Showing papers on "Coupling published in 1990"

Mutual coupling compensation in small array antennas

Abstract: A technique to compensate for mutual coupling in a small array is developed and experimentally verified. Mathematically, the compensation consists of a matrix multiplication performed on the received-signal vector. This, in effect, restores the signals as received by the isolated elements in the absence of mutual coupling. This technique is most practical for digital beamforming antennas where the matrix operation can be readily implemented. >

Amplitude death in an array of limit-cycle oscillators

Abstract: We analyze a large system of limit-cycle oscillators with mean-field coupling and randomly distributed natural frequencies. We prove that when the coupling is sufficiently strong and the distribution of frequencies has sufficiently large variance, the system undergoes “amplitude death”-the oscillators pull each other off their limit cycles and into the origin, which in this case is astable equilibrium point for the coupled system. We determine the region in couplingvariance space for which amplitude death is stable, and present the first proof that the infinite system provides an accurate picture of amplitude death in the large but finite system.

Proximity detecting apparatus

Abstract: A proximity detection system which combines the advantages of an electrostatic (electric) field coupling mechanism with those of an electromagnetic coupling mechanism in order to overcome the disadvantages of the respective individual coupling mechanisms. The system includes a coded tag (9) which is excited with an induction field, i.e., by using an electromagnetic coupling mechanism (13, 17) as has been done in the past in such proximity identification systems, but which transmits stored data back to the receiver (5) using both an electric field coupling mechanism (47, 52) and an electromagnetic field coupling mechanism (50, 53). The receiver (5), in turn, is provided with a novel preamplifier circuit arrangement (55, 73-85), so that it can simultaneously receive signals via either or both of these coupling mechanisms.

Proposal of novel electron wave coupled devices

Abstract: We propose a novel structure for electron wave devices that utilizes the mutual coupling effect between electron wave guides. The structure consists of two parallel electron wave guides with a coupling region controlled by a gate voltage. Using simple theoretical calculations, we estimate the switching time and the coupling length required for electron transfer to be 2 ps and 0.28 μm, respectively.

Observation of enhanced fundamental linewidth of a laser due to nonorthogonality of its longitudinal eigenmodes.

Abstract: In the presence of output coupling the longitudinal eigenmodes of a laser are not orthogonal. This may affect the quantum limit to the laser linewidth, in particular, if the outcoupling is high. We present experimental evidence of this effect, using single-mode semiconductor lasers with various coatings.

Analysis of mutual coupling in finite arrays of different-sized rectangular waveguides

Abstract: A Green's function approach is used to analyze mutual coupling in a finite array of different-sized rectangular waveguides arranged on a rectangular grid. In calculating the self- and mutual admittances for mode coupling, a quadruple integration over the source and observer apertures is involved. Possible means of reducing the order of integration are discussed, with the change of variables approach of L. Lewin (1951) being selected. This approach is generalized to allow coupling between different-sized apertures and leads to derivation of mutual admittance expressions for all possible combinations of transverse electric (TE) and transverse magnetic (TM) mode coupling. Calculations using these expressions are shown to be in good agreement with results published earlier by R.J. Mailloux (1969) and measured data for an antenna comprising a square waveguide and two rectangular waveguides. Coupling between closely spaced different-sized square waveguides is also investigated, and for small apertures minimum coupling is shown to occur when the aperture sidelength is about 1.15 lambda . >

Hermaphroditic coupling for anatomical thermal system

Abstract: The coupling (15) which is especially useful in an anatomical thermal system between the pad means and control unit thereof, includes a pair of parallel lumens (23,24) with the coupling being divided into two units (15a,15b) having identical hermaphroditic, engageable ends (22) and with releasable latch means (43-50) connecting the two elements of the hermaphroditic coupling.

Motor-driven power steering device

Abstract: PURPOSE:To reduce the number of parts used and enhance easiness in assembling works by forming a steering mechanism, which is fixed to a car body, etc., maneuvered through steering operation, in such a way as consolidated with a torque sensor assembly to sense the steering torque. CONSTITUTION:A steering mechanism 2 has a worm shaft 4 rotated by turning a steering wheel, and this rotation swings a sector 22, i.e., a pitman arm 23, through a ball nut 21, and thus a coupling 25 and a drag rod 24 are tracted to accomplish steering of wheels. Inside of a housing 2a of this steering mechanism 2, a torque sensor assembly 50 is fitted at the other end of the worm shaft 4. This assembly 50 is so constructed that the deflection of a spring 29 in the assembly 50 when a load greater than the set load on the spring is applied to the tip of the pitman arm 23, is sensed by a potentiometer 26 through a lever 31, etc., and in response to this output a motor for steering aid is controlled.

