Looking for a 2.4 GHz patch antenna

[JoeDreck]

Hello,

i am looking for an antenna which is working with a ground plane on the bottom side of the substrate (FR4) at 2.4GHz.

It will be placed on "biological objects" like human beeings. What is important for the right antenna in this case?

I found four similar patch antennas:

• Circular inset-fed linear polarised patch
• Rectangular inset-fed linear patch
• Circular Edge-fed linear polarised patch
• Rectangular Edge-fed Patch

I think the performance should be very similar?

I what to use this antenna with a TI/Chipcon ZigBee Transceiver and a balun (75Ω to 50Ω), could i now leave out the fed lines to the antenna. Or in other words: Is the fed line for matching only?

Thanks.

 

[WimRFP]

Re: 2.4 GHz Patch Antenna

The thin (non 50 Ohms) feed lines are part of the matching, so they cannot be removed, unless you design your own matching network. The 50 Ohms lines can be removed, shorted or extended. Based on width of trace, height and relative epsilon, you can determine the characteristic impedance of the transmission lines.

Given same size of ground plane, all these antennas will have similar performance (so I agree with your statement).

 

[JoeDreck]

Re: 2.4 GHz Patch Antenna

Actually I will use an own matching network (look at the attached picture).

So I can connect the antenna directly after the matching network?

 

[WimRFP]

Re: 2.4 GHz Patch Antenna

Your matching network transforms to 50 Ohms unbalanced, so you should not remove the non 50 Ohms transmission line sections from the antenna.

When you would connect your chip + matching directly to the edge of a half wave resonating patch, you will have significant mismatch. The input impedance at the edge of a half wave resonating patch antenna is much higher then 50 Ohms.

Other thing: if you are using an existing proven antenna design, make sure to keep the distance between ground plane and patch the same. You may know that there is relatively large spread in relative epsilon for FR4 (unless you use material with controlled er). This may lead to some performance degradation due to change in the antenna's center frequency

 

[JoeDreck]

Re: 2.4 GHz Patch Antenna

OK, thank you Wim.

So i could use the "inset-fed" antennas, because the matching is created with the help of the inset, is that right?

I want to keep the design as small as possible.

 

[tony_lth]

Re: 2.4 GHz Patch Antenna

Can you explain your project more clearly? You want to put a 2.4GHz antenna and circuits in the human body? That doesn't make sense.

 

[JoeDreck]

Re: 2.4 GHz Patch Antenna

I want to use it with a 3D acceleration sensor for tracking the movement and send it to computer for example.