×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Contact US

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

microwave freq halo's

microwave freq halo's

microwave freq halo's

(OP)
I am looking at modelling a patch antenna for 2.3ghz with both vertical and horizontal radiation patterns.Horizontal being the dominant radiation pattern. The substrate would be ptfe, but I find that the distance between the groundplane and the antenna affects the radiation pattern somewhat.Any advice on balancing effiency with good horizontal radiation patterns?

The ant is mounted on a car roof....and I am using cst ms

thanks

RE: microwave freq halo's

Your description confuses me a bit.
Is vertical and Horizontal radiation patterns the polarization of the antenna or the physical location.

The location on the roof of the car (center vs. edge) will affect results a bit more than other items.

Changing dielectric material thickness a little should primarily affect antenna bandwidth, with no change in the antenna pattern. Unless your dielectric thickness increases to between 1/4 and 1/2 wavelength.

kchiggins

RE: microwave freq halo's

(OP)
Hi,
The signal polarization needs to be mainly horizontal, aalthough I accept that the vertical influence will be there too because of the proximity to the car roof/groundplane.

RE: microwave freq halo's

Johnor,
that's unusual use of a patch antenna, the primary polarization is vertical polarization for a flat patch mounted flat attached to a car roof.  The H plane polarization is usually horizontal for angles far off broadside, but placing the antenna on a large groundplane/car roof reduces the horizontal polarization gain at low angles towards the horizon.

Why do you need Horizontal polarization?

If you really need horizontal, you need to model the ground plane effects accurately.
You'd need to mount a patch on a (?2"diameter) vertical tube with the long length of the patch wrapped around the tube horizontally. The antenna pattern shape as you look upwards in elevation will be set based on the height of the antenna off your car roof. You can get good horizon coverage if you don't mind large dips in antenna gain upwards in elevation.

kchiggins

RE: microwave freq halo's

(OP)
Hi,
I have simulated a simple patch structure with other software (mmana)and there does seems to be a reasonable horizontal pattern.I am into amateur radio as a hobby and use the works cst software during my lunch hour, to model antenna for home use.

RE: microwave freq halo's

I believe you for a single antenna simulation, The current flows along the length of the patch which would look horizontal polarization on the sides of the car and vertical polarization in front and behind the car (if you oriented the long length of the patch with the long length of the car). But adding a large ground plane to simulate the car roof in the analysis may not be possible. Horizontal polarization can't really travel across a flat car roof but vertical polarization can. If you can add a small circular or square ground plane, try it and you should see the horizontal polarization die out at the horizon. You may get in the -20 dBi gain range.

I've seen horizontally polarized omni antenna papers for patches, but they bent them horizontally around a vertical pipe.
kchiggins

RE: microwave freq halo's

(OP)
Hi,
Ok..will try this and see what results I get.I also am looking into placing two patch antennas vertically mounted &  back to back with a gnd plane inbetween and then feeding both at the same time.
Any ideas on the phasing possibilities ???

Thanks for your input.

RE: microwave freq halo's

Johnor,
that sounds ok. Will they be Horizontal polarization patches? I'll assume so.

There are four options;
In phase combiner (two patches point in same or opposite directions).
Out of phase combiner (two patches point in same or opposite directions).

 
In phase combiner, antennas facing the same direction gives deep antenna pattern nulls frontward and backwards (assumes the ground plane in direction of the car front to back).

Similar but opposite results as described above, if you use the out of phase combiner.

In phase combiner with antennas facing opposite directions gives peaks front and back, and bumps in the 10-40 degree zone either side of front and back if you have a large ground plane. If the ground plane is very short, you minimize those 10-40 degree bumps. A short ground plane idea mimics the  patch on a cylinder idea flattened. It may be best to keep the ground plane small then, face the antennas opposite and use an in-phase combiner. If you don't want to buy a combiner, you can take one coax. and solder it to two coaxes, i.e. one 50 ohm to two 50 ohmers (= 25 ohms). With short lengths of line you can match into your patch pair by moving the location of the feed. I've seen that done before to save space and cost.

Plus, your car hood is going to make some odd antenna patterns if you look upward due to the roof energy reradiating.

kchiggins.  

RE: microwave freq halo's

(OP)
Hi,
Yes, they will be horizontal, and I am expecting  the car roof to play a big part in the radiation pattern.I will hook up a network analyzer and see whats the antennas are doing when connected in/out of phase.




Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members! Already a Member? Login


Resources

Low-Volume Rapid Injection Molding With 3D Printed Molds
Learn methods and guidelines for using stereolithography (SLA) 3D printed molds in the injection molding process to lower costs and lead time. Discover how this hybrid manufacturing process enables on-demand mold fabrication to quickly produce small batches of thermoplastic parts. Download Now
Design for Additive Manufacturing (DfAM)
Examine how the principles of DfAM upend many of the long-standing rules around manufacturability - allowing engineers and designers to place a part’s function at the center of their design considerations. Download Now
Taking Control of Engineering Documents
This ebook covers tips for creating and managing workflows, security best practices and protection of intellectual property, Cloud vs. on-premise software solutions, CAD file management, compliance, and more. Download Now

Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close