Balanced BPFs implemented using IPD (integrated passive devices) technology

Perfectly balanced BPFs are realized in this paper through IPD technology. To create a symmetric structure, two three-stage coupled BPFs are combined. The resonators of the filter are made with mircostrip-line inductors and MIM capacitors. SAAO (Selectively Anodized Aluminum Oxide) and HRS (High Resistivity Silicon) substrates are used to make the filters. All of the fabricated balanced BPFs have a maximum in-band PI (Phase Imbalance) within 0.5° The maximum in-band MD (Magnitude Difference) is less than 0.25 dB. The fabricated filters are very small, at 1.5 × 1.36 mm² (SAAO) and 1.38 × 1.28 mm² (HRS), and their IL (Insertion Loss) values are 2.57 dB and 1.95 dB at 2.45 GHz, respectively.