Tektronix, Inc.

Glenn Bateman

Richard I Lane

Josef L Mader

Ronald J Bremer

Michael S Overton

Florian Gene Bell

William A Trent

Kevin B McDonald

Donald L Brand

Matthew S Harcourt

Richard E DuPuy, Jr

An instrument for depicting change in the value of a first variable as a function of a second variable comprises a display device for displaying a set of n measured values distributed along a display axis, and a sampler for acquiring a set of N (greater than n) samples of the first variable and storing values of those N samples in ordered fashion relative to a first storage domain that maps to the second variable. A set of n display samples is selected from the set of N stored samples and the values of that set of n display samples are provided to the display device. When the set of n display samples is a set of samples that are at a predetermined spacing in the first storage domain and/or occupy a selected interval of the first storage domain, a set of N1 (greater than n) samples of the first variable are acquired and their values are stored in ordered fashion relative to a second storage domain that maps to the interval of the first storage domain.

Measurement apparatus having improved sample density using nested data

An input signal is sampled by alternately coupling the input signal and a reference level to a sample storage element, whereby the magnitude of the signal stored by the storage element immediately following application of the input signal to the storage element is a function of the input signal magnitude and the magnitude of the signal stored by the storage element immediately preceding coupling of the input signal to the storage element is a function of the reference level.

Sample and hold with intermediate reset voltage outside of the magnitude

A system for expanding a waveform in a measurement test instrument has a display area containing a waveform representative of data acquired by a measurement test instrument and an active movable cursor intersecting the waveform. The system has first and second viewports with the first viewport displaying the waveform in the display area and the second viewport displaying a portion of the waveform from the first view port in an expanded form when the second viewport is in the display area. The second viewport has a center point and dimensions defined in the first viewport with the center point being defined by the intersection of the active movable cursor with the waveform and the dimensions being defined with respect with the center point. The second viewport is movable within the first viewport as a function of movement of the cursor. Means are provided for varying the dimensions of the second viewport about the cursor/waveform intersection when the first viewport is in the display area and for further expanding the waveform in a continuous manner about the cursor/waveform intersection when the second viewport is in the display area. Means are provided for replacing the first viewport with the second viewport in the display area.

Expansion windowing system for a measurement test instrument

An improved optical time domain reflectometer, OTDR, has a reference fiber interposed between an optical coupler and a front panel connector for acquiring a reference backscatter level that is independent from a fiber under test. The reference level is used to determine the quality of the front panel connection between the OTDR and the fiber under test and for verifying and adjusting transmitter and receiver circuitry in the OTDR. The reference fiber also allows the acquisition of front panel connector reflection data when a Bragg Cell is used as the optical coupler.

Optical time domain reflectometer having pre and post front panel

A method of normalizing fiber-optic loss measurements for wavelength uses a measured wavelength for a laser, a desired wavelength for the loss measurement, and a characteristic parameter for the fiber optic cable to perform a first order correction of the Rayleigh scattering from the fiber optic cable. The actual loss is measured using the laser and then corrected to produce the equivalent loss at the desired wavelength according to the equation

Wavelength normalization of fiber-optic loss measurements

An optical time domain testing instrument comprises a laser light source that is optically coupled to an optical fiber under test. The instrument further comprises a photodetector for receiving light from the fiber, and an optical amplifier optically coupled between the fiber and the photodetector.

Optical time domain testing instrument

A logarithmic amplifier includes a first diode wherein the anode receives an input signal input signal current and a standing current. The cathode of the first diode is coupled to the emitter of a PNP transistor. The collector of the PNP transistor is coupled to the anode of a second diode. A bias current is added to the emitter and substracted from the collector of the PNP transistor to provide a lower emitter impedance. The cathode of the second diode is coupled to a negative supply voltage through a load resistor. A feedback network including an emitter coupled pair of NPN transistors samples the voltage at the anode of the second diode and sinks a current from the base of the PNP transistor. The voltage at the anode of the first diode is amplified to provide a logarithmic output voltage. The output voltage may be attenuated and applied to the base of the PNP transistor.

Logarithmic amplifier with gain control

A digital time base with analog interpolation provides a variable reference voltage to assure that the period of an analog ramp between a zero value and a maximum value is equal to the time interval between range clock pulses. A time base error is determined by establishing a zero reference level on a test pulse rising edge corresponding to the zero value of the analog ramp, and then establishing a maximum level on the test pulse corresponding to the maximum value of the analog ramp initiated one clock pulse prior to the test pulse. The difference between the two levels on the test pulse represents the time base error. A microprocessor provides a corrected reference voltage as the maximum value so that the maximum delay of the analog ramp equals the time interval between clock pulses.

Digital time base with corrected analog interpolation

Non-linear amplifier systems for repetitive signals

A non-linear amplifier system comprises two amplifier stages, a limiter and correction stage and a combining stage. The first amplifier stage amplifies low input signal levels linearly and higher input signal levels non-linearly. The limiter and correction stage amplifies linearly input signal levels corresponding to low input signal levels of the first amplifier stage. The second amplifier stage amplifies non-linearly input signals corresponding to low input signal levels of the first amplifier stage. The combining stage combines the output voltage signals of the first and second amplifier stages and the limiter and correction stage. For a range of low input signal levels, the output voltage signal of the combining stage is representative of the output voltage signal of the second amplifier stage, for a range of high input signal levels, the output voltage signal of the combining stage is representative of the output voltage signal of the first and second amplifier stages, and for a crossover range of input signal levels, which is intermediate the low range and the high range, the output voltage signal of the combining stage is representative of the output voltage signal of the second amplifier stage.

Non-linear amplifier systems

A non-linear amplifier circuit that may be used to provide a logarithmic amplification characteristic. The circuit includes an amplification stage employing positive non-linear feedback for low level input signals to reduce the input capacitance of the amplifier. For large level input signals the feedback is eliminated.

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Redmond, OR, United States of America

Glenn Bateman