Abstract: A ground spring for receiving a ground end of a high-frequency test probe is described. The ground spring includes a generally annular base portion, and a number of elongated spring fingers extending from the base portion. The fingers extend generally radially inwardly from the base portion and have inner end faces that together define a substantially circular opening in a center portion of the ground spring. Each of the fingers have a tapered shape including a wider base portion end and a narrower inner end portion Each of the fingers has a longitudinal axis that is aslant relative to a reference line extending from the center of the ground spring to a center of the base portion of each finger. BMA connectors including the ground spring and test and measurement devices are also described.

Abstract: Embodiments of the invention include a method for detecting visual stress scenes in a video. First, a video that includes scenes that may cause visual stress in some viewers is received. Then, a signal representing human perceptual response from scenes in the video is generated. An envelope follower is applied to the perceptual response, from which indications that the video contains visual stress scenes may be generated. The output may also be used to control a contrast limiting circuit, which modifies the original video to remove or minimize those scenes that may cause visual stress. Additionally, output from the envelope follower may be converted to a simulated EEG signal and used to verify accurate modeling by comparing the simulated EEG signal to one measured directly from a viewer watching the same video.

Abstract: A user may easily confirm a relationship between an edited packet and the output serial data derived from the edited packet. The user may edit a packet with known method (step 104) to display a packet structure of the edited packet (step 106). A signal generator converts the packet to serial data through striping, scramble and 8b/10b conversion to display a serial data bar corresponding to the serial data derived from the packet (step 116). The user may designate a range on the serial data bar to distinctively display portions of the packet structure corresponding to the designated range (step 120).

Abstract: Systems and methods for calculating and presenting confidence interval(s) for key performance indicator(s) (KPIs) are described. For example, in some embodiments, a method may include identifying vectors representing network events observed by a network monitoring system, each vector including: a dimension, an indication of a sampling ratio with which a respective event was observed, and a value associated with the dimension. The method may also include calculating a KPI corresponding to the observed events for the dimension based, at least in part, upon the values. The method may further include calculating a confidence associated with the KPI, based, at least in part, upon the sampling ratios. In some cases, events may be observed with different sampling ratios. Additionally or alternatively, sampling ratios may include adaptive sampling ratios controlled by the network monitoring system in response to network or resource loading (e.g.

Abstract: Systems and methods for determining web page download times are described. HTTP transactions data is collected from flow records or PDUs. A subscriber IP address, HTTP URI, and referrer are extracted from the flow records. A subscriber record is identified using the subscriber IP address, and a configured web page is identified using the HTTP URI. A processing path is then determined for the HTTP transaction The processing path is selected from one of: a new page download path for a configured page, a collision path for HTTP transactions that collide with an existing page download, and a page object path for artifacts pages that are already being tracked.

Abstract: Systems and methods for data integrity scoring and visualization for network and customer experience monitoring are described. In some embodiments, a method may include receiving a first set of vectors, each vector representing a network event generated by a network testing system, each vector including a plurality of dimensions and a first plurality of values, each value associated with a corresponding one of the dimensions. The method may also include identifying a second set of vectors representing at least a portion of the network events as observed by a network monitoring system, each vector in the second set of vectors including the plurality of dimensions and a second plurality of values. The method may further include calculating a presence score as a ratio between a number of vectors in the second and first sets of vectors, and/or an accuracy score as a measure of a discrepancy between corresponding values.

Abstract: A digital-to-analog converter includes first and second pulse modulators to generate first and second pulse modulated signals in response to first and second digital values, a third pulse modulator to generate a third pulse modulated signal in response to a third digital value, and a switch/filter circuit to generate an analog signal by combining the first and second pulse modulated signals in response to the third pulse modulated signal. The first and second pulse modulated signals may be low-pass filtered before being combined. In some embodiments, the third digital value may be incremented in a single direction between transitions of the first and second digital values. In some other embodiments, the third digital value may be incremented in opposite directions between alternating transitions of the first and second digital values.

Abstract: Systems and methods for determining mean opinion scores (MOS) for variable bit rate (VBR) audio streams transmitted over VoIP networks are described. In an embodiment, a method may include monitoring a communication over a network and detecting portions of the communication including packets having a different packet payload sizes. The method may also include deriving bit rates corresponding to those portions. The method may then include calculating MOS values for each portion based on the derived bit rates, and calculating an overall MOS value for the communication based upon each individual MOS value averaged according to a distribution of packets having the different packet payload sizes.

Abstract: Disclosed is a test and measurement instrument having a multiple variable bandwidth frequency mask. The instrument includes an input processor for receiving an input signal and producing a digital signal, as well as a trigger signal generator for generating a trigger signal on the occurrence of a trigger event. A time to frequency converter converts a frame of digital data from the digital signal into a frequency spectrum having at least two frequency bins of dissimilar frequency widths. Each frequency bin has a power amplitude value. The trigger signal is generated when the power amplitude value of any of the at least two frequency bins violates an associated reference power level. In some cases the output may be shown as a density trace, and the trigger signal generated when any point of the density trace violates an associated density threshold.

Abstract: Systems and methods for determining mean opinion scores (MOS) for variable bit rate (VBR) audio streams transmitted over VoIP networks are described. In an embodiment, a method may include monitoring a communication over a network and detecting portions of the communication including packets having a different packet payload sizes. The method may also include deriving bit rates corresponding to those portions. The method may then include calculating MOS values for each portion based on the derived bit rates, and calculating an overall MOS value for the communication based upon each individual MOS value averaged according to a distribution of packets having the different packet payload sizes.

