Abstract: A method, circuit and system for determining at least one of an amplitude and a relative phase of a signal under test. A reference signal is generated based, at least in part, upon the at least one of the amplitude and the relative phase of the signal under test. The reference signal is combined with the signal under test to generate a residual signal indicative of a distortion within the signal under test. The residual signal is measured.

Abstract: Various embodiments for radio frequency (RF) noise cancellation are described. In one embodiment, an apparatus may comprise an RF noise cancellation system arranged to sense platform noise observed by a radio subsystem, create an inverse version of the sensed platform noise, and add the inverse version of the sensed platform noise to a received RF signal to remove the platform noise from the received RF signal. Other embodiments are described and claimed.

Abstract: A signal suppression filter (22) that inhibits high-frequency signals contained in power voltage and a signal separation filter (23) that prevents transmission of the high-frequency signals are provided in series on power lines (21A), (21B) connected to a power input terminal (T1), and a common-mode signal detection circuit (25) and a normal-mode signal detection circuit (26) are provided separately from each other. While bi-directionally blocking transmission of a high-frequency signal (noise) between the power supply and the device to be measured by the signal suppression filter (22) and the signal separation filter (23), the common mode signal and the normal mode signal generated in the device to be measured (3) and entering through a power output terminal (T2) are detecting separately. The analysis of the cause of occurrence of a high-frequency signal produced in the device to be measured (3) is facilitated, and proper noise countermeasure may be taken.

Abstract: A tester module is used to perform an adjacent channel leakage ratio measurement. The tester module includes a translation block, a first filter, a re-sampler, a memory, a router, a second filter and a power detector. The translation block translates a received intermediate frequency signal to a baseband signal. The first filter compensates amplitude and phase of the baseband signal for any unflatness in host hardware used to capture the received intermediate frequency signal. The re-sampler decimates the compensated baseband signal. The memory stores the decimated compensated baseband signal. The router reroutes the stored decimated compensated baseband signal to the re-sampler. The re-sampler resamples the rerouted stored decimated compensated baseband signal to perform spectrum shifting. The second filter performs a low pass filtering operation on the resampled rerouted stored decimated compensated baseband signal.

Abstract: A method (for example, machine-implemented, e.g., via a receiver), for determining whether a transmitted pulsed-signal is a linear or non-linear frequency modulated (FM) signal, includes: iteratively determining upper and lower bound slopes associated with frequency components of a pulse of a signal during a time period of the pulse; and comparing each determined upper bound slope to a previous or initial upper bound reference slope and comparing each determined lower bound slope to a previous or initial lower bound reference slope in order to determine the linearity, or non-linearity, of the signal.

Abstract: A nonlinear distortion is compensated based upon a characteristic relating to a characteristic of a device under test. An inverse characteristic measuring device measures an output signal output from the device under test as a result of supplying the device under test with an input signal generated by a signal source. Further, the inverse characteristic measuring device acquires an ideal signal output from the device under test based upon the input signal if the device under test is ideal. Moreover, the inverse characteristic measuring device acquires an inverse characteristic which is a relation of the ideal signal with respect to the output signal. This inverse characteristic is applied to a distortion compensator. The distortion compensator supplies the device under test with the input signal converted based upon the inverse characteristic. As a result, a signal output from the device under test is an ideal signal whose distortion caused by the device under test is compensated.

Abstract: Various embodiments for radio frequency (RF) noise cancellation are described. In one embodiment, an apparatus may comprise an RF noise cancellation system arranged to sense platform noise observed by a radio subsystem, create an inverse version of the sensed platform noise, and add the inverse version of the sensed platform noise to a received RF signal to remove the platform noise from the received RF signal. Other embodiments are described and claimed.

Abstract: An arrangement is for measuring characteristic parameters of intermodulation distortion of a device under test. The arrangement may include a generator of at least two tones at different test frequencies, and an attenuation path feeding the device with a replica of the two tones attenuated of a factor equal to the gain of the device. The arrangement may also include a circuit for generating a difference signal between the signal output by the device and the two tones, and a circuit input with the difference signal and measuring the characteristic parameters as a function thereof.

