Tektronix, Inc.

Picosecond Pulse Labs

Agoston Agoston

Steven H Pepper

John Ebner

David W Pratt

John E Carlson

Stanley P Kaveckis

Robert Norton

Cornelis T Veenendaal

Laszlo J Dobos

George J Caspell

John B Rettig

Andrew E Finkbeiner

Robert G Sparkes

An ultrafast sampler includes a series of Schottky diodes configured with a coplanar waveguide to form a nonlinear transmission line (NLTL) that compresses a local oscillator input to form a series of strobe pulses. Strobe pulses of opposite polarity are capacitively coupled to sampling diodes to obtain samples of a signal applied to a signal input. The samples are directed along an intermediate frequency waveguide to, for example, a signal processor such as an oscilloscope, for storage and analysis. The intermediate frequency waveguide is configured so that conductors of the intermediate frequency waveguide receive signal samples of a common polarity and strobe samples of opposite polarities so that portions of strobe pulses delivered to a signal processor are distinguished from signal samples. In an embodiment, the intermediate frequency waveguide and the strobe waveguide are symmetrically situated along a common axis, and conductors of the strobe waveguide are positioned between the axis and the conductors of the intermediate frequency waveguide. The sampling circuit is defined on a GaAs substrate and a coaxial-to-airline-to-substrate transition is configured to deliver signals from a coaxial cable to the sampling circuit. A signal output is configured to direct the signal back into a coaxial cable.

Ultrafast sampler with coaxial transition

An ultrafast sampling system includes an interposer and a sampler that include series of Schottky diodes configured with a non-parallel waveguide to form shocklines or nonlinear transmission line (NLTLs) that produce a differential strobe pulse. The shocklines are defined by non-parallel conductors that are configured as, for example, triangular, dentate, arcuate, or other shapes, or as conductors that have edges that are triangular, dentate, arcuate, or the like. The conductors are defined with respect to a substrate, and are airbridged so that at least some portions of the conductors are displaced from the substrate to reduce waveguide capacitance. Electrical connection to the sampler is made with airline having a inner conductor that is deformable to contact an input pad defined on the sampler.

Ultrafast sampler with non-parallel shockline

A time base circuit for a waveform sampling system produces a strobe signal for initiating waveform sampling an adjustable strobe delay time following detection of a triggering event in a waveform. The time base circuit includes a strobe control circuit for producing the strobe signal and a strobe sense signal in response to a strobe drive signal, a strobe drive circuit for generating the strove drive signal, an adjustable time after a trigger signal, and a trigger generator for producing the trigger signal in selective response to either the triggering event in the waveform or the strobe sense signal. The strobe signal delay time is calibrated by setting the trigger generator to produce the trigger signal in response to the strobe sense signal thereby causing the strobe drive circuit to generate the strobe drive signal periodically. A period timer measures the period between successive strobe drive signals and a microprocessor adjusts the delay time of the strobe drive circuit so that the period between strobe drive signals is equal a predetermined delay time.

Programmable sampling time base circuit

A control circuit produces a control voltage for a tunable delay line in response to the magnitude of digital input data. The magnitude of the control voltage output corresponding to any digital input magnitude is independently adjustable to compensate for any nonlinear response of the delay to control voltage input such that the time delay produced by the delay line is substantially a linear function of the digital input to the control voltage source.

Linearity correcting control circuit for tunable delay line

A pulse generator utilizes a pair of current sources acting through a pair of Schottky diode switches to provide load currents in opposite directions through a load resistor to produce an output voltage across the load resistor of magnitude proportional to the difference between the load current magnitudes. The pulse generator output voltage is abruptly driven to zero potential by applying balanced, rapid slewing voltage pulses to the Schottky diode switches, causing the switches to simultaneously divert the load currents from the load resistor. The balanced voltage pulses are developed at the terminals of a step-recovery diode by switching the step-recovery diode from forward to reverse bias state.

