Actions
Forum Thread Details
  • Replies 2 replies
  • Subscribers 219 subscribers
  • Views 293 views
  • Users 0 members are here
Related

Fun with Chip Antennas

gervasi

I'm testing a Johanson 2450AT07A0100 chip antenna.  I threw my board with the antanna on the VNA and got this:

image

Here's what it looks like with a 1nH inductor in shunt:

image

For fun I tried a 0 ohm shunt:

image

 

Then I looked at my layout.  I followed the chip ant datasheet mostly.  I'm thinking, though, if I can short the antenna and not change S11 that much something wrong with my layout or VNA methodology. 

 

Has anyone else played with chip antennas or had a similar case of a circuit being subborn to shunt loading?

Parents Reply Children
  • in reply to Former Member

    "Hello, this chip antenna is a highly grounded folded-loop type element which gives it good resislience to capacitive and some inductive loading and may be a little tricky to tune. Try using larger inductance values (i.e. 6.8nH) for shunt after a 1pF cap in series .A "pi" matching network is recommended. "

     

    Thanks for joining the group.  I've been matching with a pi network.


    image

     

    It turned out my problem was in cal'ing out the cable.  Once I got a better cal, the results made more sense. 

     

    I got a good match with a 3.3pF shunt.  It improved a little further when I used a 15pF in series. 

     

    I still got a lot of de-tuning when I held it really close to the body.  So I attempted to match it with my body next to it.  In this case I got 4.7pF in shunt with the antenna, 0.5nH in series, and 2.2pF in shunt on the radio side. 

     

    I may try approaching it from the other way as you suggested, i.e. inductance in shunt.