High frequency band-pass amplifier with adjustable impedance and oscillator including it

Claim 1

An oscillator comprising: a high frequency band-pass amplifier with adjustable impedance, said amplifier comprising a transistor connected in common base and having an emitter loaded by a resistive divider bridge including a first resistor connected to ground and to a point called the mid-point of the resistive divider bridge, connected in series with a second resistor connected to said mid-point and to the emitter of the transistor, said mid-point of the resistive divider bridge forming the input of the amplifier, said transister having a collector loaded by a parallel LC circuit one end of which is connected to a power supply voltage and having one inductive side and one capacitive side (c), two points, called the midpoints, of the inductive side (L) and or the capacitive side, respectively, (C) forming the outputs of the amplifier said transistor having a base biased by a DC supply voltage and connected to ground via a capacitor ensuring common base operation in the pass-band of the amplifier; and, a resonator connected between the input and one output of the amplifier, wherein the frequency of resonance (f O ) of the parallel circuit (LC) is equal to a chosen frequency (f O ) of the resonator, and the amplifier is adjusted such that the open loop transfer function fulfills the Berkhausen conditions only for the resonance peak of the resonator corresponding to the chosen frequency (f O ).