Tuning a variable oscillator

Claim 3

A method according to claim 1, characterized in that the reference voltage is chosen such that the portion of the resonance curve that lies above the level corresponding to this voltage is symmmetrical, wherein the difference between the maximum level of the resonance curve and the reference level can be close to 3 decibels.

Claim 4

A method according to claim 1, further characterized by the following steps: a first scanning of the resonance curve of the riNging circuit is carried out; the maximum of the curve is registered; the maximum registered is caused to decrease with a large time constant; the tuning operation proper is carried out in a second scanning of the curve, which is started at once after the first one, and the somewhat decreased maximum that was registered is used for a reference level.

Claim 5

A system of automatic tuning of an adjustable-frequency ringing circuit to a given frequency, for carrying out the method according to claim 1, characterized in that it comprises: first incremental means adapted to deliver an analog output signal the value of which is a function of the number of increments it has received, these first means being started when the system is put into service; second incremental means, identical with the first ones and connected in addition therewith, said first and second incremental means being arranged to supply the control inlet of the ringing circuit; an electronic clock, which is started when the system is put into service for imparting a synchronous delivery of successive increments from said first and second incremental means; and means for comparing a reference voltage with an analog voltage that is the output voltage of the ringing circuit to be tuned, these means being adapted, when said analog voltage becomes higher than said reference voltage, to deliver a signal which causes said second incremental means to be put into service.

Claim 6

A system according to claim 4, characterized in that each of said first and second incremental means is formed essentially by a condenser which is supplied from a circuit that yields quanta of electricity, in form of pulses, corresponding to the increments.

Claim 7

A system according to claim 4, characterized in that each of said first and second incremental means is formed of a binary counter which controls a digital-to-analog converter.

Claim 8

A system according to claim 4, characterized in that said comparing means are associated with two incoming circuits both supplied with the output voltage from the ringing circuit, the one of said incoming circuits having a large time constant whereas the other has a small one, switching means being provided and adapted to enable only the first incoming circuit when the system is put into service, and to enable only the second incoming circuit after a full cycle of operation of the incremental means.

Claim 9

A system according to claim 4, characterized in that the ringing circuit is of a type having variable capacity diodes a bias electrode of which is connected to the outlet of the incremental means and forms the control inlet of the ringing circuit.

Claim 10

A system according to claim 4, characterized in that the ringing circuit is of a type comprising increductors the control circuits of which are connected to the outlet of the incremental means.

Claim 11

A system of automatic tuning of an adjustable-frequency ringing circuit to a given frequency, according to claim 4, characterized in that each of said first and second incremental means is formed of a binary counter that directly controls the variable reactance in the ringing circuit so as to cause a selective variation of the natural frequency of said ringing circuit, the said variable reactance being formed e.g. of inductances or condensers which are poised according to a determined law and which are respectively associated with the outlets of the corresponding counters and selectively enabled depending on the binary condition of the corresponding outlets.