I have designed a microstrip patch antenna to resonate at 3.5GHz. It also resonates at around 6GhZ and 10GHz. Can you suggest me of how the higher frequencies can be suppressed to get an effective single band antenna?
Hi...
you can try this using EBG structures such as U slots or truncation of ground planes.
By choosing proper dimensions with the help of appropriate literature, it can be easily suppress the higher resonant frequencies. this is because U slots are used to introduce stop bands in the frequency response.
You could use a different antenna geometry that doesn't resonate at higher frequencies, or alternatively as Raymond has also suggested, place an FSS or low-pass filter in front of the antenna. For the latter you could add a dielectric spacer on top of your antenna with the filter, or suspend the filter above with support posts at the far edges of your antenna.
The loading of the slot results in the suppression of higher frequency bands and reduction in resonant frequency of original square patch antenna.
Please go through following paper.
http://ieeexplore.ieee.org/xpl/login.jsp?tp=&arnumber=6524288&url=http%3A%2F%2Fieeexplore.ieee.org%2Fiel7%2F6524160%2F6524254%2F06524288.pdf%3Farnumber%3D6524288
Hello Sheriba,
Have you built this antenna or is it a model that you are talking about?
How are you feeding the patch? probe fed, microstrip or some other feed mechanism?
What is the signal strength of these higher frequencies?
If you answer these questions I should be able to help you.
Hi,
Thanks all, for your responses. Let me try these and will revert back with my resuits.
Hi Usman Ali, I desire for a 3.5 GHz antenna.
Hi David Morley, I have chosen a square patch with a Microstrip Feed with inset width of (Width of the patch/10) and inset length of about 5.5mm.
Below are the obtained frequencies with its S11 parameter
3.5GHz -22.659dB ( Frequency of interest)
6.3GHz -11.67dB
8.928 GHz -15.807dB
9.65GHz -14.627dB
12.5 GHz -33.14dB
Thank You.
Is your antenna really square? if so that might be part of the problem. Normally microstrip antennas are rectangular.
The inset width should be the same as the width of the microstrip feed line. But I think the main problem may be the inset length. Increasing inset length is a method for creating a dual frequency inset fed microstrip antenna. I have attached a document that contains an empirical formula for calculating inset length.
What type of laminate are you using? At 3.5 GHz. you should be using a good RF laminate like Rogers 4003.
Good luck.
Hi David,
Thanks for your reply.
Let me try the formula you posted. That was a valid input I hope. I will work on it and get back if any issues are.
I have chosen the FR 4 Substrate. What is your suggestion on this laminate? Can I proceed with this.
Hi Prof.Jagdish Rathod ,
I have got the paper from the link. Thanks for your support.
I will look into that sir.
Hi Sheriba,
I would strongly recommend that you not use FR 4. With FR 4 as frequency increases both its dissipation factor (Df) and dielectric constant (Dk) increase. This causes significantly higher insertion loss. Impedance also changes. RF laminates typically have Dk tolerance of +/- 2%; FR 4 is +/- 10%. RF laminates have a thickness tolerance of +/- 75; FR 4 is +/- 15%.
I suggest Rogers 4003. It has good RF performance at a reasonable price.
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