- Buyers Guide
Military Microwaves Supplement
Published October 13, 2006
From: Syed Abbas, College of Aeronautical Engineering
There is no universal specification. Power handling is determined by voltage breakdown for high peak power and by allowable thermal rise due to dissipation for high average power. In addition, if the divider/combiner is all port matched, the power will also be limited by the allowable dissipation in the terminating resistor due to reflections. My own rule of thumb is that you should also allow for at least a 2:1 safety margin over any rated power level.
From: Felix Yanovsky
Yes. You do not say by "controllable" whether you mean specific or switchable. Either are possible using waveguide or microstrip slot arrays. There is a good general discussion of slot arrays in the second edition of Modern Antenna Design, Milligan, Wiley, 2005, ISBN#0-471-45776-0. There is excellent design information on microstrip slots in Microstrip Antenna Design Handbook, Garg, et al., Artech House Inc., 2001, ISBN#0-89006-513-6.
From: Sema Dumanli, Aselsan
We do not comment on or recommend specific commercial products. I am sure that Eagleware/Agilent can give you the specifics of Genesys as can Applied Wave Research regarding MWO.
From: Mustafa Acar
Many high power RF amplifiers use transformers wound on ferrite cores. At higher frequencies, stepped impedance transmission lines simulating an LC network are the method of choice.
From: Taylor Eker, METU
With careful design you should be able to get to -30 dB. The problem is frequently related to the stray capacitance at the outer conductor/ground plane interface. There is a good discussion of microstrip transitions in Chapter One of Microstrip Lines and Slotlines, Gupta, et al., Artech House, 1996, ISBN#0-89006-766-X.
From: Han-Shin Jo
The propagation charateristics are a function of loss, noise, interference, needed link margins, clutter and terrain. There is a good discussion of these factors and link budget calculations in Introduction to RF Propagation, Seybold, Wiley, 1958, ISBN#0-471-65596-1.
From: Akhilesh Jain, RRCAT
Even and odd mode impedances define the coupling between parallel-coupled lines. Normalized Zoe = SQR((1+Co)/(1-Co)) and Zoo = ((1-Co)/(1+Co)), where Co is the voltage coupling ratio. For a matched condition: Zo^2 = Zoe * Zoo and coupling in dB = -20 Log Co.
There is an extensive discussion of even and odd mode impedances with equations for calculating coupled line dimensions and references to other papers in Chapter 4 of my book Stripline Circuit Design, H. Howe, Artech House Inc., 1974, ISBN#0-89006-020-7.
From: Michael Liu, Alcatel Shanghai-bell
For indoor systems the normal practice is to keep the transmit power between 10 and 30 dBm in order to provide enough signal for the expected path loss but to avoid interference with other systems. When ATPC is enabled the maximum power can be increased since it will only be used when needed.
From: Fernando Sommariva, Fiplex Microwave Devices
I am sorry, but I cannot give you a simple answer. It depends on the circuit class, the type of active devices and the PAE of the amplifier. I think you will simply have to measure it.
From: James Canterbury, Penn State University
Yes, RF signals can be used to measure distance. The system must be designed to measure time delay of the return signal, which is not normal in present RFID systems, but it can certainly be done.
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.
Get access to premium content and e-newsletters by registering on the web site. You can also subscribe to Microwave Journal magazine.