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|Characterization of LTCC Material at G-Band|
|Keywords: LTCC, characterization, mm-wave frequency|
|A technique for characterizing dielectric materials at high millimetre-wave frequencies is presented, together with new data on the properties of dielectrics used in planar circuits. Comparative data are presented on the loss tangent and dielectric constant from difference types LTCC and alumina substrates. The primary contributions are the generation of new data on common dielectric materials at G-band. A free-space technique was used for evaluation of dielectrics at mm-wave frequency. This technique overcomes the constraint of waveguide measurement systems where at high frequency the waveguide dimensions are too small to allow insertion of the dielectric samples under test. It also overcomes the significant measurement error in the planar resonant ring technique, where conductor and dielectric losses have to be separated, as it is difficult to precisely define the surface loss in the conductor when the skin depth in the conductor is less than the rms surface roughness. Two samples of difference thickness were prepared of each type of LTCC material. For the measurement, the tiles were positioned in the far-field region between two pyramidal horns with the plane of the dielectric perpendicular to the direction of propagation of the wave. The thinner of the two sample was used as the through calibration standard. Note that the gains of the pyramidal horns were sufficient to ensure that the entire main radiation beam was enclosed within the area of the sample. The measurement data provided some useful information on losses in materials at high mm-wave frequencies. Equations to calculate the tan ä and the permittivity of the material have also been developed. The main outcomes of the work: (1) The proposed free-space measurement technique was shown to yield reasonable results at 150GHz. (2) The measured losses in high purity indicated that this still provides a viable substrate material at G-band. (3) Some of the LTCC exhibits higher loss at G-band compare to the high purity alumina. MOVED FROM SUBSTRATE MATERIALS TO CERAMIC & LTCC 5-4-09.|
|Nurul Osman, Student
University of Surrey
Guildford, Surrey GU2 7XH,