Showing papers on "Offset (computer science) published in 1984"

Synchronization preamble correlation detector and frequency estimator

Abstract: A device is disclosed which simultaneously performs sync preamble correlation detection and frequency offset estimation functions for a spread spectrum receiver. The device performs a parallel frequency search, executed by a plurality of frequency sensitive circuit channels connected in parallel. These parallel circuit channels first apply phase corrections to the subcorrelator outputs and then linearly reintegrate the corrected outputs. In each channel the phase corrections applied to each successive subcorrelator output vary with the frequency offset subregions to which the channel is designed to match. By applying approximated phase corrections of 0°, 90°, 180° or 270° in lieu of the exact phase corrections required to remove the phase shift, the need for multiplication operations in the reintegration process is eliminated, as well as the need for storing large numbers of weighting coefficients. As a result, the reintegration process involves only addition and subtraction operations and the non-linear integration process is eliminated. The detector also establishes an estimate of the input signal frequency offset at the time of detection of the preamble correlation.

Improved offset-compensation schemes for switched-capacitor circuits

Abstract: Novel switched-capacitor stages which are free from the effects of op-amp DC offset voltage are described. The op-amps used in the stage need not slew between the desired output voltage and the offset voltage as in previously described offset-free circuits. The use of the new scheme in general applications is also discussed.

A comparison between GO/aperture-field and physical-optics methods of offset reflectors

Abstract: Both geometrical optics (GO)/aperture-field and physical-optics (PO) methods are used extensively in the diffraction analysis of offset parabolic and dual reflectors. An analytical/numerical comparative study is performed to demonstrate the limitations of the GO/aperture-field method for accurately predicting the sidelobe and null positions and levels. In particular, it is shown that for offset parabolic reflectors and for feeds located at the focal point, the predicted far-field patterns (amplitude) by the GO/aperture-field method will always be symmetric even in the offset plane. This, of course, is inaccurate fur the general case and it is shown that the physical-optics method can result in asymmetric patterns for cases in which the feed is located at the focal point. Representative numerical data are presented and a comparison is made with available measured data.

Automatic machining using constructive solid geometry with Boolean combinations of primitives including tool offsets to form a machining pattern

Abstract: Constructive solid geometry is a technique of representing parts by adding and subtracting a set of primitive shapes. Automatic tool paths to machine a part with a rotating cutter are generated by taking the constructive solid geometric description of the part and replacing every primitive shape by an offset primitive, larger or smaller than the part by the cutter radius. A planar section slice of the offset part has the property that the center of the milling cutter will traverse this section curve and form the original part without gouging. To machine efficiently, a series of parallel slicing planes are taken from top to bottom through the offset part. For each section curve, numerical control machine code is generated to direct the cutter to follow that path, and the part is automatically machined. The method applies to both rough and finish cutting.

Equivalence of surface current and aperture field integrations for reflector antennas

Abstract: The "extinction theorem" is used to prove that the fields of reflector antennas determined by integration of the current on the illuminated surface of the reflector are identical to the fields determined by aperture field integration with the Kottler-Franz formulas over any surface S_{a} that caps the reflector As a corollary to this equivalence theorem, the fields predicted by integration of the physical optics (PO) surface currents and the Kottler-Franz integration of the geometrical optics (GO) aperture fields on S_{a} agree to within the locally plane-wave approximation inherent in PO and GO Moreover, within the region of accuracy of the fields predicted by PO current or GO aperture field integration, the far fields predicted by the Kottler-Franz aperture integration are closely approximated by the far fields obtained from aperture integration of the tangential electric or magnetic field alone In particular, discrepancies in symmetry between the far fields of offset reflector antennas obtained from PO current and GO aperture field integrations disappear when the aperture of integration is chosen to cap (or nearly cap) the reflector

An offset bifocal reflector antenna design for wide-angle beam scanning

Abstract: A synthesis procedure and performance results for an offset dual reflector with perfect focusing at \pm 8\deg of beam scan are presented. This bifocal antenna extends the theory of the previously reported symmetric system to an offset design. Approximations, such as the smearing of focal points into a "focal ring," are eliminated, as is blockage. The offset design affords greater design flexibility, although the synthesis is more complex. Computed and experimental results demonstrate the improved beam-scanning performance of this antenna.

Image sensor correction system

Abstract: Sensor correction circuit for maintaining offset voltages in the shift registers of a multiple channel image sensor substantially equal having a pair of control gates to permit sampling the current offset voltages in the shift registers of each channel, a pair of capacitors for storing the offset voltage samples in each channel; a clock for actuating the control gates in preset timed relation between scan lines to sample and store the current shift register offset voltages on the capacitors; and an amplifier for amplifying any difference between the offset voltage samples held by the capacitors to provide an adjusted potential for balancing any differences between the shift registers.

