Showing papers on "Pulse-position modulation published in 1988"
TL;DR: The use of differential pulse position modulation (dPPM) as an alternative coding scheme to PPM is proposed and a simple scheme that decreases the throughput of the dPPM channel but is easy to analyze is chosen.
Abstract: Because of the optimality of the pulse position modulation (PPM) technique for the infinite-bandwidth channel, it has been suggested as a technique for the bandwidth-limited channel. The use of differential pulse position modulation (dPPM) as an alternative coding scheme to PPM is proposed. In dPPM each new word begins at the end of the previous word. To avoid synchronization problems, a simple scheme that decreases the throughput of the dPPM channel but is easy to analyze is chosen. For some parameter values this restricted dPPM scheme has greater throughput (in terms of capacity and cutoff rate) than PPM. >
57 citations
TL;DR: Practical measurements on a digital PPM system handling 8Mbit/s PCM data show good correlation with theoretical results obtained from a computer model of the system, confirming that there exists an optimum number of time slots which maximises the receiver sensitivity.
Abstract: Practical measurements on a digital PPM system handling 8Mbit/s PCM data show good correlation with theoretical results obtained from a computer model of the system. It is confirmed that there exists an optimum number of time slots which maximises the receiver sensitivity, and that a digital PPM system can offer an improvement of 4.2 dB over an equivalent binary PCM system when the fibre bandwidth is several times that required by PCM.
46 citations
Patent•
27 Jun 1988
TL;DR: In this article, a modulation method and apparatus is provided which can coexist with conventional Manchester (Ethernet) coding schemes and which can be transmitted and received over twisted pair cabling.
Abstract: A modulation method and apparatus is provided which can coexist with conventional Manchester (Ethernet) coding schemes and which can be transmitted and received over twisted pair cabling. The method according to the invention is a three-level D.C.-free code without bipolar violations wherein intersymbol interference is sufficiently controllable that the received signal can be detected as a two-level code. The code has a different power spectrum than Manchester coding for the same baud rate. The modulation method is a modified frequency modulation (Miller) code comprising three levels wherein each of the transitions is of a limited duration and the transition returns to zero d.c. after a predetermined pulse duration. The modulation method may be termed pulsed modified frequency modulation or pulsed Miller encoding. The signal so modulated is intended to be transmitted over twisted pair cabling of limited bandwidth such that the cabling serves as a low-pass filter. The pulsed modified frequency modulation encoding method according to the invention produces a fundamental at a frequency which is about half of the fundamental of a Manchester coding scheme at the same bit rate.
12 citations
TL;DR: The most efficient way to encode laser diodes for maximum data rate is studied, with combining achieved by dichroic mirrors operating in conjunction with a pulse-position-modulated (PPM) format.
Abstract: The most efficient way to encode laser diodes for maximum data rate is studied. Three different system architectures are considered, with combining achieved by dichroic mirrors operating in conjunction with a pulse-position-modulated (PPM) format. The basic criterion is to maximize the data rate with increasing number of diodes, while maintaining diode power constraints and decoding bit error probability. The three systems are: power combining into a single pulse, followed by PPM encoding; parallel channels, in which each diode is separately PPM encoded; and color coding, in which diodes are encoded over a common wavelength-time slot alphabet. Data rate equations are presented as a function of the number of diodes, mirror combining losses, PPM alphabet size, and the operating optical signal-to-noise ratio. >
11 citations
Patent•
15 Sep 1988
TL;DR: In this article, a modulation equalization network associated with a phase-locked loop was proposed to achieve frequency independent modulation of the VCO. But the modulation processing was performed totally outside the phase locked loop, and the network served to provide a boost to low frequency signals from the modulation source using an integrator network.
Abstract: Several embodiments are disclosed of a modulation equalization network associated with a phase locked loop to achieve frequency independent modulation of the VCO. The equalization network is disposed to introduce the modulation signal into the control loop ahead of the loop filter but after the phase detector output. The interposed equalization network requires only a single input port to achieve a flat modulation response thereby lending itself to a modular implementation. The modulation processing is performed totally outside the phase locked loop. The network serves to provide a boost to low frequency signals from the modulation source using an integrator network while providing a high frequency response that is essentially the inverse of the phase locked loop filter response.
