Design and implementation of three branch line coupler at 3.0 GHz frequency for S-band radar system

This paper presents design and implementation of three branch line coupler (3-BLC) at 3.00GHz Frequency. The implementation 3-BLC is used for phase inverter to reduce the interfering of the side lobs antenna in FM-CW Radar that two antenna (TX-RX) installed parallel separated. The proposed design was simulated and fabricated using a low cost Fr4 epoxy substrate with 4.5 dielectric constant, thickness of substrate is 1.6 mm. Simulation and measurement result shown as graph that contains return loss (or VSWR), insertion loss and isolation. The simulation and measurement result have a good result where VSWR value is below 1.3 for all ports. The direct port (S12) of -7.38 dB, coupler (S13) of -2.25 dB and Isolation (S14) of -21.5 dB. A satisfactory agreement between on the simulation and measurement results, this 3-BLC have a good and acceptable direct port, coupler and isolation, and also produce a better return loss of input and output ports for operating on 3.00 GHz.