Showing papers on "Quadrature amplitude modulation published in 1972"
TL;DR: A coherent binary FSK modulation system is discussed, that has a low deviation ratio and uses as receiver a self-synchronizing circuit and a phase detector, which together achieve optimal decisions.
Abstract: A coherent binary FSK modulation system is discussed, that has the following properties: 1) it is phase coherent; 2) it has a low deviation ratio, h = \frac{1}{2}; 3 ) it occupies a small RF bandwidth, typically only 0.75 times the bit rate, without need for intersymbol interference correction; 4) it uses as receiver a self-synchronizing circuit and a phase detector, which together achieve optimal decisions; and 5) its error performance is about S dB better than that of conventional FSK.
239 citations
TL;DR: The optimum (minimum mean-squared-error) and optimum uniform quantizing characteristics for Laplacian- and gamma-distributed signals are given in tabular form and the performance of these quantizers in real speech pulse-code modulation and differential pulse- code modulation systems is investigated and compared with that obtained when the μ-law quantizing characteristic is used.
Abstract: The optimum (minimum mean-squared-error) and optimum uniform quantizing characteristics for Laplacian- and gamma-distributed signals are given in tabular form. The performance of these quantizers in real speech pulse-code modulation (PCM) and differential pulse-code modulation (DPCM) systems is investigated and compared with that obtained when the μ-law quantizing characteristic is used.
200 citations
TL;DR: It is shown that delta modulation encoding may be combined with digital filtering to realize either nonrecursive or recursive types.
Abstract: Digital filters are described which are based on delta modulation rather than pulse code modulation. It is shown that delta modulation encoding may be combined with digital filtering to realize either nonrecursive or recursive types. Conventional digital filter design techniques are applicable in both cases. Simulation of such filters on a small computer is discussed. Quantization noise is considered and comparisons made with the noise performance of the conventional digital filter.
37 citations
TL;DR: A digital modulation technique has been developed that has the constant level advantage of frequency-shift keying systems while retaining the error rate and threshold performance of coherently detected binary or four-phase phase-shiftkeying systems.
Abstract: A nationwide data network is planned that will employ microwave relay networks for both long-haul and short-haul interconnection. A digital modulation technique has been developed that has the constant level advantage of frequency-shift keying (FSK) systems while retaining the error rate and threshold performance of coherently detected binary or four-phase phase-shift keying (PSK). Occupied spectrum and interference characteristics of a 21.5-Mbit/s data system are compared to the more conventional 600-, 1200-, and 1800-channel message systems.
29 citations
Patent•
17 Mar 1972
TL;DR: In this article, a light-emitting diode is used to produce light in response to keying signals, and a light sensing transistor is employed to supply output signals to the light emitting diode.
Abstract: In a power-line carrier system, a keying input circuit is isolated from its corresponding keying output circuit by a light-emitting diode which produces light in response to keying signals, and by a light-sensing transistor which supplies output signals in response to light from the light-emitting diode.
9 citations
8 citations
4 citations
TL;DR: In this article, an amplitude modulator is described in which the modulation is obtained by variation of the phases of two beams with the same direction of polarization but orthogonal directions of propagation in an electrooptic material.
Abstract: An amplitude modulator is described in which the modulation is obtained by variation of the phases of two beams with the same direction of polarization but orthogonal directions of propagation in an electrooptic material. The phase modulation is transformed into an amplitude modulation by interfering the two beams using a beam splitter. The advantage of this scheme over commonly used modulators is that here the two beams have the same polarization, and traverse essentially equal paths in the crystal, thus providing greater temperature stability. Data on a first model of this type modulator, using ADP, is presented.
3 citations
TL;DR: The full-carrier single-sideband signal is of the minimal phase type with limited phase excursion and contains sufficient information to recover completely the message waveform and requires no wide-band quadrature network.
Abstract: The full-carrier single-sideband signal is of the minimal phase type with limited phase excursion and contains sufficient information to recover completely the message waveform. A receiving system is described that makes use of both the envelope and the phase information in the signal. Operation is independent of input signal level and requires no wide-band quadrature network.
2 citations
TL;DR: The spectral broadening caused by adding tone-burst modulation to a carrier already modulated by a flat-band Gaussian process is evaluated numerically and shows that even for modulation indices as small as 0.5, the spectrum of the tone bursts themselves is not a good approximation to the RF spectrum.
Abstract: Modeling the occurrence times as a Poisson process, the spectrum of a carrier frequency modulated by a random pulse train is studied. In general, the corresponding phase modulation is nonstationary, but the modulated carrier is shown to be wide-sense stationary, so that its RF spectrum can be obtained as the Fourier transform of its correlation function. Closed-form asymptotic results show that RF spectrum is proportional to ω-4if the frequency modulation is discontinuous, and as ω-6if it is continuous, where ω is the radian frequency measured from the carrier frequency. Numerically evaluated spectra are obtained for the particular case of a stationary tone-burst modulation, a form used in a proposed mobile-radio feedback diversity system. These results show that even for modulation indices as small as 0.5, the spectrum of the tone bursts themselves is not a good approximation to the RF spectrum. Finally, the spectral broadening caused by adding tone-burst modulation to a carrier already modulated by a flat-band Gaussian process is evaluated numerically. These results show that the modulation index of the bursts should be kept to unity or less in order to restrict the spectral broadening to 10 percent or less if the rms phase deviation of the Gaussian modulation is less than three radians.
2 citations
Journal Article•
TL;DR: In this article, a single-sideband phase modulation (SSBPM) technique based on the properties of binary suppressed-carrier phase modulation is proposed and shown to give performance equivalent to the double sideband version.
Abstract: Single-sideband phase modulation (SSBPM), in which a signal is simultaneously phase- and amplitude-modulated by a signal and its Hilbert transform, is shown to be suboptimum for binary signaling in white Gaussian noise. An alternative single-sideband technique based on the properties of binary suppressed-carrier phase modulation is proposed and shown to give performance equivalent to the double-sideband version.
18 Jul 1972
TL;DR: The results of this analysis show that the digital communication systems examined have error probabilities less than one part in 104 for on-tune signal-to-interference power ratios of 11 dB or greater.
Abstract: The performance degradation of noncoherent, nonerror correcting digital communication systems from simulated AM, FM, SSB and pulsed interference is examined. The on-off keyed (Al), frequency shift keyed (F1), frequency shift keyed amplitude modulated (A2) and pulse code modulated FM (F9) digital communication systems are examined for errors of commission (false alarm) and omission (false dismissal). The most susceptible digital modulation system that was examined was Al. The simulated SSB interference caused the worst degradation to all the communication systems. The results of the SSB interference measurements closely agree with the theoretical results for narrowband noise. The results of this analysis show that the digital communication systems examined have error probabilities less than one part in 10
4
for on-tune signal-to-interference power ratios of 11 dB or greater.
TL;DR: In this article, the spectral distribution of digital signals transmitted by combined amplitude and frequency modulation is derived, and the results are compared with biternary f.m. deviation and index.
Abstract: Spectra of digital signals transmitted by combined amplitude and frequency modulation are derived. Cumulative spectral-distribution curves are presented for certain values of f.m. deviation and a.m. index, and the results are compared with biternary f.m. transmission.