Abstract: An improved power-off, loop-through return-loss characteristic for a current feedback operational amplifier is provided by adding a positive feedback capacitor between the input and output of the operational amplifier. The positive feedback capacitor results in a negative capacitance input impedance for the operational amplifier that cancels stray capacitances at the input.

Abstract: A current probe transformer temperature monitoring method determines an initial transformer temperature of the current probe as a function of the winding resistance of the transformer. A relative temperature of the Hall Effect device is also determined as a function of resistance change of the Hall Effect device. The initial transformer temperature and the relative Hall Effect device temperature are combined to produce a continuous transformer temperature indicative of the temperature of the transformer. The current signal to the multi-turn winding is removed when the continuous transformer temperature exceeds a threshold temperature value and a visual indication may be provided.

Abstract: A test set used for introducing a Poisson distribution of errors into a known digital data signal to produce a test signal uses an error signal generator that produces a Poisson distribution error signal. The error signal is then combined with the known digital data signal to produce a test signal with the Poisson distribution of errors. A pseudo-random binary sequence generator is used to produce a PRBS sequence and a comparator is used for comparing the PRBS sequence with a probability control signal. The comparator sets a single bit in the output stream of zeros when the PRBS sequence is less than the probability control signal. For multiple bit Poisson distribution error signals the PRBS generator and comparator combination may be replicated m times, or a single PRBS generator may be used and a unique independent subset of the PRBS sequence is applied to each of the multiple comparators.

Abstract: A test and measurement apparatus and method wherein a software implemented phase lock loop recovers a clock signal associated with the received data signal, the recovered clock signal being used to do TIE measurement, to generate eye diagram and to do mask testing.

Abstract: A real time digital storage oscilloscope acquires a long data record in an acquisition memory and processes the data of the long data record to search for predetermined events. Upon detection of such a predetermined event, circuitry generates an event detect signal, and data comprising an acquisition frame surrounding the event is applied to a waveform processing and display system. The long data record can be replayed in order to perform additional searches throughout the data record using different search criteria, thereby permitting multiple waveforms to be displayed simultaneously, each being captured as a result of a different user-defined event. A screen display may be programmed to display a different kind of event such as Runt signal, Overshoot, or Pulsewidth Violation in each waveform, or to display multiple occurrences of the same kind of event such as Runt signal in each waveform.

Abstract: A method for generating an in-phase (I) output signal and a quadrature-phase (Q) output signal from an input signal reduces phase error in the I/Q generator by delaying-and-doubling an input signal to produce a Q output signal and delaying the input signal twice and subtracting the same from the input signal to produce an I output signal. The I/Q generator includes a first 90°-phase delay circuit receiving an input signal and outputting an intermediate Q signal; a second 90°-phase delay circuit receiving the intermediate Q signal and producing an intermediate I signal. It also includes a signal doubler receiving the intermediate Q signal and producing a Q output signal of twice the amplitude of the input signal at a 90° phase angle. Finally, the generator includes a signal differencer receiving the input signal and the intermediate I signal and producing an I output signal of substantially twice the amplitude of the input signal at a 0° phase angle.

Abstract: A method and apparatus for calibrating at least signal probes associated with a signal analysis device by storing existing input channel parameters, performing appropriate calibration procedures and restoring input channel operational parameters.

Abstract: A picture quality measurement technique using blockiness provides realtime analysis without the use of a reference signal. A field/frame of an image represented by a processed video signal is captured in a bit-map for analysis. The image is filtered to enhance edges and then correlated with a kernel having a size corresponding to the block size of the compression algorithm used in compressing and decompressing the video signal to produce the processed video signal. The correlation results are processed by comparing an average value with the maximum value to produce a picture quality rating for the processed video signal.

Abstract: A fiber-pigtailed assembly for an optical detector with low back reflection and minimal polarization-dependent responsivity has a detector surface mounted adjacent a beveled end of a fiber pigtail such that the detector surface is tilted and rotated with respect to the beveled end of the fiber pigtail. Also an external optical fiber may be coupled to the fiber pigtail with low back reflection and minimal polarization-dependent responsivity by having an input ferrule at the end of the external optical fiber, the end being beveled; by having an intermediate ferrule at a coupling end of the fiber pigtail, the coupling end being beveled while the other end of the ferrule is beveled by the same amount but approximately orthogonal to the coupling end; and by having an output ferrule on the fiber pigtail adjacent to the intermediate ferrule, the end of the output ferrule adjacent to the intermediate ferrule being beveled.

Abstract: A method of avoiding conversion spurs in a multi-conversion radio frequency receiver having a first local oscillator, an intermediate frequency filter and a second local oscillator in series generates, based on a center frequency for the intermediate frequency filter, a table of problem frequencies of the first local oscillator relative to a frequency of the second local oscillator which produce harmonic mixing products within the bandwidth of the intermediate frequency filter versus corresponding frequency offsets for the second local oscillator which retune the frequency of the second local oscillator so the harmonic mixing products are moved outside the bandwidth of the intermediate frequency filter.

Abstract: A method of synchronizing a watermark decoder with a watermark encoder uses a spatio-temporal (3D) synchronization pattern added to a data pattern to produce a watermark pattern for embedment into a signal. The spatio-temporal synchronization pattern is formed by multiplying a spatial (2D) synchronization pattern with a pseudo-noise sequence for a block of signal frames having a duration of N frames. Quadrature carrier modulation may be used to increase detectability of the watermark pattern at the watermark decoder. The watermarked signal is correlated with the spatial synchronization pattern to recover a temporal synchronization signal that is used to determine a temporal offset between the watermark encoder and watermark decoder. The temporal offset is then used to synchronize the watermark decoder with the watermark encoder.

