Auto-tuning circuit apparatus and methods

A signal generation device, comprising:

• an auto-tuning electronic circuit module for generating tuned output signals, comprising:
• a tunable resonant electronic circuit element comprising a first capacitor and an inductor in series driven by an input signal which is a square wave at a resonant frequency for providing a tuned output signal, including a voltage divider element and a tuning array element;
• and
• a control element including a sensing element for measuring output signal strength and a processing element for comparing previous output signal strength values stored in a non-transitory memory element to a current signal strength value and providing a corresponding control signal to tune the tunable resonant electronic circuit;
• wherein the voltage divider element comprises a capacitive voltage divider circuit comprising a pair of capacitors on a branch tapped between the first capacitor and the inductor;
• and
• wherein the tuning array element comprises a plurality of switched capacitors on a branch tapped between the capacitors of the capacitive voltage divider;
• and
• wherein the plurality of switched capacitors are arranged in the tuning array element so as to be switched on by the switches based on increasing capacitance value during tuning, and wherein the voltage rating of ones of the switched capacitors progressively decrease in value as the capacitance increases in value to reduce the aggregate switching capacitors' physical size.

A method for automatically tuning frequency in an auto-tuning electronic circuit module in a utility locating device, comprising:

• providing, from a control element, an input signal to a tunable resonant circuit comprising a first capacitor and an inductor in series driven by an input signal which is a square wave at a resonant frequency;
• measuring a first signal strength of an output signal from the tunable resonant circuit;
• storing the measured first signal strength in a non-transitory memory element;
• switching on one switched capacitor of a plurality of switched capacitors in the tunable resonant circuit;
• measuring a second, subsequent signal strength of the output signal;
• comparing the stored first measured output signal strength measurement with the second output signal strength measurement;
• and switching another of the switched capacitors responsive to the comparison;
• wherein the auto-tuning electronic circuit module comprises a plurality of tuning stage elements wherein each tuning stage element is in a one to one transformer arrangement with one coil.