Robert Gilchrist Huenemann, M.S.E.E.
June 29, 2015
My intellectual property involves electronic measurement methods. The first of these original ideas has been referred to as modulation domain analysis or phase digitizing. The idea was unrecognized before my use of it in the Hewlett Packard HP9540A automated transceiver test system.
Period mode frequency counters had been used to measure the deviation of a frequency modulated waveform by capturing random period measurements and storing the high and low values. I saw that it was possible to capture a measurement of every period, and thus to reconstruct all of the frequency modulated waveform. I demonstrated this in a test bed version of the HP9540A, using a pair of HP5326A frequency counters connected ‘back to back’. One took a measurement while the other was being interrogated.
Since the HP9540A product only needed to measure repetitive waveforms, it used a single HP5326A to measure an odd number of alternate periods over two successive cycles of the modulation in such a way that the measurements could be interleaved to reconstruct the entire modulation waveform. My work was described in the August 1973 issue of the Hewlett Packard Journal. It was the basis for the HP5371A frequency and time interval analyzer, which appeared in 1988. Later, other vendors introduced related instruments. The latest versions of such instruments use time stamping rather than storing individual period measurements.
My second original idea was to use Fourier analysis to recover bearing angle information from a Very High Frequency Omni Range (VOR) radio navigation signal. The VOR system is limited to an accuracy of a few degrees by its antennas, and by the propagation characteristics of radio waves. However, it is desirable to check the calibration of VOR test equipment to a higher degree of accuracy.
I demonstrated that it is possible to achieve essentially arbitrary accuracies by taking enough samples of the waveforms with sufficient resolution. I showed that accuracies of millionths of a degree were possible – far beyond what is needed in any actual application. This work was described in the Journal of the Institute of Navigation, in the Spring 1984 issue (vol. 31 no. 1).
Finally, I was the first to successfully implement an automated selftest of a Nuclear Magnetic Resonance system, in 1990.
All of these methods involve the automated control of measurement instruments by computers. I was fortunate to be working in this field in its early days. I am intensely proud of the fact that I was able to conceive, develop and demonstrate these very different measurement methods.
I made some of these inventions during a time when the United States Patent Office refused to patent anything that involved software. Their position has been reversed, but too late to do me any good. And now VOR is being augmented by the Global Positioning System. But I have no complaint. I spent some 55 years working with electronics, and I earned a decent living and a comfortable retirement. And much of my work was very satisfying.
One last thought. Automatic test equipment was inevitable. But with its advent, one test system could replace many manual test stations. This must have had a profound effect on the instrument business. I would guess that it influenced HP’s decision to spin off Agilent, and that it negatively impacted the sales of all of the other instrument vendors as well.