Abstract: In an optical system such as a ring laser gyroscope cavity, oscillations occur in many transverse modes. The desired modes are allowed to exist by suppressing undesired modes utilizing a light stop apparatus. One light stop is made by treating a dielectric mirror with an electron beam causing a phase change to occur to the undesired reflected waves. An alternative light stop is made by depositing an absorptive material on a dielectric mirror for absorbing some of the energy of the undesired modes. Both light stop embodiments are adjustable with respect to a laser wave in a resonant cavity.

Abstract: An article of manufacture is provided comprising a polycrystalline cubic aluminum oxynitride having a density of at least 98% of theoretical density, and being transparent to electromagnetic radiation in the wavelength range from 0.3 to 5 micrometers with an in-line transmission of at least 20% in this range.A method of preparing the optically transparent aluminum oxynitride is also provided comprising the steps of forming a green body of substantially homogeneous aluminum oxynitride powder and pressureless sintering said green body in a nitrogen atmosphere and in the presence of predetermined additives which enhance the sintering process. Preferred additives are boron and yttrium in elemental or compound form.

Abstract: A semiconductor device fabrication process is provided wherein a first window is formed in a first silicon dioxide layer which is disposed over the surface of a silicon layer to expose a first portion of the silicon layer. A doped region is formed in the first portion of a silicon layer exposed by the first window. A second layer of silicon dioxide is deposited over the surface of the first, previously formed, silicon dioxide layer and over the first portion of the silicon layer exposed by the first window. A second window is formed through the first and second silicon dioxide layers to expose a second, different portion of the surface of the silicon layer. A layer of silicon nitride is disposed over the second layer of silicon dioxide and through the second formed window onto the portion of the silicon layer exposed by such second formed window. The surface of the structure is then masked with windows being formed in such mask over the first and second previously exposed portions of the silicon layer.

Abstract: A metal rod rack shelf for a microwave oven wherein extension support rods are substantially prevented from being excited with high electric currents. The rack is embodied with quarter wavelength choking structures in the regions where the extension support rods connect to the rack mainframe. Accordingly, the effective short circuits in those regions are transformed to open circuits at a distance of one-quarter wavelength along the support rods. As a result, the support rods do not rise to high temperatures or radiate intense microwave fields that could cause melting of or arcing to microwave transparent brackets which mount to walls of the oven cavity and engage the rods.

Abstract: A frequency discriminator having a wide capture band is shown to comprise, in addition to a conventional phase detector having two channels fed by a signal whose frequency is to be determined (the first one of the channels containing a tuned circuit operative to shift the phase of the signal in accordance with the difference between the frequency of the signal and the center frequency of the tuned circuit and the second one of the channels containing a phase shifter operative to shift the phase of the signal by 90.degree. regardless of the frequency of the signal), a compensating circuit operative substantially to equalize the amplitudes of the signals applied to the phase detector, the compensating circuit including an amplifier in the first one of the channels to amplify the signal out of the tuned circuit, the gain of the amplifier being controlled by a signal indicative of the difference between the amplitudes of the signals fed to the phase detector.

Abstract: A coaxially fed applicator for in situ RF heating of subsurface bodies with a coaxial choke structure for reducing outer conductor RF currents adjacent the radiator. The outer conductor of the coaxial transmission line supplying RF energy to the radiator terminates in a coaxial structure comprising a section of coaxial line extending toward the RF radiator from the termination for a distance approaching a quarter wavelength at the RF frequency and a coaxial stub extending back along the coaxial line outer conductor from the termination for a distance less than a quarter wavelength at said frequency. The central conductor of the coaxial transmission line is connected to an enlarged coaxial structure approximately a quarter of a wavelength long in a region beyond the end of the outer conductor coaxial choking structure.

Abstract: A space fed antenna with a folded path to reduce the distance between a phased array and the focal point of such array is shown to be made up of: (a) a first plurality of vertically polarized antenna elements incorporated in the phased array; (b) a second plurality of cross-polarized antenna elements disposed to form a polarization-twisting screen at a distance from the first plurality of vertically polarized antenna elements equal to one-third the focal length of such elements; and (c) a third plurality of latching circulators connected between selected pairs of cross-polarized antenna elements in the polarization-twisting screen so that such pairs also may function as a feed array for the space fed antenna.

Abstract: A method for controlling a microwave oven with a microcomputer wherein a first time period corresponding to the time required to raise the temperature of a weighed food body from refrigerator temperature to room temperature and a second time period corresponding to the time required to cook the food body from an initial room temperature are calculated and stored. The microcomputer then sequentially controls the magnetron through cycles in accordance with the first and second time periods, respectively. Rather than being erased after completion of the first cycle, the first time period remains stored in the microcomputer and can be activated by the operator to provide a small incremental amount of heat to the food body after it has been cooked. Also, the operator can adjust the number of heat units per weight units used in the calculation of the cooking cycle so as to provide a food body that is cooked less or more than medium doneness.

Abstract: A method and apparatus for regulating a microwave oven to a predetermined output power level. The anode current or a voltage corresponding to it is monitored to provide a signal indicative of the actual output power of the magnetron. Time is divided into a sequence of equal time intervals, each interval corresponding to fixed number of ac line cycles. In accordance with the signal, the number of ac cycles to be supplied to the power supply for each interval to regulate the output power towards the regulated level is determined. The determined number of cycles are supplied by switching at the zero current crossings between the line and the power supply. The switching is executed so that the supplied ac cycles are distributed substantially uniformly over the particular time interval.

