Analog ramp generator with digital correction

In a swept-frequency test oscillator comprising an analog ramp generator for controlling the frequency of the swept-frequency test oscillator, the analog ramp generator comprising an analog integrator circuit responsive to a reference signal applied to the analog integrator circuit for generating an analog ramp signal to provide a control signal for the swept-frequency test oscillator, an improved correction circuit comprising:

• means for generating a corresponding digital ramp signal;
• means connected to the analog integrator circuit and to the digital ramp signal generating means for producing an error signal based on a difference between the digital and analog ramp signals;
• and
• means connected to the error signal producing means and responsive to the error signal and the reference signal for feeding back the error signal to the analog integrator circuit;
• whereby the analog ramp signal is forced to track the digital ramp signal.

A method for correcting errors in an analog ramp generator, the analog ramp generator comprising an analog integrator circuit responsive to a reference signal applied to the analog integrator circuit for generating an analog ramp signal, the correction method comprising the steps of:

• generating a corresponding digital ramp signal;
• producing an error signal based on a difference between the digital and analog ramp signals;
• and
• responding to the error signal for combining the error signal and the reference signal and feeding the combined signal to the analog integrator circuit, thereby forcing the analog ramp signal to track the digital ramp signal.