Abstract: A test and measurement instrument includes an input for receiving an input test signal and a separator that separates a data array of the input test signal into a number of different data bins. Each data bin includes a number of data points. A selector is included that determines whether the data points within a present bin of the total bins represent signal or noise. When the present bin contains noise, a processor generates a first output for the present bin. Instead, when the present bin contains signal, the processor generates a second output for the present bin. The bin outputs can then be combined to make an output array, such as a waveform display, for the instrument.

Abstract: A test and measurement instrument and method for receiving a radio frequency (RF) signal, digitizing the RF signal using an analog-to-digital converter, downconverting the digitized signal to produce I (in-phase) and Q (quadrature) baseband component information, generating one or more IQ-based time-domain traces using the I and Q baseband component information, and measuring and displaying a variety of measurement values of the IQ-based time-domain traces. The IQ-based time-domain measurement values can be automatically generated and displayed, and/or transmitted to an external device.

Abstract: An apparatus and method for splitting a wide band input signal and overlaying multiple frequency bands on each path associated with one or more digitizers. All frequencies from the split signal on each path can be fed to a mixer. The local oscillator of each mixer receives a sum of signals, which can each be set to any arbitrary frequency, as long as an associated matrix determinant of coefficients is non-zero. Each oscillator signal is multiplied by a coefficient, which can represent phase and magnitude, prior to summing the oscillator signals together. Each mixer mixes a combined signal with the input, thereby generating a set of multiple overlaid frequency bands. The digitized signals are processed to substantially reconstruct the original input signal. Thus, the wide band input signal is digitized using multiple individual digitizers. In particular, a system can support two wide band signals using four digitizers of narrower bandwidth.

Abstract: Methods and systems are described for analyzing signal impairments using a test and measurement instrument. A method may include decomposing aggregate signal impairments into signal impairments that are correlated and uncorrelated to an acquired data pattern. The uncorrelated signal impairments may be further decomposed into periodic signal impairments (e.g., PJ) and non-periodic uncorrelated signal impairments. A PDF of the non-periodic uncorrelated signal impairments may be mathematically integrated, thereby producing an estimated cumulative distribution function (CDF) curve. Random signal impairments may be estimated as an unbound Gaussian distribution. The CDF curve of the non-periodic uncorrelated signal impairments and the unbound Gaussian distribution may be plotted in Q-space on a display device. Non-periodic bounded uncorrelated signal impairments (e.g., NP-BUJ) PDF may then be isolated. Bounded uncorrelated signal impairments PDF may then be synthesized.

Abstract: A stereoscopic video temporal frame offset measurement system uses an improved signature curve generator to generate a robust signature curve for each of the left and right image sequences of a stereo video signal. The resulting signature curves are cross-correlated over a specified correlation range to generate cross-correlation coefficients. The cross-correlation coefficients are compared to a high threshold, and a temporal frame offset is generated and displayed for each cross-correlation coefficient that exceeds the high threshold. Each new temporal frame offset result is highlighted when displayed, otherwise the last result is displayed in a background fashion.

Abstract: The described test and measurement instrument includes a processor for generating a bitmap image from an input test signal, a user interface for identifying a portion of the bitmap image, and a second image generator structured to generate a second image from the identified portion of the bitmap image. The second image may be a zoomed image from the original bitmap, and the images may be time-corrected before being displayed.

Abstract: A signal acquisition system has a signal acquisition probe having probe tip circuitry coupled to a resistive center conductor signal cable with the signal cable coupled to a signal processing instrument via an input node. The input node is coupled to an input current amplifier via input circuitry. The input circuitry provides at least one of resistive and capacitive termination of the resistive center conductor signal cable. The termination of the resistive center conductor signal cable in the signal processing instrument provides a signal acquisition system where the capacitive loading of a device under test at higher frequencies is reduced by reducing the input capacitance of the probe tip circuitry resulting in an increase in the signal acquisition system bandwidth.

Abstract: A signal acquisition system has a signal acquisition probe having probe tip circuitry coupled to a resistive center conductor signal cable. The resistive center conductor signal cable of the signal acquisition probe is coupled to a compensation system in a signal processing instrument via an input node and input circuitry in the signal processing instrument. The signal acquisition probe and the signal processing instrument have mismatched time constants at the input node with the compensation system having an input amplifier with feedback loop circuitry and a shunt pole-zero pair coupled to the input circuitry providing pole-zero pairs for maintaining flatness over the signal acquisition system frequency bandwidth.

Abstract: A “density trace” according to an embodiment of the present invention is formed by measuring the density of each column of a frequency domain bitmap above a user-specified “amplitude threshold.” The density of each column equals the sum of the densities of all of the pixels in the column that are above the amplitude threshold divided by the sum of the densities of all of the pixels in the column. A density trace provides a convenient way to define and represent the occupancy for a large number of columns, and also allows density data to be quickly transmitted from one instrument or computer to another. In some embodiments, a density trace is incorporated into a trigger detector of a test and measurement instrument and used to generate a trigger signal. The trigger detector compares the density trace to a user-specified “density threshold” and generates the trigger signal when the value of any point of the density trace violates the density threshold.