Method for a compatible increase in resolution in color television systems

Abstract: Band limited standard video signals are sampled with line coupled sampling clock pulses. The sampling clock pulses are shifted from field to field by one-half a sampling interval. The sampling clock pulse rate is twice the frequency at the center of the Nyquist edge of the transmission channel. The received signal is sampled in synchronism, line coupled and offset from field to field. A video memory records the sampled values and furnishes them to the monitor at twice the sampling frequency and without flicker as a full frame. The video playback takes place at twice the line frequency or alternatively with the same line frequency and synchronous spot wobbling.

Consistency of measurement methods for the mode field results in a single-mode fiber

Abstract: The fields in the core, the far-field radiation pattern, and the transmission through an offset splice for single-mode fibers all are well approximated by Gaussian functions. However, the method used to fit the Gaussian function to measured data influences the resulting width of the Gaussian, which is called the mode field radius. Of the fitting methods studied, only maximization of the launch efficiency integral gives values of mode field radii which are consistent between near-field and far-field measurement methods. The transverse offset measurement method is consistent with these two if an unweighted truncated fit is used. Also. two published analytical formulas for the mode field radius are studied, and only one of the two gives accurate values. A third analytical formula, which is simpler and more accurate over a smaller range of wavelengths, is presented.

Alternately centered disk pack assembly and method

Abstract: A disk pack assembly for use in a disk drive has disks which are alternately diametrically offset about a spindle axis of rotation The disks are positioned as a function of their outer edges such that alternate opposite outer edges line up as though they were the outer edges of centered nominal diameter disks This results in an increase in the number of axial nodal points for potential imbalance moments and reduces the amplitude of associated vibrations Disk spacers are also alternately diametrically offset about the spindle axis so tht pairs of like components tend to balance each other to minimize potential vibrations

Microstrip antenna system with fixed beam steering for rotating projectile radar system

Abstract: A microstrip antenna system has a central two-dimensional array (preferably square having at least 16×16 elements) of integrally formed conductive dual slot microstrip radiator patches. A corporate-structured array of interconnected microstrip feedlines connects a common input/output r.f. signal feedpoint to each of the central array patches and also incorporates a fixed-angle phasing offset so as to steer the main lobe or beam of the overall radiation pattern off-center. The common r.f. signal input/output connection point is itself physically offset to one side of the overall composite of array elements. Auxiliary tapered amplitude linear arrays of dual slot patches also preferably extend on all sides outwardly from the periphery of the central array so as to reduce the side lobe amplitude and main lobe beamwidth of the overall radiation pattern. Both series-fed and series-tapped tapered amplitude feedlines are used depending upon whether the auxiliary linear array extends in the E-plane direction or the H-plane direction. The fixed phasing offset is preferably in the H-plane direction of the overall central array. Pairs of broad-banding microstrip stubs may be disposed along the corporate structure feedline in association with predetermined subsets of dual slot patches within the central array so as to increase the frequency bandwidth over which impedance matched signal feeding is achieved.

Physical address developing unit

Abstract: An expanded memory field is obtained by forming a physical address for accessing a main memory unit according to the present invention The physical address is developed following an address-mode provided in an instruction including an address field When the address-mode is a "1", physical address is provided by (i) obtaining a base offset address from a base register which is given by a base register bank as determined by a first field of the address field, and (ii) adding the base address to a displacement number determined by a second field of the address to obtain an offset address, (iii) obtaining a segment base address from a segment base address register corresponding to a segment number register determined by the first field of the address, and (iv) adding together the segment base address and the offset address A 24 bit physical address is obtained When the address-mode is a "0", the address field constitutes the offset address and the above additions are carried out

A new approach to offset reduction in sensors: the sensitivity-variation method

Abstract: A new approach to offset reduction in solid-state sensors is presented. The method is based on the application of a signal to a third port of a sensor. When the sensor has the property that the sensitivity and the offset have different responses to the third-port signal, a large reduction in the effective offset can be obtained. The method is employed on a magnetic-field-sensitive dual-collector magnetotransistor and a Hall element. It appears that the method is very successful in reducing the offset of the magnetotransistor, whereas that of the Hall element is not affected at all. This is in agreement with the analysis of the method presented.

Automatic focus offset correction system

Abstract: A small amplitude, low frequency, signal is added to the focus servo signal controlling the position of the objective lens of an optical disc storage system after focus acquisition has been achieved, so as to produce a slight defocusing effect of the light spot on the disc. The resulting variations in the read back signal is utilized by a synchronous detection circuit scheme to extract magnitude and polarity information of the focus offset present. That information is fed back to the focus servo signal to null out the focus offset, thereby assuring continual accurate focusing of the laser beam even under conditions of changes in the mechanical alignment of the optics of the storage system and/or the d.c. stability of the electronics of the storage system.

