Method and apparatus for in-line detection of satellite signal lock

A method of monitoring the strength of a received satellite signal presented to a decoder, said signal having at least one noise component and at least one signal component, wherein the noise component and the signal component are spectrally separate, said method comprising:

• deriving from said noise and signal components a derived signal value;
• comparing said derived signal value to at least one predetermined value associated with an incipient loss of signal lock;
• and
• generating an output if said derived signal value differs from said predetermined value in a predetermined manner.

A system for receiving a satellite signal having a predominantly noise frequency component and a predominantly signal frequency component, wherein the noise frequency component and the signal frequency component are spectrally separate, said system comprising:

• a satellite receiving antenna and low noise block;
• logic in communication with said low noise block for processing said noise and frequency components to obtain a derived signal value and comparing said value to a predetermined threshold associated with an incipient loss of signal lock;
• and
• a user interface linked to said logic and at least one external device and activated when said derived signal value differs from said predetermined threshold in a predetermined manner.

A system for detecting a satellite signal, said system comprising:

• at least a first filter that isolates a predominantly noise frequency component from said satellite signal;
• at least a second filter that isolates a predominantly service frequency component from said satellite signal, wherein the service frequency component is spectrally separate from the noise frequency component;
• circuits that derive a value indicative of a difference between the power levels of said noise frequency component and said service frequency component to output a difference value;
• and
• circuits that determine whether said difference value is greater or less than a first threshold value associated with an incipient loss of signal lock.

A system for receiving a satellite signal from a satellite, the system comprising:

• a satellite antenna;
• a subsystem that detects the satellite signal including a plurality of filters that isolate spectrally separate components indicative of the signal, logic that calculates a difference signal level from the components, at least one comparator that determines whether the difference signal level is greater than a threshold level associated with an incipient loss of signal lock;
• and
• a satellite signal decoder linked to the satellite antenna by the subsystem.

An accessory device for use with a satellite receiving station, said device comprising:

• at least one filter that isolates a predominantly service frequency component from a satellite signal received in said receiving station;
• at least a second filter that isolates a predominantly noise frequency component from said satellite signal, wherein the noise frequency component is spectrally separate from the service frequency component;
• circuits for determining a power value for the outputs of said first and second filters;
• and
• at least one detector that determines whether a difference level derived from the outputs of said power determining circuits is above or below a threshold associated with an incipient loss of signal lock.