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Military Microwaves Supplement
Recent Advances in Radar Technology
Using Calibration to Optimize Performance in Crucial Measurements
Published September 28, 2006
From: Qing Sun, University of Manchester
The bandwidth of a coupler is not a function of coupling factor and even/odd mode impedances. It is related to the type of coupler. For quarter-wave coupled line couplers the normal acceptable bandwidth is one octave (2:1) regardless of coupling factor. This bandwidth can be increased to as much as 25:1 by adding additional sections and cascading coupling sections. There are a number of design examples in Chapter 5 of my book Stripline Circuit Design, H. Howe, Artech House, 1974, ISBN#0-89006-020-7.
From: Ahmed Boutejdar, Universittat Magdeburg
We have seen a number of papers recently with DGS structures and good results; however, none of them have explained how to calculate the characteristics. They have been created using computer synthesis or by empirical techniques (design by fooling around).
From: Yong-Sub Lee
I am sorry but we do not do market research so I cannot answer your question. There are companies that specialize in market studies; however, their reports tend to be very expensive ($5000 to $20,000) and we do not buy them.
From: Hyun-Chul Park, Shungkjem Kwan University
While there are generic models for most devices, they are only as good as the device parameters provided by the manufacturers or measured by the user. There is a good section on device modeling in RF and Microwave Semiconductor Device Handbook, M. Golio, CRC Press, 2003, ISBN#0-8493-1562-X.
From: Kim Sang-Gyu, Integrated Technologies
I do not know of any general specification for UWB group delay. The major problem appears to be with delay spread due to multi-paths. There is an extensive discussion of delay spread in Ultra-wideband Radio Technology, Siwiak & McKeown, Wiley, 2004, ISBN#0-470-85931-8.
From: A. Kumar, Microwave Associates
Dear Mr. Kumar,
The even and odd mode impedances are the impedences between coupled lines for an unbalanced transmission system such as stripline. Common mode and differential mode impedances are related to balanced lines such as two wire lines. There is a discussion of even and odd mode impedances and methods of calculating them in Chapter 4 of my book Stripline Circuit Design, H. Howe, Artech House, 1974, ISBN#0-89006-020-7.
From: Majid Haghighat, Isfahan University of Technology
I have not seen anything written on this subject. Since heating requires the absorption of energy and pipelines tend to be very long, it is unlikely that sufficient energy could be distributed to do the job without creating a hazard.
From: SH Wong, Agilent Technologies
Dear Mr. Wong,
Video bandwidth is the final information bandwidth after downconversion from the input RF. Why it is called "video" probably dates back to early usage
From: Peter Karuga, ITACS
You will need an additional test antenna, which can be uncalibrated. Set up your measurement with the calibrated and test antennas and then substitute the homemade dipole for the calibrated antenna and compare the results.
From: Mark Kennard, Kencom Electronics
Any of the commercial materials will work at 900 MHz. The most popular materials include Woven Teflon Fiberglass, Microfiber Teflon Fiberglass, Ceramic filled Teflon and FR-4. FR-4 is usable at 900 MHz, but not all of the manufacturers control the dielectric constant. It is the lossiest but is also the least expensive and can be processed by any PCB house. If space is a consideration, the ceramic filled materials have a higher dielectric constant but are the most expensive. My personal preference is the glass filled Teflon products.
Harlan Howe, Jr. received his BS degree in optics from the University of Rochester in 1957. He has been actively engaged in the microwave industry for 48 years, first as a design engineer and then as an engineering manager. In 1990 he became the publisher/editor of Microwave Journal. He retired as publisher in 2001, but remains the editor. He is a Life Fellow of IEEE, past president of MTT-S and the recipient of an IEEE Third Millennium Medal in 2000 and the MTT-S Distinguished Service Award in 2005.
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