Nortel Networks Corporation

Mark Elwood Driedger

Wolfgang W Oberhammer

Song Zhang

An RF receiver, which is one of a network of receivers, is described which allows for a simple method of compensating for the group time delay asymmetry of an IF filter in the receiver. Compensation of the group time delay is important for time difference of arrival (TDOA) measurements for mobile location tracking applications, such as E-911 applications. The TDOA measurements are performed by the receiver network. The RF receiver includes a switch which alternately switches between two RF LO frequencies for consecutive pulse signals received from a mobile transmitter. One of the two RF LO frequencies is offset by the IF frequency on the positive side of the center frequency of the mobile transmitter signal received by the receiver. The other RF LO frequency is offset by the IF frequency on the negative side of the center frequency. The group time delay of the IF filter may be compensated for by switching between the two RF LO frequencies, performing a time of arrival (TOA) measurement for the signals corresponding to each of the RF LO frequencies, and averaging the group time delays for each TOA. A TOA estimator causes the switch to switch an RF LO oscillator between the two RF LO frequencies. A method for compensating for the group time delay asymmetry corresponding to the receiver is also described.

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Dunrobin, Canada

Mark Elwood Driedger