About dual frequency and dual circularly polarized antenna

[caocao]

HI
I want to design a dual frequency(1.9 and 2.2GHz ) and dual circularly polarized (two ports)antenna with microstrip patch ,could anyone give me any advices or papers ?
thanks

 

[Lupin]

Re: About dual frequency and dual circularly polarized anten

It's a challenging design, can u tell me some other RF performances as the crosspolarization level and Impedance Bandwidth?
Do u have weight constraints?
There are many ideas, u should tell somethin' more..

Regards
Lupin

 

[caocao]

Re: About dual frequency and dual circularly polarized anten

Hi Lupin
The design requires the crosspolarization is less than 10dB on each frequency point ,and no weight or volume constraint,bandwith is 5% .Could you give me some advice in details ?
Thanks

 

[Lupin]

Re: About dual frequency and dual circularly polarized anten

Is the bandwidth 5% at -20 -15 or -10 dB. It impacts a lot on the configuration. Do u have to build the antenna or is it just a study?
RHCP for bith the bandwidths?

Regards
Lupin

 

[soucksanh]

Re: About dual frequency and dual circularly polarized anten

Maybe it can help you

 

[caocao]

Re: About dual frequency and dual circularly polarized anten

No
I study this sort antenna is for a projects!The dual frequency and dual circularly polarized of my means is RHCP at lower fre and LHCP at higher fre.The polarization isolation is less than 15dB on each point.
Do u have any advices?

Is the bandwidth 5% at -20 -15 or -10 dB. It impacts a lot on the configuration. Do u have to build the antenna or is it just a study?
RHCP for bith the bandwidths?

Regards
Lupin

 

[Lupin]

Re: About dual frequency and dual circularly polarized anten

An idea can be the following:
-Consider a standard configuration for the Circular Polarization..let's say a monolayer corner truncated excited in probe. Put the probe so that you can excite the RHCP. Then think about the same configuration but with the probe exciting the LHCP.
So u have two configurations.. one for low frequency (RHCP) and one for high frequency (LHCP). Then put them in a stacked structure.
U have 2 probes (one for each band). The geometric centers of the two antennas can't be coinciding. Be careful of the coupling between the two antennas. U can optimise it moving one patch respect to the otherone.
The article of souckshan is too complicated and proposes too many input for every band.
It's just a first idea.

What do u think?

Regards
Lupin

 

[yuen_cityu]

What is your requirement for the radiation pattern? ( Axial mode or normal mode ). Also, the axial ratio beamwidth is important for the CP antenna. I have designed that dual frequency and dual circularly polarized antenna using helical antenna but i can't solve the problem of the isolation between two port. Pls provide more detail requirement otherwise it is difficult to give you the suggestion.

 

[zfl]

Re: About dual frequency and dual circularly polarized anten

It's really diffcult!!!! 2 ports? How about 1 port and single layer?Now,I'm working with it,but I havn't any idea! Who can help me ?and expect all talk about it!

 

[caocao]

Re: About dual frequency and dual circularly polarized anten

An idea can be the following:

U have 2 probes (one for each band). The geometric centers of the two antennas can't be coinciding. Be careful of the coupling between the two antennas. U can optimise it moving one fix respect to the otherone.
The article of souckshan is too complicated and proposes too many input for every band.
It's just a first idea.

What do u think?

Regards
Lupin

Hi
I have designed a stack antennas with two layers,top one is the RHCP in lower fre,bottom one is another.But I am looking for a dual-fre dual-CP in ONE Patch.Could u give more advices?
Regards
CaoCao

 

[Lupin]

Re: About dual frequency and dual circularly polarized anten

If I understood well, u need :

at f1 RHCP;
at f2 LHCP.

with f1<f2. This is a dual frequency antenna. If u need something else, please explain it better. What do u mean with "dual-CP in ONE fix"?

Regards
Lupin

 

[caocao]

Re: About dual frequency and dual circularly polarized anten

If I understood well, u need :

at f1 RHCP;
at f2 LHCP.

with f1<f2. This is a dual frequency antenna. If u need something else, please explain it better. What do u mean with "dual-CP in ONE fix"?

Regards
Lupin

Hi Lupin
It is right,the "Dual-CP in ONE fix" means olny one layer. Sucn as:
top---- patch (dual fre dual cp)
mid----dielectric substrate
bottom--ground

Thanks!

 

[Lupin]

Re: About dual frequency and dual circularly polarized anten

If u have to use just one layer, u'll surely have problems of coupling between the excitation ports. I'ld use a slotted patch antenna. I've done something very similar on dual frequency CP mode but with just one probe .. the real problem is the coupling...
I suggest a stacked solution as I mentioned before.
Read the Wong book aobut patch antennas. U can easily find here and choose the stacked configuration as I explained before.

Regards
Lupin

 

[yuen_cityu]

Hi Lupin,

could you give me some idea how to increase axial ratio beamwidth for CP patch antenna? ( can't using high dielectric substrate )

Thanks

 

[Lupin]

Re: About dual frequency and dual circularly polarized anten

Probably u mean Axial Ratio Bandwidth, not Beamwidth...
Anyway.. how many inputs are u using? Probe, miscrostrip, aperture coupled.. tell me more, e.g. how much bandwidth do u want to achieve?

Regards
Lupin

 

[yuen_cityu]

Nope, I mean Axial ratio beamwidth because the antenna are required to receive the signal from low elevation angle for GPS application. For general CP patch antenna, it only provides axial ratio beamwidth from -30 to 30 degree.

 

[Lupin]

Re: About dual frequency and dual circularly polarized anten

Right, u mean Axial Ratio Edge of Coverage...
R u using some e.m. code (e.g. Ensemble)?
Consider a notched circular patch in RHCP. Moving the probe along radius direction, the Input Impedance changes and so the abs(s11).. Tuning the position of the probe, u can have a bad matching (let's say about -10 dB) but a wider Axial Ratio coverage.. remember that it's related to the Crosspolarization level u want... It's a trade off between the coverage and the input reflections.. Anyway u should consider also the thickness and the dielctric constant of your monolayer strucutre for high Teta values (Teta= 0° is boradside direction).

Regards
Lupin