Abstract: An electrostatic discharge (ESD) protection device for coaxial systems ensures that center conductors of coaxial cables are discharged prior to insertion of the cables into a coaxial connector of an electronic instrument. The device includes a conductive mounting post fastened to the instrument and conductive hinge, pivotally mounted to an end of the post. The conductive hinge has a raised target area for contacting the center conductor of a conductive cable. Prior to insertion of the cable into the coaxial connector, the conductive hinge rests in a neutral position, obstructing access of the cable to the coaxial connector. When the cable is advanced toward the coaxial connector of an electronic instrument, the center conductor of the cable contacts the target area, thereby grounding the center conductor to the instrument through the conductive hinge and conductive mounting post.

Abstract: A measurement scheme measures dispersive characteristics of optical components. The scheme includes modulation phase shift measurements performed on modulated optical carriers where the carrier frequency and the modulation frequency of the modulated optical carriers are adjusted to maintain a reference modulation sideband. A reference phase term is established by the reference modulation sideband in each of the modulation phase shift measurements. Phase indices of refraction at discrete optical frequencies of non-reference modulation sidebands are extracted from the modulation phase shift measurements. The extracted phase indices are used to calculate relative group delay and chromatic dispersion as measures of dispersive characteristics of the optical component.

Abstract: A phase locking method and apparatus use an applied drive signal to acquire and maintain phase lock, and to prevent false locking in the presence of spurious signals. Locking signal and spurious signal components of a feedback signal within the feedback path of a phase locked loop are filtered and summed with the drive signal having a frequency offset from the loop's reference signal and an amplitude less than that of the locking signal and greater than that of the spurious signals. The summed signals are limited so that the overall phase of the limited signal is determined by the signal of highest amplitude. When the drive signal amplitude exceeds the amplitude of the filtered locking signal, the phase of the limited signal is determined by the drive signal. When the amplitude of the filtered locking signal exceeds the drive signal amplitude, the phase of the limited signal is determined by the locking signal.

Abstract: An optical spectrum analyzer includes a polarization modifier that eliminates polarization-dependent wavelength spreading, enabling the analyzer to have high signal selectivity and high measurement sensitivity. The polarization modifier spatially separates orthogonal polarization components of the applied optical signal into separate optical beams and rotates the relative polarization components of the beams so that the beams are incident on a tunable interference filter in a multipass configuration at a single polarization state. The optical beams are directed through regions of the interference filter which lie on a contour of substantially equal center wavelength so that each of the multiple passes through the interference filter provides for corresponding narrowing of the filter bandwidth.

Abstract: An optical noise monitor measures noise power within narrow wavelength regions between channel signals of a dense wavelength division multiplexed (DWDM) signal. The noise monitor receives the DWDM signal and cascades the signal along a multipoint travel path where the signal is incident on a series of multi-pass filters. Each multi-pass filter selects a narrow, predefined wavelength region between channel signals of the DWDM signal. Noise power within the predefined wavelength region is detected and SNR is monitored by comparing the detected noise power to the power in the channel signal. According to a first preferred embodiment of the present invention, the noise monitor includes multi-pass filters that each have reflective surfaces to guide optical energy within a predefined wavelength region through multiple passes of an optical filter.

Abstract: A network analyzer measurement method adaptively adjusts measurement parameters of the network analyzer, based on a set of measurements of a device under test (DUT) and according to a user-specified limit contour, maximum permissible measurement error or other decision criteria. Measurement speed of the network analyzer is optimized by performing subsequent measurements on the DUT using the adjusted measurement parameters. Measurement bandwidth, the number of measurement sweeps or the frequency location of stimulus points of the analyzer is optimized when characterizing the DUT.

