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My design is a two-layer circular patch antenna.dowjones said:please, explain a bit further. what do you mean with pin?. is it a shorting post close to the coaxial input?.
bear in mind that the gain of an antenna is associated to its area. if the method you use to reduce the size reduces it too much, the gain of the antenna will also be reduced!
Lupin said:Hello e.m. fans,
First of all,Football, are your data measured or calculated? Probably calculated.
What frequency are you using?
How much is the Gain of the unperturbated patch?
Anyway, considering your problem I can say that inserting a pin, a slot, a lumped element..., you can have or a broadbanding or a size reduction effect....however you have to consider that ohmic losses (working frequency plays an important role) are associated to the pin you insert. That's the first aspect.
It's quite typical for such type of structures.
the second one is that you are modifying the surface current density forcing a point of the patch to be at V=0V, so you are not using all the patch surface for radiation.. that's another reason for Gain decrease.
You have the size reduction because patch surface current "path" is deeply modified respect to a standard patch antenna. It's associated to a lower resonant frequency (lower than frequency of an unperturbated patch).
DowJones: in your equation you have to consider the different working frequencies of the 2 antennas (standard probe-fed patch, shorting pin loaded patch antennas).....The area you are considering is not linked to the size reduction effect.
Hope it can be useful
Regards
Lupin
Lupin said:Hi e.m. friends,
Football: you have a circular patch fed by a microstrip line with a shorting pin don't you? What materials are you using? What about their thickness?
These parameters can affect Antenna Gain... I'ld like to know them just because I think the unperturbated Antenna Gain ( o dBi) is too low...6-8 dBi are typical values.
Anyway, you have a Gain decrease because surface
currents distribution are modified as I said you in my previous post...
To answer your question I should know shorting pin thickness...
The frequency is relative low to consider skin effect losses..
Anyway I suggest you to use CST, HFSS, Ensemble codes.. I used very seldom IE3D so I can't help you in problems about mesh or other software aspects...
Check patch antenna pattern, you could have an unbalanced pattern..
It depends on the point where you put the shorting post..
To increase Antenna Gain, you can change dielecdtric constant and thickness or, if you have no problems about accomodation or about antenna pattern, you can use a patch antenna array...
What's your requirement about Gain?
Dowjones: Antenna Gain depends on equivalent Antenna Gain and on working frequency...the areas of the unperturbated and perturbated patch antennas of Football configuration are just the same...the working frequency decreases and it corresponds Gain decrease as well...For that reason you can speak about "size reduction" but the area you use is just the same....
Regards
Lupin
The ground plane is finite and slightly larger than the patch, and this change resonant frequency slightly. HFSS can simulat the plane of theta=90, but simulation of IE3D is not valid at theta=90.Lupin said:Football,
what do you mean by horizon direction? In a spheric reference system, Teta=90°? In that case, it's quite typical to have a very low Gain.. Do you have a groundplane don't you? As Dowjones says, patch antenna is not valid to have gain in teta= 90° but in Broadside (Teta=0°) direction.
Think about it, maybe you should change antenna typology...
Regards
Lupin
yeah, you are right that slot antenna may be my next point. So there must some question to be going to bother you.Lupin said:I agree with Dowjones, you can use a vertical dipole...
Anyway, if you want to keep microstrip technology I woul act as it follows:
- circular patch witch a circular gorund plane; ground plane size, dielectric thickness, patch size play an important role for the shape of the radiation pattern; chek it in litterature.. you have a lot of parameters to taper your pattern as you like....
dowjones said:football, why dont you check a dipole/monopole?. a dipole gives 2.15dB, and although it is not flat it is small and radiates in the horizontal direction (although linear polarization)
Lupin said:Hi Football,
if you want, you can write down your RF and mechanical requirements and with my microstrip antennas knowledge I can try to help you.
Your design sounds challenging...
Dowjones: do you study slotted patch antennas? Another idea for Football's design could be a circular patch with slotted circular ground plane...a "sort" of PBG structure to taper the pattern....
Regards
Lupin
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