Fast transition, flat pulse generator

A dual channel time domain reflectometer includes a pair of input lines connected at respective nodes to a reference flat current pulse generator and a traveling wave sampling gate, respectively. The sampling gates are actuated by a balanced strobe generator which includes a waveguide coupler for coupling a high amplitude fast rise time pulse to each of the gates simultaneously. Pulses of requisite amplitude and shape are generated by a circuit responsive to a strobe trigger input which drives a step recovery diode.

Dual channel time domain reflectometer

A tracking sample and hold phase detector operating as an error sampled feedback loop which takes signal samples during successive periods of an input signal with a sampling gate, holds the signal sample in a storage gate, and feeds back the sample to the sampling gate to allow the bias of the sampling gate to track the input signal level, thereby maintaining balance of the tracking circuit. A fast comparator detects the zero crossing level of the downconverted signal which is comprised of successive signal sample steps and has the shape of the input signal. The sampling gate comprises a diode bridge enabled by a balanced strobe, the input signal and the strobe being close or equal in frequency, the frequency of the downconverted signal being the difference frequency.

Tracking sample and hold phase detector

A reverse current transmitted through an initially forward biased step-recovery diode causes the step-recovery diode to switch from the forward biased state to a reverse biased state, thereby developing an abruptly rising reverse bias voltage across the step-recovery diode. The abruptly rising reverse bias voltage is applied across a series combination of a capacitor and a laser diode, connected in parallel with the step-recovery diode to force a short, abrupt forward current pulse through the laser diode, thereby causing the laser diode to emit a short optical pulse.

Laser diode driver

An electro-optic sampler comprises a body of semiconductor material that can be energized to emit polarized light, a photodetector device for generating an electrical output signal representative of the intensity with which light polarized in a predetermined manner is incident on the photodetector device, and a body of electro-optic material defining an optical waveguide for transmitting light from the source of polarized light to the photodetector. First and second electrodes are provided for establishing an electrical field within the body of electro-optic material. The body of electro-optic material has a spherical index ellipsoid when the first and second electrodes are at the same potential and otherwise has a non-spherical index ellipsoid.

Electro-optic sampler

A circuit for generating a succession of fast rising voltage pulses comprises an inductor connected between first and second circuit nodes, a step recovery diode connected between a reference potential level and the first circuit node, and a current switch having a first state in which it conducts current in one direction with respect to the second circuit node and a second state in which it conducts current in the opposite direction with respect to the second circuit node. An oscillator is connected to the current switch for alternately and repeatedly placing the current switch in its first state and its second state. Preferably, the oscillator comprises a SAW resonator having a high Q and a parallel LC tank circuit having a low Q, connected in a closed positive feedback loop.

Comb generators

A programmable delay generator is based upon an asynchronous or ripple counter the stages of which change state at definably different times. A full terminal count is decoded including the condition of a lowest order stage which changes state at a unique time which is different from the time at which any other stage changes, for thereby defining an unambiguous delay period. A partial terminal count programmably determines the length of circuit output and the reloading of the ripple counter with a programmable, time delay determining, initial value.

Low jitter digital delay generator

A lumped-parameter, electrical delay line having shunt capacitance including variable-capacitance diodes. A tuning voltage applied to the diodes provides electrically variable delay at low jitter and stable insertion delay.

Tunable delay line

A digital phase-locked loop circuit for recovering an external clock signal from an input serial data stream includes an up/down counter responsive to both the serial data stream and to the clock pulse output of a variable divider driven by an external clock. The up/down counter counts in a direction which depends upon whether the input data stream leads or lags the variable divider's clock pulse output. The output of the up/down counter drives an n-bit memory and a comparator such that the n-bit memory stores the n most significant bits of the up/down counter for a predetermined period of time and then provides them to the comparator for comparison with the present value of the up/down counter. A binary code is provided to the variable divider to determine its divisor depending upon whether the memory count is greater than, equal to, or less than the present count of the up/down counter. This enables an external clock to be synchronized to the input data stream while removing random noise.

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Beaverton, OR, United States of America

Agoston Agoston