Showing papers on "Pulse-frequency modulation published in 1968"

Spectral Analysis of Pulse Frequency Modulation in the Nervous Systems

Abstract: Spectral analysis is one of the more important design and evaluation tools available to the communications engineer and it could also be a key to increased understanding of the nervous system. Some results of an analysis of the spectrum of the frequency modulated pulses of the nervous system show that 1) change in average pulse frequency is the likely information-carrying parameter of a neural pulse train, since distortion-free recovery of this variable is possible by simple low-pass filtering, and 2) phase relationships existing between signal components and distortion components of a neural pulse train imply unusual distortion attenuating properties of multiple or duplicate information channels. These results are discussed in light of some known nervous system structures.

Pulse rate to analog converter

Abstract: A system for providing an analog output signal whose average amplitude is proportional to the frequency of an input signal including a constant pulse width generator responsive to the input signal for providing a series of pulses each of which has a predetermined duration at the same frequency as the input signal and an averaging circuit responsive to the series of pulses for providing an analog signal whose average amplitude is a function of the duty cycle of the constant pulse width generator.

Frequency demodulator for noise threshold extension

Abstract: Described herein is a frequency modulation signal demodulation system which utilizes the amplitude modulation information inherent in a noise-corrupted frequency modulation carrier to control the parameters of a feedback loop, through which the demodulated FM information is passed, during the occurrence of large noise-induced, pulselike disturbances in the demodulated frequency modulation information. This function is performed by a circuit configuration which includes an amplitude modulation demodulator and a frequency modulation demodulator supplied in parallel from the input to the system for deriving information signals which are respective functions of the instantaneous envelope information and the instantaneous frequency modulation information. The control of the parameters of the feedback loop may be accomplished by the instantaneous envelope information directly or by the envelope information on which some process has been performed. The description also refers to the fact that the envelope detector may have linear or nonlinear characteristics. One way in which the envelope information may be processed is by a nonlinear quantizer followed by a time delay circuit which is interposed between the envelope demodulator and the means for controlling the feedback loop which modifies the frequency modulation information signals. The final output signals may be taken from the output of the feedback loop through a low-pass filter. If desired, an equalizing filter may also be interposed between the output of the feedback loop and the final low-pass filter.

Pulse width modulation to amplitude modulation conversion circuit which minimizes the effects of aging and temperature drift

Abstract: THE ADVERSE EFFECTS ON THE OPERATION OF A PULSE WIDTH MODULATION TO AMPLITUDE MODULATION CONVERSION CIRCUIT CAUSED BY NOISE SIGNALS AND CHANGES IN TEMPERATURE ARE CONSIDERABLY MINIMIZED BY THE INSERTION OF CIRCUITRY, IN ACCORDANCE WITH THIS INVENTION, INTO THE DRIVING CIRCUIT OF SAID PULSE WIDTH MODULATION TO AMPLITUDE MODULATION CONVERSION CIRCUIT.

Apparatus and method for eliminating frequency modulation from modulated light

Abstract: The proposed apparatus and method removes the frequency modulation from an incident light beam having an arbitrary combination of amplitude and frequency modulation, and produces a purely amplitude modulated beam with an envelope simply related to the envelope of the incident beam. The apparatus comprises a third order nonlinear system for producing an output signal with amplitude proportional to the amplitude product of the square of the incident beam and a second purely sinusoidal local oscillator beam. This output beam contains the amplitude modulation information of the incident beam but does not contain any of the frequency modulation. The third order nonlinear system may include simply a single crystal such as strontium titanate or alternatively a more complex system of phase-matched difference and sum frequency generators.

The Stability of Integral Pulse Frequency Modulation Systems

Abstract: Stability of single loop feedback circuit comprising integral pulse frequency modulator and stationary linear system

An analysis of the effect of integral and sigma pulse frequency modulation on white noise

Abstract: Integral and sigma pulse frequency modulation effects on white noise, analyzing autocorrelation and spectral density functions of PFM system output

Constant frequency amplitude-to-pulse width converter

Abstract: A PAIR OF CAPACITORS ARE CAUSED TO ALTERNATEELY CHARGE AT A CONSTANT RATE THROUGH THE BASE-EMITTER PATHS OF A PAIR OF TRANSISTORS UNTIL THEIR VOLTAGES REACH FIRST AND SECOND VARIABLE THRESHOLD VOLTAGES, RESPECTIVELY. AT THE INSTANT EACH CAPACITOR REACHES ITS THRESHOLD VOLTAGE, IT IS ABRUPTLY DISCHARGED AND THE OTHER CAPACITOR STARTS TO CHARGE. RECTANGULAR VOLTAGE WAVEFORMS OF OPPOSITE PHASE APPEAR ACROSS RESISTORS IN THE COLLECTOR CIRCUITS OF THE TRANSISTORS. THE WIDTHS OF THE PULSES IN THE WAVEFORMS ARE CONTROLLED BY THE THRESHOLD VOLTAGES. BY MAINTAINING THE SUM OF THE THRESHOLD VOLTAGES CONSTANT, THE FREQUENCY OF THE WAVEFORMS WILL BE CONSTANT REGARDLESS OF PULSE WIDTH.

Microwave Phase Modulation Using Frequency Multipliers

Abstract: For communication by radio links, satellites, waveguides etc. a pulse code modulation that is realized by phase reversal (phase shift keyed) has advantages as compared to a pulse amplitude modulation because the signal-to-noise ratio can be 6 db less for the same error probability. The phase shift keying of the microwaves should be rapid (< 1ns) and the modulation losses should be small. A suitable semiconductor element for such a phase modulator is a voltage dependent capacitance diode. A simple circuit for a reflection type modulator is obtained when the diode terminates a transmission line. Then the phase of the reflected wave can be shifted by a change of the bias voltage. The lossless tuner in figure 1a is adjusted so that any residual amplitude modulation is minimized.

Spectrum Distortion Due to Frequency Instabilities in a Two-Way Coherent Doppler Radar

Abstract: The power spectral density of the intermediate frequency signal in a coherent Doppler navigation radar is derived The effects of antenna parameters, periodic frequency instabilities, signal two-way transit time, and transmitter frequency modulation noise are considered Several examples based on the measured frequency modulation noise of a solid-state source transmitter are presented The results indicate the degree of loss in signal-to-noise ratio, and spectrum broadening due to an increase in signal transit time and/or frequency modulation noise