Abstract: A combination FIFO buffer and programmable shift register having asynchronous input and output capabilities comprises a three stage system which synchronizes the incoming data stream with the memory input clock, buffers the incoming data stream and provides a variable delay for the data. The digital data stream from an input device is received by an input synchronizer having its input clocked at the clock rate of the input device clock and its output clocked at a higher internal clock rate. The data is written into two FIFO buffers, a master and a slave. The master buffer controls the read and write addresses of both buffers, so that the write address of the buffers advances only when valid data is written into the buffers, and the read address advances only when data is read out of the buffers. The slave buffer can be programmed with an offset in its read address, so it operates as a delay buffer.

Abstract: A remote receiver for laser interferometer systems is split into two parts connected by a fiber optic link. The front-end of the receiver, located near the remote interferometer optics, houses only the optical components for focusing and mixing the laser beam, and transmits the beam through an optical fiber cable. The back-end of the receiver, located remotely, houses the electronic components for detecting and measuring the frequency difference to produce the signal for the measurement electronics.

Abstract: An optical system for an interferometer compensates for changes in temperature by incorporating optics in which the reference and measurement beams follow different but optically equivalent paths through optical elements that are in thermal equilibrium. The optical elements of the interferometer are so arranged that the reference beam and the measurement beam follow equivalent optical path lengths through the interferometer, whose elements are in thermal equilibrium. That is, the path lengths through the high refractive index media of the optics are the same length and refractive index, but do not follow the same path. Because the beams are not constrained to follow the same path, fewer optical elements are needed and shorter OPLs can be used resulting in less complexity, better optical efficiency, easier alignment and lower cost.

Abstract: A feeder assembly comprising a feeder tube having metal rails mounted therein along which IC's can slide on the parts of their leads next to their body and at one end an adapter for guiding the IC's from a transport tube onto the rails. An opening in the feeder tube is provided for permitting pulses of gas to flow through the tube toward the end of the tube remote from the adapter so as to move the IC's to a pick-up pad at said remote end one at a time.

Abstract: A wavelength tracking compensator for a laser interferometer measurement system comprises a stable physical standard optical cavity and a double path, differential interferometer mounted on a baseplate. The interferometer monitors the apparent changes in the cavity's length caused by actual changes in the index of refraction of the surrounding air. The cavity is supported with a temperature compensated mount that utilizes the principle of differential thermal expansion of two different metals to create a mount which exactly matches the coefficient of expansion of the cavity material. A semi-kinematic mount supports the double path, differential interferometer and allows the interferometer to be accurately aligned to the cavity with three rotational degrees of freedom to prevent any cosine error in the cavity's optical path length measurement, to prevent polarization leakage, and to maximize optical power at the receiver.

Abstract: A low phase noise RF synthesizer comprises three phase-locked loops. In the preferred embodiment, the base RF signal, 980 to 1520 MHz in 20 MHz steps is generated by one loop, while the high resolution IF signal is generated by a fractional-N loop. The RF and IF signals are combined in a third phase-locked loop, the output sum loop, to produce the output signal. A programmable variable divider divides the IF output frequency, achieving coverage over the necessary frequency range by changing the divide number, so the fractional-N circuit only has to fill in the fine steps between the divide numbers. A reference input frequency in the fractional-N loop has each of the factors 2, 3, and 5 in its divisor, so that the output signal of the synthesizer can be multiplied by any of these factors without producing a fractional frequency.

Abstract: A bar code decoder transforms the output from a wand scanner so that it has the same characteristics as the output from a laser scanner. Once this transformation is accomplished, decoding is done using the same process and hardware to decode wand or laser scanner data. The transformation includes scaling and compensation of the wand data by a digital filter in which the input values are divided by a dynamic scaling factor to produce the output values.

Abstract: A method and apparatus is provided for measuring the timing jitter of a tributary data stream that has been multiplexed into a higher-rate multiplex stream using pulse stuffing techniques. The required jitter measurement is carried out by monitoring the relevant stuffing control bits of the multiplex stream. In one embodiment, the apparatus comprises a first microprocessor for determining the tributary stuffing ratio from the stuffing control bits, and a second microprocessor operative to determine a current jitter signal value by using both the stuff information contained in the stuffing control bits, and the stuffing ratio determined by the first microprocessor. The second microprocessor carried out its task by updating a preceding jitter signal value by incrementing this value each time a stuff occurs while decreasing the jitter signal value at a rate dependent on the stuffing ratio. Preferred algorithms are disclosed for determining both the stuffing ratio and current jitter signal value.

Abstract: A drop out trigger captures waveform data when a normally continuous input signal is disrupted or interrupted. In the preferred embodiment, a conventional trigger detects a parameter periodically satisfied by the continuous signal and resets a timer whenever a trigger event occurs. The alarm count of the timer is set for an interval slightly larger than the periodic interval. If the timer reaches the alarm count, a measurement signal is generated.

Abstract: A method and apparatus selects an appropriate sampling rate for an input signal based on a dynamic measurement of the bandwidth of the signal. In the preferred embodiment, the bandwidth of the input signal is determined by comparing the power of the entire input signal with the power of the input signal within a selected bandwidth. A discrete Fourier transform is used to perform the bandwidth analysis.

