Showing papers on "Wideband published in 1983"

Gap detection as a function of frequency, bandwidth, and level.

Abstract: The threshold for detection of a temporal gap in a noiseband was measured. A notched noise masker was used to restrict listening to a limited spectral region. Threshold was measured as a function of center frequency, bandwidth, and level. For a signal bandwidth of one‐half the center frequency, the gap threshold decreased from 22.5 ms for a center frequency of 0.2 kHz to 3.2 ms at 8.0 kHz: a wideband condition provided an estimate of 2.3 ms, a value in agreement with previously published estimates. Bandwidth manipulation showed that the variation with frequency was not due to changes in absolute bandwidth alone. The effect of changes in level was determined at three frequencies, 0.4, 1.0, and 6.5 kHz, using a signal bandwidth of half the center frequency. At all frequencies gap threshold decreased as the signal spectrum level was raised from 10 to 25 dB, but a further increase to 40 dB showed no additional improvement. At frequencies up to about 1.0 kHz, the variation of gap threshold with frequency matches well the reciprocal of the bandwidth of the auditory filter, as determined from masking experiments using a notched‐noise masker. This suggests that the temporal response of the auditory filter may limit gap detection at low frequencies.

Wideband cable network

Abstract: In an interactive wideband cable network in which several wideband services, such as television or video signals, can be provided simultaneously from a central service position to a remote wideband switch to which several customers are connected, the central service position is connected to the wideband switch by one or more passively tapped optical fibres through which fixed-time services are provided and the central service position is connected to the wideband switch through one or more dedicated optical fibres through which a customer can request and receive "on demand" wideband services.

Dual band phased antenna array using wideband element with diplexer

Abstract: A dual band, phased array antenna especially adaptable for tactical radar capable of performing search, track and identification in a hostile jamming environment The dual band array antenna is essentially two antennas sharing a common antenna aperture The two antennas possess separate feed system and beam steering control Thus, the beams for each frequency band can be steered independently and simultaneously This design utilizes an ultra-wide band radiating element which can operate over approximately an octave bandwidth encompassing two adjacent microwave bands In particular, the dual band signals can be received efficiently by the radiating element A dual band coaxial-to-waveguide transition can be used to carry the signals to a diplexer The dual band signals are separated at the diplexer and can be processed in separate feed networks The advantages of this dual band phased array technique include not only good impedance characteristics but also the absence of grating lobe formation and cross coupling problems

Wideband Interference Cancellation in Adaptive Sidelobe Cancellers

Abstract: This paper presents numerical results from a study of sidelobe cancellers operating against wideband interfering signals. The study was designed to provide information that would be useful to system designers. Among other things, we address the question of whether it is best to enhance the bandwidth capability of the canceller by using tapped delay lines or simply by using more auxiliary elements. We also develop guidance rules to help the designer determine the number of adaptive loops required for a given environment.

Integrated narrowband and wideband TDMA networks

Abstract: Time Division Multiple Access (TDMA) is being utilized widely in domestic and international communication networks. The types of TDMA networks in operation fall into two categories: Wideband and Narrowband. In the past few years, a number of Wideband and Narrowband TDMA networks have gone into operation. However, these networks have typically operated as independent nets. As the existing Wideband TDMA networks expand into cities with a smaller amount of originating traffic, a major economic problem occurs. It becomes difficult to justify the cost of a Wideband TDMA station for the smaller amount of traffic. This invention presents an approach that solves the above problem by providing an integrated network with Wideband TDMA for the large cities and Narrowband TDMA for the smaller cities.

Frequency-selective scintillation effects and decision feedback equalization in high data-rate satellite links

Abstract: Ionospheric irregularities produce signal amplitude and phase scintillations in transionospheric satellite channels When the electron-density fluctuation is large, the channel coherence bandwidth is small, causing the scintillations to decorrelate at different frequencies within the bandwidth of a wide-band signal Frequency-selective scintillation introduces delay spread and intersymbol interference, which can severely limit the usable capacity of the channel This paper, largely tutorial in nature, relates adaptive equalization techniques, which have been developed previously for other dispersive channels, to the problem of wide-band satellite links operating through a highly disturbed transionospheric channel Pertinent features of the ionospheric channel and characteristics of signal scintillations are summarized Effects of frequency-selective scintillation on high data-rate wide-bandwidth digital communication links are described in some detail Intersymbol interference caused by the loss of channel coherence over the signal bandwidth is shown, via simulations, to severely degrade the performance of a conventional coherent binary PSK receiver An adaptive decision feedback equalization technique is then shown to be a powerful method of mitigating frequency-selective disturbances in high data-rate satellite links

Wideband IF amplifier with complementary GaAs FET-bipolar transistor combination

Abstract: A wideband intermediate frequency (IF) amplifier including a GaAs FET input portion and a bipolar transistor output portion is disclosed. The high gain of the GaAs FET over higher frequencies is complemented by the high gain of the bipolar transistors at lower frequencies to provide high amplifier gain over a large bandwidth. The GaAs FET and bipolar portions are coupled by means of an equalizer circuit matching the two portions together only at the higher frequencies of the IF band to provide an inexpensive, high performance IF amplifier particularly adapted for use in a direct broadcast satellite receiver operating in the super high frequency (SHF) band.

Wideband High Gain Small Size Monolithic GaAs FET Amplifiers

Abstract: A series of two to four stage monolithic amplifiers operating with a gain of 15 to 42 dB and covering the 0.1 to 2 till 4 GHz frequency band has been realized. A high density of integration has been achieved (active area of 0.2 mm/sup 2/) as no decoupling capacitors nor inductances have been used.

A New Wideband, High Gain Suspended Substrate Line Planar Array for 12 GHz Satellite T.V.

