systems is evaluated. Specifically, the narrowband system consists of a conventional linear Predictive Coding (lpc) vocoder operating at a bit-rate of 2.4 kb/s and the wideband system consists of a Continuously Variable Slope Delta modulator cvsd operating at a bit rate of 16 kb/s. In Part 1 of this paper the properties of the narrowband-to-wideband link are investigated and in Part 2 the properties of the wideband-to-narrowband link are investigated. In part 1 the snr (signal-to-quantizing noise ratio) of the cvsd coder is analyzed over a 50-dB variation of the input signal levels and for a variety of source excitations for the lpc synthesizer. It is shown that snr improvements in the cvsd coder of 2 to 2.5 dB are possible in the slope overload region of the coder by modifying the source excitation of the lpc synthesizer and by preprocessing the input signal to the coder with an allpass filter. Both methods aid in reducing the peak factor (peak-to-rms level) of the input speech to the coder. Subjectively, however, only slight improvements in quality, if any, were observed with these modifications.

Linear filtering with wide-band noise disturbances

Abstract: We consider the analog of the linear (Kalman-Bucy) filtering problem when the observation and driving noises are random processes with large, but finite, bandwidths. We show that as the bandwidth of the noise tends to infinity there is a natural limiting Kalman filtering problem whose solution is suboptimal for the original problem. When the Kalman-Bucy filter is used as an estimator in the original problem an error proportional to the inverse of the bandwidth of the actual system noises is incurred. We compute this error and outline a design procedure based on it. The results of numerical experiments are reported to illustrate the analytical work.

Single dispersive delay line compressive receiver

Abstract: A wideband compressive receiver using only one surface acoustic wave (SAW) device in a time-multiplexed fashion. A short pulse into the SAW device generates a "downchirp" local oscillator sweep signal which, after appropriate band limiting, is mixed with the incoming signal of unknown frequency. The lower sideband is filtered out and applied to the same SAW device as an "upchirp". Timing of the resulting compressed pulse emanating from the SAW device output is related to the frequency of the unknown signal.

Wideband equaliser used in video playback channels - has two=stage network providing overall flat response characteristic at output

Abstract: The wideband equaliser comprises a pre-amplifier to the input of which is connected the output of the magnetic head of the playback system. To compensate for the HF fall-off in the response dur to head losses etc., the preamplifier in followed by a first stage equaliser with a frequency response having a sharp fall off at the lower frequencies. The second stage of the equaliser has a response which rises steadily with increasing frequency. Since simple networks are used for both parts of the equaliser, up to this point the groupo delay is independent of frequency. To allow for this, an all-pass filter is inserted. Finally, a low-pass filter suppresses frequencies above the pass band to reduce noise components in this range. The final output response of the circuit is essentially flat over the chosen frequency band. The circuit is esp. suited to television (video) tape recorders.

Calculation of wideband random-noise powers in television systems

Abstract: Expressions are derived for the loss experienced by wideband random noise with various power-density spectra in networks associated with television transmission systems. Values are tabulated for television system I with the total noise power modified by each of two weighting networks used in noise measuring circuits and/or the de-emphasis network used to complement pre-emphasis with f.m. radio transmission.

Adaptive spread spectrum receiver using SAW technology

Abstract: : A spread spectrum receiver implemented with surface acoustic wave (SAW) technology is discussed, and experimental results for the detection of a signal embedded in narrow band interference are presented. An adaptive version of that receiver is also discussed for the case of detecting a signal in the presence of a wideband Gaussian (but not necessarily white) interferer whereby an attempt is made to estimate the unknown noise spectral density. (Author)

Nonnlinear distortion offset unit

Abstract: PURPOSE:To obtain a non-linear distortion offset unit which is suitable for the use in the wideband transmission channel, by cascade-connecting a circuit which is a combination of a circuit that equalizes the linear transmission error and another circuit which sets off non-linear distortion to the given transmission system.

Wideband DC-coupled amp/schmidt

Abstract: AN ALL MONOLITHIC, dc to > I GI*, amplifier/Schmidt trigger with 8 mV rms input sensitivity has been designed using a junction-isolated 5 GHz fT process in spite of the inherent high capacitances. Included on a 1.39 x 1.59 mm chip are electronic gain control, 180’ phase switching, ECL line driver output, all biasing circuits and a one-shot LED driver. A functional block diagram is shown in Figure 1. The amplifier is composed of a cascade of three identical modified Gilbert gain cells’. The current gain of this type of circuit is set by the ratio of device input impedances which in turn are a function of their quiescent currents. Because the currents are added at the output of each stage, a cascade requires a geometric increase in the power dissipation for each additional stage. N t h even the first stage current constrained to be fairly high to obtain wide bandwidth, a cascade would be unreasonable. Modifying the gain cell by the addition of emitter resistors allows the input impedance and thus the current gain, to become independent of dc bias. Furthermore, this modification generally results in a substantial reduction in the mean squared output noise current (in2) since the expression is changed from:

