Forwarded for Marvin ____________________Reply Separator____________________ Subject: 1-10GHz source Author: "Wolak; Marvin" <marvin.wo...@marconi.com> List-Post: emc-pstc@listserv.ieee.org Date: 6/7/00 2:47 PM
A few weeks ago, there was some interest about references sources above 1 GHz. A few months ago I got tired of trying to find a source and made one myself. After some experimentation with batteries, I came up with a source which emits from 250 MHz through 10 GHz. The source emits the harmonics of 250 MHz. The source is stable to about 0.3 dB over the charge of the batteries which is from 12 to 22 hours depending on how they were charged. The field produced by the source, as tested at 3 m, is from approximately 68 dBuV/m to 85 dBuV/m in the range of 1 to 10 GHz. If anyone would like to see plots or stability graphs, let me know. If the response is overwhelming, I'll post it. Basically, what I came up with is as follows: The box is a simple aluminum project box, a circuit described below, 8 NiMh batteries (rechargeable), and a built in charger. The circuit was put together on a circuit board using a Radio Shack etch kit. A 250 MHz oscillator feeds directly into a Herotek 250 MHz comb generator. The output of the comb generator is put through a 10 dB attenuator and then connected to a sma bulkhead connector using a short coax jumper cable. The antenna is a sma m-f barrel with a wire attached to the center conductor. A case from a ballpoint pen was screwed onto the barrel to protect the wire. I tapped out the end of the pen case so the connector would screw on. Can't remember the manufacturer of the oscillator. The comb generator from herotek, (http://www.herotek.com/), has removable sma connectors on the input and output. I removed the input sma and connected it directly to the oscillator output. All in all, the circuit draws 173 mA. The power for the above is regulated by a 5V regulator with some simple power decoupling and diode protection. The first pass used AA alkaline batteries. This provided for only about 6 hours of operation. The second pass was with 6 C rechargeable alkaline batteries. This provided for about 14 hours of operation but the source stability was poor. The output at some frequencies would increase 2-4 dB over the life of the charge. Another drawback was that the batteries had to be removed to charge. I've since replaced the alkaline batteries with 8 Panasonic NiMh batteries. This has solved my stability problem (I can live with 0.3 dB variability). To charge the batteries a bought a MaHa battery charger, disassembled it, and mounted its circuitry in my box. The switchover from the load of the circuit to the charger is done through the main double pole-double throw switch. If I had to do it over, I would start from the power side. The NiMh batteries are not the best choice for a few good reasons but that was what I was stuck with if I was to keep the same box. Lead acid may be a better choice, but would require a larger project box, something like the popular EMCO Royce field source. I would be interested in feedback. There is plenty of room for improvement, and lots of talent on this board. If you have any questions, or if something is unclear, let me know. Marvin Wolak Marconi Communications Senior EMC Engineer, Product Integrity Ph: 724-742-7453 Fx: 724-742-7474 EMail: marvin.wo...@marconi.com ------------------------------------------- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Jim Bacher: jim_bac...@mail.monarch.com Michael Garretson: pstc_ad...@garretson.org For policy questions, send mail to: Richard Nute: ri...@ieee.org
