Accession Number : AD0702135

Title :   FILTER SYNTHESIS TECHNIQUES.

Descriptive Note : Final technical rept. 1 Dec 67-30 Nov 69,

Corporate Author : GEORGIA INST OF TECH ATLANTA ENGINEERING EXPERIMENT STATION

Personal Author(s) : Denny,Hugh W. ; Wilson,Charles S.

Report Date : FEB 1970

Pagination or Media Count : 65

Abstract : Several active filter techniques for the reduction of receiver interference in the 225 to 400 MHz range are described. Positive feedback Q multiplier techniques were extended to include (1) the use of multiple feedback loops to achieve a high order of stable multiplication in each stage and (2) the use of cascaded stages of Q-multiplied resonators to obtain improved skirt selectivity. Negative resistance Q multiplication was achieved over a wide frequency range through the development of a common collector transistor amplifier that exhibits stable negative resistance properties in the UHF region. The negative resistance amplifier was incorporated into a breadboard model of a tunable filter which employs both active and passive stages to produce a high Q response characteristic with high skirt selectivity over the entire band. An AM cancellation filter that achieves suppression of an unwanted signal by cancellation via a synthesized replica of the signal was developed. The breadboard model demonstrated a suppression capability of 30-35 dB for AM signals and about 50 dB for CW signals. To enhance the capabilities and versatility of UHF active interference suppression filters, linearization techniques for broadband solid state amplifiers were investigated. The application of negative feedback and the use of the push-pull mode of parallel operation provided a significant reduction in harmonic generation while retaining good gain-band-width characteristics in amplifiers of one-watt power output capabilities. (Author)

Descriptors :   (*RADIOFREQUENCY FILTERS, DESIGN), (*RADIOFREQUENCY INTERFERENCE, REDUCTION), SYNTHESIS, ULTRAHIGH FREQUENCY, FEEDBACK AMPLIFIERS, NEGATIVE RESISTANCE CIRCUITS

Subject Categories : Electrical and Electronic Equipment

Distribution Statement : APPROVED FOR PUBLIC RELEASE