{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,7,30]],"date-time":"2026-07-30T16:57:42Z","timestamp":1785430662254,"version":"3.56.0"},"reference-count":26,"publisher":"MDPI AG","issue":"7","license":[{"start":{"date-parts":[[2026,7,6]],"date-time":"2026-07-06T00:00:00Z","timestamp":1783296000000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"National Science & Technology Council","award":["NSTC 113-2221-E-018-009"],"award-info":[{"award-number":["NSTC 113-2221-E-018-009"]}]},{"name":"National Science & Technology Council","award":["NSTC 112-2221-E-030-009-MY3"],"award-info":[{"award-number":["NSTC 112-2221-E-030-009-MY3"]}]},{"award":["NSTC 113-2221-E-018-009"],"award-info":[{"award-number":["NSTC 113-2221-E-018-009"]}],"id":[{"id":"https:\/\/ror.org\/02kv4zf79","id-type":"ROR","asserted-by":"publisher"}]},{"award":["NSTC 112-2221-E-030-009-MY3"],"award-info":[{"award-number":["NSTC 112-2221-E-030-009-MY3"]}],"id":[{"id":"https:\/\/ror.org\/02kv4zf79","id-type":"ROR","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Micromachines"],"abstract":"<jats:p>The contribution of this paper is to propose the design and experimental validation of split-type dual- and tri-band bandpass filters (BPFs) based on highly miniaturized substrate-integrated coaxial cavities (SICCs). The proposed split-type multiband filter design achieves exceptional circuit-area efficiency within the SIW-related (substrate-integrated waveguide) split-type filter category. The size-reduced SICCs are fabricated using two substrates of different thicknesses. The coupling matrix method is employed to synthesize the responses of the example dual- and tri-band filters. The proposed dual-band filter achieves a circuit size of 0.17 \u03bbd \u00d7 0.17 \u03bbd, with insertion losses of 0.78 and 0.89 dB for the two passbands, and isolation between the passbands exceeding 15 dB. For the tri-band filter, the circuit size is 0.27 \u03bbd \u00d7 0.34 \u03bbd, with the insertion losses of 0.96, 2.6, and 1.21 dB across the three passbands, accompanied by similarly effective isolation. Experimental results validate the circuit designs and performance, demonstrating strong agreement between measured and simulated data.<\/jats:p>","DOI":"10.3390\/mi17070814","type":"journal-article","created":{"date-parts":[[2026,7,6]],"date-time":"2026-07-06T14:56:42Z","timestamp":1783349802000},"page":"814","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["Split-Type Multiband Filter Design Using Ultra-Miniaturized Substrate-Integrated Coaxial Cavities"],"prefix":"10.3390","volume":"17","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-8278-0033","authenticated-orcid":false,"given":"Ming-Chih","family":"Chen","sequence":"first","affiliation":[{"name":"AI Development Center and Graduate Institute of Business Administration, Fu Jen Catholic University, New Taipei City 242062, Taiwan"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Ci-Fang","family":"Jheng","sequence":"additional","affiliation":[{"name":"Department of Electronic Engineering, National Changhua University of Education, Changhua City 50074, Taiwan"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Gawn-Wei","family":"Su","sequence":"additional","affiliation":[{"name":"Wistron Corporation, Taipei 11469, Taiwan"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-0942-8217","authenticated-orcid":false,"given":"Chung-I G.","family":"Hsu","sequence":"additional","affiliation":[{"name":"Department of Electrical Engineering, National Yunlin University of Science and Technology, Yunlin 64002, Taiwan"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-9112-0187","authenticated-orcid":false,"given":"Min-Hua","family":"Ho","sequence":"additional","affiliation":[{"name":"Department of Electronic Engineering, National Changhua University of Education, Changhua City 50074, Taiwan"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2026,7,6]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"3265","DOI":"10.1109\/TMTT.2005.855749","article-title":"Design techniques for dual-passband filters","volume":"53","author":"Macchiarella","year":"2005","journal-title":"IEEE Trans. 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