Showing papers on "Frequency-division multiplexing published in 1976"

Frequency multiplexing light source with monolithically integrated distributed‐feedback diode lasers

Abstract: A frequency multiplexing light source is realized by monolithically integrating GaAs‐GaAlAs distributed‐feedback diode lasers with different grating periods and passive waveguides on a GaAs substrate. The lasers with wavelength separation of ∼20 A are modulated independently, and the output beams are obtained from a common launching waveguide.

Generation of single-sideband signals in multiplex communication systems

Abstract: A review of the theoretical and practical aspects of singlesideband (SSB) generation is presented. It will be pointed out how evolving methods and technologies have influenced, or might influence, the designs and what analytical concepts they required for a theoretical understanding of the various "mechanisms" involved.

A Statistical Analysis of Transmit Power Control to Compensate Up- and Down-Link Fading in an FDMA Satellite Communications System

Abstract: The application of 14/12 GHz and higher allocated frequency bands in commercial satellite communications systems has been retarded by the problem of slow deep fading due principally to rain attenuation on the earth-station-to-satellite and satellite-satellite-to-earthstation radio links. The large carrier-to-noise ratio (C/N) margins required to ensure good link performance for a large percentage of time may be excessive, and a more sophisticated method of dealing with fading is required. The methods available fall broadly into two categories, one employing diversity and the other adaptive compensation techniques. This paper examines a link compensation method, namely up-link power control at the transmitting earth station, that effectively reduces the effects of both up- and down-link fading in a frequency-division multiple-access (FDMA) satellite system having a large number of accesses. The transmitted level of each carrier accessing the satellite transponder is dynamically adjusted to compensate the combination of up- and down-link fading experienced by the carrier. While this leads to wide variations in individual carrier levels into the satellite, the assumed independence of fades on the down-link to each of the receiving earth stations means that variations in multicarrier TWT operating point tend to be small (providing no one earth station receives a highly disproportionate share of the traffic). By essentially pooling among many links the effects of deep fades simultaneously present on only a few links, this technique will reduce C/N variations on individual carriers, thereby reducing required fade margins. This paper derives expressions for the earth-station-to-earth-station link fade probability density function (pdf) with and without transmit power control. The theoretical effects of noisy estimates of the up- and down link fades and quantization of the transmitted powers are considered. Simple asymptotic expressions applicable when the number of accesses is large are also derived. Computed results demonstrate that transmit power control can substantially reduce the fade margins required in homogeneous single channel per carrier (SCPC) systems operating in the 14/12 GHz band. Some detection and control problems associated with a practical implementation of the scheme are introduced.

Microwave guide with lateral access - has opening with slotted metal sheet to provide frequency multiplexing or de-multiplexing

Abstract: A wave guide with lateral access provides multiplexing or demultiplexing of frequency. It minimises any perturbation, of propagation within the principal guide. The guide has a first rectangular part (1) which provides a propagation of waves in two distinct frequency bands. The two bands are a low band and a high band. It also has a second rectangular part (2) which provides propagation in the high band. There is an opening (ABCD) between the second part (2) and the first part (1). This opening (ABCD) provides multiplexing or demultiplexing. The opening (ABCD) has a grid (3) formed by a thin metal sheet (4) and two slots (5, 6).

Surface-acoustic-wave multiplexing techniques

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.

Telephone set and system utilizing frequency division multiplexing

Abstract: The telephone set comprises a programmable carrier generator which supplies the same variable frequency to an amplitude modulator receiving the local voice signals, and to a synchronous demodulator which makes it possible to reconstitute, without band pass filtering, the voice signals of any set with which it is communicating among those of other sets. The double side band amplitude modulated signals supplied by each set are frequency-division multiplexed on one of the two ways of a telephone artery, the other way of which distributes them to the sets after conversion of all the carrier frequencies into conjugate frequencies thereof. The programmable generators of the calling and called users in communication are respectively tuned to the frequencies of such a pair of conjugate frequencies.

Computation of Interference into Angle-Modulated Systems Carrying Multichannel Telephone Signals

Abstract: It is commonly known that, in order to calculate the demodulated noise power of the wanted frequency division multiplexedfrequency modulated (FDM-FM) signal due to interference, the convolution between the power spectra of the wanted FM signal and interference is required to be obtained. This concise paper shows a simple approach to calculate this convolution without direct calculation of the power spectrum of the FDMFM signal when the power spectrum of the interference is given (by measurements or calculation) and the highest and lowest channel frequencies of the baseband signal and rms frequency deviation of the wanted FDM-FM signal are known. Since the calculation of the FDM-FM signal power spectrum is not an easy problem in some cases, this approach makes much simpler an accurate evaluation of the output noise power due to interference.

Telephone transmission system comprising digitally processing frequency multiplexor and demultiplexor

Abstract: The invention relates to telephone transmission systems in which frequency multiplexing is carried out by digital processes It consists in substituting to a computation step of an analytical signal a computation step of a much simpler complex signal The ultimate signal obtained is not compatible with standard multiplexing apparatus, but may nevertheless be transmitted along ordinary channels

A Study on Gaussian Two-User Channels

Abstract: : In this report, we study the Gaussian two-user channel which is an extension of an ordinary Gaussian channel with single input and output to the one with two inputs and two outputs and where the independent formations are transmitted between two input/output pairs simultaneously. Two achievable regions called TS and FDM1 are compared. TS is obtained by simply time-sharing the two superposition modes introduced in the previous paper and FDM1 corresponds to the frequency division multiplexing where only one of the two signals is transmitted in each of the two sub-bands. A fairly tight outer bound to the achievable region is obtained by utilizing the capacity region of the corresponding Gaussian broadcast channel. Properties of two kinds of frequency division multiplexing FDM2 and FDM3 which make use of the superposition modes are studied and the achievability attained by these two kinds of multiplexing is discussed using the results of computation. (Author)

Bi-Directional Multi-Station Command/Information Bus

Abstract: : The suitability of dielectric waveguide as a transmission medium in data bus applications has been presented in this report The feasibility of the concepts has been demonstrated through a Model 400 Dielectric Waveguide Data Bus System The system operates at millimeter-wave frequencies (22 to 30 GHz) and has two frequency division multiplexed (FDM) data channels, each of which can carry data at rates of up to about 10 Mb/s The system demonstrates multi- channel bi-directional data transfer capabilities over a 100 ft dielectric cable In this report the design features and test results of a tunable bandpass ring coupler are also presented These couplers are used in the Model 400 System for coupling signals to and from the data bus In addition to hardware demonstration of dielectric waveguide systems, their concepts have been used to obtain a data bus configuration for a specific aircraft For this purpose, flight control signals of the YF-16 aircraft were chosen as an illustration The data bus configuration for this aircraft has been presented in a block diagram form It shows that the dielectric waveguide system can fully accommodate all the signal flow requirements

Telephone repeater telecontrol equipment - sends interrogating signal and receives signal from selected repeater

Abstract: The telecontrol equipment is used with telephone repeater which are part of a long distance telephone system with frequency division multiplexing. The equipment has units, which are part of the terminal station. It has a signal generator (43) which can send an interrogating frequency to a group of repeaters. It also has a selective receiver (47) which receives the signal from the repeater selected by a coupling unit (46). The interrogation signal and the received signal can be measured by the terminal station. The repeated section of the system incorporates a quartz oscillator.