"Jim Lux" wrote in message
...
amdx wrote:
"nx7u" wrote in message
oups.com...

Yes to both.
A corner-fed patch is roughly circularly polarized...I say roughly
because there are some other pertubations typically made to force the
sense of the CP, and also to improve the circularity.
But if the feed is just offset a bit (like 1/4-3/4 rather than
1/2-1/2)...well that should act similarly to an offset-fed dipole, so
you'd have higher input impedance and some feedpoint reactance. And
the pattern linearity would be more elliptical (patches typically have
relatively high crosspolar response anyway).


Ok, to make sure I understand;
If I put the feed on the lowerhalf of the patch the antenna would be
vertically polarized?
And, if I put the feed on the left or right half of the patch the
antenna
would be horizontally polarized?
Now to complicate things, I see some patches split the difference and
put
the feedpoint on the left side of the lowerhalf. What does that do?
Thanks, Mike

My next trick is to put 4 Patch antennas on one plate, I'm looking for
the proper
spacing between Patches. My guide at this point is this site,
http://www.darc.de/distrikte/g/T_ATV...d-Array-GB.pdf
the author puts 4 biquads on one plate with proper phaseing and impedance
matching.
The author uses .8 wavelength vertical and .9 wavelength horizontal
spacing betwen centers.
I'm thinking 1.0 wavelength between centers is correct, but open to some
correction factor
for some (unknown to me) characteristic.
Any help and leads appreciated,
Thanks. Mike

You can space patches quite closely or far apart. It typically depends on
how hard you want to work on your feed network, because closer spacing
increases the mutual coupling, which makes it harder to get the right
phasing. OTOH, spacing them too far apart gives you grating lobes in the
pattern. 1 wavelength is quite far. Consider, for instance, that most
patch antennas are on some sort of substrate with an epsilon1, so the
actual patch size is substantially smaller than a free space
halfwavelength. If your substrate epsilon were, say, 2.2, then the patch
would be roughly 0.5/sqrt(2.2) or about 0.34 lambda(freespace) on a side.
At this size, spacing them on half wavelength centers would be easy.

Some other aspects that might drive how you lay out the patch array is how
you intend to feed them. If you're feeding them with a microstrip on the
edge, then you have to find room for the feedline on the top and the feed
network. If you feed them from the bottom (probe feed) it's a bit easier
to build your feed network on the back side. You can also slot feed the
patches.

The patch I'm building uses an air dielectric so I'm using about .47 Lambda
on a side.
This site is my guide; http://www.rc-cam.com/gp_patch.htm
I'm feeding with coax thru the backplate with the center conductor to the
Patch. (probe feed)
Since the Patches are 0.47 Lambda, 1.0 Lambda spacing would leave 0.56
Lambda between Patches.
Probably to much. At 0.5 Lambda the patches would almost touch. Probably to
close.
So it's between 0.5 and 1.0 Lamda.
What criteria do I use to choose the spacing?
I looked at this page and it shows 0.2, 0.3, 0.4, and 0.5 Lambda
http://images.vertmarkets.com/CRLive...nArticle5a.pdf
Although for my antenna I think those numbers should be doubled, (0.4, 0.6,
0.8, and 1.0 Lambda.
What criteria do I use to choose the spacing?
Thanks, Mike