Hi there,
I have already try all ways in increasing and decreasing the patch size of my radiator of my antenna design. By the way, I need to achieve 9 GHz for weather radar application and I am using array antenna with proximity coupling and both substrates are FR4. Please refer to the attachment for my design. I am thinking of changing the shape of the array antenna. But I do not know which shape is suitable for my design to increase the resonant frequency to 9GHz. The highest resonant that I can get is around 7.6GHz but the dual polarization only happens at 6GHz by seeing the S11 and S22 s-parameters result. My design is made of 2 substrate of FR4 using proximity coupling technique where the first substrate will be used as the radiator and the second will be the orthogonal feed line to obtain dual polarization. Please kindly give some advice. Thank you very much!
You can use some substrates with lower permittivity values (try with 2.2) or decrease the thickness of the substrate.
May you explain how can you determine the dual polarization only by seeing the S-parameters?
From your query, it is clear that, you want to design an antenna (rectangular patch) at 9GHz. Due to loading effect, you are not getting results. I would suggest you to design the same for 2 element array (single polarization, not dual). Observe the result. If resonant frequency decreases, please tune your design parameter to get 9GHz. Then go for 4 element array. Tune it again. Then go for dual polarization...What are the antenna parameters?
Thanks Anvesh Kumar Nella, I will try that later.
Hamza Nachouane. From what I know, to determine dual polarization, i can see the s11 and s22 return loss. Both of their return has to be more than -10dB in the same resonant frequency and in this case is 9GHz.
Sudipta Maity. Thanks! I am able to obtain higher resonant frequency with 2 element array. However, I have a problem in getting the design bandwidth. i have set my specs to 500MHz of bandwidth at the resonant frequency. I am getting around 10 GHz for my resonant but I can tune them by changing the size of my array antenna. Can I improve the bandwidth through slots?
If it works properly at 6 GHz then you will need to make the patches approximately 67%as wide and long and reduce the spacing between patch centres to 67% of what it is. If you are getting circular polarization by quarter-wave difference in line lengths you will need to reduce the length difference between your side feeds and top and bottom feeds by to 67% of what it is - it should be an odd multiple of a quarter wavelength at 9 GHz. I can't tell if you have equal length feeds which are then fed quarter wave out of phase at the inputs
I am confused. The antennas on one diagonal seem to have the opposite direction of circular polarization to the antennas on the other diagonal. Is this deliberate? Do you want a null on bore-sight?
Thanks. Malcolm White! I can already obtained 9GHz by using 1 by 2 Array. but the total efficiency is very high for both s11 and s22. I have noticed it is high due to i am using FR4 instead. I do not want to get null on bore-sight. I just want to have dual polarization to reduce cumulative attenuation along the path of propagation of the antenna.
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