Abstract: A calibration circuit and method thereof. In the example method, a common-mode voltage may be detected at an output port of a mixer. At least one common-mode feedback voltage may be generated (e.g., at one or more common-mode feedback circuits) based on the detected common-mode voltage. A loop gain may be adjusted in response to a gate control signal (e.g., received at a controller, such as a second order Intecept Point (IP2) controller). An impedance may be adjusted at the output port of the mixer and a current applied to the output port of the mixer may be adjusted based on the at least one common-mode feedback voltage. The example method may be performed by a calibration circuit (e.g., an IP2 calibration circuit).

Abstract: An apparatus selectively generates a disturbance in a three-phase supply voltage provided to a load. The apparatus includes input connections for receiving a first phase voltage, a second phase voltage and a third phase voltage of the three-phase supply voltage. The apparatus includes a voltage disturbance generator for selectively adjusting the amplitudes of the first, second and third phase voltages according to a first test method, a second test method or a third test method. Output connections are provided for connecting to the load to provide the load the first, second and third phase voltages as altered according to the first, second or third test method. In the first test method, a phase-to-phase voltage disturbance is introduced between the first and second phase voltages by altering the amplitude of the first phase voltage against the second phase voltage.

Abstract: Embodiments of the invention include a test circuit having an auxiliary low power test signal generator, filters, and a detector to test a power switch. The generator sends an auxiliary low power test signal having a different frequency than a power signal for the switch to an input of the switch. The detector detects the auxiliary low power test signal at an output of the switch. Test circuit filters are used to filter out the power signal from reaching the auxiliary low power test signal generator or the detector circuit. A circuit of the test circuit is tuned to the test signal's different frequency to ensure that the detector only detects the test signal when the switch is in one position. Thus, by detecting or sensing the test signal across the switch, the detector can detect whether the switch is operating properly.

Abstract: A method for computer aided design of semiconductor chips which minimizes sensitivity to latchup is provided. The method evaluates electron transmission, reflection and absorption at geometric shapes that represent components of the semiconductor.

Abstract: Briefly, a system that may facilitate system and line loop back diagnostic operations. In one possible implementation, a first transceiver may transmit test signals to a second transceiver. The second transceiver may include a transmitter with the capability to reduce jitter in received test signals prior to transmission of received test signals back to the first transceiver. The first transceiver may determine path integrity characteristics based on the test signals transmitted from the second transceiver.

Abstract: According to one embodiment, a signal from a power supply line is caused to pass through a high pass filter, and a first signal is generated by adding a voltage-divided signal to the signal. In addition, a second signal obtained by adding the voltage-divided signal to an identification voltage is generated. A comparator outputs a comparison result of comparing a voltage of the first signal with a voltage of the second signal, and a counter counts up a count value when the voltage of the first signal is higher than that of the second signal. A sample hold circuit sample-holds the count value just before the counter is reset.

Abstract: A control arrangement and method is provided for detecting and responding to disturbances in electrical power systems. In a preferred arrangement, an integration is initiated that is based on a comparison of actual voltage of a source and a reference voltage. When the integration exceeds a predetermined value, the source is considered unreliable. Also in a preferred arrangement, a determination is made as to whether or not the disturbance is a downstream fault condition. For example, this is useful for applications where a transfer is made from a first source to a second source when predetermined disturbances are detected. In this manner, the transfer of the load to a second source is avoided which would continue the supply of the downstream fault. Additionally, the arrangement distinguishes between various degrees of disturbances to permit appropriate response based on the severity and type of disturbance. For example, a first immediate response, i.e.