10 citations
TL;DR: This paper discusses the interaction of error, correction, interleaving and modulation format in relation to intersatellite communication by optical technologies, concentrating on the performance and design of pulse position modulation with Reed—Solomon codes, helical interleaves and various forecast strategies.
Abstract: This paper discusses the interaction of error, correction, interleaving and modulation format in relation to intersatellite communication by optical technologies, concentrating on the performance and design of pulse position modulation and a variant, differential pulse position modulation with Reed—Solomon codes, helical interleaving and various forecast strategies.
9 citations
TL;DR: It is shown that the structure of block codes, when used in conjunction with on-off keying signaling, renders these codes fairly inefficient with respect to obtaining reasonable CMG on the optical channel, and the authors propose using pulse-position modulation with more than one pulse per word to obtain reasonableCMG while consuming small amounts of bandwidth.
Abstract: Coding for avalanche photodiode (APD)-based direct-detection optical channels is investigated using a simple channel model that clearly points out the difference between the signal-dependent optical noise channel model and additive white Gaussian noise channel model. Coding and modulation are viewed as a single entity and the coding/modulation gain (CMG) is used to analyze and construct good codes for APD-based optical receivers. It is shown that the structure of block codes, when used in conjunction with on-off keying signaling, renders these codes fairly inefficient with respect to obtaining reasonable CMG on the optical channel. In contrast, codes (or modulations) that use fewer channel ones (pulses) than information ones per block can offer substantial CMG on the optical channel. For bandwidth-constrained applications, the authors propose using pulse-position modulation with more than one pulse per word to obtain reasonable CMG while consuming small amounts of bandwidth. >
7 citations
28 Nov 1988
TL;DR: Pulsewidth-constrained signals are developed for use on the degraded direct-detection optical channel and a two-dimensional representation for these signals is obtained and used to design a trellis-coded-modulation (TCM) system.
Abstract: Pulsewidth-constrained signals are developed for use on the degraded direct-detection optical channel. A two-dimensional representation for these signals is obtained and used to design a trellis-coded-modulation (TCM) system for use on the optical channel. The theoretical advantage of optical TCM is shown, through use of the cutoff rate, to range from 7.5 to 9 dB, depending on the throughput rate of the system. The practical potential is shown, through the actual design of a TCM system, to be as high as 6.7 dB. >
7 citations
TL;DR: In this paper, the harmonic analysis of various pulse width modulation strategies used for the DC-AC converters is presented and an efficient harmonics computation algorithm for piecewise continuous periodic waveforms has been derived.
Abstract: This paper presents the harmonic analysis of various pulse width modulation strategies used for the DC-AC converters. An efficient harmonics computation algorithm for piecewise continuous periodic waveforms has been derived. Fourier coefficients of experimentally obtained waveforms or simulation results can be calculated efficiently. Harmonic performance analysis of natural sampling, modified subharmonic control, symmetric/asymmetric uniform, sinusoidal pulse width modulation, and pulse position modulation strategies have been studied. Results can be used as guidelines for the modulation strategies selection in the PWM inverter design.
6 citations
Patent•
26 May 1988
TL;DR: In this article, a method of cyclically forcing framing bit error onto every D-spaced framing bit of the DS3 signal during an initial ON period of an ON-oFF modulation cycle, the ON period and the modulation cycle having lengths such that no more than two verification attempts are required to complete reframing of the signal in the presence of the framing bit modulation, and wherein the modulation spacing, D, is selected so as to provide a low probability of coincidence between the framing-bit Modulation Spacing and a verification window following a secondary re-search.
