Variable frequency generator with timer-controlled automatic frequency control loop

Claim 2

A variable-frequency generator comprising: an adjustable oscillator; a frequency counter receiving the output of said oscillator; a presettable digital frequency selector; a comparison circuit connected to receive the output of said counter and a signal from said selector; a control circuit for varying the operating frequency of said oscillator; a timer with a fixed operating cycle; switch means responsive to said timer for periodically connecting said comparison circuit to said control circuit for readjusting said operating frequency in a sense reducing any disparity between said output and said signal; and a sweep voltage generator inserted between said comparison circuit and said control circuit, said sweep voltage generator having a fixed operating period corresponding to an aliquot part of a timer cycle.

Claim 3

A variable-frequency generator comprising: an adjustable oscillator provided with a feedback loop; a frequency counter receiving the output of said oscillator; a presettable digital frequency selector; comparison means connected to receive the outputs of said counter and said selector for generating respective command signals in response to a disparity of either sign between said outputs; and an auxiliary frequency counter in said feedback loop connected to said comparison means for increasing or decreasing its count, in accordance with the type of command signal generated thereby, to readjust the operating frequency of said oscillator in a sense reducing said disparity.

Claim 4

A variable-frequency generator comprising: an adjustable oscillator provided with a feedback loop; a frequency counter receiving the output of said oscillator; a presettable digital frequency selector; comparison means connected to receive the outputs of said counter and said selector for generating respective command signals in response to a disparity of either sign between said outputs; and an auxiliary frequency counter in said feedback loop connected to said comparison means for increasing or decreasing its count, in accordance with the type of command signal generated thereby, to readjust the operating frequency of said oscillator in a sense reducing said disparity.

Claim 5

A frequency generator as defined in claim 2, further comprising a timer, said comparison means including a coincidence gate and test circuit, said test circuit being connected to receive a recurring timing pulse from said timer and a trigger pulse from said coincidence gate in response to identity of said outputs, the type of said command signal depending upon the relative order of occurrence of said pulses.

Claim 6

A frequency generator as defined in claim 3, further comprising an integrating network energized by said test circuit, said network including a storage condenser and a source of charging voltage therefor, the polarity of said charging voltage depending upon said relative order of occurrence and determining said type of command signal.

Claim 7

A variable-frequency generator comprising: an adjustable oscillator; a frequency counter receiving the output of said oscillator; a presettable digital frequency selector including two independently settable units for selection of a lower and an upper frequency limit; a control circuit for varying the operating frequency of said oscillator; a timer; a comparison circuit; a sweep voltage generator inserted between said comparison circuit and said control circuit; and switchover means controlled by said timer for alternately connecting said unit to said comparison circuit, the latter further receiving the output of said oscillator and working through said sweep voltage generator into said control circuit for readjusting said operating frequency in a sense reducing any disparity between said output and respective signals from said units.

Claim 8

A variable-frequency generator comprising: an adjustable oscillator; a frequency counter receiving the output of said oscillator; a presettable digital frequency selector including two independently settable units for selection of a lower and an upper frequency limit; a control circuit for varying the operating frequency of said oscillator; a timer; a comparison circuit; a sweep voltage generator inserted between said comparison circuit and said control circuit; and switchover means controlled by said timer for alternately connecting said unit to said comparison circuit, the latter further receiving the output of said oscillator and working through said sweep voltage generator into said control circuit for readjusting said operating frequency in a sense reducing any disparity between said output and respective signals from said units.

Claim 9

A frequency generator as defined in claim 5 wherein the sweep voltage generator includes a source of control voltage with a substantially trapezoidal profile starting from a variable base level, said comparison circuit being periodically switchable by the timer to vary the base level in response to a signal from one of said units and to vary the slope of said profile in response to a signal from the other of said units.

Claim 10

A frequency generator as defined in claim 5 wherein the sweep voltage generator is a source of continuously varying voltage of reversible slope connected to said comparison circuit for alternate slope reversals in response to identity between the outputs of the frequency counter and a signal from one or the other of said units, respectively.