Title :
Novel active RF tracking notch filters for interference suppression in HF, VHF, and UHF frequency hopping receivers
Author :
Ghadaksaz, Masood
Author_Institution :
GTE Lab. Inc., Waltham, MA, USA
Abstract :
The author describes a novel low-loss, highly selective, fast electronically tunable RF active notch filter with wide passband which has been developed to suppress strong fixed and frequency-agile CW and narrowband interfering signals. The design concept is based on the principle of using maximum realizable L/C ratio for the notch resonator to achieve optimum selectivity with a minimum number of tunable notch resonators, and the synthesized negative resistance of an RF capacitive transistor to overcome the dissipation losses in the passive elements to produce high-Q RF resonators. This approach allows compact lumped-element construction of highly selective notch filters with low passband insertion loss at radio frequencies using low-cost surface mount chip components. Experimental confirmation of the design feasibility was achieved using several developmental HF and VHF active varactor-tuned notch resonators and filters with regard to canceling the effects of parasitic losses in the passive notch resonator, notch resonator selectivity as a function of L/C ratio, peak attenuation, passband bandwidth and passband insertion loss and broadband stability
Keywords :
active filters; frequency agility; interference suppression; notch filters; radio receivers; radiofrequency filters; 2 to 400 MHz; HF; UHF; VHF; active RF tracking notch filters; active varactor-tuned notch resonators; design; frequency hopping receivers; interference suppression; low-loss highly selective fast electronically tunable filter; wide passband; Active filters; Insertion loss; Interference suppression; Low pass filters; Narrowband; Passband; RF signals; Radio frequency; Resonator filters; Signal synthesis;
Conference_Titel :
Military Communications Conference, 1991. MILCOM '91, Conference Record, Military Communications in a Changing World., IEEE
Conference_Location :
McLean, VA
Print_ISBN :
0-87942-691-8
DOI :
10.1109/MILCOM.1991.258410