Westinghouse Electric Corporation

Abb Power Td & Company

Northrop Grumman Systems Corporation

Carlo F Petronio

Robert M Oates

Mark G Kraus

Robert C Miller

Charles W Einolf, Jr

Peter J Chantry

Karl C Koch

James C Belz

The microwave field intensity of a cell type atomic clock is stabilized through time division feedback control of the power of the microwave signal implemented by a microcontroller. The depth of the microwave dip is calculated from differences in measurements of the optical signal when the microwave signal is dithered around the atomic transition frequency of the active medium, and measurements taken when the optical signal is dithered around the optical wavelength of the active medium while the microwave signal is adjusted to produce no microwave absorption, either by reducing the microwave power to zero or by detuning it from the atomic transition frequency of the active medium. RF synthesizers suitable for regulating microwave power include a synthesizer using a step recovery diode for frequency multiplication and having the power to a driver amplifier or the bias applied to the diode regulated. A digital synthesizer can also be used to generate a regulated microwave signal.

Apparatus and method for microwave field strength stabilization in cell

As the dielectric constant and the halfwave voltage of electro-optic crystals having a fourfold axis of rotary inversion are oppositely dependent on the absolute temperature, but their product is nearly independent of temperature, temperature compensation in an ac voltage measuring system utilizing such an electro-optic crystal is provided by measuring the time averaged current through the crystal. Good electric isolation is achieved by a current sensing circuit which produces a pulsed light signal having a pulse rate proportional to the time averaged current through the crystal. The pulsed light signal is converted to an electrical signal for input to a digital computer which calculates therefrom, and from a reference current and voltage measured at a reference temperature, and a time averaged voltage measurement, a temperature correction factor which is applied to the crystal halfwave voltage used by the computer in calculating the instantaneous value of the voltage to be measured. A look up table containing empirically derived values related to the calculated correction factor can be used to generate a correction factor adjusted for leakage through the crystal, fringing of the field produced by the voltage to be measured, and residual temperature dependence of the electro-optic crystal. In a practical embodiment of the invention, shield rings surround both ends of the electro-optic crystal to reduce fringing of the electric field.

Electro-optic voltage measuring system with temperature compensation

In a measuring device including a magnetic-optic current transformer (2) defining an optical path having an input (4) and an output (6) and having an optical transmission characteristics such that the relation between optical energy supplied to the input (4) and optical energy arriving at the output (6) is a function of an electrical parameter being monitored, an electrically driven photoemitter (8) disposed for supplying optical energy to the optical path input (4), a photodetector circuit (10, 12) optically coupled to the optical path output (6) for producing an electrical signal representative of the optical power arriving at the output (6), and a control circuit (14,16) connected between the photodetector circuit (10,12) and the photoemitter (8) for controlling the light energy supplied by the photoemitter (8) and forming with the transformer (2) a high pass filter having a corner frequency, the control circuit (14,16) is composed of an amplifier (20) and a first compensation unit (24,26) connected to form a negative feedback path of the amplifier (20) for supplying a negative feedback signal which is linearly proportional to the optical power emitted by the photoemitter (8) for causing the corner frequency value to be independent of the relative between the optical power at the input (4) to the path and the optical power at the output (6) of the path; and a second compensation unit (R.sub.3,R.sub.4) is operatively connected for causing the corner frequency value to be independent of the temperature of the control circuit (2).

Current monitoring circuit error compensation

A dual media network interface module includes an electrical network interface and an optical network interface each having a transmit port to which signals to be transmitted on the associated network are applied and a receiver port at which signals received on the network are generated. The receiver port of each interface is connected to the transmitter port of the other interface so that signals received on either network are retransmitted on the other network. Blocking circuits block the receiver signal of a LAN which is transmitting during the transmitting interval plus an interval which exceed the worst case propagation time for the associated network to prevent endless repetition of a signal. A preferred form of the module includes a pair of controller interfaces having transmit ports and receiver ports connected to the corresponding ports of the other controller interface and of the electrical and optical network interfaces to provide bidirectional communications between all devices connected to the module. The modules can be used to interface electrical and optical nodes in a network, to expand both electrical and optical networks, and to interconnect various combinations of electrical and optical local area networks.

Dual media local area network interfacing

An optical receiver especially useful for digital fiber optic systems operating a high pulse rates, converts the pulsed current signal generated by a PIN diode into a pulsed voltage utilizing a current to voltage converter comprising an FET input transistor, a complimentary cascoded bipolar transistor, and a large feedback resistor to reduce noise while providing a wide band width and dynamic range. The pulsed voltage signal is amplitude limited in a limiting amplifier and passed through a low pass filter to remove excess bandwidth and further reduced noise before being applied to a high speed comparator which generates the digital output. The pulsed voltage signal is passed from the current to voltage converter to the limiting amplifier through an emitter follower coupling transistor to isolate the open loop gain of the current to voltage converter so that its band width will not be changed with load.

Fiber optic receiver

A plurality of proximity sensors are disposed in a turbine flow guide to measure flow guide-to-turbine blade tip distance at various points around the flow guide. The sensor signals are detected and the peak-to-peak voltage of the detected signals provides an indication of the desired distance measurement. The signals are also monitored and if ambient operating conditions causes the signals to exceed predetermined positive or negative thresholds, corrective signals are generated so as to bring the detected signal back into an acceptable range. A proximity sensor is also provided to measure axial movement of the rotor to which the blades are attached so that the other sensor signals can be modified as a function of the measured axial position.

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Pittsburgh, PA, United States of America

Carlo F Petronio