Abstract: A method and apparatus for analyzing jitter in a signal. The signal is buffered to form a sequence of signal vectors and a time interval error function is calculated for each the signal vector. A time interval error spectrum is then calculated by transforming the time interval error function using a discrete Fourier transform. An average time interval error spectrum and an average power spectral density function are then calculated as averages of the amplitude of the time interval error spectrum and its amplitude squared, respectively. Parameters of the signal jitter are estimated from the average time interval error spectrum and the average power spectral density function.

Abstract: A technique for measuring spectral components, such as noise and distortion, of a non-coherently sampled test signal containing at least one tone of known frequency includes modeling the spectral components of the at least one tone, including the effects of leakage, based upon frequency of the at least one tone and a plurality of known sampling parameters. A DFT is taken of the sampled test signal, and the DFT is adjusted based on the modeled spectral components. The adjusted DFT is substantially leakage-free and directly reveals spectral components of the test signal, including low-power components that would ordinarily be lost in the leakage errors.

Abstract: A distortion measurement method uses alternative measurements to determine the distortion of a DUT, depending on the ratio of the distortion at an output of the DUT to distortion of a source stimulating the DUT. The method includes calibrating the VNA at a distortion frequency, measuring a first gain of the DUT with the source and the receivers of the VNA set to the distortion frequency, and measuring a second gain of the DUT with the source of the VNA set to a fundamental frequency and the receivers of the VNA set to the distortion frequency. When the second gain is less than a predesignated threshold, a match-corrected source signal is acquired and used with the first gain and the second gain to determine the distortion of the DUT. When the second gain is not less than the predesignated threshold, a match-corrected DUT output signal is measured and used with the first gain and the second gain to determine the distortion of the DUT.

Abstract: A signal under measurement is transformed into a complex analytic signal using a Hilbert transformer and an instantaneous phase of this analytic signal is estimated. A linear phase is subtracted from the instantaneous phase to obtain a phase noise waveform. The phase noise waveform is sampled in the proximity of a zero crossing point of a real part of the analytic signal. A differential waveform of the sample phase noise waveform is calculated to obtain a differential phase noise waveform. An RMS jitter is obtained from the phase noise waveform, and a peak-to-peak jitter is obtained from the phase noise waveform.

Abstract: A control arrangement and method is provided for detecting and responding to disturbances in electrical power systems. In a preferred arrangement, an integration is initiated that is based on a comparison of actual voltage of a source and a reference voltage. When the integration exceeds a predetermined value, the source is considered unreliable. Also in a preferred arrangement, a determination is made as to whether or not the disturbance is a downstream fault condition. For example, this is useful for applications where a transfer is made from a first source to a second source when predetermined disturbances are detected. In this manner, the transfer of the load to a second source is avoided which would continue the supply of the downstream fault. Additionally, the arrangement distinguishes between various degrees of disturbances to permit appropriate response based on the severity and type of disturbance. For example, a first immediate response, i.e.

Abstract: According to one embodiment of the present invention, a system (100) for measuring overall jitter is disclosed that includes a data converter (102) that measures a signal to generate a first measurement set (212) and a second measurement set (214), which are used to compute overall jitter. According to one embodiment of the present invention, a method for measuring overall jitter is disclosed. The data converter (102) generates the first measurement set (212) and the second measurement set (214) by measuring the signal. The overall jitter is computed using the measurement sets (212 and 214). According to one embodiment of the present invention, a system (400) for measuring internal jitter is disclosed that includes a splitter (404) that splits a signal into an input signal (406) and a clock signal (410). The data converter (102) measures the input signal (406) to generate a first data set and a second data set, which are used to compute the internal jitter of the data converter (102).

Abstract: The object of this invention is to reduce the cost of an amplification device that has a distortion detection loop that uses an amplifier to amplify the signal subject to amplification and detect the distortion arising in said amplifier, and a distortion removal loop that removes the distortion detected by the distortion detection loop from the signal amplified by said amplifier.

Abstract: There is provided an apparatus for and a method of measuring a jitter wherein a clock waveform XC(t) is transformed into an analytic signal using Hilbert transform and a varying term &Dgr;&phgr;(t) of an instantaneous phase of this analytic signal is estimated.

