designing gps antenna
Hi Billano786,
Last semester, I designed GPS antenna, but it was big. GPS system works around 1.575 GHz. If you calculate the patch antenna size, it becomes very large wrt antenna used in GPS receivers. Lambda/2 gives the patch size. Therefore, engineers in the industry use different methods to reduce the size of the antenna.
Moreover, you can find these antennas are generally probe fed microstrip antennas. You can find information about this in "Advances in Microstrip and printed Antennas" by Kai Fong Lee, Wei Chen.
rgds,
lkuzu
I have seen quite a number of GPS antennas. They are all microstrip based with a LNA. I think that they are circularly polarized.
Indeed they are to be used at 1575 MHz as mentioned by you. However, I do not know anything beyond this. Any help regarding this is welcomed.
Hi again,
They are using LNA because these are active antennas. I mean they want to increase the gain of the antenna. Search for "active antennas".
As you said, these antennas are circularly polarized (CP) either Right Hand or Left Hand. If you trim the corners, you can achieve CP antennas.
My humble opinion, you can find some information about these antennas on the internet. And You need antenna design software such as Ansoft HFSS, Ensemble, Sonnet em, Zeland IE3D. I used for my design only HFSS.
Some other books: Antenna Theory by Balanis, Antennas by Stutzman and Thiele.
Regards,
lkuzu
Hi,
Try the PIFA or IFA antenna.
The best book for this kind antenna:
-I. Hirasawa, Kazuhiro II. Haneishi, Misao, "Analysis,design and measurement of small and low-profile antennas".
ARTECH HOUSE, INC., pp.161 - 180
Regards.
Clandestino
does any one have this book as an ebook and can share it
this would be great
LNA & Quadrifilar helix for GPS:
http://www.ien.it/~brida/LNAGPS.htm
harlan1
I have designed a patch antenna for GPS application:
dual band stacked patch antenna with dual input in RHC polarization.
Tell me if you want to know something more about it.
Regards
Lupin
If you end up with a QHA type of antenna, you can reduce the size by winding the copper wires on a thick-walled Teflon cylinder. It's about ten years ago when I designed a couple of these for a satellite application, but I'd remember that Kilgus, Sharaiha & Terret and Tranquilla have written some articles also on QHAs on a dielectric support. Search the IEEE Transactions' archives for these names.
Hobbie
GPS antenna must be a CP antenna.
GPS satellites transmit Right Handed Circularly (RHC) polarized signals which might become LHC polarized after reflection on the ground. Thus, high cross polarization rejection is needed for receiving antenna. You may need 1.227 GHz and 1.575 GHz. Radiation pattern wise, hemispherical coverage with desirable sharp slope in horizontal directions. Good impedance match required with LNA because of weak signal received. LNA can be purchased from mini-circuits at a good price. Patch, helical and spiral antennas are all suitable design depending on your application. Personally, I prefer patch. Suitable material for patch can be FR4 or the the more expensive Duriod. Trim corners to obtain circular polarisation and include slots within patch to tune out unwanted mode propagation and reduce antenna size. Hope this helps.
Cheers,
Element7k
U can cut the corners to achieve a CP if u use a probe fed patch with one input.. however two inputs are preferred for what concerns radiative requirements.
Regards
Lupin
LNA suggestion. If you need only one band. Building one with gain of 15-18 dB and noise factor of 1.6-1.8 dB should be no problem with use of BFP 420 or similar transistor and you will beet cheep integrated amplifiers by at least 2 dB for the same price. If you need additional stage than Mini Circuits o RF Micro devices are good choice.
Nice app notes are available at www.infineon.com
i think that the corner truncated patch antenna is good choice for L1 band with Circular polarization. i design one with VSWR=1.12 and 5.2 dB Gain with ROG4003
Unless you are using the antenna for military applications or in a super-accurate surveying system you will only need L1 1575 MHz. it is right hand circulary polarized. As othere replies mentioned, patch antenna is probably the best solution you can have for a reasonable size. I personaly do not like the helical antennas because you don't get a better performance than a patch and they are much bulkier.
Be sure to incorporate the LNA as close to the antenna as possible (preferably on the back side of the patch).
If your antenna will not have a lign of sight with the sky, using a circulary polirized antenna will not give you any benefits. In that case you are probably better of using an Inverted-F antenna.
"i think that the corner truncated patch antenna is good choice for L1 band with Circular polarization. i design one with VSWR=1.12 and 5.2 dB Gain with ROG4003".
Hi SAJ25, can you provide me with the dimensioning of the corner truncated patch at L1 band?
Thanks in advance,
Lupin
hi lupin
5*5cm the patch size
and 10*10 cm for the substarte.
Hi,
did you investigare the possibility to have nulling function?
It can be useful in navigation.
Regards,
Lupin