Abstract: A pulse-width-modulated motor drive includes means for the derivation of a signal representative of the torque by sensing the DC-link current directly, or indirectly, and by dividing the sensed signal by the modulation index of the motor drive to obtain proportionality through the duty-cycle long range succession.

Abstract: In this paper we consider differential detection of narrowband binary FM, using a detector which utilizes a delay line whose delay period is dependent on the value of the modulation index. The error-rate performance is computed for this receiver and compared with that of the limiter-discriminator receiver. In contrast to the previously published results for one-bit delay differential detection, it is shown that variable delay differential detection yields performance comparable to limiterdiscriminator detection.

Abstract: A new setup is presented that solves the isolation problem, optimizes the recovery of the light signal, and prevents any unwanted reflex in a Michelson scheme on an interferometric fiber sensor. Phase modulation (PM) and frequency modulation (FM) are both treated as the result of the fiber-optic-induced phase shift. The demodulation aspect involved in the FM detection is investigated especially in order to establish a direct link between the modulation index and the integral phase shift. A novel approach that permits the direct FM–index recovery is also reported. PM– and FM–demodulating processes are tested experimentally to detect the phase shift induced by a 20-Hz dynamical deformation on the fiber. The FM results are compared for small values of phase shift with the ones given by the PM scheme, whereas for large values of phase shifts, they are compared with others obtained directly from the spectral display. The measurements confirm the linear behavior of the fiber-strain sensor in the four decades of values, show the correctness of the analysis, and point out the possibility of using the fiber-strain sensor with engineering values of deformation.

Abstract: An apparatus for recording audio and video signals comprises a signal processing circuit (14,20) for producing a processed video signal and a frequency-modulated audio signal obtained by frequency-modulating a predetermined carrier in response to an input audio signal, a magnetic recording device (16,17,18a,18b) for recording both said frequency-modulated audio signal and said processed video signal in oblique tracks arranged successively on a magentic tape using a first recording mode wherein the oblique tracks are formed with spaces between each adjacent two thereof or a second recording mode wherein the oblique tracks are formed to be immediately adjacent to each other, and modulation control means (13,15) for controlling the frequency-modulation carried out by the signal processing circuit (14,20) to produce the frequency-modulated audio signal, so that the frequency-modulated audio signal is obtained by frequency-modulation with a first modulation index in the first recording mode and with a second modulation index larger than the first modulation index in the second recording mode.

Abstract: A commercially available GaAlAs diode laser has been modified to provide a stable dynamic single longitudinal mode laser. The laser was modulated with a power modulation index of more than 50 percent at microwave frequencies while operating in a single mode. Small signal modulation efficiency for optical power and frequency was measured together with the corresponding phase delays relative to the modulation current, in the frequency range 0.5 to 4 GHz. As predicted by the standard rate equation model, the laser frequency modulation index normalized to the power modulation index was a constant, independent of laser drive current and modulation frequency, and had a value of about 4. The phase advance of the frequency modulation relative to the power modulation was close to 90 deg over most of the frequency range, also in agreement with the rate equation model.

Abstract: In the TDMA subscriber loop radio communication system, large carrier frequency deviation exists in burst signals from subscribers to a base station. A modulation/demodulation technique, which is suitable for the burst transmission with large frequency variation, is studied in this paper. First, problems in the terrestrial TDMA system and clarified and it is shown that the use of conventional FSK-discriminator detection causes large CNR degradation due to the variation. Next, differential FSK-Partial Response Detection (DFSK), which can cope with the frequency variation and has a simple structure, is proposed and its principle and structure are described. Furthermore, the intersymbol interference and adjacent channel interference characteristics are evaluated theoretically and the bit error rate (BER) characteristics are evaluated experimentally. As a result, the optimum modulation index and IF-band reception band path filter are obtained. Finally, the optimum transmission system of DFSK designed for wide-band Digital Radio Subscriber Loop System using 26-GHz band is described. DFSK is shown to be a practical and promising modulation/demodulation system for a terrestrial TDMA communication system, on which a large demand is expected in the future.