Abstract: In connection with blind source separation, proposed herein, inter alia, are: expectation-maximization equations to iteratively estimate unmixing filters and source density parameters in the context of convolutive independent component analysis where the sources are modeled with mixtures of Gaussians; a scheme to estimate the length of unmixing filters; and two alternative initialization schemes.

Abstract: A system for determining a composite signal level at which a signal path begins to generate non-linear distortion. A reference test signal, which is preferably a short-duration burst of repeatable broadband energy, is passed through the signal path and received on a digital signal acquisition unit. An impaired received reference test signal is comprised of the transmitted reference test signal, linear distortion components, and non-linear distortion components. The impaired received reference test signal is digitally processed to reveal the non-linear distortion components. The impaired received reference test signal may be processed with a stored reference test signal to find a time-domain impulse response from which the uncorrelated distortion energy can be measured.

Abstract: The present invention provides a measurement system and a method of determining characteristics associated with a waveform that compensate for distortion associated therewith. In one embodiment, the measurement system includes a monitoring device that detects distortion in a waveform propagating along the transmission medium. The measurement system further includes a computational subsystem that generates a precompensation signal and precompensation value as a function of the distortion in the waveform. The precompensation value substantially compensates for the distortion when inserted into the waveform as a function of the precompensation signal.

Abstract: A distortion reduction system uses upstream signal information from carrier frequencies in a signal to be amplified, to determine at least one frequency for the distortion generated by an amplifier amplifying the signal. A sample of an output is taken, and a distortion detection circuitry is used to detect the amplitude of the distortion at least at the one frequency. In response to the amplitude of the distortion at the one frequency, the processing circuitry provides gain and/or phase control signal(s) to adjust the relative phase and/or gain between combining distortion products to reduce the amplitude of the distortion.

Abstract: An inversion in-phase component and a non-inversion in-phase component of a modulation signal inputted from a quadrature modulation section of a sample machine captured in a pair of signal lines, and an inversion quadrature component and a non-inversion quadrature component of the modulation signal, are computed by a pair of computers, respectively. In addition, these components are analog/digital converted at a pair of analog/digital converting sections, and then, are stored in a waveform storage memory. A modulation characteristics analyzing section performs predetermined computation processing of the storage data, thereby analyzing modulation characteristics of the modulation signal. A balance/imbalance switching section is provided at each one of the pair of signal lines, and the signal lines are grounded, whereby a state for transmitting a modulation signal of a balance transmission format is switched to a state for transmitting a modulation signal of an imbalance transmission format.

Abstract: The present invention, generally speaking, provides a method and apparatus for accurately measuring a communications signal. In accordance with one aspect of the invention, DC offset effects and nonlinearities attributable to a communications amplifier are made spectrally separable from DC offset effects and nonlinearities attributable to the measurement apparatus. Spectral separability may be accomplished, for example, by adding an offset frequency to a local oscillator used by a downconverter of the measurement apparatus. As a result, the signal of interest is moved away from baseband (zero frequency) to the offset frequency. Similarly, other nonlinearities in the video amplifier (such as third order distortion) manifest theselves mostly at harmonics of the offset frequency. Hence spectral separability between the power amplifier characteristics and these nonlinear impairments of the measurement system is achieved.

Abstract: A test system for measuring a frequency response of a signal path 148 by transmitting a short duration burst test signal 234 from a remote point 152, capturing an impaired burst test signal 432 on a digital signal acquisition unit 416, and analyzing the received signal by digitally processing it with an unimpaired burst test signal 434. A dynamic range test can also be performed with the same burst test signal by removing the energy in a part of the frequency band with a notch filter 232, and then increasing the power of the burst test signal level until non-linear distortion occurs. The distortion products will fill-in the notch, allowing the clipping threshold of the signal path to be measured. A burst trigger signal 244 generated by the transmitter device 201 causes a digital signal acquisition unit to acquire an impaired burst test signal.

