phased array antenna frequency pulling

- December 7, 2023 at 6:32 pm
  
  Alexander Skerbitz
  Subscriber
  
  Hello,
  I am designing a phased array antenna using a linear array of inset-fed microstrip patch antennas. I first designed the element to radiate at 2.4 GHz (don't need any appreciable bandwidth) and then expanded to an array. Here is a picture. element spacing is standard lambda/2. The problem is when I simulate the whole array, the active S parameters at the ports drop from 2.4GHz to about 2.3GHz (and I have played with which elements are on, relative energy strength, phase shift etc.). I include graphs below to illustrate. I understand that there is going to be coupling with the fields, especially since it is on microstrip, but I need to know whether I need to tune/redesign this design to radiate at 2.4GHz, if this is just error on my part with simulation, or if I can just ignore the sim results and have this antenna radiate well at 2.4GHz. Also, for the antenna designers, is this a common issue? how do you deal with it?
  I used lumped ports at each of the feed lines on the edge of the board to excite the radiators.
  Perhaps my matching is poor? Maybe I need to extend the board size? I don't know. Would love some help with this. Thanks.
- December 8, 2023 at 8:10 pm
  
  Faezeh Ladani
  Ansys Employee
  
  Hi Alexander,
  In general, it is expected to see different performance of the antenna when placed in array, compared to stand alone. Yet, it is up to user to navigate design challenges. We can only provide guidance on using the tool (here HFSS).
  If you have access to customer portal, you can file a support case and we can double check the setup. Otherwise, I suggest you go through some of HFSS Open Examples as well as online help to double check the setup in your design. Moreover, check if all the patches got a good mesh. If all this is set, then HFSS results are reliable and based on your objectives, you can decide whether to modify/tune the design or move forward.
  Also, note that HFSS has a special workflow for simulating finite arrays. In this case, the array is still small, so your approach of copy/pasting the element is fine. But for larger arrays, make sure to take advantage of 3D Component finite array approach. We have an open example about it: From File>Open Examples>HFSS>Antennas>FiniteArray_Radome_77GHz_3D_CADDM