Abstract: In this thesis, the performance of Limiter Discriminator (LD) receiver, Differentially Coherent (DC) receiver and Coherent Detection-Differential Decoding (CD-DD) receiver is analyzed for the detection of M-ary CPFSK signals under various signal impairments. -- The analysis is first carried out for the detection of M-ary CPFSK with modulation index -- [special characters omitted] -- in wideband channels. The effect of symbol timing errors and baseband symbol pulse shaping is considered. It is shown that CD-DD detection has better performance and less sensitivity to timing errors than LD detection and DC detection whereas LD detection and DC detection yield approximately the same performance both in the presence and in the absence of symbol timing errors. -- The bandlimiting effect of the front-end filter of the three receivers is then considered. An effective methodology is developed to take into account the effect of Intersymbol Interference (ISI). As in wideband channels, it is shown that even in bandlimited channels, CD-DD detection yields better performance and has less sensitivity to ISI than LD detection and DC detection whereas the latter two detection schemes have almost identical performance and sensitivities. -- The performance evaluation of LD detection of M-ary CPFSK with arbitrary modulation index, in both wideband and bandlimited channels, is also considered in order to determine the optimum modulation index which minimizes the error probability. It is shown that the performance of LD detection can be improved by increasing the modulation index above -- [special characters omitted] -- . A variable delay differential detection technique which employs a delay interval dependent on the modulation index is analyzed for the detection of binary CPFSK signals with arbitrary modulation index in bandlimited channels. The performance of the variable delay differential detector is shown to be comparable with the performance of LD detector. -- Finally, the numerical results obtained for the detection of quaternary CPFSK and octonary CPFSK in bandlimited channels are verified by digital computer simulation.

Abstract: The effect of a noisy reference carrier on the performance of International Comet Explorer (ICE) Sequential decoder is analyzed. Ideal reference models for frame deletion probability are given for the Telemetry Processing Assembly (TPA) and the Linkabit (LS4815) sequential decoders. Based on these ideal reference models the deletion probability in the presence of noisy reference carrier is computed for both the high and the low data rate cases. A medium data rate performance model is then derived using an interpolation method. The derived medium rate performance model depends on the phase locked loop bandwidth-integration time product. Results are obtained for frame length 1024 bits, data bit rates of 1024 bps and 512 bps, modulation index of 60 deg, and threshold loop bandwidths of 10 Hz and 3 Hz. The medium rate model agrees with experimental data to within measurement uncertainty. For the 10 Hz loop bandwidth and modulation index of 60 deg at frame deletion rate of 0.0001, the required total received power to noise ratio is 36 dB. The analysis given is general and applicable to any sequential decoder, provided that the ideal reference model of the decoder is available.

Abstract: The combination of coding and low index modulation can result in both bandwidth and power efficient modem design. The low index modulation format is obtained by using a frequency division and multiplication network to alter the modulation index of ? for convertioned MSK to a lower value. This lower value modulation index in concert with restricted range encoding provides a system that can achieve a 2 bits/sec/Hz bandwidth efficiency at a power level equivalent to that required for MSK. The design concepts are such that data rates in the hundreds of megabits/second are practical.

Abstract: PURPOSE:To obtain the recording and reproducing system with excellent noise resistivity even for a low lightness part by emphasizing the low lightness part in a luminance signal and executing phase modulation by using the emphasized luminance signal. CONSTITUTION:The low lightness part is emphasized from the luminance signal EY(t) at a gamma circuit 1 and the signal becomes a luminance signal E'Y(t). A main carrier 4 outputted from a reference signal generator 3 is subject to phase modulation (modulation index mp is taken as mp<=1.3) by the luminance signal E'Y(t) whose low lightness part is emphasized at a PM modulation circuit 5 and becomes a carrier luminance signal CY(t). The carrier luminance signal CY(t) is amplified by an amplifier 6 and inputted to a synthesis circuit 7. On the other hand, the carrier luminance signal CY(t) in a reproducing signal 10 reproduced by a video head 9 in the corresponding reproducing system is separated by a high pass filter 11 and inputted to a PM demodulation circuit 13 after AM noise is eliminated by a limiter 12. The luminance signal E'Y(t) outputted from the PM demodulation circuit 13 is emphasized for the low lightness part, then it is corrected by a De-gamma circuit 2 and restored into the original luminance signal EY(t).

