Method of and apparatus for position location and tracking of a vehicle or the like by the reception at the vehicle of pulsed radio navigation signals as of the Loran-OC type and the like, with an autonomous loop antenna-receiver

Apparatus for radio navigation signal vehicle location having, in combination, a pair of orthogonally crossed loop antennas for receiving radio-frequency navigation signals from navigation transmitters;

• a corresponding pair of radio-frequency receiver channels, one for each of the pair of loop antennas;
• + and -45.degree. phase-shifters respectively inserted into the channels and connected to an adder to combine the phase-shifted signals, thereby to render the loop antenna pattern omnidirectional.

In apparatus for receiving radio-frequency navigational signals emanating from Loran-C master and slave station transmitters, and acquired by a pair of crossed loop antennas, a receiver system having, in combination, a pair of radio-frequency receiving receiver channels to be respectively connected to the pair of antennas, each channel receiver provided with a bandpass filter connected to a corresponding phase shifter and to a Loran-C signal envelope deriver in turn connected to a channel signal selector also inputted from the corresponding bandpass filter and an adder connected to the phase shifter of each channel;

• each channel signal selector being connected to a hard limiter and thence to a microprocessor for performing digital analyses on the signals, including correlations to determine the stronger channel signal and to provide selection control of the signal selectors.