Bandpass filter with an active element
AssigneeRCA Corporation
InventorFranco N. Sechi
Life of this patent
Estimating the term…
Abstract
An amplifier including an in phase feedback signal to therefore exhibit negative resistance is receptive of an input alternating signal which includes a frequency F. The output of the amplifier is coupled to a resonator adjusted to a center frequency F and having undesirable resistance which is offset by the negative resistance of the amplifier. The resonator includes an inductor and adjustable capacitor arranged either in series or in parallel with the amplifier to therefore change the value of F.
Claims19
A bandpass filter for passing radio frequency signals, including frequency F, over a given range of frequencies comprising in combination:
- a circuit reference point;
- an output terminal;
- a negative resistance means including first and second amplifying means connected in cascode between said reference point and said output terminal with said first amplifying means coupled between said second amplifying means and said reference point and responsive at an input terminal thereof to said radio frequency signals which include said frequency F for amplifying the same, means for feeding back in phase a sufficient portion of the signal appearing at said output terminal to the junction of said first and second amplifying means for producing a negative resistance at said output terminal relative to said circuit reference point;
- and
- an inductor and a capacitor coupled to said output terminal to form a resonant circuit having a center frequency of said F and having undesired resistance which is offset by said negative resistance.
Dependencies are inferred from the claim text.