Showing papers on "Frequency-division multiplexing published in 1982"

Radio communication system using frequency division multiplexing for transmission between a master station and a plurality of remote stations

Abstract: A point-to-multipoint radio communication system includes a master station and a plurality of remote stations which communicate with the master station using frequency division multiplexing. Each remote station transmits on a separate frequency, but the respective frequencies of transmission by the remote stations are closely spaced so as to be contained within the band which is centered on a single licensed frequency. Thus, the system may operate with only a first licensed frequency for communication from the master station to the remote stations and a second licensed frequency for communications from the remote stations to the master station.

Communication set and method

Abstract: A telephone communication method provides simultaneous duplex channels between respective pairs of stations over a single wire pair highway by frequency division multiplexing. Each duplex channel has a predetermined pair of carrier frequencies, but only carrier frequency pairs of channels in use for communication are present in the highway at any time. On initiating a call, a station seeks for a free channel and reserves it by generating the "go" carrier of the free channel modulated with the call sign of the desired station, and also generating an alert signal. Quiescent stations respond to the alert by seeking a "go" carrier with call sign data and, on identifying their own call sign, generating the corresponding return carrier to set up the channel.

Real-time Spatial Filtering Utilizing the Piezoelectric-elasto-optic Effect

Abstract: A novel approach to frequency multiplexing of images is presented. By modulating each image pixel at a different (temporal) frequency, the entire image can be transformed into an electrical signal utilizing a single detector. The electrical current of the detector is proportional to the spatial Fourier transform of the image, allowing one to perform spatial frequency manipulations in the time domain. The multiplexing is obtained by using a two-dimensional array of piezoelectric-elasto-optic modulators. By utilizing these effects one makes use of the mechanical resonance of the crystals simplifying the electrical signals needed for excitation. It is shown that a similar (or the same) modulator can be used for image reconstructions; i.e. performing the inverse Fourier transform. Preliminary results obtained with quartz crystals prove the feasibility of this approach.

Frequency Division Multiplexing Optical Processors

Abstract: This paper describes a method by which optical time- and space-integrating processors may be generalized and expanded by accommodating vector inputs. Many architectures using this frequency division multiplexing approach are presented, demonstrating new operations and generalizations of old ones.© (1982) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Wavelength Division Multiplexing in Optical Communication Systems

Abstract: Taking into account parameters of realized components for wavelength division multiplexing systems with multimode graded index fibers, it is shown that such a system has no advantage compared to a single wavelength system operating at an optimum wavelength. We therefore propose a new wavelength division multiplexing system with very small optical frequency separation of some GHz in connection with a single-mode fiber and heterodyne receiver. The components for such a future system can be realized by using integrated optics.

Recording system for plurality of channel of audio signal

Abstract: PURPOSE:To make the discrimination of content of audio signals of a plurality of channels easy, by specifying the frequency of a pilot signal to almost (2N+ 1)/2 times the video signal horizontal scanning frequency in frequency multiplexing. CONSTITUTION:The frequency of a pilot signal used for the discrimination of content of a plurality of chnnel audio signals is restricted to almost (2N+1)/ 2 times the horizontal synchronizing signal to avoid the cross modulation noise with an FM modulation video signal. That is, a difference signal of stereo audio or a sub-audio signal is inputted from an input terminal 2, and after a pilot signal in different frequency is added at an adder 10 according to stereo audio and double audio, the result is modulated in an FM modulator 4. The pilot signal is a signal formed from a horizontal synchronizing signal in frequency fH from an input terminal 11 at a 2.5 multiplication circuit 13 and a 3.5 multiplication circuit 14. Thus, the reproduced S/N of the pilot signal is increased and the discrimination of content of a plurality of channel audio signals is made easy.

Both polarized wave multiplexer

Abstract: A modular arrangement of directional RF filters provides frequency multiplexing of signal sources at earth stations which are transmitting on two orthogonal polarizations. Each of the modules consist of a pair of 3dB hybrid couplers coupled to each other through identical bandpass filters such that a signal applied to one of two input ports is outputed exclusively through an associated one of two output ports. The passbands of each of the modules are mutually exclusive. The output ports of each module are coupled to an output port of two adjacent modules, and two main outputs are taken from the two outer modules. The signals from the two main outputs are applied to two antennas having mutually orthogonal polarizations. The present invention may also be used as a demultiplexing receiver.

Multimode fiber optic wavelength division multiplexing

Abstract: Optical wavelength division multiplexing (WDM) systems, with signals transmitted on different wavelengths through a single optical fiber, can have increased bandwidth and fault isolation properties over single wavelength optical systems. Two WDM system designs that might be used with multimode fibers are considered and a general description of the components which could be used to implement the system are given. The components described are sources, multiplexers, demultiplexers, and detectors. Emphasis is given to the demultiplexer technique which is the major developmental component in the WDM system.