View Single Post
Old Jan 12, 2010, 03:56 PM
Old Man Mike is offline
Find More Posts by Old Man Mike
Registered User
Old Man Mike's Avatar
Joined Sep 2007
1,803 Posts
Originally Posted by va3mw View Post
Hi Mike

Can you share with me the dimension of the CPOD. I'll bet you also have some polar charts on it.

I can likely get it on an antenna range as well, unless you have already done that (I would be surprised if you have not done something similar).

Hi Mike,

This antenna has been extremely difficult to design for two reasons:

1) I could find no antenna modeling programs that allow auto optimization of the LHCP to RHCP ratio (Axial Ratio). This is the key parameter of the design since the objective is to use the multipath resistance of a single direction circular radiation. It took many weeks of model optimization by hand to achieve aproximately 20 dB ratio AND maintain reasonable gain and SWR.

2) At 1280 Mhz the implemenation of the model was another big challenge. Even the smallest solder pad on the PWB acts like a top hat and changes the antenna performance. Also, we wanted to make it easy to assemble and keep the total weight down. After two attempts, Rusty was able to do the CNC milling of a PWB layout which performs to the model prediction. He also made a mirror image of the antenna so I could do LHCP to RHCP ratio measurements.

Given the special milled PWB and critical dimensions of the antenna, I would rather not try to detail all the dimensions. This is just not an antenna that can be easily built without the milled PWB. Once we have completed all the testing and are satisfied with the final implementation, I think Rusty will be able to offer the antenna pieces or completed antenna. It will be up to him. I do the fun design and he does the hard layout and production.

Now if you have access to an Anechoic Antenna Test Chamber, then I might be interested in sending you a RH and LH version of the antenna for ratio testing. Send me an email and we can discuss it further.

You asked about polar plots. In this case 3D plots of the LHCP and RHCP is more useful:


Old Man Mike is offline Find More Posts by Old Man Mike
Reply With Quote