From: Wiz [mailto:[email protected]] Sent: Thursday, February 12, 2004 7:37 AM To: EMC Forum Subject: High Frequency Measurements
Hello, I have a need to make radiated measurements up to 40 GHz. I uses a low loss cable that gives me enough dynamic range up to 18GHz. The cable is very short and I have to move my measurements equipment out to the antenna. I know I need to get a pre-amp and mixer, but what do I do about the cable loss? I have called many places and I cannot find good enough cable to measure to 40 GHz. The other alternative is waveguides as I understand. Those would, I assume, be coupled directly to the input of the mixer. This does not allow for antenna height adjustments form 1 to 4m as required. I have seen other test reports where high frequency data was taken where the antenna was held at about 1meter. I can understand this since emissions will likely be very directional at those frequencies. Is it acceptable to make measurements with the receive antenna at 1 meter only? Thanks for any information you can provide... Wiz Wiz: I use United Microwave coax up to 18 GHz. Above 18 GHz, I use HP-11970A and 11970K waveguide mixers. These mount directly to the horn antenna waveguides. My HP-8562A analyzer provides a LO output to each mixer, and receives back a IF. Both the LO & IF are low enough to allow me to use the United Microwave cable there too. About the only way this setup could be better would be to add a waveguide amplifier between each horn and mixer pair. (I assume you know that you can obtain flexible waveguide, although it is quite expensive.) I use this in the military test scenario, where the test antenna does not need to be moved, and the test specimen to antenna test distance is 1 meter. It would be interesting to see if there is any benefit in moving your measurement antenna more than a few feet vertically when doing OATS testing between 18 GHz and 40 GHz.. Ed Ed Price [email protected] WB6WSN NARTE Certified EMC Engineer & Technician Electromagnetic Compatibility Lab Cubic Defense Applications San Diego, CA USA 858-505-2780 (Voice) 858-505-1583 (Fax) Military & Avionics EMC Is Our Specialty This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ieee-pses.org/ To cancel your subscription, send mail to: [email protected] with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: [email protected] Dave Heald: [email protected] For policy questions, send mail to: Richard Nute: [email protected] Jim Bacher: [email protected] All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
