GPS receiver utilizing a communication link
AssigneeSnapTrack, Inc.
InventorNorman F. Krasner
Life of this patent
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Abstract
A precision carrier frequency signal for calibrating a local oscillator of a GPS receiver which is used to acquire GPS signals. The precision carrier frequency signal is used to calibrate the local oscillator such that the output of the local oscillator, which is used to acquire GPS signals, is modified by a reference signal generated from the precision carrier frequency signal. The GPS receiver locks to this precision carrier frequency signal and generates the reference signal. In another aspect of the invention, satellite almanac data is transmitted to a remote GPS receiver unit from a basestation via a communication link. The remote GPS receiver unit uses this satellite almanac data to determine approximate Doppler data for satellites in view of the remote GPS receiver unit.
Claims39
A method of calibrating a local oscillator in a mobile GPS receiver, said method comprising:
- receiving a precision carrier frequency signal from a source providing said precision carrier frequency signal;
- automatically locking to said precision carrier frequency signal and providing a reference signal;
- calibrating said local oscillator with said reference signal, said local oscillator being used to acquire GPS signals.
A mobile GPS receiver comprising:
- a first antenna for receiving GPS signals;
- a downconverter coupled to said first antenna, said first antenna providing said GPS signals to said downconverter;
- a local oscillator coupled to said downconverter, said local oscillator providing a first reference signal to said downconverter to convert said GPS signals from a first frequency to a second frequency;
- a second antenna for receiving a precision carrier frequency signal from a source providing said precision carrier frequency signal;
- an automatic frequency control (AFC) circuit coupled to said second antenna, said AFC circuit providing a second reference signal to said local oscillator to calibrate said first reference signal of said local oscillator, wherein said local oscillator is used to acquire said GPS signals.
A method of using a basestation to calibrate a local oscillator in a mobile GPS receiver, said method comprising:
- producing a first reference signal having a precision frequency;
- modulating said first reference signal with a data signal to provide a precision carrier frequency signal;
- transmitting said precision carrier frequency signal to said mobile GPS receiver, said precision carrier frequency signal being used to calibrate a local oscillator in said mobile GPS receiver, said local oscillator being used to acquire GPS signals.
A basestation for providing a calibration signal for use in a mobile GPS receiver to calibrate a local oscillator in said mobile GPS receiver, said basestation comprising:
- a first source for a first reference signal have a precision frequency;
- a modulator coupled to said first source and to a second source of satellite data information said modulator providing a precision carrier frequency signal;
- a transmitter coupled to said modulator, said transmitter for transmitting said precision carrier frequency signal to said mobile GPS receiver, said precision frequency signal being used to calibrate said local oscillator, said local oscillator being used to acquire said GPS signals.
A method of deriving a local oscillator signal in a mobile GPS receiver, said method comprising:
- receiving a precision carrier frequency signal from a source providing said precision carrier frequency signal;
- automatically locking to said precision carrier frequency signal and providing a reference signal;
- using said reference signal to provide a local oscillator signal to acquire GPS signals.
A mobile GPS receiver comprising:
- a first antenna for receiving GPS signals;
- a downconverter coupled to said first antenna, said first antenna providing said GPS signals to said downconverter, said downconverter having an input for receiving a local oscillator signal to convert said GPS signals from a first frequency to a second frequency;
- a second antenna for receiving a precision carrier frequency signal from a source providing said precision carrier frequency signal;
- an automatic frequency control (AFC) circuit coupled to said second antenna, said AFC circuit being coupled to said downconverter to provide said local oscillator signal which is used to acquire said GPS signals.
Dependencies are inferred from the claim text.