Microwave Antenna Design

Guest

The first step in designing your antenna (and indeed anything else) is to carefully establish exactly what you intend to accomplish with the device and under what conditions it must operate. In other words, the first step is a set of specifications and parameters that describe every pertinent aspect of the project.

For a microwave antenna this will include frequency of operation or bandwidth of frequencies. You need to do a path analysis to determine path losses or in some fashion determine how much gain you need. You will need to make decisions about the polarization of the the signal you intend to transmit or receive, vertical, horizontal, circular, right or left handed. How tight must your bandwidth be? What about vertical lobe and horizontal lobe 3dB width. Back lobe radiation? I'm starting to bog down in detail here, but these are some of the RF considerations to start with.

You will also want to think about mechanical aspects of your design. Your choice of design or antenna type will largely be driven by your operating frequency, required gain, bandwidth limitations, power-handling needs, and cost. Then you will select from various design approaches or types of radiating structure. There are many, both active and passive. Structural weight, mounting brackets or hardware, possible wind and/or ice loading, ability of the materials to withstand environmental effects like rain, hail, sand, salt, UV radiation all must be considered. And not only for the antenna itself but for whatever structure it is mounted on.

The physical location of the antenna must be considered also. Will it be in close proximity to the public--read RF safety issues here. How will you protect the public or deny them close access? What about vandalism? What about physical access for erection, maintenance, and removal when its useful life has ended? Satellites use lots of microwave antennas and its kind of difficult to maintain them!!

Also, you must consider how you will get power and/or signal to or from (or both) the antenna--safely--efficiently--cost effectively.

Actually, almost any conductive material can be used as an antenna--a coat hangar suspended from some fish line will work for some applications.

Get back to us with a more precise idea of what you want to build and there are many here who would get a kick out of helping you design something. Or hook up with an Elmer at your local Ham Radio club. This is right down their alley. Check out the ARRL Handbook for lots of info on antenna design.

Lonnie

Try simulation software like CST Microwave or Ansoft HFSS, EZNEC, SuperNEC etc.

Try microstrip antenna technologies. They are easy to design and build, and also are cheap (only a blank PCB and the chemicals to draw your design on it). The mythical book of Balanis Antenna Theory has a chapter on microstrip that explains an easy introduction to the topic.

Gustavo Sutil. gustavosutil (at) gmail.com

Check out http://www.turnpoint.net/wireless/cantennahowto.html