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AssigneeTrue Heading AB
InventorsNils WILLART, Bengt JOHANSSON, Anders BERGSTRÖM
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Method for determining the time of receipt by a radio receiver (320,330,340) of a binary coded radio message emitted by a sender (310), whereby the radio signal is received by the receiver so that an analogue electrical signal is achieved, which analogue signal is sampled and optionally demodulated, whereby the data content of the message is determined based upon the demodulated signal as a stream of data bits, which stream of data bits comprises a predetermined signal element whose time of receipt is determined. The invention is characterised in that a digitally stored, constructed comparison signal is created based upon the said stream of data bits, so that the constructed comparison signal is constructed to correspond to the sampled signal, in that a time variable which maximizes a correlation between the constructed comparison signal and the sampled signal is determined, and in that the time variable is then used to correct the said time determination of the receipt of the predetermined signal element.
Method for determining the time of receipt by a radio receiver of a binary coded AIS (Automatic Identification System) message, sent by a sender in the form of a first signal which is a modulated radio signal, wherein the first signal is received by the receiver using an antenna so that a second signal in the form of an analogue electrical signal is achieved, which second signal is sampled and optionally demodulated, which sampling and demodulation can be performed in any order, which sampling is performed using an AD converter, and a digitally stored third signal in the form of a sampled and optionally demodulated signal is achieved, wherein the data content of the message is determined from the third signal as a stream of data bits, which stream of data bits comprises a predetermined signal element whose time of receipt is determined, and wherein the time of receipt of the message is determined based on the timing of the predetermined signal element, wherein a digitally stored, constructed comparison signal is generated on the basis of said stream of data bits, and the constructed comparison signal is constructed to correspond to the third signal, wherein an optimum value is determined for a time variable, which time variable indicates a time position of the constructed comparison signal relative to the third signal and for which optimum value a correlation between the constructed comparison signal and the third signal is maximal, and wherein the optimum value of the time variable is used to correct the determination of the time of receipt of the predetermined signal element.
Receiving device arranged to receive a binary coded AIS (Automatic Identification System) message, sent by a transmitter in the form of a first signal which is a modulated radio signal, which receiving device comprises an antenna arranged to receive the first signal and achieve a second signal in the form of an analogue electrical signal, an AD converter and an optional demodulation device, which AD converter and optional demodulation device are arranged to sample and possibly demodulate the said analogue signal, which sampling and demodulation can be performed in any order, and achieve a digitally stored third signal in the form of a sampled and optionally demodulated signal, which receiving device furthermore comprises a decoding device, arranged to decode the third signal and achieve the data content of the message as a stream of data bits, which stream of data bits comprises a predetermined signal element whose time of receipt is determined, and wherein the receiving device is arranged to determine the time of receipt of the message based on the timing of the predetermined signal element, and the receiving device comprises a time determination device, arranged to determine the time of receipt of the predetermined signal element, wherein the timing determination device is arranged to generate a digitally stored, constructed comparison signal on the basis of said stream of data bits, so that the constructed comparison signal is constructed to correspond to the third signal, wherein the timing determination device is arranged to determine an optimum value for a time variable, which time variable indicates a time position of the constructed comparison signal relative to the third signal and for which optimum value a correlation between the constructed comparison signal and the third signal is maximal, and wherein the timing determination device is arranged to correct the said timing determination of the receipt of the predetermined signal element using the optimum value of the time variable.
Dependencies are inferred from the claim text.