Offset gradient fields in nuclear magnetic resonance imaging systems

Abstract: The null point in the gradient field of an NMR imaging system is offset from its nominal position in the static magnetic field by application of a bias field to the gradient field The bias field produces a substantially uniform offset in the field intensity at every point in the gradient field Alternatively, null point offset may be achieved by controll- ably superimposing two gradient fields of separately located null points

Signal processor for matrix arrays

Abstract: Matrix arrays, in particular infra-red arrays, suffer from non-uniformity in output from the individual elements in the array. This is due to each element in the array having for example, its own characteristic responsivity and leakage current, and is seen in the array output as a pattern of offset values. These offset values must be removed from the output of the array if useful digital information is to be obtained. One known method of doing this is to show the array a black body at a known uniform temperature and use the output from the array to cancel the offset values. However, the dynamic range of the system is directly related to the range of offset values obtained and also to the size of the digitizer. Large-size digitizers have relatively slow sampling rates and in order to have a higher sampling rate, a small-size digitizer must be used. The signal processing system described herein corrects for offset values and is able to provide a high sampling rate by using a small-size digitizer.

Correction of offset and gain errors in RF receivers

Abstract: Sampled and digitized in-phase and quadrature phase signals are algebraically accumulated in offset accumulators, the contents of which are periodically employed to adjust the value of offset correction factors added to each signal path. Additionally, the absolute values of the in-phase and quadrature phase signals are accumulated in gain accumulators, the contents of which are periodically employed to adjust the gain factor multiplier in one of the signal paths.

Offset DPSK and a Comparison of Conventional and Symmetric DPSK with Noise Correlation and Power Imbalance

Abstract: The bit error rate performance of binary DPSK with an arbitrary offset of the phase change vector is derived in the presence of noise correlation and power imbalance, and the special cases of conventional DPSK (0 phase change offset) and symmetric DPSK ( \pi/2 phase change offset) are compared. Precise conditions are given for optimum offsets, and it is shown that, from a practical standpoint, conventional DPSK gives the optimum performance of any offset scheme, and outperforms symmetric DPSK by an order of magnitude and more in error rate when the noise correlation becomes significant. It is also found that performance improvement over conventional DPSK can be realized, provided the noise correlation is known, by making the bit decision regions in phase space unequal, thereby demonstrating that the MAP estimator for DPSK without correlation is no longer optimum when the noise is correlated.

Offset continuation in theory and practice

Abstract: Offset continuation is a technique that was recently proposed for the dip moveout correction. This correction can be carried out in the time-wavenumber domain using a proper partial differential equation that links sections with different offset. It has been shown that a single spike in a common-offset section—corresponds to a semi-elliptically shaped reflector with foci located at the source and receiver in the section migrated after dip moveout correction. The sections that result after offset continuation, stack, and migration are thus a superposition not only of semicircles, but also of semi-ellipses with different lengths of axes. This effect smears the migration alias-noise which, without offset continuation, would appear as migration circles not close enough together to interfere destructively. Offset continuation can improve the quality of seismic sections in several ways: —the velocity analyses are more readable, less dispersed and dip independent; diffraction tails arrive with the same normal moveout velocity as the apex and thus diffraction-noise can be “stacked out”; —noise produced by aliasing in the migrated section is reduced. In this paper we give a practical and conceptual interpretation of the offset continuation method, with a generalization to three-dimensional volumes of data. A critical examination of several synthetic and field data examples shows the actual possibilities and advantages of offset continuation.

Nc data making device for die machining

Abstract: PURPOSE:To select most suitable machining method and to process most properly and rapidly, by tracing the model of die by a probe of touching sensor and measuring its shape at sequential interval and processing the data by CPU. CONSTITUTION:Trace the model of a die by a probe 103 of touching sensor 102, and its curved-face shape is measured at sequential interval, and the data is inputted to a CPU1. The CPU1 stores the measured point group input data to a curved-face point group data area 8. Next the data at the curved-face point group data area are subdivided into micro unit and stored at an interpolation process data memory device 10. And then, offset processing is done for the probe 103 of touch sensor 102 with respect to all the interpolation data at the device 10 to obtain the actual data of curved-face, and the data are once stored at a curved-face shape memory device 11. After the processing point calculation process is done according to the curved-face data, curve data and input data for processing method, the value which is obtained by a tool radius offset processing at a tool offset processing device 16 are stored at a tool route data memory device 17.

