Abstract: A high impedance attenuator for use in a test and measurement instrument employs compensation to adjust the low frequency attenuation to match the high frequency attenuation exhibited by the attenuator, rather than attempting to adjust the high frequency attenuation exhibited by the attenuator. In an alternate embodiment of the invention, compensation to adjust low frequency attenuation is employed in a feedback loop and an opposite compensation is applied in a parallel attenuation stage to stabilize the input resistance. In yet another embodiment of the invention, compensation to adjust low frequency attenuation is employed by means of an R-C time constant of an additional R-C circuit in a feed forward loop. This additional time constant is matched to the R-C time constant of the input R-C network. The input resistance of the attenuator is not changed.

Abstract: A butt joined electronic module has first and second coplanar transmission structures that are independently aligned in a proximate abutting relationship. The coplanar transmission structures are formed on respective first and second electrical elements that are secured on respective independently positioned and mechanically joined carrier and housing. The first and second coplanar transmission structures are electrically coupled together via substantially flat electrical conductors. The carrier and housing are bonded together as a single module.

Abstract: A frequency domain analysis system incorporated into time domain measurement instrument has duration and resolution controls that respectively adjust the acquisition time intervals of a waveform record in seconds and adjusts the number of digital data samples over a specified duration. The duration of the acquisition waveform may be controlled using the duration control adjustment, a sample rate adjustment and a record length adjustment. The resolution controls concurrently adjusts the sample rate and the record length of the acquisition waveform while maintaining the duration constant. A movable and variable length frequency spectrum gate is applied to the digital data samples of the acquired waveform. A window filter is applied to the digital data samples within the gated region a spectrum analysis generator generates frequency domain values over the gates waveform record.

Abstract: A measurement receiver demodulator has a first processing channel for producing a filtered signal sample output where the signal samples are processed through a transmission system receiver filter and a second processing channel producing an unfiltered signal sample output where the signal samples are not processed through the transmission system receiver filter. The first processing channel down converts digitally modulated IF signal samples and filters the down converted signal samples using a combined transmission system receiver filter and front end hardware compensation filter. A synchronizer produces timing phase and rate offset parameters that are applied to a resampling filter to synchronize the filtered signal samples to symbol instances of the symbol modulation. The filtered, time-aligned signal samples are scaled using a derived scaling factor. A pilot offset level, if present, is estimated and removed.

Abstract: An optical fiber harness has a unitary plastic body that is formed into a substantially circular member and a straight member. The straight member intersects the circular member forming a chord through the circular member. At least a first attachment member extends from the straight member for securing the optical fiber harness onto a circuit board. Tabs extend outward from the circular member for receiving an optical fiber.

Abstract: A surface mount probe point socket has a housing with base and a socket extending from the base. The base has a length and width sufficient for attaching the housing to a circuit trace using an electrically conductive material while adding minimal inductance and capacitance to the circuit trace. The socket has a height and diameter for supporting a measurement probe in the housing while adding minimal inductance and capacitance to the measurement probe. A probe point contact is disposed in the bore of the socket for receiving a probe point disposed in the end of the measurement probe to secure the probe in the housing. Two surface mount probe point sockets may be joined together with an alignment gage and attached to adjacent circuit traces to produce a surface mount probe point socket system for differential measurement probes.

Abstract: A removable mechanical attachment system has first and second removable attachment members with each removable attachment member having first and second links. Each link has a base and at least a first extension member extending from one side of the base. The links are secured to respective surfaces of first and second electrical sections with at least one of the extension members of the first and second links of each of the first and second removable attachment members extending past open end faces of the first and second electrical sections. The electrical sections are positioned in a proximate abutting relationship at the open end faces with the extension members extending past the open end faces of the electrical sections overlapping the other extension members of the first and second removable attachment members. A bonding material is applied to the overlapping extension members to join the extension members together.

Abstract: A telecom mask testing zoom function draws mask. pixels into a raster memory. In this way, the mask is treated as a waveform. Comparison of the mask pixels and waveform pixels to detect collision between a waveform pixel and a mask pixel (i.e., a mask violation) is performed substantially in real time, as the pixels are being composited into the raster memory by the rasterizer. The mask is scalable and repositionable by the rasterizer under control of a controller, because it is treated as a waveform. The mask is lockable to the waveform because both are stored in pixel form in raster memory by the rasterizer under control of the controller.

Abstract: An electronic system includes a source of test data, which, if the test data source is operating properly, is a pattern of a limited number of data words successively repeated. A memory device is coupled to the test data source and stores the test data. A memory test circuit compares the stored test data to successively repeated pattern data words and generates a signal to indicate whether the stored test data is the same as the successively repeated pattern data words.

Abstract: An adapter for a multi-channel, low input capacitance signal probe head has a housing with a cavity formed therein that receives one of a mating plug or receptacle portion of multi-channel, controlled impedance connector. The housing has probe head retention members formed in the sidewalls and alignment flanges disposed adjacent to the probe head retention members that are received in the signal probe head. The adapter includes a substrate having first and second arrays of contact pads formed on the respective top and bottom surfaces of the substrate. The first array of contact pads mate with electrically conductive elastomer signal contacts of the signal probe head and the second array of contact pads mate with the contact pads of the transmission lines of the plug or receptacle. Screws extend through bores in the signal probe head and engage threaded pins in the retention members.