Wideband absolute calibration system

Abstract: An absolute calibration system for a wideband superheterodyne receiver in which a fixed-frequency signal source supplies an IF signal to the mixer for conversion to an RF signal. The RF signal produced in this manner passes through the RF components of the receiver to the input port of the receiver where it is detected by a wideband detector. The video output signal from the detector provides an indication of the RF gain of the receiver required for calibration. The calibration results provided by the IF signal are compared to that provided by a single frequency, absolute calibrated RF source to produce a correction factor which is applied to the IF calibration data over the entire RF band.

Wideband 1.064 micrometer detector evaluation

Abstract: Several types of communications detectors for use in a 400 Mbps 1.064 micrometer laser communication system were evaluated and characterized. The communication system Bit Error Rate (BER) performance was measured, and test results for the best detector of each type are summarized. The complete BER curves are presented. The 400 Mbps 1.064 micrometer communication system receiver test bed is described. The best performance levels which can be achieved by focusing the signal to diffraction limited spots on the photosensitive area are cited.

The Design, Implementation and Operation of Bidirectional Wideband CATV Networks for Two-Way Video Audio and Data Services

Abstract: This paper describes the design, implementation and maintenance of the broadband two-way CATV systems. These systems are used for distribu-tion of video and audio signals, both one-way and two-way, as well as two-way data and interactive services. Several experiments will be describe dutilizing such two-way services. The unique system concept employing a hub design with radial trunk lines willbe shown to be a most powerful concept in implementing these services.

Wide-band rotary transformer—Unbalanced current analysis

Abstract: Performance of a wide-band rotary transformer with approximately 1000:1 bandwidth (80 kHz-80 MHz) is described A previous paper [1] gave theoretical analysis and experimental results based upon lossless balanced, transmission line theory This paper extends the results to the case of a shielded transformer, and uses a combination of balanced and unbalanced line theory to account for losses and predict frequency response Theoretical results are confirmed by data measured on a prototype coupler

Performance Comparison of Bipolar Alternate Mark Inversion and Conditioned Diphase Waveforms Over Wireline Media

Abstract: : This report was prepared for the Defense Communications Agency to study the performance of two waveforms competing for implementation in the Defense Communications System. The waveforms, Bipolar Alternate Mark Inversion (BAMI) and Conditioned Diphase (CDtheta), were studied both from a theoretical standpoint and with experimental breadboard hardware designed and built in- house. Theoretical performance curves for both waveforms operating in wideband gaussian noise were developed and the hardware was tested against wideband gaussian noise. The results of testing the waveform over Griffiss AFB cable plant are presented along with computer-generated distributions of data bit errors encountered. The effects and problems involved in recovering timing information from two waveforms are not covered in this report. The results indicate that, with white gaussian noise as the only transmission impairment, the two waveforms perform nearly identically. Their performances are also close when operation is over cables with moderate amounts of intersymbol interference and attenuation. However, when intersymbol interference and attenuation are severe (long calbes, high data rates, and poor-condition cables), BAMI has an advantage of approximately 30 percent, expressed in terms of maximum usable bit rate for a given length of cable. Another conclusion reached was that impulse noise is the limiting impairment of the Griffiss AFB cable plant.

Specialized drive waveforms for the parametric acoustic source

Abstract: In addition to its narrow beamwidth and wideband capability, the underwater parametric acoustic source has the advantage of maintaining a relatively constant beamwidth over a wide range of difference frequencies. However, for some applications the beamwidth of the difference frequency is narrower than desired or adjustable beamwidth is required. This paper describes techniques by which the beamwidth at a given difference frequency can be increased and varied over a 3 to 1 range by controlling the input waveform and amplitude to the transducer. The effect of the waveform changes on the harmonic content of the difference frequency energy is also discussed. The relatively low efficiency of the source prompts investigation of methods to increase overall efficiency. Techniques to improve efficiency through the use of waveforms suitable for switching drivers are described and supported by experiment.

Wideband Acousto-Optic Radiometry

Abstract: The technique of acousto-optic spectrum analysis can be used to improve the signal to noise of r.f. signals by the noncoherent integration of photoelectrons in a properly configured optical sensor. The requirements placed upon the sensor and acousto-optic device to obtain a given processing gain, resolution, analysis bandwidth, and dynamic range are discussed for bulk optical devices.© (1977) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.