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Using Calibration to Optimize Performance in Crucial Measurements
Published November 13, 2006
From: Hadi Ghazian, Tarbiat Modares University
The power handling of waveguides is a function of dimensions, surface finish, conductivity, dielectric strength of the insulation material (air, etc.), air pressure and the frequency of operation with respect to cut-off frequency. There is a good discussion with design equations in Microwave Engineering-Passive Circuits, P. Rizzi, Prentice Hall, 1988, ISBN#0-13-586702-9. There are also a number of useful charts, including the effect of pressure and gases in Microwave Engineers' Handbook - Vol. 1, T. Saad, Artech House Inc., 1971, ISBN#0-89006-002-9.
From: Omar Timsah, Z Solution
I am sorry, but your question is a communications systems question, which is outside my area of expertise. However, I can suggest two references that may be helpful to you:
From: Muhammad Ahmed, SUPARCO
There is a good discussion of DRO design with a sample layout and design equations in Chapter 5 of RF and Microwave Oscillator Design, M. Odyniec, Artech House Inc., 2002, ISBN#1-58053-320-5.
From: Kathi Vamsi Krishna, RF Arrays Systems Ltd.
The standard technique for suppressing evanascent and higher order modes has been the strategic placement of lossy material in the structure. I do not know of any references on the subject. My personal experience has been by "trial and error" - mostly error.
From: Amr Kenawy, Etisalat - UAE
I do not know. I suspect that it is a function of the type of antennas and the difference in power levels between them. There is a good general discussion on propagation problems that may be helpful to you in Introduction to RF Propagation, J. Seybold, Wiley, 2005, ISBN#10-0-471-65596-1.
From: Shanthi B, Commercial Cellphone Makers
It is the most preferred because it is simple, fast, accurate and the calibration fixtures are relatively inexpensive to make and stable over time.
From: Mark McWhorter, Honewell Space Systems
It is good to hear from you. I hope all is well. When in doubt, Maxwell wins. In his book, High Frequency Techniques, Wiley, 2004, ISBN#0-471-45591-1, Joe White has a symplified discussion of Maxwell's equations, which indicates that they are not in-phase.
From: Robert Patterson, Experimentalist
Considering the size of your cavity, it will be very difficult to make a solid dielectric filler. I suggest that the simplest way to load the cavity will be with a dielectric liquid. A number of chemical manufacturers can probably supply you with data since these materials are frequently used in transformers. There is a very old table of dielectric properties of liquids in Reference Data for Radio Engineers, which was originally published by ITT Corp. in 1943. My copy is the fourth edition dated 1956 and does not have an ISBN number. However, you should be able to find a copy in any reasonable technical library.
From: Klaus Sauerbier, Rohde & Schwarz FTK GmbH
The paper is too old to be on our web archive; however, if you will provide us with your mailing address we will send you a hard copy.
From: Arun Kumar, Broadwave Technologies
The bandwidth calculation is the same as for multiple quarter-wave transformers. The original paper on this type of divider is "A Class of Broadband, Three-port TEM Mode Hybrids" by S. Cohn, MTT-Transactions 16, No. 2, February 1968, pp. 110-118. Consolidated design equations and curves are included in Chapter 3 of my book Stripline Circuit Design, H. Howe, Artech House Inc., 1974, ISBN#0-89006-020-7.
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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