Abstract: A method of modulating a DS3 signal for addition thereto of an auxiliary, transparent signalling channel, the DS3 signal having framing bits which provide a predetermined pattern for which frame-finding circuits hunt to demultiplex the payload of the DS3 signal. The method comprises cyclically forcing an framing-bit error onto every D-spaced framing-bit of the DS3 signal during an initial ON period of an ON-oFF modulation cycle, the ON period and the modulation cycle having lengths such that no more than two verification attempts are required to complete reframing of the signal in the presence of the framing-bit modulation, and wherein the Modulation Spacing, D, is selected so as to provide a low probability of coincidence between the framing-bit Modulation Spacing and a verification window following a secondary reframing hunt.
6 citations
TL;DR: A post-disaster signalling system from mine to surface, using through-the-earth electromagnetic propagation of a 1950 Hz carrier, phase modulated by a repeating 255 bit maximal length sequence, is discussed.
Abstract: A post-disaster signalling system from mine to surface, using through-the-earth electromagnetic propagation of a 1950 Hz carrier, phase modulated by a repeating 255 bit maximal length sequence, is discussed. Coherent integration up to 4.46 min allows output pulse detection on a CRT at input signal-to-noise ratios down up -30 dB, which is about 30 dB less than required for the present pulse transmitter system. The system offers vastly increased reliability along with some combination of increased range, signal processing delay time, smaller transmitter antenna, and reduced power. It avoids a manual signal search period and permits more accurate automated or manual null-seeking emitter location. After location, it can be used with pulse position modulation (PPM) for communication. It should also be valuable for measurements to determine geological properties. >
28 Nov 1988
TL;DR: In this article, the minimum Euclidean distances for binary three-hop and four-hop schemes and power spectra for three-and four-hops were derived for each scheme.
Abstract: Multihop phase-coded modulation (MHPM) using asymmetric modulation indices corresponding to the bipolar data+1 and -1 is considered, and numerically obtained values of the minimum Euclidean distances for binary three-hop and four-hop schemes and power spectra for three-hop schemes are provided. It is shown that improved error probability is obtained compared to conventional MHPM with essentially no bandwidth expansion. >
Book•
01 Jan 1988
TL;DR: This book discusses Signal Generation, Angle Modulation Transmission, Single-Sideband Communications Systems, and Solutions to Odd-Numbered Problems, all of which relate to television.
Abstract: Preface. 1. Introduction to Electronic Communications. 2. Signal Generation. 3. Amplitude Modulation Transmission. 4. Amplitude Modulation Reception. 5. Single-Sideband Communications Systems. 6. Angle Modulation Transmission. 7. Angle Modulation Receivers and Systems. 8. Transmission Lines. 9. Wave Propagation. 10. Antennas and Waveguides. 11. Basic Television Principles. Appendix A. Solutions to Odd-Numbered Problems. Index.
23 Oct 1988
TL;DR: Uncoded and coded optical pulse position modulation (PPM) systems are compared for both direct and heterodyne detection, and it is seen that the performance of a coded system is improved over an uncoded system in direct detection by using Reed-Solomon codes.
Abstract: Uncoded and coded optical pulse position modulation (PPM) systems are compared for both direct and heterodyne detection. Simulations of these systems with different code rates are included, and the gains obtained in the coded cases are reported. By using Reed-Solomon codes, it is seen that the performance of a coded system is improved over an uncoded system in direct detection. As the code rate is reduced, the system performance gets better. Among the three different code rates tested, the code rate of 1/3 seems to be the best choice. The same applies to the heterodyne detection system. When Reed-Solomon codes are applied to a heterodyne system, it is observed that the efficiency of the system improves. >
02 May 1988
TL;DR: In this article, both Q-switching and cavity dumping modulation methods are available for the envisioned diode-pumped Nd:YAG laser source, and numerical calculation results are presented for cavity-dumping.
Abstract: The extremely energy-efficient pulse-position modulation (PPM) format is being actively developed as a basis for optical communications with deep-space probes. Attention is presently given to different modulation schemes for the efficient production of laser pulses over a broad range of repetition rates. Both Q-switching and cavity dumping modulation methods are available for the envisioned diode-pumped Nd:YAG laser source. Numerical calculation results are presented for cavity-dumping.
