Method for tuning a GPS antenna matching network

In a portable wireless communications device, a system for tuning a Global Positioning System (GPS) antenna matching circuit, the system comprising:

• an antenna for receiving radiated Satellite Vehicle (SV) signals, with an interface for supplying conducted SV signals;
• a GPS modem having an input to accept the SV signals, the GPS modem measuring SV carrier-to-noise ratio (C/N) and supplying a tuning value signal at an output;
• a tunable matching circuit having a first input connected to the antenna interface, a second input to receive the tuning value signal, and an output connected to the GPS modem input, the matching circuit selectively tuning the impedance of its input to the antenna interface in response to the tuning value signal;
• and
• wherein the GPS modem supplies a first tuning value, measures the SV C/N associated with the first tuning value and a first search time interval, supplies a next tuning value, measures the SV C/N associated with the next tuning value and the first search time interval, and selects the tuning value associated with the highest SV C/N to tune the matching circuit.

In a Code Division Multiple Access (CDMA), a system for tuning a Global Positioning System (GPS) antenna matching circuit, the system comprising:

• a CDMA cellular transceiver having a wireless interface to send a Request GPS Assistance Acquisition message to a communicating base station (BS) and an output to supply a received list of available SVs;
• a GPS antenna for receiving radiated Satellite Vehicle (SV) signals, with an interface for supplying conducted SV signals;
• a GPS modem having an input to accept the SV signals, the GPS modem measuring SV carrier-to-noise ratio (C/N) and supplying a tuning value signal at an output;
• a tunable matching circuit having a first input connected to the antenna interface, a second input to receive the tuning value signal, and an output connected to the GPS modem input, the matching circuit selectively tuning the impedance of its input to the antenna interface in response to the tuning value signal;
• and
• wherein the GPS modem has an input to receive the list of available SVs from the cellular transceiver prior to measuring SV C/N using the first tuning value and the first search time interval, wherein the GPS modem supplies a first tuning value, measures the SV C/N associated with the first tuning value and a first search time interval, supplies a next tuning value, measures the SV C/N associated with the next tuning value and the first search time interval, and selects the tuning value associated with the highest SV C/N to tune the matching circuit.

In a portable wireless communications device including a Global Positioning System (GPS) antenna with a selectively tunable matching circuit, a method for tuning the matching circuit, the method comprising:

• accepting a first matching circuit tuning value;
• measuring satellite vehicle (SV) carrier-to-noise ratio (C/N) associated with the first tuning value in a first time interval segment;
• if the SV C/N exceeds a minimum threshold, selecting the first tuning value to tune the matching circuit;
• if the SV C/N does not exceed the minimum threshold, accepting a second tuning value;
• measuring SV C/N associated with the second tuning value in a second time interval segment;
• and
• if the SV C/N exceeds a minimum threshold, selecting the second tuning value to tune the matching circuit.