초록 ▼

An electronically adjustable capacitor (varactor), an active element such as a Field Effect Transistor arranged to exhibit negative resistance, and an inductor are arranged as a frequency tunable resonator suitable for use at microwave frequencies. The negative resistance of the active element may b

An electronically adjustable capacitor (varactor), an active element such as a Field Effect Transistor arranged to exhibit negative resistance, and an inductor are arranged as a frequency tunable resonator suitable for use at microwave frequencies. The negative resistance of the active element may be adjusted to compensate for the resistance of the other resonator components such that the resonator exhibits very high Q and therefore high selectivity and low loss. The resonator may be used as a filter element in a tunable filter. Alternatively the negative resistance of the active element may be adjusted such that the resonator exhibits net negative resistance and may be incorporated in a tunable reflection type amplifier.

대표청구항 ▼

An electronically frequency tunable resonant circuit, comprising in combination: a capacitance means, the value of which is electronically adjustable; an inductance means coupled in combination with said capacitance means arranged to resonate at a selected one of a range of frequencies dependent on

An electronically frequency tunable resonant circuit, comprising in combination: a capacitance means, the value of which is electronically adjustable; an inductance means coupled in combination with said capacitance means arranged to resonate at a selected one of a range of frequencies dependent on the value of said capacitance; said combination also including resistance means; a field effect transistor (FET) characterized by a negative resistance, arranged with said combination to offset the resistance of said resistance means, said FET including a source terminal, a drain terminal, and a gate terminal; and means for providing a feedback path for said FET to produce negative resistance between said source and drain terminals.