{"id":160409,"date":"2021-07-15T15:00:48","date_gmt":"2021-07-15T15:00:48","guid":{"rendered":"\/forum\/forums\/topic\/analysing-the-s11-with-and-without-a-head-model-in-front-of-an-antenna\/"},"modified":"2021-08-13T04:16:08","modified_gmt":"2021-08-13T04:16:08","slug":"analysing-the-s11-with-and-without-a-head-model-in-front-of-an-antenna","status":"closed","type":"topic","link":"https:\/\/innovationspace.ansys.com\/forum\/forums\/topic\/analysing-the-s11-with-and-without-a-head-model-in-front-of-an-antenna\/","title":{"rendered":"Analysing the S11 with and without a head model in front of an antenna"},"content":{"rendered":"
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Hello,<\/p>\n

I am simulating a system having an antenna in front of a head model. I am running simulations for 2.85 – 3.55 GHz at separate single frequency setups with frequencies at 0.1 GHz interval. The antenna dimensions are 30mm x 44.4 mm. So the far field at 3.5 GHz is at 4.6 cm. I have placed the head model at 4.5 cm away from the antenna. So that it is in the far-field. I have placed radiation boundary at lambda\/4 distance from the antenna radiating planes (lambda at 2.75 GHz). <\/p>\n

I am having the following issue: for frequencies above 3.25 GHz, the S11 for the system with head model is coming smaller than the S11 without the head model in the system. But with the head model the reflections should be higher. Can anyone help me figure our why this is happening? I am attaching the S11 plots for the system with head model and for antenna only. <\/p>\n

(In the figure, 'ant' means antenna only simulation. '0 to 80' means I have rotated the antenna at different angular positions around the head, i.e., 0 degree, 10 degree etc., keeping 4.5 cm distance from the head, when there is a small blood clot placed inside the head. 'without blood' means when there is no blood clot inside the head. Here the S11 for 'ant' should be less than the other plots where there is head in front of the antenna. But it is showing small reflections when the head is removed form the system, keeping all the other setup the same, for example the radbox size.) What can be the reason for getting smaller reflection when there is head model, at frequencies above 3.25 GHz? The presence of head model should produce more reflections at every frequency. <\/p>\n

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