×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

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!
  • Students Click Here

*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

Jobs

PCB Patch Antenna

PCB Patch Antenna

PCB Patch Antenna

(OP)
I am trying to design a circularly polarized patch antenna to operate at 915MHz for an RFID reader.  I intend to print the design on a PCB, as that sounds like a reasonable solution, and cheap which is a constraint.  The antenna needs to be circularly polarized, and have a (max-allowed) gain of 9 dBic.

In thread247-288566: 915Mhz Circular Patch RFID antenna
I see that Tony you said you were trying to do this, I feel as if you could be of assistance, but I would appreciate any tips in trying to tackle this problem.

RE: PCB Patch Antenna

The gain is a bit high. You'll need to use air dielectric to enlarge the element to increase the gain compared to normal patch antennas (usually +5 dBic is typical). So about a 6" square element, etched circuit card. Raised off the ground on plastic posts over a ground plane. Probe location(s) depend on height of circuit card above the ground plane. Your ground plane needs to be larger than you'd probably want so the patch doesn't radiate around the back and reduce your gain. You may need to put it in a metal box to minimize size and add a director + shaped metal in front of the antenna.

Feeding it with a 90 hybrid purchased part makes the antenna design easier than trying to manufacture it without a 90 hybrid.

What is your price and volume target?

 

RE: PCB Patch Antenna

(OP)
Hi thanks for the reply, I've been simulating various antenna designs on HFSS, all on FR4 PCBs, and yes i see that the gain is limited.  The bigger problem seems to be that the bandwidth is very small.  I have tried the truncated corners design due to its simplicity and single feed line, but i suspect it may not be the best one -- is there a better one?  I'd really like to stick with the microstrip patch.

I am trying to produce 5-10 to test a system, with less than $500 for the antennas.

I appreciate any further design suggestions.   

RE: PCB Patch Antenna


I did some modeling: we can get you Circularly polarized 9 dBic Gain at 915 MHz if footprint/ ground plane will be 250 x 250 mm. If you still did not find your solution I offer to construct and send you hand-made prototype for small fee. Tuned properly. It will be suspended plate, truncated patch; probe-fed; terminated with SMA connector. No covers. You can then copy it and build your own.

If you need just one or two Antennas you will be better off buying them from http://www.microcom.us/mt262006trhak.html
Probably the same, slightly larger ground plane.

 

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!


Resources