TL;DR: In this article, a general introduction to bidirectional optical intersatellite links is given, and the design, principles and link budget are presented, and four subsystems (transmitter, receiver, optical channel and acquisition/tracking system) are described.
Abstract: This paper gives a general introduction to bidirectional optical intersatellite links. The design, principles and link budget are presented, and the four subsystems—transmitter, receiver, optical channel and acquisition/tracking system—are described. GaAlAs semiconductor laser and a silicon avalanche photodiode are used as the optical transmitter and receiver. Pulse polarization position modulation is used to obtain a higher sensitivity. The acquisition/tracking signal is extracted from the top-modulation data stream. The effect of background noise is analysed, and direct detection and heterodyne detection are compared.
TL;DR: This paper analyzes the critical areas in optical communications systems, placing particular emphasis on the modulation/demodulation techniques used in the ISL communications subsystem design for the ESA/PSDE programme.
Abstract: This paper analyzes the critical areas in optical communications systems, placing particular emphasis on the modulation/demodulation techniques used in the ISL communications subsystem design for the ESA/PSDE programme. A 4-PPM/QPM demodulator has been designed, and problems of implementing the system at high data rates have been addressed. Maximum likelihood demodulation techniques and slot and frame synchronization were used. An attempt was made to devise a way to achieve synchronization tracking without using unique words along data patterns. Finally, for the optical ISL the use of coding is suggested as a way to relax link budget requirements. Coding could reduce problems caused by pointing subsystem instabilities. The use of on-board soft decoding without system bandwidth expansion is also foreseen.
11 Apr 1988
TL;DR: An experimental transmitter/receiver system constructed to study the practical performance of Zero-synchronous modulation (ZSM), a spectrally-efficient combined AM/FM scheme proposed by Lockhart and Al-Jalili (1982), is described and some results presented.
Abstract: Methods of embedding data in conventional DSB-AM signals are of interest in a number of applications including radiodata services for HF sound broadcasting. The data signals carry information which can be used by specially equipped receivers for various display and control functions such as automatic retuning when the transmission frequency is changed. In the case of DSB-AM, frequency modulation of the carrier in addition to the usual envelope modulation can provide a data channel but unless the data rate is very small the modulated signal is likely to exceed its allocated bandwidth. Zero-synchronous modulation (ZSM) is a spectrally-efficient combined AM/FM scheme proposed by Lockhart and Al-Jalili (1982) which permits data to be embedded in DSB-AM without significantly increasing the bandwidth or distorting the envelope. An experimental transmitter/receiver system constructed to study the practical performance of ZSM is described and some results presented.
28 Nov 1988
TL;DR: It is concluded that unless chirping characteristics of lasers are greatly improved, low-chirp modulation schemes such as the Mach-Zehnder interferometer type modulation, electroabsorptiontype modulation, and the DPSH-IM will be adopted for multigigabit long-distance optical transmission systems.
Abstract: Compares four intensity modulation schemes in terms of their spectrum broadening and transmission characteristics. The schemes examined are direct modulation, Mach-Zehnder interferometer type modulation, electroabsorption type modulation, and a direct phase-shift and self-homodyne intensity modulation (DPSH-IM) method proposed here. The dispersion-limited transmission distance of these schemes has been estimated by computer simulation. It is shown that direct modulation of currently available distributed feedback lasers suffers large waveform distortions due to chirping and chromatic dispersion in the fibre. It is concluded that unless chirping characteristics of lasers are greatly improved, low-chirp modulation schemes such as the Mach-Zehnder interferometer type modulation, electroabsorption type modulation, and the DPSH-IM will be adopted for multigigabit long-distance optical transmission systems. >
Patent•
21 Dec 1988
TL;DR: In this paper, the PPM signal data data pulse is discriminated by a comparator circuit 9 and the result of the comparison is detected as a prescribed pulse when the result is coincident.