Abstract: A pre-metal deposition cleaning process for bipolar semiconductors includes a two step boron glass etching procedure: a chemical etchant consisting of DI, H.sub.2 SO.sub.4, HNO.sub.3 and HCl (500:65:325:163) heated to 80 deg. C. followed by a 10:1 (DI:HF) dip. The semiconductor wafer is then annealed in forming gas. Then the boron glass etching procedure is repeated. The initial etch removes any B-Si-O glass present at base contacts. The anneal removes any fluorine clustered under the boron skin, and the final etch removes any retained B-Si-O-F phase from the anneal step. The cleaning procedure produces bipolar semiconductors with low V.sub.be. The procedure can also be used for rework of high V.sub.be wafers without the anneal and the second boron glass etch steps.

Abstract: Apparatus for measuring the A.C. characteristics of an electronic circuit under test having signal generators and a signal measuring device synchronized by a clock signal from a control device. The signal generators and the control device are electrically isolated from the measurement device so that reference potential fluctuations in the signal generators or in the control device do not affect the measurement. The synchronizing clock signal is transmitted from the signal generators to the measurement device through a shielded twisted pair cable terminated at each end by a high impedence connection.

Abstract: A digital bar code slot reader provides low first bar error rates and a wide scan speed range for bar codes on laminated badges and tags, and is also capable of reading bar codes on paper. The reflectance waveform from the bar code is differentiated in order to find the regions of high slope. The differentiated signal is peak detected to find the amplitude of the slope occurring at the initial card edge. This peak detected value is used to generate thresholds to be compared to the differentiated reflectance signal during the rest of the scan. When the slope of the reflectance signal is above the positive threshold or below the negative threshold, a switching signal is produced. To compensate for the lower amplitude output of the differentiator at low scan speeds, one of the amplifiers in the circuit produces a higher gain at low frequencies than at high frequencies.

Abstract: A device for evaluating the accuracy and dynamic response of a digital to analog converter (DAC). A digital word generator which provides inputs to the DAC and a sampler which samples the analog output signal from the DAC are triggered by a stream of clock pulses. Clock pulses for the sampler pass through a fixed delay line, to provide time for the DAC to stabilize. Clock pulese for the digital word generator pass through a pulse swallower capable of eliminating clock pulses to phase shift the digital word input to the DAC one step with respect to the sampler trigger signal, to move the sampling point to the next step in the cycle of the digital input waveform.

Abstract: Apparatus for measuring the A.C. characteristics of a circuit element under test maintains a stable D.C. bias voltage across the component under test by sensing the difference between the output voltage of the D.C. bias voltage source and the voltage drop across the circuit element under test, to control the D.C. bias voltage applied and to compensate for variable voltage drops in the measurement circuit. The apparatus compensates both for the fixed resistance in the circuit and for the variable resistance due to changing the range resistor.

Abstract: A package for discrete components is hermetically sealed, has very low parasitic inductance and capacitance, small size, 50 ohm input and output leads and is suitable for surface mount applications. The package comprises a ceramic base and a ceramic lid, hermetically sealed together with a solder glass seal. The ceramic base has metallized areas deposited on only the top side, to which the leads are brazed. The contacts of the component are mounted directly to the leads. After brazing, the braze and leads are nickel plated. Then a photoresist mask layer is applied to the area where the solder glass seal will be made and the photoresist is cured. The nickel plating is deoxidized and the gold plating is applied. Next, the photoresist layer is removed, exposing the nickel plating and alumina in the seal area so that the lid can be attached with the solder glass to form an effective hermetic seal.

Abstract: Calibration of a vector modulator is done using a scalar detector to measure the amplitude of the RF output signal, phase shifters to adjust the relative phases of the I and Q components of the RF carrier, and variable attenuators in the I and Q modulation signal input lines to adjust the relative amplitude of the modulation signals. DC signal sources provide reference signals for the I and Q modulation inputs, carrier leak compensation signals, and calibration signals for balancing the amplitude of the I and Q modulation signals. An iterative four step calibration process is followed until no change in the results is observed. The quadrature phase error is minimized by adjusting the phase shifters. The carrier leakage is minimized by adjusting the carrier leak compensation sources to minimize RF output with the modulation inputs grounded. The amplitudes of the I and Q modulation signals are balanced by adjusting the attenuators until the output amplitudes are equal.

Abstract: Memory integrity is maintained in a system with a hierarchical memory using a set of explicit cache control instructions. The caches in the system have two status flags, a valid bit and a dirty bit, with each block of information stored. The operating system executes selected cache control instructions to ensure memory integrity whenever there is a possibility that integrity could be compromised.

Abstract: An instrument for measuring the characteristics of a circuit element has a plurality of SMUs for applying test signals to the terminals of the circuit element and measuring the resulting output signals. A control circuit compares the output signal value to a reference value while varying the test signals. The test signal is varied by an integrator which operates in two modes, a search mode with no feedback to quickly bring the output signal to the approximate value of the reference, and a feedback mode to hold the output signal at the reference value while a measurement is made. The parameters for setting stable operating conditions for the feedback loop with the circuit element being tested are stored in a memory of the control circuit.

Abstract: A low power bar code detection circuit is provided. The detection circuit, because of the sensitivity of its internal amplifiers, is capable of reading reflected bar code images even in high ambient light, for example, in sunlight. This sensitivity is accomplished by having a high gain of the photodetected bar code signal by amplifying it with a transresistance preamplifier. The low power is accomplished by using a pulse-modulated light source for producing reflected images and having intermediate amplifier stages of the detection circuit conduct only at the peak amplitudes of the detected image signal.