Abstract: A pole and zero analyzer determines the poles and zeroes of a device by applying a stimulus signal to the device, detecting the stimulus and response signals and computing the auto- and cross-spectra. An estimated transfer function is least squares fit to a measured transfer function obtained from the auto- and cross-spectra and the poles and zeroes are obtained as the roots of the estimated transfer function. A weighting function may be used to emphasize certain desired regions of the frequencies of interest in the determination of the least squares fit. The orders of the poles and zeroes are modified until an optimum fit is reached.

Abstract: A pole and zero analyzer determines the poles and zeroes of a device by applying a stimulus signal to the device, detecting the stimulus and response signals and computing the auto- and cross spectra. An estimated transfer function comprising a rational fraction of two Chebyshev polynomials is least squares fit to a measured transfer function obtained from the auto- and cross-spectra and the poles and zeroes are obtained as the roots of the estimated transfer function. Inaccuracies due to noise and computational error are minimized by the use of the Chebyshev polynomials.

Abstract: A phase detection method for use, e.g., in impedance measurements, permits accurate phase detections to be performed at a high measurement speed. Two reference signals, phase shifted by 90.degree. from each other, and an input signal are applied to two phase detectors and phase detection is performed. The two reference signals are then both incrementally phase shifted by a predetermined amount and the measurements are again made. Phase incrementation and measurements are repeated until the original phase is reattained and the measurements are then averaged.

Abstract: The individual RAMs comprising the memory space of a computer may be of various sizes and are automatically located within a memory space during initialization and address enable information is stored in ID-RAMs on each RAM card. Shift registers on the RAM cards are connected in series and an ID bit is serially clocked through the shift registers during initialization. At each clock pulse the contents of the shift registers are written to the ID-RAMs of each RAM card. The presence of an ID bit at a specific memory location in an ID-RAM on a RAM card indicates that card is to be enabled when the memory location address is accessed; the location of the ID bit within the memory location indicates the particular RAM on the RAM card to be accessed. A detector monitors a transfer of the ID bit between adjacent shift registers so that card memory boundaries, and RAM size, may be known.

Abstract: An aligner for aligning a mask and a wafer during photolithography of a semiconductor chip uses detection of the differential capacitance between two sets of conductive fingers on the mask and ridges on the wafer. An A.C. signal is coupled between the ridges and the fingers and the phase or amplitude of the signals is detected. An aligner utilizing multiple groups of ridges and fingers allows rotational alignment or two axis lateral alignment. An aligner having reference ledges to which the mask and the wafer are capacitively coupled allows alignment when the distance between the mask and the wafer is too great to permit meaningful capacitive coupling between the mask and the wafer to occur.

Abstract: A high pressure metering pump has a duty cycle consisting of an aspiration portion where liquid is aspirated into a pumping chamber, a compression portion where the aspirated liquid is compressed to feed pressure, a feed portion where a part of the compressed liquid is expelled out of the pumping chamber, and a decompression portion where the liquid remaining in the pumping chamber is expanded to aspiration pressure. A measurement and control apparatus for the pump comprises a controller for adjusting and keeping constant the mean flow rate of the pumped liquid on the aspiration side or on the high pressure side of the pump. The apparatus further comprises a detector for detecting the transition point between the compression and feed portions and/or between the decompression and aspiration portions. The detector derives a control signal for the pump speed and for the optimal opening instant of an externally actuated input valve of the pump from the phase relationships of said transitions.

Abstract: A binary signal comparator for comparing the level of an unknown signal to a reference signal during a time window period has a first flip-flop for detecting a difference at the start of the period and a second flip-flop for detecting a difference at any later time during the period. The outputs of the two flip-flops are combined in an OR combination so that the final output produces a comparison of the two signals during the entire time window period.

Abstract: A high accuracy pen plotter includes an automatic sheet feeder for feeding individual sheets of paper from a paper tray to a platen for plotting. A microprocessor, various stepper motors and encoders allow for accurate and repeatable positioning and alignment of the sheet of paper to be plotted. The sheet of paper is automatically fed from the tray to the platen, is pulled entirely free from the tray, is aligned against a reference edge and may be forcefully ejected from the plotter after plotting is finished.

Abstract: A signal receiver having a frequency selective sampling detector which accepts a bandlimited analog signal and outputs uniformly spaced, digital samples of the signal's quadrature and in-phase components. The center frequency, phase reference and sample interval for the detector are derived from a single reference clock. The bandwidth of the detector is variable while maintaining the same center frequency.

Abstract: A bi-directional pen plotter includes two pen stables and a pen holder located between the two pen stables for snatching a pen from either pen stable and for inserting a pen into either pen stable. There are four distinct stops to the motion of the pen holder at each pen stable depending on the four possible combinations of pen locations. Measuring the relative distances travelled by the pen holder in an initialization procedure the positions of all of the pens in the system may be determined uniquely.

