Let's Get History Right

I enjoyed reading your "Microwave Memories" column in the March Microwaves & RF, until I got to the last paragraph describing the near-palm-sized newly released varactor diode circuit.

For your information, the "circuit" is not a circuit at all. It is a tray or carrier containing a 10 x 10 array of varactors, each about 0.1 in. in diameter and maybe 0.1 to 0.15 in. in length. The diodes were shipped in carriers like these. Today's chips ship in similar waffle packs.

Whereas today's larger digital chips could easily completely cover a penny, you could put at least eight of these varactors on a dime. Compare one of the 100 diodes with the size of the gentleman's finger to get an idea of their true size. Thus, microwave components built with these diodes would be no bulkier than many of today's designs.

However, today's designs might perform better. This is because parasitic reactances introduced by the varactor package degraded bandwidth over what can be achieved today with MMIC and MIC chip and wire technologies. Fortunately, the parametric amplifiers that you mentioned were sent packing by GaAs FET amplifiers in the mid-1970s.

My suggestion to you is to ask a grizzled veteran to verify your facts before you get letters from old timers like me who designed microwave VCOs using similar TI varactors in 1968. By the way, several of these oscillators would easily fit in the gentleman's palm.

Keep up the good work.

John Eisenberg
John A. Eisenberg and Associates
Los Altos, CA

What a pleasure it was to get your letter; thank you so much for writing! I apologize for misrepresenting the varactor diode in our February issue. Not being in the microwave industry at that time, I made the mistake of thinking the terminology in the ad was the same as it was today. Luckily, folks like you are out there to set me straight. In fact, we're putting together our 50th anniversary issue for November, and we would love to have some feedback from folks from the industry's early days. If you or your peers would have any desire to contribute, please let me know.

Nancy Friedrich,

In the April Design Feature "Fractal Microstrip Antenna Aids Wideband Application," we incorrectly spelled the author's name as "Abolfazi Azari." In fact, the correct spelling is "Abolfazl Azari." We sincerely apologize for the error.

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