GPS Receiver Self-Blanking for Co-Located Cellular Jamming
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Solution Overview
Problem
Integrated GPS receivers in wireless communications devices face interference from co-located cellular transceivers, leading to disrupted signal processing due to radio frequency coupling and latency issues in automatic gain control, which existing solutions do not adequately address.
Innovation Solution
The implementation of a self-detection and self-blanking mechanism within the GPS receiver, using a synchronized blanking signal to eliminate jamming signals based on the detected pattern of interference, while maintaining automatic gain control and freezing or suspending correlator outputs during interference periods.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If GPS receiver and cellular transceiver are integrated in close proximity to reduce device size, then device compactness is improved, but radio frequency interference from cellular antenna to GPS antenna increases
Solution Approach 1:
An automatic gain control (AGC) circuit is introduced as an intermediary component between the GPS antenna and GPS receiver. The AGC circuit monitors the strength of received GPS signals and dynamically adjusts the gain to compensate for interference from the cellular transceiver, thereby maintaining proper signal levels despite the harmful RF coupling caused by close integration.
2Reliability
If AGC circuit reduces gain in response to increased signal strength from cellular antenna coupling, then signal strength is controlled, but latency is introduced when transitioning from transmit to idle or receive mode
Solution Approach 1:
The system performs preliminary action by detecting when the cellular transceiver is about to transition from transmit to idle or receive mode and preemptively adjusting the AGC gain before the transition occurs. This anticipatory adjustment eliminates the latency that would otherwise occur when the AGC circuit reacts to signal strength changes after the transition has already happened.
Solution Approach 2:
The AGC circuit employs feedback mechanisms where the GPS receiver continuously monitors signal strength and provides feedback to the AGC control logic. This feedback loop enables dynamic, real-time adjustment of the gain to maintain optimal signal levels despite varying interference conditions from the cellular transceiver operations.
3Duration of action of stationary object
If GPS receiver operates during cellular transceiver transmission, then continuous GPS positioning is maintained, but interference from cellular RF signals disrupts GPS signal reception and decoding
Solution Approach 1:
The system dynamically adjusts the AGC gain based on the operational state of the cellular transceiver. When the cellular transceiver is in transmit mode, the AGC circuit dynamically reduces gain to compensate for increased interference. When the cellular transceiver transitions to idle or receive mode, the AGC dynamically increases gain to maintain sensitivity. This dynamic adaptation allows continuous GPS operation despite varying interference conditions.
Data Source
AI summary
A method for eliminating or reducing interference in a receiver, for example, interference in a satellite positioning system receiver caused by a co-located TDMA transmitter, including detecting (210) the presence of a jamming signal, generating a synchronous blanking signal (220), and reducing the jamming signal by blanking (230) the receiver with a blanking signal. In one embodiment, the jamming signal is detected in the receiver, for example, at a correlator output of a satellite positioning system receiver.