Method and system for improved reconstruction of video images in line sequential chroma format

Abstract: A method and system for reconstruction of chroma component segments in a line sequential chroma format television system. Filtering of a received line sequential chroma signal is employed to reconstruct missing chroma components and to attenuate phantom frequency components greater than one half the spatial sampling rate. Digital and analog filters are disclosed for implementation of such post filtering. The luminance component of the line sequential signal is delayed at the transmitter to synchronize the reconstructed chroma segment with its corresponding luminance segment with the use of minimal hardware at the receiver. Horizontal offset chroma sampling is used along with such post filtering to decrease transmission bandwidth requirements without sacrificing horizontal resolution at the receiver.

Apparatus for controlling the air-fuel ratio of an internal combustion engine

Abstract: The invention is directed to an apparatus for controlling the air-fuel ratio, in particular of an internal combustion engine. The apparatus includes a sensor responsive to this ratio such as an oxygen sensor or the like and a circuit arrangement for evaluating the sensor output signal. The circuit arrangement includes means to compensate for the offset voltage influence thereby permitting a precise control of the air-fuel ratio in a Lambda range in which the dependent relationship between the sensor output and the sensor input signals is barely distinctive. For this purpose, the influence of the offset voltage of the control amplifiers used is measured at regular or irregular intervals and stored in analog or digital format. On the one hand, this stored quantity may be used to apply to the inputs of the control amplifiers a compensating voltage acting in opposition to the input offset voltage or, on the other hand, to subtract from the operational amplifier output the voltage portion resulting from offset voltages. The apparatus of the invention is also suitable for controlling the air-fuel ratio of heating equipment.

A predicted signed switching time high precision satellite attitude control law

Abstract: A bang-bang control law is presented for use in three axis gas jet attitude control systems where precise pointing is required within stringent mass and power limitations. A switching boundary similar to the time optimal one for a double integrator adapts to a disturbance acceleration estimate, a fixed magnitude offset from the phase plane origin being changed in sign whenever the boundary is crossed. The latter feature facilitates optimal acquisition of the ideal limit cycle of preset amplitude, the number of thruster operations being automatically minimized to prolong valve life. In order to render performance largely independent of the iteration period of the microprocessor or digital computer assumed for implementation, at least two successive switching times of the desired control function are predicted, being signed to include the sense of control to be applied. The control law is able to function in the presence of disturbance torques ranging in magnitude from a small fraction of the avail...

Differential amplifier circuit

Abstract: PURPOSE:To attain low offset by applying offset cancellation while a negative feedback loop for setting the gain of a differential amplifier circuit is opened. CONSTITUTION:A switch SW1 gives an input IN and a reference voltage Vref slectively to a non-inverting input IN(+) of a differential amplifier Amp. A switch SW2 switches an inverting input IN(-) to an output OUT or the non-inverting input (+). When the switch SW2 is thrown to the position of a contact (a), the offset voltage of the differential amplifier Amp. is amplified largely by the open loop gain and then outputted. The offset voltage output and the reference voltage are compared by a voltage comparator circuit VC to apply offset concellation. Since the offset voltage is amplified very largely, the offset voltage of the circuit VC itself is neglected.

Offset compensating circuit

Abstract: PURPOSE:To suppress a noise of an output signal in case of a non-signal input, and also to compensate exactly an offset voltage by executing an integration of a code bit of an output signal of an A/D converter except a case when a prescribed code is outputted as the output signal concerned. CONSTITUTION:A code bit of a digital output signal OUT of an A/D converter 4 is integrated by an integrator 5, an offset correcting voltage VCMP is generated, and it is applied to a circuit system by a filter 6. A code detecting circuit 7 generates an integration inhibiting signal SINH in case when the output signal OUT is, for instance, +''0'', and inhibits an integral operation in an integration circuit 5. Accordingly, in case when an input signal IN is a non-signal, it is fed back so that the output signal OUT becomes +''0'', and an offset compensation of the output voltage OUT is executed. In this case, since the output signal OUT is not varied from +''0'', generation of an unnecessary noise component is prevented.

Preliminary study on offset scan-corrected reflector antenna system

Abstract: Preliminary study on offset shaped dual reflector antenna systems has been carried out to assess the feasibility for multibeam satellite applications. The two-dimensional offset shaped reflector antenna geometry is generated by first creating the nodal points according to a bifocal condition and then connecting the nodal points by smooth curves to form the profiles of the main and subreflectors. The three-dimensional geometry is created by body revolution. The offset geometry is obtained by properly tailoring the three-dimensional geometry. This offset shaped reflector antenna system has an inherent astigmatism which can be either fully or partially compensated. For applications requiring a scan range in azimuth more than \pm 5 beamwidths, the offset shaped dual reflector antenna systems offer better scan performance (in terms of peak gains) than offset Cassegrain geometries at the expense of the performance of the on-axis beams. In elevation with a 16 beamwidth scan range, the shaped design provides 0.3 dB less scan loss than the Cassegrain design.