LTCC Broadside Coupler Design with Branch Lines for Enhanced Performances

This paper proposes a compensation technique to enhance return loss and directivity of a broadside coupler by using additional branch lines. The use of branch lines at all ports results in improvement of impedance matching for the tight coupled broadside coupler. The equal-division broadside couplers with and without compensation have been designed and fabricated by employing low temperature co-fired ceramic (LTCC) process. The measured results of the proposed coupler exhibit more than 8.0 dB improvement of return loss and isolation compared with those of the conventional one at the center frequency of 3.5 GHz. The measured results show good agreement with the simulated ones, considering the fabricated shrinkage error of LTCC process.