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Showing papers on "Frequency-division multiplexing published in 1975"


Patent
19 Feb 1975
TL;DR: In this paper, a new system and technique for cancelling interference in frequency agile ceiving systems is proposed, where main and auxiliary signals are supplied to a pair of multiple loop side-lobe cancellers which are capable of being tuned to different frequencies.
Abstract: A new system and technique for cancelling interference in frequency agile ceiving systems Main and auxiliary signals are supplied to a pair of multiple loop side-lobe cancellers which are capable of being tuned to different frequencies At the same time, under the control of a timing clock, plural frequencies are selected and multiplexed between two channels at the time of a radar pulse transmission The side-lobe cancellers and radar are coupled to the channels such that each caneller operates at a given frequency for two consecutive pulse periods, with the radar transmitting at said given frequency during the second pulse period By continuously cycling between the two channels, each canceller is operating at the proper frequency to cancel interference even though the radar is changeing frequency on a pulse to pulse basis

39 citations


Journal ArticleDOI
TL;DR: A new algorithm is proposed for the digital implementation of the M -channel SSB-frequency-division multiplexing (FDM) modulator and demodulator, which is computationally attractive and inherently insensitive to parameter quantization.
Abstract: A new algorithm is proposed for the digital implementation of the M -channel SSB-frequency-division multiplexing (FDM) modulator and demodulator, which is computationally attractive and inherently insensitive to parameter quantization.

21 citations


Proceedings ArticleDOI
01 Jan 1975
TL;DR: In this article, a combination of time division (TDM) and frequency multiplexing was used for the transmission of vehicle power, status, command, and video signals over a small diameter coaxial cable.
Abstract: The multiplex system described was designed for use on the NAVFAC Snoopy vehicle, a small remotely manned tethered undersea vehicle developed at the Naval Undersea Center. Using a combination of time division (TDM) and frequency multiplexing, the system allows simultaneous transmission of vehicle power, status, command, and video signals over a small diameter coaxial cable. Digital vehicle and status signals are TDM encoded, frequency modulated, and then transmitted via the tether cable to the vehicle (or control station) receiver. At the receiver the signals are frequency demodulated, TDM decoded, and sent to the appropriate function. The power and video signals are simply frequency multiplexed onto the tether cable, along with the frequency modulated command and status signals.

8 citations


Journal ArticleDOI
TL;DR: Methods are presented for the transmission of wideband digital signals above and below the frequency division multiplexing (FDM) baseband spectrum of analog microwave systems and it is shown that a Data Above Voice (DAV) system and a Data Under Voice (DUV) system are practical hybrid systems.
Abstract: Methods are presented for the transmission of wideband digital signals above and below the frequency division multiplexing (FDM) baseband spectrum of analog microwave systems. In particular, it is shown that a Data Above Voice (DAV) system employing a 1.544 Mbit/s data channel above FDM channels and a Data Under Voice (DUV) system employing 1.544 Mbit/s channel below 720 FDM channels, are practical hybrid systems. Theoretical models of hybrid transmission are disucssed and the DAV/DUV methods are compared. A conceptual hybrid system design procedure is introduced and field measurement results on an 8 hop 6 GHz system are presented, comparing favorably with theoretical predictions.

7 citations



Proceedings ArticleDOI
06 Nov 1975
TL;DR: In this paper, the use of both a LED source and double hetrojunction GaAlAs Lasers is discussed for a low-loss Corning fiber within a tactical ruggedized cable.
Abstract: A broad class of army communication applications are contemplated for optical waveguides. Of principal interest is the multimode low-loss fiber. A few potential applications include: (a) long haul TDM cable, (b) local distribution cable used to connect telephone users to central switches within a command post, (c) antenna remoting via fiber optic guide, (d) computer interconnections. The cost effectiveness of these cables vs. conventional cable is a critical issue that will be treated in detail within this paper. Exploratory developmental models that utilized a low-loss Corning Fiber within a tactical ruggedized cable are presented. The use of both a LED source and double hetrojunction GaAlAs Lasers is discussed. Also treated is the design of cable modems, interfaces and repeaters.© (1975) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