Electronically controlled force application mechanism for exercise machines

Abstract: A force development system for the application of controlled variable speeds and torque forces in exercise machines utilized to strengthen and develop body muscles of an exercising person. The system includes a constant speed high torque electric drive motor mechanically coupled to a dynamic clutch device in which the controlled coupling of the rotary force input assembly of the clutch to the rotary force output assembly of the clutch is accomplished via electromagnetic coil activation of metallic powder particles forming coupling particle chains between the input and output assemblies of the clutch. Alternatively, the dynamic clutch of the system may be a fluid clutch containing electrorheological fluid. The force development system of the invention also includes a speed reduction device between the dynamic clutch and the exercise machine to which the system is applied. An electronic sensor, interconnected to a microprocessor, senses the speed, motion and torque force of the system's output shaft. A control unit (interconnected to the drive motor, the electromagnetic coil of the dynamic clutch and the microprocessor) is directed by the microprocessor (in relation to the speed and torque force information sensed by the electronic sensor) and in turn controls the coupling torque of the dynamic clutch whereby controlled variable speeds and resistive forces are applied to the resistive force mechanism of the exercise machine.

Torque coupling system

Abstract: A torque coupling system includes an impeller that is connected to one end of an impeller shaft without the use of threads. The connection is made by cement and dowels. A drive system for the shaft includes a hollow coupling into which the other end of the shaft can be fitted. The shaft includes longitudinally extending slots formed at its end. The coupling includes spaced, longitudinally extending keys adapted to be fitted into the slots formed in the shaft. The drive system also includes a torque limiter that is connected intermediate the coupling and a drive motor. If the drive motor is an electric motor, the motor can be provided with automatic shut-down circuitry that is activated in the event of a current/torque overload. Visual and aural alarms are provided to alert the user that a shut-down has occurred.

Universal finite-size effects in the rate of growth processes

Abstract: Kinetic roughening of the growing surface generates universal finite-size corrections in the growth rate of films and crystals. For thin films the correction scales with the film thickness h as h- alpha perpendicular to ; for thick films it scales with the substrate size L as L- alpha //, where a/sub ///=2(1- zeta ) and alpha perpendicular to =2(1- zeta )/z in terms of the kinetic roughening exponents zeta and z. For ballistic deposits this implies a similar correction in the density. The coefficient of the correction is proportional to the KPZ coupling constant lambda . For one-dimensional substrates alpha /sub ///=1 and alpha perpendicular to =2/3. These predictions are corroborated by computer simulations of growth and deposition on one- and two-dimensional substrates, and by exact results for one-dimensional models. Different exponents apply in the weak results for one-dimensional models. Different exponents apply in the weak coupling regime and at kinetic roughening transitions.

Tube coupling with gasket retainer

Abstract: A tube coupling assembly particularly suited for ultra-high vacuum applications comprises a pair of coupling components having through passages and abutting end faces. Each end face includes an annular continuous rib or bead. A threaded coupling nut acts to drive the ribs into sealing engagement with the opposite sides of flat annular sealing washer gasket positioned between the end faces. To prevent relative rotation between the end faces and the sealing gasket, as well as to prevent torque transmission to related system components, protrusions are provided which engage the coupling components to produce a driving connection between the gasket and/or the two coupling components prior to engagement of the ribs with the gasket. Also, a resinous plastic bearing washer is used between the coupling nut and the associated coupling component to reduce torque transmission during make-up.

Coupling of slow waves near the lower hybrid frequency in JET

Abstract: The physical properties of the JET lower hybrid antenna have been investigated numerically with a two-dimensional computer code based on the linear coupling theory. The antenna is made from an array of multijunction units which divide the incident power along the toroidal direction. The main properties of this new coupler are investigated and compared with those of the conventional grills generally used in previous lower hybrid experiments. In the light of this study, the general design of the multijunction antenna is presented; the importance of the geometrical parameters of the multijunction unit (e.g. choice of the location of the E-plane junctions, septum width between waveguides) is stressed. These parameters are optimized and their values are taken into account in launcher manufacturing. With such an optimization, the electric field enhancement in each secondary waveguide is minimized for an electron density at the launcher of about 1018 m−3, the power reflection coefficient is below 1.5% and the 'n1-weighted antenna directivity' is expected to lie between 60% and 70% in a large range of plasma densities around the optimum density. By using two shorted passive waveguides on each side of the antenna, the edge effects are reduced. The effect of the accessibility limit on coupling is also investigated.

