A compact 3-dB 90º directional coupler in integrated passive devices manufacturing process for LTE applications

A compact 3 dB 90° directional coupler is fabricated by integrated passive device (IPD) process on SI-GaAs substrate for long term evolution (LTE) application. The operating frequency is between 800 MHz to 915 MHz, which is the LTE application frequency band 5 and band 8. At the center frequency of 875 MHz, the proposed coupler achieved -0.8 dB of insertion loss and -3.5 dB of coupling. The reflection coefficient S₁₁ and the isolation S₃₁ are -23.13 dB and -25 dB, respectively. It has 0.6 degree of phase error over the frequency range. This work can be a good candidate for 3-dB divider/combiner and bandpass filter as well as for balanced power amplifier (PA) application.