LTCC Full-Matching Marchand Balun

In this paper, one full-matching Marchand balun is implemented in LTCC. To realize resistors to achieve matching at both balanced ports, co-fired surface resistors are employed at the top and bottom layers in the design. For demonstration, one sample balun operating at 2.4 GHz is designed, simulated, fabricated and measured. The measured return loss for the unbalanced port is found to be better than -10 dB over the frequency band from 2.0 GHz to 2.8 GHz, or around 33%. The measured return losses for the both balanced ports are better than -10 dB across the operating band. The measured amplitude and phase imbalance between both balanced output ports are within 1 dB and ±2°, respectively, over the passband. It is observed that the measured and simulated results are in reasonably good agreement.