Coupling means between a light source and a bundle of optical fibers and method of making such coupling means

Abstract: This coupling means comprises a sleeve containing a bore in which is located a bundle of optical fibers, at least some of which are of compression-deformable material. The input ends of the fibers, which receive light from a light source, are located in a predetermined plane. The bore tapers from a relatively large diameter at a location in a second plane spaced from said predetermined plane to a relatively small diameter at said predetermined plane. The tapered bore is of such a size that the optical fibers therein are laterally compressed and the compression-deformable fibers are so deformed in transverse cross-section relative to their normal cross-sections that the fibers more completely fill the bore in its relatively small diameter region than in said second plane.

Torque coupling system for graphite impeller shafts

Abstract: A torque coupling system includes an impeller that is connected to one end of an impeller shaft without the use of threads. The connection is made by cement and dowels. A drive system for the shaft includes a hollow coupling into which the other end of the shaft can be fitted. The shaft includes longitudinally extending slots formed at its end. The coupling includes spaced, longitudinally extending keys adapted to be fitted into the slots formed in the shaft. The drive system also includes a torque limiter that is conected intermediate the coupling and a drive motor. If the drive motor is an electric motor, the motor can be provided with automatic shut-down circuitry that is activated in the event of a current/torque overload. Visual and aural alarms are provided to alert the user that a shut-down has occurred.

Coupling of fast waves in the ion cyclotron range of frequencies to H-mode plasmas in DIII-D

Abstract: Measurements of low power ( 1 mW) antenna loading are used to study the coupling of a compact loop antenna structure to plasmas in the divertor configuration in DIII-D heated by neutral beam injection (NBI) or electron cyclotron heating (ECH). When a transition to the H-mode regime occurs during NBI, the antenna loading resistance drops by approximately a factor of two. This coupling decrease is due to a steepening of the edge density profile near the separatrix, accompanied by a reduction in edge density in the scrape-off layer. During edge localized modes, the opposite effects occur, and the antenna coupling increases transiently. The loading measurements are compared with theoretical calculations which take into account the measured density profiles as well as the conducting side-walls of the recessed antenna housing. Absolute agreement between the theoretical and the experimental results is obtained, including the correct dependence on the density, antenna position, RF frequency and antenna geometry. The theoretical interpretation of the results is discussed, together with the technological implications for future high power experiments.

On a new torque sensor for tendon drive fingers

Abstract: A new type of torque sensor is proposed for finger actuation with N actuators and tendons per N external degrees of freedom. The finger joint around a drive pulley is proportional to the tension difference on both ends of the pulley. Using a coupling mechanism between tendons, this tension difference can be measured directly without sensing individual tendon tensions. On the basis of this idea, a tension differential-type torque (TDT) sensor is proposed. With a single body of small size and fewer signal lines, the TDT sensor has several advantages over the conventional approach, which obtains the torque by attaching two tension sensors at both ends of the drive pulley and feeding sensor signals to a differential circuit. The basic principle of the TDT sensor is described, together with the design orientation. The dynamic and static characteristics are examined with the introduction of equivalent rotational stiffness, which is useful for examining system stability. The specially designed TDT sensors were implemented in a two-fingered robot hand, and the effectiveness of the sensor was confirmed. >

Band‐edge photorefractive effect in semiconductors

Abstract: We report here for the first time, two‐beam coupling energy transfer using the Franz–Keldysh electrorefractive effect in photorefractive semiconductors. A large beam coupling gain coefficient (Γ=2.8 cm−1) exceeding the absorption coefficient (α=2.0 cm−1) is obtained in undoped semi‐insulating GaAs using the new photorefractive process. The new photorefractive process differs from conventional photorefractivity in that the direction of energy transfer is dictated by the direction of an externally applied electric field. Using a moving grating technique and combining the electrorefractive grating with the conventional electro‐optic grating, a very large gain Γ=16.3 cm−1 (α=3 cm−1, crystal length l=4mm) resulting in net amplification by more than a factor of 200 has been demonstrated.

Distributed feedback lasers

Abstract: Improved single-modedness is achieved in distributed feedback (DFB) lasers by minimizing the feedback provided at or near the ends of the DFB grating. The feedback may be minimized at one or both ends of the grating. Feedback is controlled by reducing the coupling to the grating. Coupling is reduced by reducing the depth of the grating's teeth and/or by increasing the spacing of adjacent teeth.