4 citations


Patent
16 Jul 1975
TL;DR: In this article, the location of a tethered undersea vehicle is determined by functionally operating elements on the vehicle, the end of a main cable and a support ship by projecting an acoustic signal from the distal end of the main cable.
Abstract: The location of a tethered undersea vehicle is determined by functionally operating elements on the vehicle, the end of a main cable and a support ship. An acoustic signal is projected from the distal end of the main cable and is received by several hydrophones carried on the vehicle. Frequency multiplexing the time deployed or different phases of the received acoustic signal and transmitting them back to the support craft, permits a processing of the multiplexed signals. This processing gives a visual indication of the vehicle's location with respect to the end of the cable. Since ocean currents can cause a catenary effect in the main cable as it hangs in several thousand feet of water, or the support ship might drift off-station, the tethered vehicle cannot be pulled away from an object of interest on the ocean's floor.

3 citations


Proceedings ArticleDOI
01 Jan 1975
TL;DR: In this paper, two approaches to frequency division multiplexing using SAW devices are described, one using a 9-channel filter array, where the signal combining and splitting is performed using wide-band power splitters.
Abstract: Two approaches to frequency division multiplexing using SAW devices are described. The first one uses a 9-channel filter array, where the signal combining and splitting is performed using wide-band power splitters. Two of these filter arrays were used in a data link, with data rates up to 7.5 Mbit/s for a total data rate of 67.5 Mbit/s. The second approach uses offset multistrip couplers to channel a wide-band signal into various narrow-band outputs according to frequency. Consequently, this approach exhibits lower insertion loss and is especially suitable for a large number of channels. An 8-channel MSC multiplexer has been constructed with less than 10-dB insertion loss.

2 citations


Proceedings ArticleDOI
06 Nov 1975
TL;DR: Guided optical cable system design methodology is developed by considering the application criteria and the interactive process of performing system-level conceptual design trades as mentioned in this paper, and practical examples of user evaluation criteria are presented.
Abstract: Guided Optical Cable System design methodology is developed by considering the application criteria and the interactive process of performing system-level conceptual design trades. The design impact of user performance requirements and other user considerations are identified, and practical examples of user evaluation criteria are presented. The cyclic process of interacting component hardware capabilities with system-level design implementations is presented by defining the interaction of spatial and electronic multi-plexing, frequency-division multiplexing and time-division multiplexing, and baseband analog and digital modulation base trades. Optical link budgets for these implementation concepts are presented to show the effects of source power, source line width, optical cable losses and dispersions, and receiver sensitivities. The paper is concluded with an example that shows the use of guided optical communications systems is best optimized when inherent characteristics are exploited by the conceptual designer.© (1975) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

2 citations


Proceedings Article
01 Jan 1975

2 citations


Journal ArticleDOI
TL;DR: The design of a low-cost FM-microwave satellite-ground-station receiver that is capable of accepting 12 contiguous color-television equivalent-bandwidth channels using a wide-band FM format and frequency division multiplexing (FDM) of the channels is described.
Abstract: The design of a low-cost FM-microwave satellite-ground-station receiver is described. It is capable of accepting 12 contiguous color-television equivalent-bandwidth channels in the 11.72-12.2-GHz band using a wide-band FM format and frequency division multiplexing (FDM) of the channels. Each channel has 36 MHz of usable bandwidth with a 4-MHz guard band and provides a CATV compatible output. The overall system specifications are first discussed. Then consideration is given to the design, fabrication, and evaluation of the different subsystems in the receiver.



Journal Article
TL;DR: In this article, a voice communications system that employs frequency division multiplexing to add four voice channels to existing hardwired, audio-range circuits, is described, using phase-locked loop technology.
Abstract: A voice communications system that employs frequencydivision multiplexing to add four voice channels to existing hardwired, audio-range circuits, is described. Phase-locked loop technology is used in the project, utilizing this new class of monolithic circuit. A study of an existing soundpowered telephone system is made and the compatibility of the multiplexing scheme within this system is investigated.