Abstract: Frequencies fx between the measurement harmonic (mth-degree harmonic) and the (m±1)th-degree harmonics are determined from an expression of fx=(fs*m)±{(fs/n)*k)} where n and k are each an integer. Currents of inter-harmonics of the frequencies fx above and below the measurement harmonic are injected into an inject point in a power system in n cycles of the fundamental wave. Voltage at the inject point based on the injected currents and currents at least either upstream or downstream from the inject point are measured. Admittances for the inter-harmonics above and below the measurement harmonic on at least either the upstream or downstream side from the harmonic inject point are calculated from the measurement results. Interpolation processing based on the calculation results is performed, thereby finding and determining an admittance for the measurement harmonic.

Abstract: A test unit for measuring crosstalk in twisted pair cable. The test unit has an output signal balance (OSB) circuit that compensates for parasitic capacitance at its output terminals. The OSB circuit has a voltage controlled capacitance connected in circuit with each output terminal to control the effective capacitance between the output terminals and ground. The bias voltage for the variable capacitances is calibrated by a method in which the voltage for one of the variable capacitors is held constant while the voltage for the other capacitor is varied in voltage levels. A test signal frequency sweep is applied to the test unit output terminals. First and second voltage values are obtained and a final bias voltage value is calculated from using these two values.

Abstract: A system that utilizes a reference signal for testing signal paths for complex frequency response (linear distortion), and non-linear distortion. This reference signal, which is also known as a ghost canceling reference signal or a training waveform, has excellent properties for channel characterization. The reference signal is a waveform that operates for a major time interval that is subdivided into multiple minor time intervals. During each minor time interval, a sine wave oscillates at a constant angular velocity or frequency. The sine wave frequency may take uniform steps between the minor time intervals, or it may skip a group of frequencies. The phase of the waveform may optionally be continuous between the end of one minor time interval and the start of the next minor time interval. This waveform is generated by loading the time sample values from a digital memory into a digital to analog converter (D-A), or by rapidly reprogramming a numerically-controlled oscillator.

Abstract: A non-contact probe provides information as to relative amplitudes of harmonics of a current or voltage waveform as well as total harmonic distortion. The probe includes a non-contact sensor with an amplifier coupled thereto. Output signals from the amplifier are digitized and analyzed in a programmed processor. Output from the processor provides a display of relative harmonic amplitudes as well as an indicator of total harmonic distortion.

Abstract: A method employed in a condition monitoring unit (CMU) for monitoring a circuit breaker or interrupter to obtain a substantially undistorted version of a waveform suffering from saturation distortion comprises employing a current transformer (CT) to measure a current waveform. The output of the CT is prone to be a partially distorted waveform. The invention is generic in the sense that it does not require parameters associated with the CT characteristics or with the burden impedance on the secondary side of the CT. A digital representation of the partially distorted waveform is obtained, and then undistorted portions of the partially distorted waveform are identified by comparing the amplitude of the partially distorted waveform within a sliding window to a pair of boundary values and identifying as undistorted those portions having an amplitude between the boundary values. Next, distorted portions of the waveform are separated from the undistorted portions, thereby yielding a data record with holes.

Abstract: A non-contact probe provides information as to relative amplitudes of harmonics of a current or voltage waveform as well as total harmonic distortion. The probe includes a non-contact sensor with an amplifier coupled thereto. Output signals from the amplifier are digitized and analyzed in a programmed processor. Output from the processor provides a display of relative harmonic amplitudes as well as an indicator of total harmonic distortion.

Abstract: A method and apparatus for fast response and distortion measurement of a signal transfer device. A computer processor generates a multitone test signal of predetermined duration and stores it in a memory. The test signal is read out, converted to analog form, if necessary, and applied to the input of a device under test. The output produced by the device under test in response to the test signal is acquired and digitized, if necessary, and a Fast Fourier Transform is performed on the acquired data to determine its spectral characteristics. Frequency response, harmonic distortion, intermodulation distortion, phase distortion, wow and flutter and other signal transfer characteristics are measured by the CPU by analysis of the output signal.

