Clock, frequency reference, and other reference signal generator with frequency stability over temperature variation

An apparatus to generate a harmonic reference signal, the apparatus comprising:

• a reference resonator configured to generate a first reference signal having a resonant frequency, the reference resonator comprising a first component having a first temperature dependence;
• a plurality of switchable circuits couplable to the reference resonator, at least one switchable circuit of the plurality of switchable circuits having a second temperature dependence opposing the first temperature dependence to maintain the resonant frequency within a predetermined variance over a temperature variation;
• and
• a coefficient register to store a plurality of control coefficients;
• wherein each switchable circuit of the plurality of switchable circuits comprises:
• a first reactance coupled in series with a first switch;
• a resistor;
• a second reactance coupled to the resistor;
• and
• a second switch coupled in series to the second reactance or to the resistor;
• and
• wherein the first switch is responsive to a control coefficient of the plurality of control coefficients to electronically couple or decouple the first reactance to or from a voltage, a ground potential, or the reference resonator, and
• wherein the second switch is responsive to an inverted control coefficient of the plurality of control coefficients to electronically couple or decouple the second reactance or the resistor to or from a voltage, a ground potential, or the reference resonator.

An apparatus to generate a periodic signal, comprising:

• an resonant LC tank circuit configured to generate a periodic reference signal at a first frequency at a differential output thereof;
• and
• a switchable capacitive module electrically coupled to a first node of the differential output of said resonant LC tank circuit, said module comprising a plurality of switchable circuits electrically coupled in parallel to the first node;
• wherein each switchable circuit of the plurality of switchable circuits comprises:
• a first capacitor electrically coupled in series with a first switch;
• a second capacitor electrically coupled in series with a resistor;
• and
• a second switch electrically coupled to the second capacitor and/or the resistor;
• wherein the first switch is responsive to a corresponding first control signal that operates to modify an amount of impedance applied to the first node by selectively coupling or decoupling the first capacitor to or from the first node;
• and
• wherein the second switch is responsive to a corresponding second control signal that operates to modify an amount of impedance applied to the first node by selectively coupling or decoupling a series combination of the second capacitor and resistor to or from the first node.