Design and Analysis of Dual-Loop Patch Antenna with Hybrid for Self Injection Locked Sensor Application

In this project, a double loop patch antenna system with a hybrid coupler is designed at 2.4 GHz operating frequency for Self injection locked wireless sensor application. The double loop patch antenna system consists of a double loop patch and a hybrid 90° coupler to generate a phase shift of 90° at the output component relative to the input. It has a narrow bandwidth ranging from 2.34 GHz to 2.46 GHz, with a return loss of -13.88 dB and a resonance frequency of 2.4 GHz. It uses 50Ω microstrip lines for impedance matching, the coupler has <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathbf{S 2 1}$</tex> (Isolated port) of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathbf{- 1 3. 2 2 ~ d B, ~ S 3 1 (C o u p l e d ~ p o r t) ~ o f ~ - ~} \mathbf{2. 9 1 ~ d B, }$</tex> S41(Through port) of -4.92 dB and S11(Input port) of -16.36 dB. For the double loop patch antenna system, when excitation is applied individually at Port 1 and Port 2, the phases of S11 (return loss) remain almost the same, with small acceptable difference. The double-loop patch antenna system attains a peak gain of 2.80 dB at 2.4 GHz. Overall, the design is implemented using Ansys HFSS with dimensions of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$96 \text{mm} \times 92 \text{mm}$</tex>. FR4 material, having a dielectric constant of 4.4 and a height of 1.6 mm, is used.