Abstract: A frequency dither technique is used for reducing spurs due to phase increment errors in a direct digital synthesizer output sinusoid. The spurs for a desired output frequency are calculated and, if the spurs fall within a phase locked loop bandwidth, a pair of phase increment values are used representing a pair of frequencies that average to the desired output frequency and the spurs of which fall outside the phase locked loop bandwidth.

Abstract: A multi-channel, low input capacitance signal probe head has a housing that receives one or more substrates having input signal pads exposed on one end of the substrate. The substrate is positioned in the housing such that the signal contact pads are exposed at an open end of the housing. A removable signal contact holder mounts to the housing and supporting electrically conductive elastomer signal contacts. The holder is disposed over an open end of housing such that the elastomer signal contacts engage the input signal pads. A probe head retention member is provided for securing the multi-channel signal probe head to a device under test.

Abstract: Measuring wireless network performance from a remote site uses a mobile handset that may include an appropriate world wide network browser. A user connects the mobile handset to the remote site via the wireless network which is coupled to the world wide network. Once the connection is made, application software at the measurement site sends commands to the mobile handset and in response the mobile handset sends measurement data to the application software. The application software processes the data to provide information about the wireless network performance including analyses for predictive and diagnostic purposes, since measurement data from many handsets, many locations and many base stations at many times may be collected at one central location.

Abstract: In a test and measurement instrument having M signal input channels, individual samples representing a signal from each channel are compared to mask pixels to detect non-compliance with a given specification. Initial mask and waveform positions on a display screen of the oscilloscope are determined by an AUTOSET TO MASK function. Comparison of 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 a raster memory by a rasterizer. Acquisitions are performed simultaneously and repeatedly. Acquired waveforms from all M signal input channels are sequentially compared to the mask and drawn on screen during the following acquisition period. Thus, M waveforms can be tested for compliance with a telecom mask substantially within a single acquisition time period.

Abstract: A motion compensation improvement for a compression encoder minimizes redundant edge information in a current image from a video input signal being input to the compression encoder. The current image is compared with a reference image from the video signal, which images may be the entire picture or a sub-region of the picture, to provide a spatial shift difference between the images, the spatial shift difference having an integer part and a high precision fractional part. From the high precision fractional part and specified constants for the compression encoder a shift value is calculated such that, when shifted, the current image is aligned with a quantizer motion vector grid in the compression encoder. The shift value is then used to resample the current image to make the desired shift prior to input to the compression encoder, thereby minimizing redundant edge information.

Abstract: A touch controlled zoom and pan of graphic displays is achieved using only a touch screen and rotary knob by designating various areas on a touch screen. Touching one of the designated areas determines the function to be performed—zoom along one axis or in two dimensions or pan along one axis or in two dimensions. The zoom or pan is then performed in response to the rotation of a rotary encoder knob. For panning dragging the touch along an axis in lieu of rotating the rotary encoder knob performs the function. Alternatively the same designated areas may be used to determine either the zoom or pan function by using either a “touch and hold” technique for zoom or a “touch and go” technique for pan.

Abstract: A high speed x/sine(x) correction circuit for a digital to analog converter (DAC) functions by implementing a filter with an impulse response that approximates a sine(x)/x response. Each digital data value of an input signal to be converted by the DAC is considered a separate impulse. Each impulse, or initial pulse, is used to create a first reflection pulse by delaying the initial pulse by one clock cycle, inverting the delayed initial pulse and multiplying the delayed initial pulse by a constant less than one, such as dividing the delayed initial pulse by right-shifting the digital data value of the delayed initial pulse. The first reflection pulse is added to the input signal in the clock cycle it is generated prior to input to the DAC. A second reflection pulse may be generated in like manner from the first reflection pulse with an additional clock cycle delay for optimum results, both reflection pulses being added to the input signal in the clock cycle they are generated prior to input to the DAC.

Abstract: An elastomeric mat is formed by extruding transparent or translucent elastomeric material. Columns made of the same material guide light from an LED source directly to a light port on top of the column, and diffuse the light substantially throughout the column. A coating of opaque material is used to surround the length of the columns to prevent leakage of light. When mounted adjacent to a front panel, off-axis performance is substantially increased over the prior art by, in effect, bringing the light-emitting source adjacent to a clear port of the front panel. The columns of translucent or transparent elastomeric material function as light pipes, and are formed when making the eleastomeric mat. The columns may be cylindrical or rectangular. Either a rectangular or a cylindrical column of translucent or transparent elastomeric material can convey light to illuminate a legend printed directly on top of the column.

Abstract: An audio/video processing engine that is programmable for processing digital video and digital audio simultaneously, either in parallel or concurrently, has an audio/video I/O processor that communicates with a single programmable hardware processor having reconfigurable logic blocks. The single programmable hardware processor communicates with both a general purpose processor and an optional digital signal processor for adjunct processing. The general purpose processor has a flash memory for initializing the programmable elements of the audio/video processing engine and has data links for remote accessing for programming, control and monitoring. The flash memory is accessible by the single programmable hardware processor, and may be reloaded remotely via the general purpose processor.