462Mhz Planar Antenna Help

[stapleford]

Trying to design a 462MHz planar antenna that can be etched onto a flex circuit. The area I have to work with is about 1.60" x 2.00" . This needs to be optimized for receive only. Is it better to design a sqaure/rectangularl patch or a spiral strip type of layout? Also what formula would I use to determne the lenth needed?

 

[Higgler]

Difficult task with those dimensions. A patch will work only if your dielectric is 10.
I think PIFA type antenna is a good option but these require room at the edge of your circuit card with no metal chassis around it.

Specify your bandwidth, substrate thickness, desired gain and antenna pattern direction, that'll help.

As a reference, I have an FR4 quarter wave patch, 0.060" substrate, 3.75 inches long x 2" wide, 390 MHz frequency, that'd put your frequency (462 MHz) at 3.17 inches length (for the same material and antenna type) and if you changed that to dielectric 10.0 you'd arrive at your desired 2.00 inches length. Bandwidth would be narrow, 15 Mhz or less for 0.060" thickness.

This is not your average patch design, very sensitive to tolerances and materials.

kch

 

[stapleford]

I was able in increase the area where I can fit the antenna.

Here are the current card spcifications:

Size : 1.70" x 2.30"
Card Thickness : .005" copper to copper with gold plating
Direction: Omni
The card edges sit in a plastic holder so there would be no metal to cause issues.

Would I need to chage the material from FR4 to a Rogers or something like that to get a higher dielectric?

 

[Higgler]

Yes, dielectric of 10 is needed for a standard 1/4 wave shorted patch.

FR4 is roughly 3.7-4.2 dielectric and isn't very well controlled, you really have to measure it yourself.

I think if you might still have a concern if the rest of your circuit card is physically small.

If you're not too familiar with quarter wave shorted patch designs then you may be in better shape making a PIFA antenna at the end of the circuit card. I'd research that as an option.

Your gain will probably end up -5 dBi max. and somewhat omni.


kch
PS:Is this for a commercial design requiring high volume production, i.e. it has to be absolutely accurate, or are you just making an experiment qty=1?

 

[DaveAA1A]

If you are still active with this project, have you investigated the idea of using a UHF FET front end and building an E-probe in that small area?

Always a good way to get a smaller but efficient antenna.

Regards, Daveaa1a