Antenna modeling in smartphone devices, using electromagnetic simulation software, has improved significantly by allowing the simulation of the antenna behavior in complex environments surrounding the antenna. Thus, current electromagnetic software allows the simulation of handheld antennas regarding not only the human presence (such as human head and hand) but also the presence of nearby components (such as cameras, batteries, displays, and speakers).
The phantom head model, called SAM (Specific Anthropomorphic Mannequin), was first introduced in 2002. The material inside the plastic shell has specific electrical properties, that is, dielectric constant and conductivity that are modeled closely to the real human head. Modeling the hand was more difficult and it took longer to get to the final set of phantom hands.
Antenna designers had to face the challenge of designing antennas with performance that had to meet various operators’ requirements with different environment conditions. In certain phone designs where the antenna is external or when there is enough antenna volume for the internal antenna design, it is not a problem to meet all operators’ requirements. When the design is limited due to industrial or mechanical designs, then antenna variants for different markets are needed, each one of them meeting the operator’s requirements of their market while the over-the-air (OTA) performance in the roaming market can be relaxed a little bit.
Simulation at Phone Level
After the antenna design is complete, the next step is to include it in the complete phone. This enables the evaluation of the coupling effects of neighboring objects such as the battery, camera, flash capacitors, etc., as well as the influence of dielectric materials such as the housing and display screen.
Simulation at Body LevelA final simulation for the smart mobile phone is to evaluate it in the presence of a human body, with particular emphasis on the head and hand. In accordance with IEEE standards, such as 1528, the Standard Anthropomorphic Model is used as the head model. The frequency dependent dielectric properties of the tissue simulating liquid are also defined by this standard and can be modeled as a dispersive material in the simulation tool.Such a simulation can give important insight into how the SAM phantom or the homogeneous body models affect the performance of the mobile phone. Here it can be seen Return loss data of Bluetooth antenna degraded and also there is higher resonance frequency shift.
Simulated Return Loss and Radiation PatternThe radiation pattern and radiation efficiency is also affected with Presence of SAM and Hand model.Presence of hand and head make antenna pattern directions ( Red curb) while it can be seen that without head and hand model antenna pattern (Blue curb) is nearly omnidirectional.
Simulation at Body Level – MIMO Antenna
SAM phantom is also affecting the performance of the MIMO antenna system. Here it can be seen Return loss data of MIMO antenna is shifted at lower frequency side also at 2.4 GHz antenna resonance is good.