Wideband Electronically Tunable Filters for Vhf-uhf Band
Author: George H. THIESS
Publisher:
Published: 1965
Total Pages: 92
ISBN-13:
DOWNLOAD EBOOKMeasurements of linewidth and Q have been made at frequencies from 90 Mc to 1000 Mc on 40 gallium substituted YIG resonators. Both spheres and discs were measured by a dynamic technique in which a resonator coupled energy between two coaxial lines. A complete description of the experimental setup is given and the data obtained is analyzed. The measured Q of gallium substituted YIG was found to be too low for practical filters at frequencies below 200 Mc at all temperatures from room temperature up to the curie temperature of the resonator. It is also predicted, from theoretical considerations, that at no other temperature higher than 10 K, is the Q likely to be any higher. It is recommended that further development of low magnetization materials be carried out, with the special aim of producing materials free of gradients and with low cutoff frequencies. The insertion loss of the UHF filter was typically 3 to 4 db across the 300 Mc to 1000 Mc band. The VHF filter was approximately 4 db except at 90 Mc where it rose to 11.5 db. It is concluded that YIG filters are probably not practical at frequencies below 200 Mc unless improved materials become available. (Author).
