Constant amplitude variable frequency sweep generator

Claim 2

In a servo sweep generator for producing a sawtooth output voltage in synchronism with an input signal derived from the cylinder ignition of an internal combustion engine, the combination which comprises: first charge storage means, charge supply means for supplying charge to the first charge storage means at a selected rate, means responsive to the occurrence of each input signal for discharging the charge storage means, a source of reference voltage, comparing means responsive to the occurrence of each input signal for comparing the voltage across the first charge storage means with the reference voltage during a predetermined time interval, said predetermined time interval being small as compared to the time interval between successive input signals, and means under the control of the comparing means for setting the rate of the charge supply means.

Claim 3

The combination as defined in claim 1 wherein the comparing means includes: a comparator having a pair of input circuits, an output circuit and a control circuit, the comparator being arranged to provide an output signal on the output circuit thereof which is representative of the difference in the magnitude of the input signals applied to the input circuits thereof in response to the application of a control signal to the control circuit, and integrating means connected between the first charge storage means and one input circuit of the comparator, the other input circuit of the comparator being connected to the source of reference voltage, the output circuit being coupled to the charge supply means and means responsive to the occurrence of the input signal for supplying a control signal to the control circuit of the comparator.

Claim 4

The combination as defined in claim 1 wherein the means for setting the rate of the charge supply means includes second charge storage means coupled to the output circuit of the comparator.

Claim 5

The combination as defined in claim 3 wherein the predetermined time interval is less than five percent of the time interval between input signals.

Claim 6

The combination as defined in claim 4 including a field effect transistor connected between the second charge storage means and the charge supply means.

Claim 7

In a servo sweep generator for producing an output voltage in response to a periodic input signal derived from the cylinder ignition of an internal combustion engine, the combination which comprises: a sweep capacitor, a current source connected to the sweep capacitor, the current source including an input circuit and being arranged to supply charge to the sweep capacitor at a rate which Is proportional to the amplitude of a signal applied to the input circuit thereof, a discharge switch connected across the sweep capacitor and responsive to the occurrence of each input signal for discharging the sweep capacitor, a comparator having a pair of input circuits, an output circuit and a control circuit, the comparator being arranged to provide an output signal on the output circuit thereof which is representative of the difference between the signals applied to the input circuits in response to the application of a control signal to the control circuit thereof, direct current restoring and integrating means coupled between one input circuit of the comparator and the sweep capacitor, a source of reference voltage connected to the other input circuit of the comparator, switching means responsive to the occurrence of each input signal for applying a control signal of predetermined duration to the control circuit of the comparator, a sample and hold capacitor, amplifying means connected between the output circuit of the comparator and the sample and hold capacitor to establish charge across the sample and hold capacitor which is proportional to the output signal from the comparator, and means for coupling a signal proportional to the voltage across the sample and hold capacitor to the input circuit of the current source.

Claim 8

In a servo sweep generator for producing an output voltage in response to a periodic input signal derived from the cylinder ignition of an internal combustion engine, the combination which comprises: a sweep capacitor, a current source connected to the sweep capacitor, the current source including an input circuit and being arranged to supply charge to the sweep capacitor at a rate which Is proportional to the amplitude of a signal applied to the input circuit thereof, a discharge switch connected across the sweep capacitor and responsive to the occurrence of each input signal for discharging the sweep capacitor, a comparator having a pair of input circuits, an output circuit and a control circuit, the comparator being arranged to provide an output signal on the output circuit thereof which is representative of the difference between the signals applied to the input circuits in response to the application of a control signal to the control circuit thereof, direct current restoring and integrating means coupled between one input circuit of the comparator and the sweep capacitor, a source of reference voltage connected to the other input circuit of the comparator, switching means responsive to the occurrence of each input signal for applying a control signal of predetermined duration to the control circuit of the comparator, a sample and hold capacitor, amplifying means connected between the output circuit of the comparator and the sample and hold capacitor to establish charge across the sample and hold capacitor which is proportional to the output signal from the comparator, and means for coupling a signal proportional to the voltage across the sample and hold capacitor to the input circuit of the current source.

Claim 9

The combination as defined in claim 6 wherein the last named means includes a field effect transistor.

Claim 10

The combination as defined in claim 6 wherein the comparator is a differential amplifier.

Claim 11

The combination as defined in claim 6 wherein the time duration of the control signals is less than five percent of the charging time interval of the sweep capacitor.