Abstract: An error correction method improves measurement accuracy of a vector network analyzer by reducing reflection measurement errors for a broad class of devices, such as filters, switches, cables, couplers, attenuators, and other passive devices tested by vector network analyzers (VNAs) that are reciprocal, having a forward transmission coefficient S.sub.21 and a reverse transmission coefficient S.sub.12 that are equal. Errors due to impedance mismatches at the load port of a transmission/reflection (T/R) test set are corrected without impacting the measurement speed of the VNA. The source port of the T/R test set is calibrated and a reflection measurement is performed while an impedance matched thruline standard of known electrical length is coupled between the source port and load port of the T/R test set. The reflection measurement is corrected for the electrical length of the thruline standard to obtain a reflection measurement of the load port of the T/R test set.

Abstract: A filter calibration system uses the reflection characteristics of a tuned filter, such as a YIG-tuned filter (YTF), to establish a correspondence between a control signal applied to the filter and the passband center frequency of the filter. This correspondence enables tuning characteristic of a YTF stored during a baseline characterization of a spectrum analyzer to be corrected to compensate for temperature changes and changes in operating parameters of the spectrum analyzer. The filter calibration system uses components within the spectrum analyzer to perform the calibration so that the manufacturing cost of the spectrum analyzer is not increased. The spectrum analyzer's local oscillator provides a stimulus signal that is applied to the YTF. A mixer within the spectrum analyzer detects reflections of the stimulus signal by the YTF while control signals applied to the YTF are varied to correspondingly adjust the passband center frequency of the YTF.

Abstract: A measurement method adjusts the IF bandwidth of a network analyzer to increase measurement speed for high dynamic range devices. According to the first preferred embodiment of the present invention, the bandwidth of the IF filter is adjusted for each corresponding measurement sweep of the network analyzer. The forward transmission and reflection characteristics of the device under test are measured using a first IF bandwidth, and the reverse transmission and reflection characteristics of the device are measured using a second IF bandwidth. When high measurement sensitivity of the forward transmission parameter of the high dynamic range device is sought, the first IF bandwidth is selected to be narrower than the second IF bandwidth. When high measurement sensitivity of the reverse transmission parameter of the high dynamic range device is sought, the first IF bandwidth is selected to be wider than the second IF bandwidth.

Abstract: A feed forward apparatus and method discipline a clock signal by a reference signal in digital telecommunication networks. A synthesizer correction term within the feed forward apparatus and method includes a frequency correction term so that when one frequency correction term is selected in place of another frequency correction term the phase of the clock signal remains free from extraneous frequency or phase variations during the transition between frequency correction terms. Alternatively, the synthesizer correction term includes a phase correction term so that phase coherence between the reference signal and the clock signal results.

Abstract: A sampling timebase system uses the frequency stable clock signal present in digital systems to accurately reconstruct waveforms that are synchronous with the clock signal. The sampling timebase system provides a strobe signal having a precisely controlled time delay relative to a trigger event. An interval counter is programmed to count a specified number of the cycles of the clock signal, providing for coarse time delay adjustment of the strobe signal in time increments determined by the period of the clock signal. A fine delay generator triggered by the terminal count of the interval counter provides for fine adjustment of the time delay of the strobe signal. The interval counter and fine delay generator are programmable to progressively vary the time delay between the strobe signal and the trigger event relative to cycles of the waveform. The strobe signals, when applied to a sampler, enable sufficient samples to be acquired to reconstruct selected segments of the waveform.

Abstract: A phase detection apparatus produces a phase difference signal in response to the phase difference between two applied input signals. The phase detector includes a lead/lag indicator receiving the input signals, and a logic block receiving the input signals. The logic block generates an output signal in response to the time delay between corresponding amplitude transitions, such as rising edges, of each of the input signals. The lead/lag indicator records which one of the two input signals leads in phase and generates an enable signal that steers the output signal from the logic block to one or the other of the phase detector's two output terminals.

Abstract: A light-emitting diode assembly incorporates a power shunting element that provides electrical over-stress protection to a light-emitting diode (LED) and prevents damage to the LED from electrostatic discharge (ESD). The power shunting element is coupled in parallel to the LED within the LED assembly and protects the LED by diverting electrical current from the LED and limiting the voltage across the LED to a clamp voltage when a threshold voltage across the LED is exceeded.