Abstract: An RF power amplifier distortion measurement system measures amplitude and phase distortion of a microwave/RF power amplifier by phase quadrature down-conversion of each of an RF amplifier's input signal and amplified output signals to baseband in-phase (I) and quadrature (Q) components, and performing RF amplifier distortion measurements on these down-converted baseband I and Q signals. The derived error measurement signal is remodulated to RF by phase quadrature up-conversion circuitry to produce an up-converted RF signal that corresponds to the RF distortion component contained in the RF output signal produced by the RF power amplifier.

Abstract: A circuit to discriminate the source of harmonic distortion of the output voltage comprises voltage sensors coupled to the output terminals of a source of electric power and to a point of regulation remote from the source for sensing the output voltage waveform present at each of these locations. The circuit then utilizes these two sensed waveforms to discriminate the source of any harmonic distortion between the source of electric power and the utlization equipment. This circuit calculates the percentage total harmonic content of each of the sensed waveforms, and compares them to determine the source of distortion. If the percentage total harmonic content sensed at the point of regulation is greater than that sensed at the terminals of the source of electric power, the source of distortion is discriminated to be the utilization equipment; otherwise, the source of distortion is identified to be the source of electric power.

Abstract: A method and apparatus for fast response and distortion measurement of a signal transfer device. A computer processor generates a multitone test signal of predetermined duration and stores it in a memory. The test signal is read out, converted to analog form, if necessary, and applied to the input of a device under test. The output produced by the device under test in response to the test signal is acquired and digitized, if necessary, and a Fast Fourier Transform is performed on the acquired data to determine its spectral characteristics. Frequency response, harmonic distortion, intermodulation distortion, phase distortion, wow and flutter and other signal transfer characteristics are measured by the CPU by analysis of the output signal.

Abstract: A pulse-based LAN cable test instrument that processes time-domain cross-talk measurement information in order to troubleshoot and quickly locate sources of cross-talk as a function of distance along the LAN cable system is provided. A pulse-response time record between a pair of transmission lines of the LAN cable system is first acquired. A series of steps to process the time-domain pulse response data in the time record are then performed to enhance the ability of the user to locate and troubleshoot the primary contributors to NEXT along any point of the LAN cable system. The pulse response data are first normalized as a function of distance from the LAN cable test instrument in order to compensate for losses along the LAN cable. Next, the pulse response data are integrated over the time record and the absolute value of the pulse response data is calculated to more clearly show the individual sources of cross-talk within the overall LAN cable pulse response.

Abstract: Wow and flutter of a tape player is measured by playing a recording of a constant frequency test tone, digitally sampling and storing each period of the tone over a test interval, subtracting the average period from each period to obtain deviation data, calculating the FFT of the deviation data, and then calculating power magnitude and wow and flutter. The apparatus includes an interface board which squares the signals from the player, and a desktop computer having a timing board for gating a counter for each square wave pulse to sample the periods, a memory for storing the samples, and a CPU programmed to analyze the samples according to the test method.

Abstract: A spectrum analyzer (10, 70) employs a method of reducing the amplitude of harmonic and spurious signals (102, 104, 112) introduced into a frequency-domain output spectrum by, for example, nonlinearities in a mixer (12, 78) or an ADC (20, 92). The method employs acquiring and digitizing a normal time-domain data record of an input signal, transforming the time-domain data record to a normal frequency-domain record (30), and storing the normal record. Next, a local oscillator (14, 76) driving the mixer is frequency shifted, and an additional time-domain data record is acquired, digitized, transformed, and stored to produce a shifted frequency-domain data record (40). Then, the shifted data record is mathematically realigned (50) with the normal data record and the normal and realigned data records are combined to produce a frequency-domain data record (60) having reduced harmonic and spurious signal amplitudes.