Abstract: A pen-lift system is provided which can achieve high speed plotting while maintaining line definition of drafting quality. The system includes a pen-lift mechanism for raising and lowering the pen, a pressure control system in order to provide a constant pen force for different kinds of pens, a velocity controller for varying the vertical velocity of the pen in response to changes in platen height and relative lateral pen position, and a position controller for sensing the present pen height relative to the platen and for actuating the pen-lift mechanism to achieve the desired pen-lift heights for different plotting situations.

Abstract: A digitizer circuit for converting analog waveforms displayed upon a CRT screen into digital signals suitable for storage in memory employs a microprocessor to determine, from user-specified parameters, the times at which the output of the CRT vertical amplifier is to be sampled. The user has great flexibility in defining sample resolution and the location of the sample window on the displayed waveform in which the samples are to be taken and is permitted to intensify the sample window on the CRT display before any samples are taken in order to view the sample window in relation to the remainder of a displayed waveform.

Abstract: A thermal ink jet printer utilizes a printhead resistor which has a central conductive region to excite bubble growth and to cause ejection of ink droplets. The existence of the central conductive region causes bubbles to be created which are toroidal in shape and which fragment during collapse, thereby randomly distributing the resultant acoustic shock across the surface of the printhead resistor and minimizing cavitation damage.

Abstract: An optical shaft angle encoder uses novel slit emitters having a long, narrow, configuration coupled with collimation lenses to utilize emitted light beams having an improved degree of collimation in an axis perpendicular to radial axes of a rotating code wheel and, thereby, to provide a higher quality generated electrical waveform which is used to describe shaft rotation. The slit emitters are narrowed to improve collimation uniaxially and lengthened to increase the total power of the emitted light.

Abstract: A thermal ink jet printer emits discrete drops of a variable volume in order to create a printed gray scale. A pulse train of packets of pulses is used to generate drops comprising packets of connected or merged droplets; the reciprocal of the pulse repetition rate is greater than the bubble collapse time and the pulse packet rate is less than the maximum single droplet emission rate of the print head. The individual droplets within the packet merge in flight to create a single drop whose volume depends upon the number of pulses contained within the pulse packet. The summing of impulses generated by the individual pulses is also useful so that drops of ink may be emitted by a resistor which is physically undersized for the particular ink being used.

Abstract: A thermal ink jet print head is provided having a new and improved barrier design. Two barriers are provided for each resistor, the barriers partially surrounding the resistor. The barriers are spaced apart to provide ink feed channels to the resistor and are arranged to impart angular momentum to the ink relative to the resistor during refill on bubble collapse.

Abstract: A three state driver for an inductive load, e.g., a stator winding of a variable reluctance motor, allows the use of charge, idle, and discharge states in which a positive voltage, a short, and a reverse voltage are connected across the inductive load, respectively. An H-bridge comprising two electronic switches and two diodes is used to switch the inductive load voltages as commanded by a comparator circuit which compares the load current to a desired load current.

Abstract: A thermal ink jet printer is disclosed in which ink droplets are ejected from an orifice by the explosive formation of a vapor bubble within the ink supply due to the application of a two part electrical pulse to a resistor within the ink supply. The electrical pulse comprises a precurser pulse and a nucleation pulse; the precurser pulse preheats the ink in the vicinity of the resistor to a temperature below the boiling temperature of the ink so as to preheat the ink while avoiding vapor bubble nucleation within the ink supply and the subsequently occuring nucleation pulse very quickly heats the resistor to near the superheat limit of the ink.

Abstract: An apparatus is disclosed for propelling ink droplets from an ink jet nozzle which uses an expanding bubble as a driving mechanism. Unlike other thermal ink jet devices, the ink itself is not used to provide the driving bubble. Rather a two fluid system is disclosed whereby a flexible membrane is used to maintain separation between a working fluid and the ink. A bubble is thermally created in the working fluid which distends the membrane and causes ink on the other side of the membrane to be expelled from an ink jet orifice. The membrane is in direct physical contact with the surface of the bubble-generating resistor and a quantity of the working fluid lies between the resistor and the membrane in pockets created by roughening the surface of the membrane or by roughening the surface of the resistor; alternatively, pockets between the membrane and the resistor may be provided by particulates contained within the working fluid which provide local separations of the membrane and the resistor.

Abstract: A housing for interfacing a fiber optic cable with a semiconductor device allows simple insertion and removal of the cable by application of an axial force. The housing exerts a spring-like gripping force upon the cable and axially aligns the cable to the semiconductor device in order to minimize loss of transmitted light. A portion of the gripping force is translated into an axial force by a slanted ridge within the housing which acts upon a ridge on the cable to cause the cable to be forcefully abutted to the semiconductor device.