Abstract: A calibration method for an oversampling acquisition system uses a digital calibration signal that has a period between edges that is unrelated to the period of a sample clock. The calibration signal in input in parallel to a plurality of samplers, each of which is clocked at a different time by a delayed version of the sample clock, to produce a plurality of sequential samples per sample clock period. Edge transitions of the calibration signal are counted that occur between adjacent ones of the samplers, and are accrued over an acquisition period to produce a plurality of edge counts. The edge counts are then processed to produce control signals to adjust the sample clock delay for each sampler so that the time intervals between the sequential samples are essentially uniform.

Abstract: A unique test pattern is used for measuring timing parameters of RGBHV analog video signals. For horizontal timing a horizontal line includes within an active video region left and right portions at a first level and a central portion at a second level, the left, right and central portions having a defined percentage relationship to the number of pixels of the horizontal line within the active video region. Also optionally included are left and right border portions just prior to and just after the left and right portions respectively. Measurements are done in pixels for the horizontal line from a horizontal sync pulse to each transition of the unique test pattern, and the horizontal timing parameters are derived from such measurements.

Abstract: A “no dead time” data acquisition system for a measurement instrument receives a digitized signal representing an electrical signal being monitored and generates from the digitized signal a trigger signal using a fast digital trigger circuit, the trigger signal including all trigger events within the digitized signal. The digitized signal is compressed as desired and delayed by a first-in, first-out (FIFO) buffer for a period of time to assure a predetermined amount of data prior to a first trigger event in the trigger signal. The delayed digitized signal is delivered to a fast rasterizer or drawing engine upon the occurrence of the first trigger event to generate a waveform image. The waveform image is then provided to a display buffer for combination with prior waveforms and/or other graphic inputs from other drawing engines. The contents of the display buffer are provided to a display at a display update rate to show a composite of all waveform images representing the electrical signal.

Abstract: A method for improving performance and flexibility of serial data analysis in test instruments, is independent of data bit rate, encoding scheme or communication protocol embodied in the serial data. The serial data is input to a transmitter section, where it is demultiplexed into a plurality of multi-bit lanes, such as n bits for each of N lanes. The N lanes are then encoded into characters, the encoded N lanes having m bits per lane where m>n. Bit stuffing is used to adjust the data rate and/or to insert qualifiers. The stuffed, encoded N lanes are then multiplexed into N serial lanes, which are output from the transmitter section for input to a receiver section at a data rate that is optimal for the receiver section. In the receiver section the N lanes are deserialized, decoded and input to a word recognizer to generate a trigger event signal.

Abstract: A filter equalization technique for an analog signal path, such as in an instrument that simultaneously measures a signal over a band of frequencies, uses magnitude measurement data for high frequency bands for which phase-calibrated sources are not readily available. A sinusoidal signal source together with an accurate power meter is used to provide a stepped frequency input over a desired frequency band to the analog signal path with an accurate measured magnitude. The output of the analog signal path is digitized and the resulting frequency magnitudes are computed. Then the resulting power meter results are deducted from the frequency magnitudes measured each time by the instrument to determine the magnitude response of the analog signal path. Using a Hilbert transform the corresponding phase response is determined based on a minimum phase assumption over the desired frequency band. From the magnitude and phase responses an inverse or digital equalization filter may be designed for the analog signal path.

Abstract: A protocol test device has at least two channels which each have a transmit and a receive side, the protocol test device being designed to switch a signal transmitted from a first channel to the receive side of a second channel. A method for determining, by approximation, a transmit time of a data package in the protocol test device includes the following steps: a) transmitting a signal via the transmit side of the first channel, b) forwarding the signal to the receive side of the second channel, and, c) in the receive side of the second channel allocating a time stamp to the signal.

Abstract: A method of trace delay error compensation for measurements that are taken remotely from the signal source or receiver of a circuit uses data available from a computer aided design (CAD) tool to characterize electrical connections to an instrument measurement point, such as a connectorless probe, which is remote from the signal source or receiver. Extracted parameters from the CAD data are applied to signals acquired by the probe to adjust the signal timing and/or shape to more accurately represent the signal information timing at the signal source or receiver or other remote location of interest to a user. The corrected signals at the desired location may be displayed by a measurement instrument.

Abstract: A method for recovering a clock from a serial data stream for use in producing “eye” diagram measurements includes determining an initial recovered clock from the serial data stream based upon transition edges. Time interval error values are then determined as a function of the transition edges and corresponding initial recovered clock times. Time interval error values are interpolated for initial recovered clock times not associated with transition edges to produce a complete set of time interval error values. The complete set of time interval error values are lowpass filtered to produce a filtered set of time interval error values. The clock for the serial data stream is reconstructed from the filtered set of time interval error values.

Abstract: A noise rejection filter for a trigger circuit uses an algorithm that updates the filter output monotonically so long as the signal slope remains unchanged, maintains the filter output at a constant level when the signal slope changes but the difference between the sample value and the filter output is less than or equal to a hysteresis value, and changes the signal slope while updating the filter output when the difference is greater than the hysteresis value. This maintains the peaks of the input signal at the filter output. The noise rejection filter may be used in a trigger circuit prior to a comparator so that the trigger signal from the comparator accurately reflects the signal pulse width at a desired trigger level and trigger events are detected when the desired trigger level is near the peaks of the input signal.

