GPS RECEIVER WITH IMPROVED IMMUNITY TO BURST TRANSMISSIONS

• US 20100150284A1
• Filed: 12/14/2005
• Published: 06/17/2010
• Est. Priority Date: 12/14/2005
• Status: Active Grant

• Current Assignee: SIGE Semiconductor Limited (Skyworks Solutions Incorporated)
• Original Assignee: SIGE Semiconductor Limited (Skyworks Solutions Incorporated)
• Inventors: Fielder, Anne, Fulga, Stefan, Fielder, Dennis Arthur
• Granted Patent: US 7,761,072 B2
• Time in Patent Office: Days
• US Class Current: 375/345
• CPC Class Codes: G01S 19/21 Interference related issues ; Issues related to cross-correlation, spoofing or other methods of denial of service
• CPC Class Codes: G01S 19/37 Hardware or software details of the signal processing chain
• CPC Class Codes: H04B 1/3805 with built-in auxiliary receivers

Abstract

GPS signals are typically weak and thus easily interfered with by other radio transmissions in the same or adjacent frequency bands. Interference can be especially problematic when the GPS receiver is co-located with a communications device that includes a radio transmitter, such as a cellular telephone. The transmitted signal from the co-located communication device can overload (or saturate) the GPS receiver front-end designed to receive weak GPS signals. In such a situation no useful information can be extracted from the received GPS signals originating from the GPS satellites. Described herein is a novel apparatus and method that can be used to minimize the effect of co-located interference on a GPS receiver.

Claims

1. A method of operating a radio receiver, the method comprising:

coupling a signal identifying a received signal overload condition into an automatic gain control (AGC) component;

controlling a gain value of the AGC component based on the signal identifying the received signal overload condition;

when a signal overload condition is identified;

capturing a given value of the gain value that occurred at a point in time prior to the received signal overload condition being identified;

during the signal overload condition;

instead of using the AGC component to control the gain applied to a received radio signal, coupling a locally generated bit pattern into a radio receiver back-end in response to a presence of the signal identifying the received signal overload condition, the locally generated bit pattern selected such that when processed causes less noise to accumulate in the radio receiver back-end than if a bit-stream derived from the received radio signal were processed directly using the gain of the AGC component;

after the received signal overload condition is identified to have ended;

setting the gain value of the AGC component to the given value and processing the received radio signal using the gain of the AGC component.

3. The method of claim 1, wherein the step of controlling a gain value further comprises:

disabling the operation of the automatic gain control component; and

maintaining the gain value at a level equal to that which occurred prior to the received signal overload condition being identified until after the received signal overload condition is identified to have ended.

4. The method of claim 1, wherein coupling a signal identifying the received signal overload condition into the AGC component comprises coupling a transmission indication signal from a transmitter co-located with the radio receiver into the AGC component.

5. The method of claim 1, wherein the locally generated bit pattern is an alternating sequence of high and low binary values.

6. The method of claim 1, wherein the locally generated bit pattern is a pseudo random sequence.

7. The method of claim 1, wherein the locally generated bit pattern has the property of an average value tending rapidly towards zero with a substantially zero value standard deviation.

2. (canceled)

8. A radio receiver for receiving radio signals, the radio receiver comprising:

an automatic gain control (AGC) component adapted to control a gain value of the automatic gain control component based on a signal identifying a received signal overload condition;

a converter for deriving a bit-stream of digital data from a received radio signal; and

a data modifier for substituting the bit-stream of digital data with a locally generated bit pattern in response to a signal identifying the received signal overload condition, the locally generated bit pattern being selected such that when processed it causes less noise to accumulate in the radio receiver back-end than if the bit-stream of digital data were processed using the gain of the AGC component;

wherein when a signal overload condition is identified the AGC is configured to;

capture a given value of the gain value that occurred at a point in time prior to the received signal overload condition being identified;

wherein during the signal overload condition;

instead of using the AGC component to control the gain applied to a received radio signal, the data modifier couples the locally generated bit pattern into the radio receiver back-end;

wherein after the received signal overload condition is identified to have ended the AGC is configured to;

set the gain value of the AGC component to the given value and process the received radio signal using the gain of the AGC component.

9. The radio receiver of claim 8, wherein the signal identifying the received signal overload condition is a transmission indication signal from a transmitter co-located with a front-end of the radio receiver.

10. The radio receiver of claim 8, wherein the radio receiver is a GPS (Global Positioning System) receiver.

11. The radio receiver of claim 8, wherein the radio receiver is further adapted to down-convert the received radio signal from a Radio Frequency (RF) to an Intermediate Frequency (IF), wherein the received radio signal is combined with a locally generated RF signal within a mixer to produce a down-converted copy of the received radio signal.

12. The radio receiver of claim 8 further adapted to receive a transmission indication signal from a transmitter co-located with the radio receiver and to relay the transmission indication signal to the automatic gain control component.

13. The radio receiver of claim 8 wherein the data modifier comprises a data input connected to receive the output of the converter and a control input to receive the signal identifying the received signal overload condition, the data modifier generating and substituting the locally generated bit pattern for the bit-stream of digital data that is input to a correlator when the signal identifying the received signal overload condition indicates an overload condition.

14. The radio receiver of claim 8, wherein the radio receiver is a GPS receiver.

18. The radio receiver of claim 8, wherein the signal identifying the received signal overload condition is from a GSM (Global System for Mobile) phone transmitter.

20. The radio receiver of claim 8, further comprising:

an antenna for receiving an radio frequency (RF) signal;

a low noise amplifier coupled to the antenna;

a filter coupled to the low noise amplifier;

a mixer including a voltage controlled oscillator for down converting the RF signal coupled to the filter;

an intermediate frequency (IF) filter for filtering the down converted IF signal coupled to the mixer and coupled to the AGC component;

wherein the converter is an analogue-to-digital converter coupled to the AGC component and the means for substituting the bit-stream is a data modifier coupled to the analogue-to-digital converter;

wherein the radio receiver is adapted to perform down-conversion of at least one radio signal received at a radio (RF) to an IF, to derive a bit stream of digital data from at least one radio signal after it has been down converted to the IF, and to process the bit stream of data.

15. A method of limiting the effect of interfering transmission on a GPS receiver, the method comprising:

controlling a gain value of an AGC component based on a signal identifying a received signal overload condition provided by a transmitter local to the GPS receiver;

wherein the step of controlling a gain value comprises;

when a signal overload condition is identified;

capturing a given value of the gain value that occurred at a point in time prior to the received signal overload condition being identified;

during the signal overload condition;

instead of using the AGC component to control the gain applied to a received radio signal, coupling a locally generated bit pattern into a radio receiver back-end in response to a presence of the signal identifying the received signal overload condition, the locally generated bit pattern selected such that when processed causes less noise to accumulate in the radio receiver back-end than if a bit-stream derived from the received radio signal were processed using the gain of the AGC component;

after the received signal overload condition is identified to have ended;

setting the gain value of the AGC component to the given value and processing the received radio signal using the gain of the AGC component.

19. The method of claim 15, wherein the signal identifying the received signal overload condition is from a GSM phone transmitter.

16. (canceled)

17. (canceled)