Abstract: A low capacitance probe contact has electrically conductive contacts having fingers with opposing interior flat surfaces forming a slit there between. The fingers extend in a first direction with a mounting member extending in the opposite direction having a flat surface that is parallel to the flat surfaces of the fingers. The first and second electrically conductive contacts are secured to respective first and second electrically conductive contact pads formed on a substrate with the flat surfaces of the mounting members being positioned on the contact pads. The substrate and the electrically conductive contacts are captured within a housing having first and second members. One member has a base and extending sidewalls forming a recess that receives the substrate and the electrically conductive contacts and the other member has a periphery coextensive with the first member to capture the substrate and the electrically conductive contacts therein.

Abstract: A measurement test instrument voltage management system for an accessory device has a accessory device interface that provides a voltage to a memory device in the accessory device. A sensing circuit receives a sensing signal from the accessory device when it is connected to the interface. The sensing circuit generates an interrupt signal that is coupled to a controller. The controller initiates the generation of a clock signal that is coupled to the accessory device through the interface to retrieve accessory device data stored in the device memory. The controller determines if the connected accessory device is a valid device capable of being supported by the measurement test instrument. The controller generates an enable signal for a valid and supported device that is coupled to a voltage switching circuit. The voltage switching circuit generates at least a first output voltage that is coupled to the accessory device via the interface to provide power to the accessory device.

Abstract: An incremental bus structure for a modular measurement instrument includes interface connector structural elements interconnecting segments of a system bus. The system bus contains electrically conductive lines with the system bus having at least one subset of N electrically conductive lines. Each interface connector is part of a measurement module and has at least one set of N electrically conductive input and output contacts corresponding with the N electrically conductive lines. The first input contact of the set of N contacts for each connector is coupled to an electronic element associated with its measurement module and the second and subsequent input contacts are connected to the first and subsequent output contacts.

Abstract: A method for controlling a digital oscilloscope locates a crossing level in an eye diagram (also including a crossing time), of a communications signal. The method includes the steps of locating the crossing time using a horizontal histogram box; and locating the crossing level using a vertical histogram box placed at a horizontal location substantially at the located crossing time.

Abstract: A deskew fixture has a multilayer circuit board from which pairs of mirrored signal launch contact extend from both sides of the circuit board. One pair of contacts is coupled to electrical ground and the other pair is connected via equal length, electromagnetically coupled strip lines to a signal source. Probe holders are mounted on the circuit boards to support measurement probes with the probing contacts of the measurement probes coupled to the signal launch contacts. Additional pairs of signal launch contacts may be provided with one pair receiving a positive signal from the signal source and another pair receiving a negative signal via equal length, electromagnetically coupled strip lines from the signal source for deskewing differential measurement probes.

Abstract: A clock recovery system includes a source of a data signal having transitions, an injection-locked oscillator having a free-running frequency and generating a clock signal, and a free-running frequency adjustment circuit. The free running frequency adjustment circuit includes a transition density detector for detecting the density of the transitions in the data signal; a phase error detector for detecting the phase error between the clock signal and the data signal; and a correlator for adjusting the free-running frequency of the injection locked oscillator in response to the correlation between the detected transition density in the data signal and the phase error between the data signal and the local oscillator.

Abstract: An electrical standoff has a dielectric substrate with opposing horizontal surfaces and at least two opposing vertical end walls. A transmission structure having planar elements is formed on the at least one of the horizontal surfaces with the planar elements of the transmission structure extending to the two opposing vertical end walls. The electrical standoff is formed from a wafer of dielectric material having at least a first transmission structure formed thereon. A low temperature water soluble wax is applied over the transmission structure and a protective covering is placed over the water soluble wax. The wafer is sawn to form the electrical standoff with the electrical standoff having two opposing sawn vertical end walls intersecting the planar elements of the transmission structure. The protective covering and the low temperature water soluble wax are removed from the electrical standoff.

Abstract: A probe tip adapter for a measurement probe has at least a first electrically conductive element with a bore at one end and a probing contact formed on the other end. The bore of the electrically conductive element has an electrically conductive elastomer disposed therein having sufficient tensile strength, compression set, hardness, deflection force, elongation and percent recovery for repeatably securing the electrically conductive element to the probing tip of the measurement probe. The probing contact may be configured as a probing tip having a shaft that tapers at one end to a point and as a square pin adapter with a bore formed in the electrically conductive element that receives a spring contact. The probe tip adapter is useable with both single ended and differential measurement probes.

Abstract: A probe head holder for a measurement probe head has a probe head mount and a highly elastic, high hoop strength retention member that flexibly secures the measurement probe head to the probe head holder. The probe head mount has a first surface adapted to receive the measurement probe head and a second surface extending from the first surface having at least a first groove formed therein normal to the first surface. The retention member is positioned around the holder and the probe head with a portion of the retention member being disposed in the groove. The probe head holder may be attached to a probe arm of a probing station.

Abstract: An optical system having a first order spectral range that is usable in an optical spectrum analyzer receives an broadband optical test signal and a optical calibration signal and couples the optical signals via two optically isolated paths to separate optical detectors. First and second pairs of optical fibers, with each pair having an input fiber and an output fiber, are positioned in a focal plane of a collimating optic that has an optical axis. The fiber pairs are symmetrically positioned on either side of the optical axis with the input fibers positioned on one side of the optical axis and the output fibers positioned on the opposite side of the optical axis. The input fibers receive the optical test signal and the optical calibration signal. The output optical fibers are coupled to first and second optical detectors. An optical calibration source generates second order or greater spectral lines that fall within the first order spectral range of the optical system.