Abstract: PURPOSE:To simplify circuit configuration of a demodulating section by binary encoding a binary information series, modulating and transmitting it, and after multiplying modulated wave in receiving side, reproducing the series of binary information by the action of a 1 bit delay sine detector. CONSTITUTION:A binary information series (an) inputted from a terminal 1 is converted to a binary series (bn) in a polybinary precoder 2. This value bn is given by a sum that makes the value of 2L-2 past data and the value of present an divisors, and polybinary encoding suitable to obtain phase continuous FSK modulated wave is performed. A modulating section 4 generates phase continuous FSK modulated wave having maximum value of L-1/2 modulation index of (h) by this pulse train. This modulated wave is sent to a transmitting section 5 and transmitted from an antenna. On the other hand, the receiving side receives 6 a receiving signal and after multiplying the modulated wave by a (L-1/2)/h multiplying circuit 7, binary discriminates 9 by the action of a 1 bit delay sine detector 8 and reproduces original series of binary information.

Abstract: Using the S-band communications system, shuttle orbiter can communicate directly with the Earth via the Ground Spaceflight Tracking and Data Network (GSTDN) or via the Tracking and Data Relay Satellite System (TDRSS) The S-band frequencies provide the primary links for direct Earth and TDRSS communications during all launch and entry/landing phases of shuttle missions On orbit, S-band links are used when TDRSS Ku-band is not available, when conditions require orbiter attitudes unfavorable to Ku-band communications, or when the payload bay doors are closed the S-band communications functional requirements, the orbiter hardware configuration, and the NASA S-band communications network are described The requirements and implementation concepts which resulted in techniques for shuttle S-band hardware development discussed include: (1) digital voice delta modulation; (2) convolutional coding/Viterbi decoding; (3) critical modulation index for phase modulation using a Costas loop (phase-shift keying) receiver; (4) optimum digital data modulation parameters for continuous-wave frequency modulation; (5) intermodulation effects of subcarrier ranging and time-division multiplexing data channels; (6) radiofrequency coverage; and (7) despreading techniques under poor signal-to-noise conditions Channel performance is reviewed

Abstract: Problems and solutions for the far end measurement of frequency characteristics of the baseband response of a multimode fiber due to dispersion are presented. Also described is a configuration of the measuring equipment of the baseband response. For the latter, the following are important: (i) removal of the effect of the material dispersion; (ii) stabilization and leveling of the modulation level; (iii) stabilization of the optical output level; and (iv) removal of the effect of the reflected light from the output end and the input end of the fiber. Solutions for these problems are: (i) single-mode oscillation of the semiconductor laser by reduction of the modulation index; (ii) stabilization and leveling of the modulation level by a negative feedback loop that monitors the modulation level of the backward light of the laser; (iii) stabilization of the optical output by a negative feedback loop that monitors the output level of the backward light of the laser; and (iv) removal of the effect of the reflected light by means of oblique incidence and small input aperture angle. When the baseband characteristic of a fiber a few kilometers long is measured, irregular variations are observed. A solution to this problem is also included.

Abstract: It is shown theoretically that the directly modulated laser diode, with the modulation frequency of its injection current comparable to the relaxation oscillation frequency, exhibits period doubling route to chaos as the modulation index of current is increased. The effect of spontaneous emission factor on the chaotic behavior in the laser diode is also studied.