US 4,360,790 A · Varactor controlled push-pull oscillator

Abstract

An oscillator arrangement is disclosed which is controllable in its frequency and which comprises a control input for frequency variation and a transformer output, whose frequency-determining oscillating circuit possesses, as a controllable reactive element, two varactor diodes which are connected in opposing fashion and whose capacitance largely represents the oscillating circuit capacitance. Two feedback oscillator circuits are combined to form a push-pull circuit in that the output terminals of the oscillator circuits are connected in respect of d.c. to a reference potential by way of a central tap of the primary winding of a common output transformer. In addition, the two varactor diodes are oppositely poled and interconnected in respect of d.c. by way of the opposite terminals of an oscillating circuit inductance and, at their opposite terminals, are each connected to respective bases of transistors of two oscillator circuits, the emitters of the transistors being connected together and by way of respective resistors to a power supply and the collectors being connected together by way of opposite terminals of the primary winding of the output transformer. In order to form the control input, the oscillating circuit inductance is provided with a central tap.

Claims14

Dependent claims

An oscillator arrangement which is controllable in frequency, comprising:

a frequency control input;
a frequency-determining circuit including two varactor diodes connected in opposing fashion, the capacitance of said varactor diodes largely representing the oscillating circuit capacitance, and an inductance having first and second terminals connected to respective varactor diodes and a tap connected to said frequency control input;
an output transformer including first and second terminals and a tap connected to a reference potential;
and
a pair of feedback oscillator circuits each including a first terminal connected to a respective varactor diode, a second terminal connected to a respective transformer terminal to provide push-pull operation, and an emitter terminal connected to the emitter terminal of the other.

2 more elements

An oscillator arrangement having controlled frequency, comprising:

a frequency control input;
a control voltage source connected to said frequency control input and having an internal resistance;
an absorption wave trap connected to said frequency control input and to a reference potential, said absorption wave trap having a resonant frequency greater than twice the middle frequency of the frequency range;
a first resistor connected in parallel to said absorption wave trap and having a resistance equal to said internal resistance and at least five times smaller than the surge impedance of said absorption wave trap;
an inductor including a pair of terminals, and a tap connected to said frequency control input;
an output transformer including a pair of terminals, and a tap;
a second resistor connecting said transformer tap to the reference potential;
a pair of transistors each including a base, an emitter and a collector, said collectors connected to respective terminals of said output transformer;
third and fourth resistors connecting respective emitters to an operating potential;
first and second capacitors connected in series between said base of one of said transistors and the reference potential, said emitter of said transistor connected to the junction of said series-connected capacitors to a. c. couple to said base to its respective emitter, and third and fourth capacitors connected in series between said base of the other of said transistors and the reference potential, said emitter of said transistor connected to the junction of said series-connected capacitors, to a.c. couple said base to its respective emitter;
a pair of voltage dividers connected to respective ones of said bases for establishing the operating points;
and
a pair of varactor diodes connected in opposing fashion between respective ones of said bases and respective ones of said inductor terminals to form oscillating circuits.

10 more elements

Dependencies are inferred from the claim text.

Varactor controlled push-pull oscillator

Life of this patent

Varactor controlled push-pull oscillator

Life of this patent

Abstract

Claims14