Abstract: PURPOSE:To decrease a burden on a software and to obtain a high speed of a discriminating processing by executing the discrimination of PPM signal data with a hardware. CONSTITUTION:A timer circuit 3 generates a clock signal and converts the pulse width of a PPM signal data pulse to the number of this clock signal. In the time of one pulse of PPM signal data, the number of the clock signal outputted by this timer circuit 3 is counted. A register 7 of an initial setting register group 4 stores a reference clock number to correspond to the pulse width the specified data pulse of a PPM signal, the clock number counted by the timer circuit 3 and the reference clock number in a memory circuit 7 are compared and the type of the PPM signal data pulse is discriminated by a comparator circuit 9. When the result of the comparison is coincident, this data pulse is detected as a prescribed pulse.
Patent•
10 Feb 1988
TL;DR: In this paper, the authors proposed to suppress the expansion of a band area, by thansmitting a bit of information as a signal block of constant length, dividing each signal block to the constant number of time slots, and generating and transmitting optical pulses at the positions of plural time slots corresponding to the bits of information to be transmitted.
Abstract: PURPOSE:To suppress the expansion of a band area, by thansmitting a bit of information as a signal block of constant length, dividing each signal block to the constant number of time slots, and generating and transmitting optical pulses at the positions of plural time slots corresponding to the bit of information to be transmitted. CONSTITUTION:One signal block starts at a time ts, and ends at a time te, and those times ts-te are divided into N-number equally, and at an individual time area obtained as a result, that is, K-number of positions of the time slots, the optical pulses are generated. In one signal block, there are combined (NCK)- number of positions (time slots) of the optical pulses. To increase the number of combination, it may possible to change the number of the optical pulses per signal block. The position of the optical pulse in an individual signal block, is decided by the bit of information to be transmitted. By using plural number of optical pulses per signal block, it is possible to compress a required transmission line band width compared with a case using a conventional system of pulse position modulation system.
Patent•
07 May 1988
TL;DR: In this article, a radar system produces monocyclic pulses by switching 228 a DC power supply 65 to a wideband antenna 204, 206 in accordance with the output of a signal generator.
Abstract: A radar system produces monocyclic pulses by switching 228 a DC power supply 65 to a wideband antenna 204, 206 in accordance with the output of a signal generator 212. The transmitted pulses are very broadband and thus will not interfere with any narrowband receiver. The receiver mixes 230 received signals with the output of a template generator 232 so that only signals received a certain time, set by delays 235, 236, after transmission are received. These are then integrated 250, digitized 256, and integrated again 262 to allow rejection of noise and returns from a different transmitter operating at different times. An analagous communication system (Figs 1-4), using pulse position modulation to encode an audio signal, is also described.
Patent•
07 May 1988
TL;DR: A radar system produces monocyclic pulses by switching 228 a DC power supply 65 to a wideband antenna 204, 206 in accordance with the output of a signal generator 212, and an analagous communication system, using pulse position modulation to encode an audio signal is described.
Abstract: A radar system produces monocyclic pulses by switching 228 a DC power supply 65 to a wideband antenna 204, 206 in accordance with the output of a signal generator 212. The transmitted pulses are very broadband and thus will not interfere with any narrowband receiver. The receiver mixes 230 received signals with the output of a template generator 232 so that only signals received a certain time, set by delays 235, 236, after transmission are received. These are then integrated 250, digitized 256, and integrated again 262 to allow rejection of noise and returns from a different transmitter operating at different times. An analagous communication system (Figs 1-4), using pulse position modulation to encode an audio signal, is also described.
Patent•
07 May 1988
TL;DR: In this article, a radar system produces monocyclic pulses by switching 228 a DC power supply 65 to a wideband antenna 204, 206 in accordance with the output of a signal generator.
Abstract: A radar system produces monocyclic pulses by switching 228 a DC power supply 65 to a wideband antenna 204, 206 in accordance with the output of a signal generator 212. The transmitted pulses are very broadband and thus will not interfere with any narrowband receiver. The receiver mixes 230 received signals with the output of a template generator 232 so that only signals received a certain time, set by delays 235, 236, after transmission are received. These are then integrated 250, digitized 256, and integrated again 262 to allow rejection of noise and returns from a different transmitter operating at different times. An analagous communication system (Figs 1-4), using pulse position modulation to encode an audio signal, is also described.