Thin film bulk acoustic wave filter

Markku Ylilammi, Juha Ellä, Jyrki Kaitila, Meeri Partanen

    Research output: Contribution to journalArticleScientificpeer-review

    52 Citations (Scopus)


    Thin film bulk acoustic wave (BAW) resonators (FBAR) are fabricated on a silicon nitride bridge using a ZnO piezolayer on a glass substrate and surface micromachining by standard thin film technology. These resonators exhibit a coupling constant kt2 = 7.8% at the first thickness extensional wave mode and are used as impedance elements in a ladder filter in the 1-GHz frequency band of mobile telecommunications. An electrical equivalent circuit is used to characterize the properties of the resonators and to show how the performance of the filter depends on the parameters of the resonators. 2.5% bandwidth, 2.8-dB insertion loss, and 35-dB selectivity are obtained in a filter with six resonators. The technology can be used to manufacture miniature microwave filters without any additional inductances.
    Original languageEnglish
    Pages (from-to)535-539
    JournalIEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control
    Issue number4
    Publication statusPublished - 2002
    MoE publication typeA1 Journal article-refereed


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