Abstract: A new type of planar antenna using low loss Suspended Substrate Lines (S.S.L.) has been studied for 12 GHz satellite TV reception. The design and optimisation of the S.S.L. feed network and of the antenna element are presented. A 4 × 4 element planar array using this design is described giving better than 2:1 VSWR in the frequency range of 11-13 GHz. Its gain of about 22 dB from 11.6 to 12.6 GHz gives an antenna efficiency lying between 90% and 70% in the above mentioned bandwidth.

Worst-Case Jamming for Frequency-Hopping Code Acquisition

Abstract: This paper is concerned with the description, analysis and optimization of an FH spread spectrum code acquisition system in the presence of partial-band noise interference plus thermal noise. The system employs matched-filter detection with hard per-channel decisions and a multiple-test verification logic. The results show that a robust jamming strategy is wideband, independently of the jammer-to-signal power ratio, and that performance is fairly sensitive to the limiter threshold setting.

High Frequency AO Bragg Deflector Using a Single-Crystal ZnO Thin Film

Abstract: This report describes acoust-optic (AO) Bragg deflectors using ZnO thin film. The single-crystal ZnO films on sapphire have been grown by RF magnetron sputtering and measured to have about 1.2 dBcm-1 attenuation for guided 0.63 µm laser light and to have about 4% mechanical coupling coefficient, k2, for 1st order mode of SAW. These excellent properties of ZnO film have realized a high diffraction efficiency of 50% with 1 W input power of SAW at about 1 GHz on AO Bragg deflector. The suitable design of interdigital transducers (IDT) will make it possible to realize the wideband AO Bragg deflector.

Design Of Wideband Acousto-Optic Bragg Cells

Abstract: The design of wideband acousto-optic Bragg cells is described. Techniques for optimizing the device performance parameters are discussed. These techniques have been applied to increase the diffraction efficiency of wideband Bragg cells. Experimental re-sults obtained at 0.633 and 0.83 micrometer have demonstrated GHz bandwidth and diffrac-tion efficiencies of about 10 percent per RF watt.

Wideband HF Channel Prober: System Description.

Abstract: : The high-frequency, extended-line-of-sight (HF ELOS) channel, which is planned as the primary intra-task-force communication link, is a multimodal channel involving modes of widely disparate characteristics. The surface-wave mode is relatively broadband, while the sky-wave modes are substantially more limited in bandwidth because of the inherently dispersive character of the ionospheric propagation medium. Environmental factors such as sea state, seawater temperature and salinity, atmospheric-refractive-index vertical profile, and ionospheric conditions all exercise strong influences over the link characteristics. A definitive data base from which to infer the broadband signaling characteristics of the channel is not presently available. The Wideband HF Channel Prober is a very short pulse (1-microsec) HF radio sounder with the necessary sensitivity, time resolution, and processing speed to monitor and record the details of the pulse response of the channel. To exploit fully the average-power capabilities of most high-power transmitters, a coded PM sequence is transmitted rather than a single pulse. The period of the PN sequence is designed to be comparable with the expected reverberation time of the channel. Correlation processing in the receiver results in a processing of gain of the order of 34 dB.

Diversity Transmission of M-Ary Orthogonal Signals in a Hostile Environment

Abstract: This paper discusses some aspects of the problem of making good decisions when the signals are M-ary (M = 2K) orthogonal waveforms transmitted over a channel that may include intentional jamming. The diversity may be simple as with fast frequency hopping or more complex as with error correction coding. Optimal processing with constant wideband Gaussian noise is presented to give a reference. Performance of this processor is also evaluated with optimized partial band (or time) noise jamming. Departing from optimality, two techniques that operate on the k individual bits associated with an M-ary symbol are discussed and performance is evaluated for the jamming environments mentioned previously. A ratio-threshold quantization technique with a corresponding recombination rule is presented. Finally, an example application of 8-ary FSK modulation combined with rate 1/2, constraint length 7 convolutional coding is used to illustrate the utility of this sub-optimal processing technique.

Superconductive Tapped Delay Lines for Low-Insertion-Loss Wideband Analog Signal-Processing Filters

Abstract: : Transversal filters have been realized as miniature superconductive tapped electromagnetic delay lines. The low loss of superconductors permits the use of a compact stripline structure which offers useful delay at microwave frequencies. Taps are realized as backward-wave couplers or a impedance discontinuities. Chirp filters are formed by cascading such couplers of increasing length. Pulse expansion and compression have been demonstrated over a 2.6-GHz bandwidth. By weighting the taps, side-lobe levels have been reduced to 25 dB below the peak output. A coupled-mode analysis has been employed for predicting the response of this class of filters and has achieved very good agreement with experiment. The analysis also predicts that, if coupling were increased to reduce insertion loss below about 10 dB, significant phase distortion results with a commensurate degradation of side-lobe levels.

Analysis of the element pattern shape for circular arrays

Abstract: Recent theoretical and experimental investigations have established the phase-mode technique for directional pattern synthesis in circular arrays of nonisotropic sources. For non-isotropic sources the possibility of phase-mode stability has emerged, indicating wideband directional patterns. In the letter a further examination analysing the shape of the element pattern for phase-mode stability is presented.

Strip-Line Resonator Filters Having Multi-Coupled Sections

Abstract: The design criteria for microwave filters with multi-coupled strip-line have been developed One of the advantages of this method is that it provides a line-spacing which is five times wider than with the conventional method Higher production yield is therefore obtainable in designing wideband or millimeter-wave filters with the use of thin dielectric substrate

New monopulse tracking radar

Abstract: A tracking radar which employs a new frequency-comparison monopulse technique by means of sum and difference frequencies is described. A Cassegrain antenna with a five-horn feed transmits and receives two carrier frequencies, and tracking errors due to target glint and thermal noise are reduced by using a wideband FM technique.