Temperature compensation circuit for a crystal oscillator and associated circuitry

A communication device having a transmitter, a receiver and memory and having a temperature compensation circuit, comprising:

• the memory being programmed to provide predetermined digital data in response to a temperature signal, the predetermined digital data programmed to vary as a function of a deviation over temperature of elements of a local oscillator circuit, the memory inhibiting changes to the provided predetermined digital data while an associated radio circuit is transmitting or receiving;
• a signal generator being electrically coupled to the memory, the signal generator providing a temperature compensation signal to the local oscillator circuit corresponding to the predetermined digital data from the memory;
• and
• the local oscillator circuit for generating local oscillator signals includes a temperature dependent crystal oscillator comprising:
• a tuning circuit electrically coupled to the crystal oscillator, the tuning circuit adjusting an output frequency of the crystal oscillator in response to the temperature compensation signal;
• a temperature sensor electrically coupled to the memory and providing the temperature signal to the memory in response to an ambient temperature of the crystal oscillator;
• and
• a voltage regulator providing a regulated voltage to the signal generator, the voltage regulator being electrically coupled to the temperature sensor.

A method of temperature compensating a crystal oscillator, comprising the steps of:

• providing a memory programmed with digital data corresponding to a deviation over temperature of at least one of the group selected from the crystal oscillator, a signal generator, a voltage regulator, a temperature sensor, and a tuning circuit coupled to the crystal oscillator;
• driving the temperature sensor with the voltage regulator such that a temperature-dependent signal corresponding to an ambient temperature is provided;
• coupling the temperature-dependent signal to the memory such that digital data corresponding to a frequency variation of the crystal oscillator at the ambient temperature is provided;
• applying the digital data to the signal generator when an associated radio circuit is not transmitting or receiving such that a temperature compensation signal is provided to the tuning circuit of the crystal oscillator;
• and
• biasing the signal generator with a temperature characterized regulated voltage from the voltage regulator such that variations in the regulated voltage are compensated in the digital data so as to improve temperature compensation of the crystal oscillator.