Microwave Integrated Circuit Techniques.
Final rept. 15 Apr 72-15 Apr 73,
GENERAL ELECTRIC CO UTICA NY AEROSPACE ELECTRONIC SYSTEMS DEPT
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The significance of this research and development to the Air Force is that the evaluation of the microwave transmission properties of Coplanar Waveguide demonstarte it to be inferior to presently used microstrip in nearly every respect. The objective of this program was to fully characterize Coplanar Waveguide CPW for its potential use as a microwave integrated circuit MIC transmission medium. Coplanar waveguide is more easily fabricated than presently used microstrip on alumina. In addition, semiconductor devices are readily incorporated on CPW thus further reducing cost of circuit fabrication. Transmission properties investigated included phase velocity, characteristic impedance and transmission loss. These properties were evaluated as they relate to circuit dimensions and substrate thickness. Substrate material utilized to support the CPW in this investigation included alumina, with relative dielectric constant equal to 9.6 and barium tetratitanate with dielectric constant equal to 38. A laser metal removal facility with trimming accuracy of 0.25 mil was utilized to trim circuitry while making measurements thus producing a large amount of expreimental data. CPW on both substrate materials was found to be susceptible to spurious modes of propagation, with barium tetratitanate being worse than alumina. In addition to the spurious mode problem, the transmission properties of CPW are inferior to those of microstrip alumina in every repect.
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