Pre-acquisition frequency offset removal in a GPS receiver
AssigneeGeneral Electric Company
InventorsDaniel David Harrison, Jerome Johnson Tiemann
Life of this patent
Estimating the term…
Abstract
A direct sequence spread spectrum receiver samples an incoming signal and stores the sample in memory. Prior to sampling and storage, the incoming signal is translated to an IF signal. Also prior to storage, the IF signal is corrected for a frequency offset signal. The frequency offset may be caused by many sources, Doppler shift or local oscillator error, for example. Once the signal is corrected for the frequency offset, the signal sample is stored in memory. The signal sample is read from memory as necessary to process the signal. Such a receiver is useful in global positioning satellite (GPS) signal processing where the incoming signal contains several satellite transmissions encoded with CDMA encoding.
Claims24
In a direct sequence spread spectrum receiver capable of receiving a plurality of signals from respective transmitters, apparatus comprising:
- a tuner for receiving at least one of said signals and producing an intermediate frequency signal, said tuner including a converter for sampling said intermediate frequency signal;
- means for removing frequency offset from the output signal of said converter, thereby producing a corrected signal;
- a memory for storing said corrected signal;
- and
- processing means for processing said corrected signal.
In a direct sequence spread spectrum receiver capable of receiving a plurality of signals from respective transmitters, the method comprising:
- receiving an input signal having a signal carrier frequency;
- generating a local oscillator signal having frequency which is offset from said carrier frequency;
- mixing said input signal with said local oscillator signal to produce an intermediate frequency signal;
- converting said intermediate frequency signal to a multiple-sample digital representation thereof;
- mixing said multiple-sample digital representation with a frequency offset signal to produce a corrected frequency signal;
- storing said corrected frequency signal in a memory;
- and
- processing said corrected frequency signal.
Dependencies are inferred from the claim text.