Abstract: An optical fiber coupling system has high insertion loss repeatability. A lens expands the mode size of a source fiber connected to a test instrument or other source, reducing insertion loss sensitivity to positional and angular alignment of the bare input fiber with the source fiber. Index matching fluid reduces the effect of the cleave angle of the input fiber on insertion loss. The optical fiber coupling system is calibrated by substituting a through fiber of similar type and length in place of the input fiber. According to a first preferred embodiment of the present invention, a capillary tube contains the index matching fluid. According to a second preferred embodiment of the present invention, the index matching fluid is contained in a reservoir enabling optical signals to be coupled to optical components having multiple input fibers.

Abstract: A phase detector provides a digital output having a linear relationship to the phase difference between a reference signal and an applied input signal. The phase detector counts the number of cycles of the reference signal within a time interval determined by the difference in arrival times of corresponding amplitude transitions of the reference signal and the input signal. A digital output representing the number of counted cycles is produced. A dither generator adds random time variation to the time interval over which the reference signal cycles are counted to introduce a corresponding random variation in the digital output.

Abstract: A wavelength monitor detects wavelength drifts of component channel signals within multi-wavelength light signals. Multiwavelength light incident on the wavelength monitor is cascaded along a multipoint travel path. Within the travel path, the component channel signals are incident on a series of wavelength discriminators arranged on an optically transmissive member. Each wavelength discriminator is selectively transmissive to a predetermined one of the channel signals and is reflective to the remaining component channel signals of the multi-wavelength light signal. According to a first preferred embodiment of the present invention, the optical transmission through each wavelength discriminator varies monotonically according to variations in the wavelength of the predetermined channel signal. Each selectively transmitted channel signal is intercepted by a detector which produces an output current that is mapped to corresponding signal wavelengths.

Abstract: A high-data density, high-data rate scanning memory device reads and writes data using a plurality of probes. The scanning memory device comprises a memory composed of a matrix of cell arrays each containing a submatrix of memory cells, a plurality of probes having a one-to-one correspondence to each cell array, and a positioning device that operates to simultaneously change the positions of probes relative to the cell arrays. Each of the cell arrays has a cell array status memory for storing information designating whether the cell array is functional or whether the cell array is defective. If the number of defective memory cells detected within each cell array exceeds some predetermined number, the cell array is designated as defective. Defective cell arrays are logically replaced by functional cell arrays. Error correction is applied to the data to reduce reading and writing errors by the scanning memory device and to maintain the integrity of data stored in the memory.

Abstract: An optical cross-connect switch incorporates a pin grid actuator to selectively position optical elements relative to optical beams in the switch. A high density array of aligned, optically reflective elements is attached to the ends of independently selectable and moveable pins in the pin grid actuator. The pin grid actuator is the type extensively used in dot matrix printers. Linear motion of the pins causes the reflective element attached to the pin to intercept optical beams provided by input fibers coupled to the switch. Intercepted optical beams are redirected to designated output fibers, also coupled to the switch. A staggered arrangement of the input and output fibers equalizes all of the signal pathlengths through the switch, regardless of which pin in the pin grid actuator is selected. According to an alternate preferred embodiment of the present invention, multiple optical cross-connect switches are cascaded using a staggered arrangement of interconnecting fibers.

Abstract: A noninvasive blood chemistry measurement method and system isolate measurement contributions due to a patient's blood to accurately measure blood chemistry. In accordance with a first preferred embodiment of the present invention a noninvasive blood chemistry measurement method decreases the blood volume within a patient's body part relative to the normal blood volume in the body part and performs a baseline measurement. Blood volume is then increased and a second measurement is performed. Comparison of the second measurement to the baseline measurement isolates the measurement attributes of the patient's blood. In accordance with a second preferred embodiment of the present invention a noninvasive blood chemistry measurement system decreases blood volume by applying mechanical pressure to a body part. In accordance with a third preferred embodiment of the present invention, blood volume in the body part is decreased using a pressure cuff.