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Patch antenna and WLAN requirement

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snkhan

snkhan

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requirement to establish wlan

Hi

Patch antenna are usually not omnidirectional. I want to ask what are the specific requirement for the pattern of WLAN antenna and Patch antenna are suitable for this kind of applications
 

dual patch antenna gain

Sometimes a properly designed patch antenna can also provide a wide horizontal radiation pattern that is well suited for WLAN access points.
One idea is a family of dual-patch antennas:
As well known, a patch antenna usually utilizes a planar conductive patch disposed parallel to a big ground portion and separated from the ground portion by a thin dielectric layer. A feed point is provided to communicate electromagnetic energy to or from the patch. Antennas of this nature may be inexpensively manufactured and may be readily formed into low cost, light weighted phased antenna systems. Though the traditional patch antenna has much advantage mentioned above, a drawback is that it has a big ground portion resulting in a large size of the antenna. Another drawback is that the radiating pattern of the traditional patch antenna is not omni-direction, thus the scope of the use of the traditional antennas is limited.

The typical family of dual-patch antennas of the prior art comprises a dielectric substrate and two electrically conducting rectangular shape elements formed on both sides of the dielectric substrate. The element on one side of the substrate is the mirror image of the element on the other side of the substrate. Each of the elements acts, in effect as a ground portion for the other. The antenna has much smaller size because the antenna does not have a very big absolute ground portion. Additionally, the antenna has good radiating pattern of omni-direction.
However, there are some difficulties with the dual-patch antenna. First, the input impedance of the antenna is tuned by varying the location of the feed point, which cannot obtain excellent efficiency. Second, the bandwidth of the antenna is narrow. Usually, to increase the bandwidth of a patch antenna, the thickness of the dielectric substrate is increased, which easily results in impedance mismatching between the antenna and its feeding cable. For an antenna design, impedance matching is one of the most important factors. The impedance mismatching causes a portion of the feed power to be reflected to the signal source rather than to be radiated to the free space. The greater this reflected feed power, the less power that is radiated from the antenna, thus reducing the gain of the patch antenna. So the gain of the patch antenna is sacrificed to achieve wider bandwidth in such resolution. Third, the dielectric substrate of the traditional patch antenna will introduce insertion loss, which does not fit a high gain application.
Hence, in this art, a dual-patch air parch antenna with high performance, simple structure and low cost to overcome the above-mentioned disadvantages of the prior art will be described in detail in the following embodiments
Click to expand...

About patch antennas:
http://www.emtalk.com/mwt_mpa.htm
http://www.emtalk.com/tut_1.htm
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patch antenna wlan homemade

Let me be more specific and i am talking about single patch with probe fed.
The last example given by u the pattern is not omnidirectional
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scope wlan requirement

For WLAN Antenna requirement u can refer chapter 4 of the book Antenna for Portable Devices
 

    snkhan

    snkhan

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Thanks its really a very nice source of help
 

There is no need for a WLAN access point antenna o be omni directional. Actually a reflector antennas are ideal when there is a need for beam control. I'm not sure why manufacturers use omni directional rubber duckies in access points. Probably to suite everyone's needs. Yet I have seen many people use home made reflectors to improve the patterns and signal strengths. Afterall you don't want your network covering the neighbours property, do you?
 

A have designed a couple of WLAN patch antennas, so I can say, that they are suitable for this purpose. The critical parameters include gain and return loss of the antenna. Tha gain depends on losses in the feeder and substrate and also on the radiating pattern. The narrower the beam, the higher the gain. For higher gain, you need higher number of patches, but losses also increases. The return loss is also important parameter, according to my experiences, there can be designed patch antennas with RL<-15 dB even RL<-20 in whole frequency band. And it is also possible to design an omnidirectional patch antenna.
 

I have went to a market and look many WLAN transceivers both for commerical and home applications. Interestingly all of them use simple wire monopole antenna (That surely do not have omni-directional pattern).
I have seem different kind of design for WLAN and pattern varies with reference to the antenna type. I wonder since WLAN is employed technology might have some standard pattern.
 

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