Circular Polarization 5.5 GHz Double Square Margin Antenna in the Metal Framed Smartphone for SIL Wireless Sensor

The wireless sensor network system requires complex configuration component of the electromagnetic feeding network circuit for SIL (Self Injection Locked) wireless sensor on the smartphone metal-framed, and inexpensive material, especially for the electromagnetic component. 5.5 GHz Double Square Margin Microstrip Antenna with 90-degree hybrid directional coupler for SIL Wireless sensor. it is the novel shaped microstrip Antenna with the free frequency, simpler configuration, and low-cost material at the 5.5 GHz for SIL wireless sensor. This system is an important part component of SIL wireless sensor that is package consists of a 5.5 GHz Microstrip antenna with the Double Square Margin, and 90-degree hybrid directional coupler to produce 90-degree phase difference with two input and two output. The Antenna has single band and narrow bandwidth with the frequency is 4.41 GHz until 5.58 GHz under -10dB S parameter and frequency resonance 5.5 GHz, the radiation pattern is directional and the gain is 6.83 dB and 50 ohm line strip impedance, The 90-degree hybrid coupler has S11 of -31.29 dB, S21 of 31.48 dB, S31 of -3.58 dB, and S41 of -3.81 dB that all is specification has a good operation. And overall size of the proposed antenna system is 100 mm times 55.7 mm with FR4 (Phenolic White Paper) with a dielectric constant is 4.4 that has 50 ohm.