Arthur Pini

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Consultant

I am a technical support specialist and electrical engineer with over 50 years experience in the electronics test and measurement industry. I have supported oscilloscopes, real-time spectrum analyzers, frequency synthesizers, digitizers and arbitrary waveform generators for leading manufacturers.


Arthur Pini

's contributions
  • 10.27.2016
  • Digital oscilloscopes: When things go wrong
  • Hello Joan, Thanks for your interest in the article and your comment. In my experience scopes with bandwidths of 1 GHz or lower generally still have a single pole Gaussian response (BW=0.35/Tr). Higher bandwidth scopes use DSP to achieve flat or 'brickwall' responses(BW=0.45/Tr). Teledyne LeCroy scopes, with which I have the most experience, offer the user a selection of time domain responses. The Teledyne LeCroy WaveMaster series provides responses that optimize Pulse Response, or maximum Flatness. Quotes from the User Help for the optimize function: "A group delay compensation minimizing preshoot, Pulse Response most resembles the response of an analog oscilloscope by controlling group delay to be slightly non-zero at the highest frequencies. In addition, a fourth-order Bessel frequency response is implemented. Eye Diagram is a flat group delay compensation resulting in equalized preshoot and overshoot. This selection improves the symmetry of serial eye diagrams. In addition, a fourth-order Bessel frequency response is implemented. Flatness is a flat group delay compensation with a brick-wall frequency response. While this provides the fastest rise time, there is also a slight penalty of more preshoot and overshoot compared to Eye Diagram mode. This selection is most often used in narrow-band RF measurements where it is desired to maintain constant magnitude response over the oscilloscope passband. " So the user can select the best response to match the application Art
  • 10.27.2016
  • Digital oscilloscopes: When things go wrong
  • Hello GS, I would be happy to answer your questions but need a venue which supports graphics. Please contact me at arthurapini@gmail.com and give me your e-mail address. Thanks Art
  • 09.29.2016
  • FFTs and oscilloscopes: A practical guide
  • Hi Jim, Appreciate your comments. You do have the best of both worlds with an RF spectrum analyzer and an FFT. My home lab has an old LeCroy LT342 scope (purchased at a LeCroy internal auction) which does include FFT. I had to leave my RF spectrum analyzer behind when I moved from NY to FL. You can digitize the IF using a PCIe based digitizer. Most digitizers offer support software with FFT capability. I have used digitizers from Spectrum Instrumentation (http://spectrum-instrumentation.com/en ) along with their SBench 6 software. The software is free if you want to give it a try. Art
  • 09.29.2016
  • FFTs and oscilloscopes: A practical guide
  • Greetings, Thanks for your interest in the article. The frequency domain averaging used in most scopes is based on averaging the power at each frequency. This is done by averaging the magnitude squared (power) and then taking the square root to present average magnitude. It is similar to what you describe in the RF spectrum analyzer. The scope used in this article is a Teledyne LeCroy WaveRunner , which offers FFT output formats in power spectrum, power spectral density, magnitude, magnitude squared, phase, real, and imaginary. Any of these formats can be averaged, so it is possible to average the real and imaginary FFT output components to obtain a 'vector' average. This type of average would require a stable synchronous trigger for any meaningful output. It is also possible to average the phase component but the result is difficult to interpret because the phase only has meaning at frequencies where the signal has significant components and at the other frequencies it only has random phase values. As Michael has mentioned most scopes can average in the time domain and/or the frequency domain so it is a users choice as to what will accomplish the desired measurement goals. Art
  • 04.07.2016
  • Oscilloscope tricks 21 to 30
  • Greetings tominsr, Thanks for our interest in the articles. If you click on the links '10 Tricks that extend oscilloscope usefulness' or '10 More tricks to extend oscilloscope usefulness' above they will bring up the first two articles. Art
  • 03.02.2016
  • Create a stimulus-response system with an AWG and digitizer
  • Hi Steve, Thank you for your comment. I looked at the specifications for the J2150A and, being an impulse generator, it would be an alternative for the swept sine in making the frequency response measurement on the filter. The digitizer/AWG combination used in this article was a Spectrum M4i.4451-x8, 500 MS/s, 250 MHz, 14-bit digitizer and an M4i.6631-x8, 1.25 GS/s, 400 MHz, 16 bit, arbitrary waveform generator. The AWG has the advantage of being able to create a almost limitless range of waveforms. So for the other applications like the quadrature signal generation and replay of the waveform captured by the oscilloscope it is a better choice. Regards Art
  • 12.10.2015
  • Measure frequency response on an oscilloscope
  • Hi Jim, I used to work for Nicolet Scientific back in the 70's and early 80's. They designed and manufactured real time spectrum analyzers, the precursors to the SR780. Stanford Research does a good job getting the cost out of instruments. After that I went on the scopes, arbitrary waveform generators and digitizers. Art