Abstract: A laser system capable of producing multiple pulses comprising a single optical resonator having multiple discharge regions and multiple sets of electrodes and preionizers. The optical resonator is folded and the beam passes through all of the discharge regions. Since the multiple discharges occur within the same resonator, multiple identical pulses are produced and since the discharge regions are separated, the shock wave and medium inhomogeneity produced by a discharge in one discharge region will not disturb the others. The overall mirror separation and electrode spacing define a Fresnel number suited for single transverse mode operation.

Abstract: A byte-addressable memory system having an array of transceivers with control logic which enables memory to be addressable on individual byte boundaries rather than on two byte (word) or four byte (longword) boundaries. The memory system has two independent even-address and odd-address segments allowing parallel access to two longwords (eight bytes or one quadword) simultaneously. Logic determines which of the eight bytes should be placed on a four byte bus and the sequential order of the bytes on the bus. The entire operation takes place in one memory cycles time period and can start at any byte address.

Abstract: A comparator circuit is provided for producing a voltage across the base and collector electrodes of an output transistor to drive the output transistor to either a conducting condition, or a nonconducting condition, selectively in accordance with an input signal. A switching circuit, responsive to the input signal, is coupled between a current source and the base electrode of the output transistor for electrically coupling the current source to the base electrode of the output transistor when the output transistor is driving from the conducting condition to the nonconducting condition and for electrically decoupling the current source from the base electrode of the output transistor when such output transistor is driving from the nonconducting condition to the conducting condition. With such arrangement, when the switching circuit couples the current source to the base electrode of the output transistor, the current source provides a discharge circuit for base charge in the output transistor.

Abstract: Automatic focusing apparatus comprising a beam focusing assembly disposed for directing through an axially spaced focal spot a scanning light beam having a periodic translational movement characterized by a first fundamental frequency component, a focus evaluating assembly disposed for detecting adjacent the focal spot a periodic translational movement of the focused beam characterized by a fundamental frequency component which is compared with said first fundamental frequency component to determine the relative phase relationship, and a target positioning assembly disposed for automatically positioning a selected surface of a target at the focal spot in accordance with the periodic translational movement of the focused beam and said determination of relative phase relationship.

Abstract: A bidirectional switch for selectively switching a microwave frequency signal between one of two signal paths. The switch includes a pair of field effect transistors, and a pair of transmission lines coupled together at one end thereof to provide a common port. Each second end of each microwave transmission line is coupled to a drain electrode of one of such field effect transistors to provide a branch port at each second end of each microwave transmission line. The electrical lengths of each transmission line are selected in accordance with the operating wavelength of the circuit to provide an impedance corresponding to an open circuit at one end, when a short circuit is provided at the opposite end. A signal is coupled between the common port and a selected one of the branch ports, in response to a pair of complementary binary control signals fed to the gate electrodes of the FETs.

Abstract: An adjustable two-port microwave network having digitally controlled switches which enable the network to be set to a plurality reflection and transmission coefficients. The network facilitates the collection of a plurality of measurements which are necessary to characterize a non-linear device. An embodiment of the network is constructed using a 3dB directional coupler feeding two identical power divider networks each comprising two cascaded directional couplers. One divider network is connected directly to the coupled port of the 3dB directional coupler and the other divider network is connected through a phase shifter to the output port of the 3dB directional coupler. The non-linear device to be characterized is connected to the input port of the 3dB directional coupler and for this application, the isolated port is terminated in its characteristic impedance.

Abstract: A plurality of microwave semiconductor devices is provided by plating a thin conductive layer on a surface of a wafer of semiconductor material, masking selected portions of the thin conductive layer, and plating unmasked portions of the thin conductive layer to form a thicker, apertured support layer with the apertures in the support layer providing a thin contact. After forming the thicker, apertured support layer, substantial portions of the semiconductor material are removed to form the semiconductor devices as a plurality of mesa shaped diodes, with each one of the semiconductor mesa shaped diodes being formed on a corresponding one of the thin contacts, and with the plurality of mesa shaped diodes being mutually supported by the support layer and integrally formed thin contacts. Each contact and the support are selectively etched to pattern portions of the support and thin contacts into a frame.

Abstract: A method of producing a control signal for a range gate in a pulse Doppler radar, the method encompassing the steps of periodically determining the range slip of a selected target and then changing the position of a range gate during each range sweep in accordance with the determined range slip.

Abstract: A microwave cooking system comprising a thermally insulated holder for food bodies having a thermally reflective shield for reflecting thermal radiation from the food bodies to thereby reduce the loss of heat by radiation through the thermal insulation layer while providing for propagation of microwave energy into the food body through the thermal insulating portion of the food holder.

Abstract: A reflector type radio frequency antenna having: a feed for producing a difference radiation pattern with a cone-shaped null region; and, a reflector having a surface disposed to reflect a portion of the energy in the difference radiation pattern and having the edge disposed in the cone-shaped null region. With such arrangement, since the edge of the reflector is disposed in the null region of the difference radiation pattern such edge is not radiated with energy which could otherwise illuminate such edge, scatter, and thereby generate unwanted side lobes in the free space antenna pattern.

Abstract: A coupling between a stainless steel exhaust manifold of a recuperative heat exchanger and a plastic flue pipe. The internal integrity of the manifold is maintained by spot welding a mounting bracket to the outside thereby defining a slot between parallel portions of the bracket and the manifold. The flue pipe inserts through coaxial circular apertures in the bracket and the manifold. A shoulder of an annular protrusion on the outside of the flue pipe presses against an O-ring seated in an inwardly directed step of the circular aperture in the manifold thereby providing an airtight seal. The flue pipe is secured in the described position by a bifurcated retainer clip slid down into the slot thereby engaging portions of the opposite shoulder of the annular protrusion.