Abstract: A analog calibration signal including at least one frequency component is generated by a very pure signal source, such as a digital oscillator and a digital-to-analog converter (DAC) that has been calibrated to be ultralinear. The analog calibration signal is converted by an analog-to-digital converter (ADC) to a digital signal. The digital signal is digitally compensated in accordance with compensation coefficients to produce a compensated digital signal. The compensated digital signal is digitally processed to isolate and measure distortion components, and the compensation coefficients are adjusted in response to the distortion components in order to reduce the distortion components. Feedback causes the distortion components to be minimized so that the compensation coefficients correct the nonlinearity in the analog-to-digital converter.

Abstract: Abnormal changes in the non-linear characteristics of electronic components are an indication of abnormal conditions such as impending component or system failure. To detect such abnormal changes in nonlinearity, an electronic circuit is subjected to a calibration signal including at least one frequency component. Nonlinearity in the electronic circuit causes distortion components to be generated from the calibration signal. Preferably the nonlinearity is characterized by compensation coefficients that digitally compensate the nonlinearity. The compensation coefficients are adjusted in a feedback loop in response to measured values of the distortion components, so that the distortion components are minimized. At the end of the adjustment process, the transfer function of the electronic circuit is specified by the compensation coefficients, which are stored in memory.

Abstract: A cable crosstalk measurement system provides fault diagnostic information to locates faults in addition to providing a crosstalk versus frequency function to test and troubleshoot LAN cables. In a preferred embodiment, a narrow pulse is introduced into one twisted pair of a standard LAN cable, and another twisted pair in the same cable is monitored for crosstalk signal coupling. A measurement system digitizes crosstalk signals using sequential sampling of repetitive signals to provide a waveform record that is a reconstructed equivalent time representation of a real-time crosstalk signal. A microprocessor performs a fast Fourier transform of the waveform record to provide crosstalk versus frequency information, while the waveform record is also examined for higher-than-acceptable amplitude levels to locate poor quality or faulty connectors and cables.

Abstract: A line interface circuit (12.sub.1) having a digital interface (18) and an analog interface (20) coupled to the digital interface by a transmission path (23, 26) may be tested by launching a digital value into the digital interface while the analog interface is terminated by termination impedance (35). The digital value launched into the line interface circuit is converted to an analog signal within the circuit which appears across the termination impedance, creating a voltage that is sensed back on the transmission path. This sensed voltage is convened within line interface circuit back to a digital value for output at the digital interface in response to the originally launched digital test value.

Abstract: A method and apparatus for fast response and distortion measurement of a signal transfer device. A computer processor generates a multitone test signal of predetermined duration and stores it in a memory. The test signal is read out, converted to analog form, if necessary, and applied to the input of a device under test. The output produced by the device under test in response to the test signal is acquired and digitized, if necessary, and a Fast Fourier Transform is performed on the acquired data to determine its spectral characteristics. Frequency response, harmonic distortion, intermodulation distortion, phase distortion, wow and flutter and other signal transfer characteristics are measured by the CPU by analysis of the output signal.

Abstract: A dynamic range tester which simultaneously generates two signals, each of hich is composed of a clean signal plus an excess quantity of independent and isolated random noise is disclosed for use in producing real world signals which can be used to provide a simulated operating environment within which to evaluate the dynamic range or evaluate the processing gain of an electronic or acousto-optic system. The power level of the signal and power level of the noise in each of the two outputs of the dynamic range tester can be independently varied such that a range of signal-to-noise ratios may be set-up in each output.

Abstract: A system for determining a composite signal level at which a signal path begins to generate non-linear distortion. A uses a reference test signal, which is preferably a short-duration burst of repeatable broadband energy, that is passed through the signal path and received on a digital signal acquisition unit. An impaired received reference test signal is comprised of is formed from the transmitted reference test signal, linear distortion components, and non-linear distortion components. The impaired received reference test signal is digitally processed to reveal the non-linear distortion components. The impaired received reference test signal may be processed with a stored reference test signal to find a time-domain impulse response from which the uncorrelated distortion energy can be measured.