How to find the feed location for a rectangular patch antenna?

[khilji3774]

Re: How to find the exact location for feeding coaxially a rectangular patch antenna

Hi Khalid A .....
I am using a substrate polyester with permitivity 1.39, but polyester is not available in CST material library, now what i ahve done is that i have picked a new material and asiigned it the permitivity value of 1.39. does it will work? or i should add other parameters like conductivity, young's modulus etc. and if yes where to find these parameters?

 

[khaled.ayman]

Re: How to find the exact location for feeding coaxially a rectangular patch antenna

Yes that will work for you. There's just one parameter you might want to assign which is the Tangent delta under the tab "Conductivity" in the new material window. This represents the losses in your material, if you leave it 0 that means your material is loss-less.

 

[khilji3774]

Re: How to find the exact location for feeding coaxially a rectangular patch antenna

but sir along with the loss tangent we have to specify the frequncy also. what i found is the tangent loss of polyester is 0.1 but the frequency is not specified. and once i put the tangent loss in material properties the antenna return loss changed from -40db t0 -18db and the gain decreased from 8.15db to 0.17db?

 

[khaled.ayman]

Re: How to find the exact location for feeding coaxially a rectangular patch antenna

I think Tan delta of 0.1 might be a bit too high. For example I'm now using a substrate with Er=4.4 and tan delta=0.018

And just leave the frequency to zero. It will automatically adjust.

 

[khilji3774]

Re: How to find the exact location for feeding coaxially a rectangular patch antenna

ok sir....
one thing more when we adjust the x,y feed positions for a normal rectangular patch before introducing slots in the patch or ground, after slotting did we need to adjust the x feed again or it should remain the same?
and what kind of slot you prefer that should help us in acheiving highier miniaturization? and is there any guidline for doing slots in the patch or ground?

 

[khaled.ayman]

Re: How to find the exact location for feeding coaxially a rectangular patch antenna

Hi khilji,

Let me just say that I haven't done a great deal of slot antennas so based on the papers I've read I believe your slot size should be in the range of lambda/2 or lambda/4 according to your operating frequency. The most common is a rectangular slot, so you might want to try starting off with that. If you go on the internet or IEEE explore and search for microstrip antenna with slot, you'll get some designs and ideas to start with.

For the feed position I believe it may change after you add your slots. So try changing them and see if your matching improves.

 

[sandeepagari]

Re: How to find the exact location for feeding coaxially a rectangular patch antenna

i have a query. need help. i am making a simple circular patch antenna with coax feed. i am just getting confused with the dimesnions of the coax cable. how to select the dimensions of the coax ? inner pin, coax ?? dimension od substrate is 40,40,1.6. and circular patch radius is 10. units are in mm.

 

[pkg]

Re: How to find the exact location for feeding coaxially a rectangular patch antenna

Sir, i designed MPA for Er=3.55, h=1.524 and fr= 6 GHz.
i got lowest S11 at 5.8 GHz frequency.
1.what is the reason for the difference?
2.what is the meaning of meshing operation?
i am using HFSS13.0. please explain me sir.

 

[khaled.ayman]

Re: How to find the exact location for feeding coaxially a rectangular patch antenna

Sir, i designed MPA for Er=3.55, h=1.524 and fr= 6 GHz.
i got lowest S11 at 5.8 GHz frequency.
1.what is the reason for the difference?
2.what is the meaning of meshing operation?
i am using HFSS13.0. please explain me sir.

It's normal to have a slight shift in frequency between your design and simulation. On HFSS you can decrease your height or MPA dimensions to reach the 6G frequency.

Increasing the mesh size simply means your structure will be divided into smaller pieces, thus having more accuracy, but at the cost of more simulation time and CPU memory usage.

 

[pkg]

Re: How to find the exact location for feeding coaxially a rectangular patch antenna

i considerd height of antenna in x-axis, width of patch in y-axis and length of patch in z-axis.
location of feeding
yf = W/2;
zf= L/(2*sqrt(Ereff)).
i hope ...i helped u..

 

[khaled.ayman]

Re: How to find the exact location for feeding coaxially a rectangular patch antenna

i have a query. need help. i am making a simple circular patch antenna with coax feed. i am just getting confused with the dimesnions of the coax cable. how to select the dimensions of the coax ? inner pin, coax ?? dimension od substrate is 40,40,1.6. and circular patch radius is 10. units are in mm.

If you scroll back through this discussion to post #13 you will find the detailed explanation.

 

[pkg]

Re: How to find the exact location for feeding coaxially a rectangular patch antenna

dear K A,
sir,i read your post and i designed patch antenna. i feed as you say. but i do not good result. where i commited mistake.please check my design and feeding point location.

 

[khaled.ayman]

Re: How to find the exact location for feeding coaxially a rectangular patch antenna

Hi pkg,

I took a quick look at your structure. I don't understand the "PMLGroup"? and the "SweepFace" in you Rad boundary?? Once I start the sweep a lot of warning appear concerning boundaries!

Anyways the coaxial feed looks fine to me. I suggest you remove all those unnecessary PMLGroup and Face sweep, then try again.

Here's one of my patch designs to take as a reference (just ignore how I set up the coaxial feed since this is an old simulation) for the boundaries, excitation, radiation box, solution setup, etc...

I hope this helps.

- - - Updated - - -

Also check this tutorial

 

[sandeepagari]

Re: How to find the exact location for feeding coaxially a rectangular patch antenna

thanx

but my doubt is, i want to know how to select the dimensions of the coax cable? height, radius of coax pin,probe etc?? i have a tutorial of microstrip antenna with coax feed. now i have to make a circular patch with coax feed. will the dimensions of the coax be same?? if not, how to get the dimensions? or i have to take dimensions u have written in every case ???
thanx in advance

 

[khaled.ayman]

Re: How to find the exact location for feeding coaxially a rectangular patch antenna

Dimensions are the same.

 

[nivash]

Re: How to find the exact location for feeding coaxially a rectangular patch antenna

hello sir i am working in ads ***** version. designing an dual band patch with u slot using coaxial probe feed. in my simulation i hav an error report as

ERROR : Port 1 is not inside a conductive region.
WARNING : Could not resolve port 1.
Generating mesh at 4GHz...
WARNING : Transmission Line Port 1 modified to be an Internal Port, because a
Transmission Line Port cannot be inside the circuit.
WARNING : Unable to correctly process port 1.
ERROR : Ports cannot be embedded inside a structure on a slot layer
and must be put on an outside edge

help me to solve this problem. if u hav any formula or tutorial plz send me.

 

[prety]

Re: How to find the exact location for feeding coaxially a rectangular patch antenna

K.A sir could you help me regarding pifa designing on 3.5 GHZ IN HFSS ....
I want to ask about the height of substrated what it should be if i am taking subatrate fr4....
thanks and regard
prety

 

[khaled.ayman]

Re: How to find the exact location for feeding coaxially a rectangular patch antenna

Hi,

First sorry for the late reply, I haven't been checking this forum as frequent. Please let me know if still need help.

 

[prety]

Yes k.a sir u can still help me