Internal expansion coupling device

Abstract: An internal expansion coupling (12) for fitting within and joining together two tubular members or pipes (T) in end-to-end relationship. The coupling (12) includes a sheet-like member (12) with overlapping ends (14, 14'). The sheet-like member (12) is covered with a continuous sleeve of elastomeric material (24) having at least one outstanding rib (30) which is adapted to be compressed against the inside wall of the tubular member (T). The coupling is expended by coacting threaded elements (42, 43, 50).

Loss analysis of laser diode to single-mode fiber couplers with glass spheres or silicon plano-convex lenses

Abstract: The single-mode laser diode to single-mode fiber coupling efficiency is analyzed for couplers with glass ball lenses and silicon plano-convex lenses, respectively. The contributions of the different origins of loss are given. It is found that in nearly all cases, most of the total loss is determined by the spherical aberration of the lends that collects the divergent laser diode (lens 1). This loss is calculated for a variety of glass ball lenses and silicon plano-convex lenses are shown to be dependent on the laser diode spot size (or divergence angle). The minimum loss of a coupling configuration is determined with good accuracy by the parameters of lens 1; a single additional parameter, the effective laser diode spot size (or effective divergence angle) for the laser diode; and the coupling arrangement. The calculated losses are compared with experimental values. In most cases, theory and measurement agree very well; differences are discussed. >

Coupling apparatus with double clutches

Abstract: To stably control clutch engagement torque of a multidisk friction plate clutch provided between two rotary members, without being directly subjected to the influence of friction plate wear or of fluctuations in friction coefficient between two clutch plates, the coupling apparatus comprises a pilot clutch, a main clutch and dual cam ring members disposed between the two clutches. When the pilot clutch is engaged by an actuator in a first direction, since a first slidable cam ring rotation is limited by the pilot clutch relative to a second fixed cam ring, the first slidable cam ring is shifted in a second opposite direction by a cam thrust force to engage the main clutch. The coupling apparatus is suitably incorporated in a differential gear assembly mounted on automotive vehicles in order to controllably and stably limit the differential motion between two shafts.

Theory of spinconversion in XH3-systems

Abstract: In a simple model of (mechanically and magnetically) isolated methyl groups with mutualintramolecular dipolar coupling between the nuclear magnetic moments of the three protons the conversion rate (i.e. for the symmetry changing transitionsE a,b ↔A) is investigated. It turns out, that within the model of a fixed rotational axis only half of theE-symmetric rotor states can convert intoA-symmetric ground states. The usual coupling to the phonon bath of thermal lattice excitations is considered in lowest order perturbation theory, and used to describe the temperature dependence of shift and broadening of tunnelling-and librational lines by inelastic neutron scattering (INS). For the two possible types of this phonon coupling,breathing andshaking, a different temperature dependence of the conversion rate is obtained. The temperature dependence of the INS-spectra and of the conversion rate are predicted to be mutually interdependent. Only in case of a non zero phonon coupling of breathing type a non vanishing conversion rate at zero temperature is found; this rate is estimated to be proportional toω 3 .

Mode coupling in circular-cylindrical system and its application to fingerprint resonators

Abstract: Coupled-mode equations are given in the circular-cylindrical coordinate system for the evaluation of two-dimensional fingerprint resonators. The general form of coupled-mode equations is outlined. The coupling coefficients are found for transverse electric and transverse magnetic modes. The quality value Q is defined, and a numerical evaluation is given. A detailed derivation of the coupled-mode equations is given. >

Torque limiter arrangement for rotating device

Abstract: A torque limiter arrangement is used for a rotating device like a door mirror The arrangement controls relative rotation between a fixed element and a rotational element which are drivingly connected by a drive unit That is, a first clutch is released when a relative torque not less than a fixed first torque is effected between the fixed element and the rotational element A second clutch is released when a relative torque not less than a fixed second torque is applied between the fixed element and the rotational element A first spring is operatively connected with the first clutch to determine the first torque A second spring is operatively connected with the second clutch to determine the second torque

A more accurate analysis and design of coaxial-to-rectangular waveguide end launcher

Abstract: An electromagnetic model is developed for the analysis of the coaxial-to-rectangular waveguide transition of the end-launcher type. The model describes the coupling mechanism in terms of an excitation probe which is fed by a transmission line intermediate section. The model is compared with a coupling loop model. The two models have a few analytical steps in common, but expressions for the probe coupling model are easier to derive and compute. The two models are presented together with numerical examples and experimental verification. The superiority of the probe model is illustrated, and a design method yielding a maximum voltage standing wave ratio of 1.035 over 13% bandwidth is outlined. >