Integrated oscillator and radio telephone using such an oscillator

A radio-telephone apparatus used for emitting or receiving radio-electric signals in a given range of frequencies, which apparatus comprises an antenna and filtering system allowing reception of a signal having a frequency which is selected within said range of frequencies, in which apparatus a frequency conversion, from the frequency to be selected to an intermediate frequency, is realized by means of a mixer receiving the selected radio-electric signal and a signal emitted at the output of a local oscillator, said signal having a frequency which is measured by a control module which supplies a tuning voltage at the output allowing control of the frequency of the output signal of the local oscillator such that said frequency is equal to the difference between the frequency to be selected and the intermediate frequency, wherein the local oscillator is an oscillator intended to provide an output signal having a frequency which is variable as a function of a tuning voltage, comprising:

• a passive part having two output terminals between which the output signal is taken, and an input terminal intended to receive the tuning voltage, and comprising two series-arranged variable capacitances, thus forming a capacitive branch whose extremities constitute the output terminals, and of which a junction point between the variable capacitances constitutes the input terminal, the output terminals being connected to a first power supply terminal via two inductances having equal nominal values,
• an active part comprising a first and a second transistor each having a biasing terminal, a reference terminal and an output terminal, the output terminals of the first and second transistors being connected to the output terminals of the passive part, the reference terminals of said transistors being connected to a second power supply terminal via a current source, the biasing terminals of the first and second transistors being connected to the output terminals of the second and first transistors, respectively, via two coupling capacitances having equal nominal values,
• characterized in that, the first and second transistors being bipolar transistors whose bases, collectors and emitters constitute the biasing terminals, the output terminals and the reference terminals, respectively, the passive part comprises two high-pass filters, each being inserted between one of the collectors and one of the variable capacitances.

An oscillator comprising:

• a transistor having a base, an emitter and a collector, said collector being connected to a first power supply and being an output of said oscillator, and said emitter being connected to a second power supply;
• a variable capacitance having a first terminal and a second terminal, said first terminal being connected to an input terminal of said oscillator;
• and
• a high pass filter connected between said collector and second terminal of said variable capacitance.