Abstract: A wander gamut display for perturbation analysis is created by determining from a periodic input data signal and a reference clock a frequency offset and frequency drift rate for the input signal. The frequency offset and frequency drift rate are input to respective orthogonal axes of a Cartesian display together with a wander limit bounding box that defines the wander gamut. Values that fall outside the bounding box on the display indicate wander that may result in data errors.

Abstract: A method of attaching measurement data to an area map on the display of a test instrument includes importing a map for display covering a desired spatial region. Appropriate points of interest are overlaid on the map. A user selects measurement data to be attached to the map and, upon selection such as by “tapping” a touch sensitive screen, a measurement icon is positioned on the map where the selected measurement data was acquired. A thumbnail of the selected measurement data is overlaid on the measurement icon to show both the type of measurement and actual measurement results. Also indicia of quality/strength for the measured signal may be tagged to the measurement icon, such as by changing the color of the border of the measurement icon accordingly. A direction arrow may also be associated with the measurement icon to indicate an orientation of the test instrument when the measurement data was selected.

Abstract: A realtime video quality measurement instrument may be configured for both double-ended and single-ended operation. For double-ended operation reference and test video signals are stored in respective buffers and spatial/temporally aligned. Desired quality measurements are performed on the aligned frames of the test and reference video signals according to stored setup instructions. For single-ended operation the reference video signal and a signature for the reference video signal are pre-stored together with the desired quality measurements for the frames of the reference video signal. Then the test video signal is received, signatures determined, and the test and reference video signals aligned using the signatures. The desired quality measurements are then performed on the aligned frames of the test and reference video signals.

Abstract: A variable passband ARMA filter has as inputs a signal to be filtered, a reverse version of the signal to be filtered and a variable coefficient to produce as an output a filtered signal. The variable coefficient is generated by a variable equivalent sample rate coefficient converter having as inputs an initial coefficient and a variable resampling rate parameter which controls the passband.

Abstract: A system and method for communication monitoring in a mobile radio network uses a distributed system having one or more processing devices coupled to different links of a serving switching entity of the mobile radio network. The processing devices extract current deciphering parameters from data on the different links, including an additional deciphering parameter set obtained from a subscriber data base entity, from the data flow of the connection, and from each packet data unit as the sequence number of data packets (PDUs) making up the data. The current deciphering parameters are stored in a deciphering parameter providing device so they are available for other processing devices upon request, the deciphering parameter providing device being coupled to the processing device(s) by a communication link such as a LAN or WAN.

Abstract: A mixed signal measurement instrument provides for the display of both analog and logic signal waveforms using a “no dead time” architecture. For a logic signal all trigger events are detected, the logic signal is sampled at a high rate to produce a sampled logic signal data, the sampled logic signal data are delayed to provide a pre-trigger delay and then are drawn in real time in response to the detected trigger events. A FIFO is used to delay the sampled logic signal data, with the position of the trigger event on the display being determined coarsely by an effective depth of the FIFO. The sampled logic signal data may also be compressed into compression codes prior to the FIFO. A fast drawing engine receives the sampled logic signal data from the FIFO as either data samples or compression codes, and draws a logic waveform using four rows of the drawing engine memory—one row for each of four logic states.

Abstract: A logic analyzer having clock channels and data channels includes digitizer followed by a digital filter in each channel, the digital filter compensating for losses in signal fidelity in a signal under test. The resulting enhanced multi-bit samples are stored in respective waveform memories for subsequent display as analog waveforms and as logic data. The multi-bit samples from each channel are re-sampled by a regenerated sample clock to determine the logic values of the signal at precise times. For high speed serial data, each channel is divided into multiple clock channels and sampling channels, the outputs from the clock channels being phase adjusted to provide a precise sample clock to the sampling channels and the outputs from the sampling channels being combined to form a serial data output.

Abstract: A system for simultaneous ACLR measurements encompassing multiple wireless communications channels provides a dual channel processing. The input signal is down converted to produce a wideband signal that is input simultaneously to both a wideband channel having a high speed, low resolution ADC and a narrow band channel having a low speed, high resolution ADC. The resulting data streams from the ADCs are processed by a DSP to provide the simultaneous ACLR measurements.

Abstract: A pattern sequence and state transition trigger generator provides a trigger when a specified transition from one pattern/state to another pattern/state occurs in a set of input signals. Decoders detect each specified pattern/state from the set of input signals to produce a prior value and a current value representing the transition. The prior value is slightly delayed and combined with the current value to produce an overlap when the specified transition occurs, which in turn generates the trigger.

Abstract: A method of generating an MPEG sequence for multiple component analog video measurements modifies a general purpose encoder and provides an MPEG encoded signal to test a device under test (DUT) component analog output that is valid in both RGB and YPbPr in both pulse and bar and that solves digital RGB cross-talk due to aliasing of Cb and Cr in 4:0:0 and 4:4:4 formats. The general purpose encoder is modified by removing vertical pre-filtering and post-filtering, altering quantization tables alternate scanning for vertical redundancy, and turning off motion estimation. The input to the MPEG encoder is pre-aliased to provide minimum digital cross-talk after MPEG compression by repeating every other sample.

Abstract: A method of pattern identification and bit level measurements for a high speed digital signal using an oscilloscope converts an input waveform into a bit stream sequence. From the bit stream sequence pre-defined patterns are identified and overlaid on each other to form a superimposed pattern. A center region for each bit of the superimposed pattern is identified, and appropriate voltage measurements within the respective center regions are taken for the bit levels.