I have been working really hard on micro strip patch antenna design using HFSS, and I do understand fringing effect in patch antenna but my question is how does the fringing effect will affect the antenna parameters like Directivity, gain, BW, return lost etc.
for example have a set of antenna design ( various design picture is attached below) how does the fringing effect will result in different antenna design. and one more thing is there any other effect I have to consider in various antenna design as shown below. what which design would be best ? if possible do explain me with reference to the design I have attached with.
please do give me a detailed explanation in context to the problem I have stated above. your answer would be great helpful
Thank you
the fringing effect makes the effective electrical length of the patch longer than its physical length.Thus, the resonance condition depends on Leff not L. So all the antenna parameters depends on Leff not more from L. You can find a detailed analysis in this document: http://www.ece.mcmaster.ca/faculty/nikolova/antenna_dload/current_lectures/L21_Mstrip2.pdf.
the fringing effect makes the effective electrical length of the patch longer than its physical length.Thus, the resonance condition depends on Leff not L. where Leff=L+2deltaL. So the every single parameters of the antenna depends on Leff. you can find a detailed explanation in this document: http://www.ece.mcmaster.ca/faculty/nikolova/antenna_dload/current_lectures/L21_Mstrip2.pdf
Also, to add to the above answer, the radiation mechanism in patch antenna is due to the fringing fields. Hence, a wider patch provides a wider dimension from which fringing can occur and hence is more suitable as a radiator than a narrower one which is used more as a transmission structure.
For a half wavelength long rectangular microstrip antenna, the fringing fields at both sides are of opposite polarity (since they are half wavelength apart or 180 degrees apart in phase). Therefore, if the fringing fields at both edges are decomposed into orthogonal components, the vertical components cancel out due to opposite polarity, while the horizontal component stays intact. This gives rise to 2 radiating slots on the edges, which is the major reason for the radiation mechanism of a microstrip antenna.
For details of radiation mechanism due to radiating slots arising from fringing effects, please refer to Microstrip Antennas by Inder Bahl and Prakash Bhartia.
Generally, fringing fields increase due to increase in antenna width, substrate height and due to decrease in substrate dielectric constant. As fringing fields increases then gain, bandwidth and efficiency are improved due to increase in radiated power.
For clear information, please refer "Broadband micro strip antennas by girish kumar" in 2nd chapter.
As explained by others, fringing effect offers different length (Leff). Hence, as far as design process is concern, one has to design physical dimension for higher frequency than the operating one. In directly all parameters are affected by the dimensional design.
The feeding mechanism you have shown in your figure are unprotected to fringing. This will affect your input impedence and radiation, in turn, pattern
Fringing effect comes due to electric field lines which makes the antenna size wider after excitation. The main cause of fringing effect is due to width and position of feed in antenna. Fringing fields help in radiation and give more directive radiation pattern but resonant frequency is shifted from your desired frequency.
I suggest to spend a little time to review the antenna theory related to the patch antenna design.
Figure 1. The antenna patch and the feed line are not matched.
Figure 2. You can control the level of matching by adjusting the length of the offset.
Figure 3. It looks a dipole antenna not patch antenna.
Figure 4-5. It is not a good design that can be analyzed with a theoretical notion.
Figure 3-4. Here you are changing the ways of the current ligne, so the real length of the patch. that results in the varying of the resonant frequency.
Dear Hamza Kaouach thank you for the review.
In my design above I haven't calculated any of the parameters but I made the design just to make my question clear as I am confused on how the fringing effect of each of the design affect the performance of the antenna. for example comparing design #2 and #3 there is two more slots in #3 so obviously there would be more fringing effect in #3 so how does it makes the difference?
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