Abstract: In a sequential-transmission phase measurement radionavigation system, such as the OMEGA radio-navigation system, phase correction signals are transmitted by a network of transmitting stations to provide phase corrections over a predetermined area. Each phase correction transmitting station compares the measured phases with preset theoretical phases and provides a phase correction signal for each measured phase. The phase correction signals are time multiplexed with a multiplex frequency between 10 and 30 times the repetition rate of each of the sequential transmissions of the radio-navigation system, the multiplexing being synchronous with the sequential transmissions. The multiplexed signal is phase modulated on a carrier with a low modulation index. At a receiver the multiplexed phase correction signal is demodulated and demultiplexed to provide the phase correction signals which are used to modify the measured phases at the receiver.

Abstract: A speech-controlled switching arrangement for communication systems in which the speech signals are transmitted in the form of digital signals obtained by code modulation, comprising a plurality of pulse group analyzers coupled to respective transmission channels from which analyzers the output pulses are applied to a comparator circuit after integration for the purpose of generating a switching control signal, while each pulse group analyzer is provided with a digitally defined threshold characterizing a given fixed modulation index.

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.

Abstract: : The results of a study of a phase locked modulation technique applicable to phase coherent FSK are presented. This technique employs a continuous phase, frequency shifted, phase locked loop to produce controlled, non-instantaneous, frequency transitions between the mark and space frequencies. Operational and spectral analyses have been conducted, and spectral data have been calculated for the modulated carrier signal and its corresponding effective modulating signal. It is shown that effective modulation wave-shaping can be achieved and that the corresponding signal bandwidths can be controlled within certain limits by variation of the loop parameters, undamped natural frequency and open loop gain. Representative data are presented, corresponding to a selected class of loop parameters, as a function of modulation index and the ratio of frequency transition time to bit length.

Abstract: A computer search was made for the optimum second- and third-order bandpass filters for use in narrow-band FM and PM systems. The optimum filter for minimum distortion was found to be near the Bessel filter. The results were fairly independent of modulation index and bandwidth.

Abstract: The fact that spike discharges of spontaneously active cochlear nerve fibers demonstrate phase locking in response to low‐frequency sinusoidal stimuli at signal levels substantially lower than those required to generate a change in spike discharge rate has led us to investigate the properties of the following response criterion. We evaluate the index of modulation of the spike discharge rate as a result of the sinusoidal stimulus. Period histograms are modelled as an inhomogeneous Poisson process. Using maximum likelihood techniques, we estimate the index of modulation and the phase difference between the stimulus and the response. We have acquired data similar to “tuning curves” showing as a function of frequency the stimulus level necessary to maintain an arbitrary fixed level of modulation along with the corresponding stimulus‐response phase relations for the complete response‐band of fibers with low CF ( 3 kHz). We compare these results to those obtained using other response criteria, and examine their relationship to cochlear mechanics and cochlear microphonics. [This investigation was supported by PHS research grants from the National Institutes of Health.]