Welcome to EDAboard.com

Welcome to our site! EDAboard.com is an international Electronics Discussion Forum focused on EDA software, circuits, schematics, books, theory, papers, asic, pld, 8051, DSP, Network, RF, Analog Design, PCB, Service Manuals... and a whole lot more! To participate you need to register. Registration is free. Click here to register now.

PCB antenna for 868 MHz

Status
Not open for further replies.

tdma

Junior Member level 2
Joined
Oct 28, 2009
Messages
24
Helped
0
Reputation
0
Reaction score
0
Trophy points
1,281
Activity points
1,452
I had some free space on my PCB and thought, let's draw a PCB antenna. You see a 1.5 mm trace in the lower part of the PCB with the length of a quarter wavelength for 868 MHz. Right next to the PCB will be a battery compartment, so clearance is absolutely not respected I'm afraid.

Is this gonna work or better just draw a pad and connect a wire to it?

Please comment, thanks.
 

biff44

Advanced Member level 5
Joined
Dec 24, 2004
Messages
4,975
Helped
1,369
Reputation
2,734
Reaction score
1,045
Trophy points
1,393
Location
New England, USA
Activity points
37,375
My comments would be:

+ good thing it is at the edge of the board
+ good thing that the ground plane does not extend under the antenna trace
- I do not see any means for tuning it, either at the base or at the open circuited end of the antenna. When you install this in the final housing, and place it wherever it is going to live, you often find that those external things are pulling the resonant frequency of the antenna. At that point you either respin the board, or IF you have some oneboard tuning elements, just change a capacitor value slightly to re-resonate it on-frequency
- Expect whatever you mount this to, like a table top surface, to impact the resonant frequency and radiation pattern
- since you have a big ground plane and many bulky components all to one side of the antenna, expect a drop in radiation pattern (maybe as much as 12 dB) in that direction

And, just one aside, you do realize that if this is laid down on a table, it will have a horizontal polarization. You need the receiving antenna on the other end to be the same polarization for it to work well.

Rich
 
Last edited by a moderator:

tdma

Junior Member level 2
Joined
Oct 28, 2009
Messages
24
Helped
0
Reputation
0
Reaction score
0
Trophy points
1,281
Activity points
1,452
Thanks for your comments.
I will add capacitor pads for tuning.

If I lay this PCB flat on a table, how will the reception under the table be?
 

vfone

Advanced Member level 5
Joined
Oct 10, 2001
Messages
5,442
Helped
1,568
Reputation
3,139
Reaction score
1,177
Trophy points
1,393
Activity points
34,514
Is hard to predict antenna pattern without an EM simulation, but I think this antenna will work fine.
 

Status
Not open for further replies.

Part and Inventory Search

Welcome to EDABoard.com

Sponsor

Top