WIDE BAND ELECTRONICALLY TUNABLE FILTERS
Technical note. no. 1, 1 Jul-30 Sep 1962
WATKINS-JOHNSON CO PALO ALTO CA
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Work on hysteresis, linearity and temperature compensation in YIG filters is discussed and measurements are reported for hysteresis using both core iron and hypernik pole piece in a WJ-501 filter 2-4 kmc reciprocal bandpass filter. Hysteresis amounts to about 0.1 percent of the tuning range for hypernik pole pieces. Linearity and temperature compensation measurements are reported for core iron pole pieces. Linearity is -2 mc and resetability -3 mc. With the filter adjusted for minimum temperature coefficient at 3 kmc the temperature coefficient at 4 kmc was maximum of 0.1 mcoC. A four stage X-band bandpass filter and a 2 stage X-band band-reject filter are described. The X- band bandpass filter suffers from band distortion above 11 kmc as also does the band-reject filter. Even below 11 kmc some improvement of the X-band band-pass filter will be necessary to meet the objectives of the program. The X-band band-reject filter gave the required 50 db rejection at single frequencies but the two resonators gave tracking difficulty. Initial studies of strip line circuits for use below 8 kmc are also outlined.
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