Hello, i want to know how can i design a Series feed network in hfss?
what steps can i take?
For example here, i want to design 2×1 patch array antenna With series feed as shown in fig, but i don't know: for the Feed Width of second patch, i should use 70ohm impedance or 50ohm (same Feed Width of the first patch)?? which one is correct?
Help please
Hi there, I think you might have to change the positions of the two patches. The bottom patch should occupy the top patch position and vice versa. Then the one with inset fed will be on the top (according to the figure) and the normal patch antenna will be down. In this case the feed line width for the inset fed patch should be decreased (use higher values of impedance), than the normal patch feed line width.
Because when using inset fed structure at the end of the elements, the total input impedance will be determined by the terminal element (inset fed patch), because this should be the one with lowest impedance.
Usually case, high impedance is seen (that is why decreased feed line width) , but the impedance will be reduced by moving the feed inward towards the center of the patch (inset fed).
The width of feed line depends upon the edge impedance of the Patch, e.g. when you are using inset fed patch, the inset goes inside patch to a point where its impedance is 50Ohms and then you can straight-a-way use 50Ohm microstrip line for feeding. If another patch is fed in series to this then you have to keep in mind that the impedance of the two patch should match with each other. So you decide the impedance of the transformer accordingly. e.g. in the first design you have posted the microstrip is of 70 Ohms, but the edge impedance of both the patches is something else so you need a QWT between edge of patch and 70Ohm line to match the impedance, on both ends of 70 Ohm line.
For series-fed patch array, the feed line width should be a small fraction of the patch width in order to avoid blockage of the radiating edges. On the other hand, extremely narrow lines suffer from high losses and are more vulnerable to fabrication error. Considering these limits, any feed line can be used in the design [Ref.: High-Isolation Antenna System for X-band Synthetic Aperture Radar]. Of course, these feed lines are for patches which are not directly attache to the SMA connector (upper patch in your figs).
You have to match the impedance of the patch which is directly attached to the SMA connector (lower patch in your figs). This matching can be done through inset feed method or using matching transformer.
Hope it helps.
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