Means and method for maintaining synchronization of a spread spectrum or other receiver clock

A system for maintaining synchronization of a clock signal with an incoming signal comprising:

• a first oscillator having an output clock signal to be synchronized with said incoming signal;
• means for controlling the frequency of said first oscillator by said incoming signal;
• a second oscillator having a more stable free-running frequency stability than said first oscillator;
• first means for causing said second oscillator to track said first oscillator when said incoming signal is phase synchronized with said output clock signal;
• and
• second means for causing said first oscillator to track said second oscillator when said incoming signal level is below a predetermined threshold level.

In a spread spectrum receiver, a means for maintaining a clock signal in phase synchronism with a code modulated on a received carrier signal, comprising:

• a first clock signal generator;
• a code generator having a coded output signal corresponding to said modulated code and whose phase and frequency is controlled by said first clock signal generator;
• first means for controlling said code generator by said first clock signal generator so that said code generator coded output signal has a predetermined phase relationship with respect to said modulated code when said first clock signal generator is phase synchronized with said modulated code;
• a second clock signal generator having a more stable free-running frequency stability than said first clock signal generator;
• means for controlling the frequency of said second clock signal generator by said first clock signal generator when said code generator is phase synchronized with said modulated code;
• and
• second means for controlling the frequency of said first clock signal generator by said second clock signal generator when said carrier signal level is below a predetermined threshold level.

A method for maintaining synchronization of a first oscillator with an incoming signal comprising the steps of:

• controlling the frequency of said first oscillator by said incoming signal when said incoming signal is phase synchronized with said first oscillator;
• controlling the frequency of a second oscillator having a more stable free-running frequency stability than said first oscillator by said first oscillator when said incoming signal is phase synchronized with said first oscillator;
• and
• controlling the frequency of said first oscillator by said second oscillator when said incoming signal level is below a predetermined threshold level.