Apparatus and method for receiving and proessing Loran signals
First Claim
1. A method of receiving and processing Loran C radio navigation signals comprising the steps of:
- (a) receiving a radio signal containing the Loran C signal of interest;
(b) sampling the received signal at periodic points in time and providing data corresponding thereto;
(c) determining and synchronizing the group repetition interval of the Loran C signal of interest contained in the data; and
(d) ensemble averaging together signal data synchronized to the group repetition interval over two or more group repetition intervals.
2 Assignments
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Accused Products
Abstract
A radio signal containing Loran C pulses from stations of interest is received and periodically sampled to convert the input signal to sample data. The data is assigned to memory locations within an acquisition memory at positions in the memory which correspond to specific times within the group repetition interval (GRI) of the Loran chain of interest. A GRI counter assigns the locations in the memory to which the data are written and cycles the memory after the completion of each GRI so that new data corresponding to a new set of pulses from the master and secondary stations of the Loran C chain will be assigned to essentially the same memory locations as data acquired during a previous GRI. The new data is ensemble averaged with the old data contained in the memory locations and the averaged data stored back in the memory. As data is collected and averaged over a sufficient number of GRI'"'"'s, any signals present in the received radio signal which are not synchronous with the GRI will tend to be averaged out, improving the signal to noise ratio of the Loran C pulses in the memory. Averaging of the sampled input signal over several GRI'"'"'s in this manner minimizes the effect of sporadic noise, continuous wave interference and cross rate interference. After completion of the averaging process, the data in the acquisition memory may be searched to determine the time differences between the master and secondary pulses in a manner normally carried out in Loran C receivers.
11 Citations
19 Claims
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1. A method of receiving and processing Loran C radio navigation signals comprising the steps of:
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(a) receiving a radio signal containing the Loran C signal of interest; (b) sampling the received signal at periodic points in time and providing data corresponding thereto; (c) determining and synchronizing the group repetition interval of the Loran C signal of interest contained in the data; and (d) ensemble averaging together signal data synchronized to the group repetition interval over two or more group repetition intervals.
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2. A method for receiving and processing Loran C navigational signals comprising the steps of:
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(a) receiving a radio signal containing the Loran C signal of interest; (b) sampling the received signal at periodic points in time and providing data corresponding thereto; (c) storing the data in a memory at memory locations which correspond to selected points in time during the group repetition interval of the Loran C chain of interest; (d) averaging subsequently received data on a point by point basis with the data stored at the locations in the memory and storing the results in the memory locations to replace the originally stored data such that the new data are sampled at the same points in time during the group repetition interval as the old data with which it was ensemble averaged. - View Dependent Claims (3, 4, 5, 6)
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7. A method of receiving and processing a Loran C navigational signal comprising the steps of:
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(a) receiving a radio signal containing the Loran C signal of interest; (b) sampling the received signal at periodic points in time to provide data corresponding thereto; (c) storing the data in a recirculating memory which circulates periodically with a period corresponding to an initially chosen group repetition interval; and (d) averaging subsequently acquired data sampled from the received signal with the data stored in the memory and writing the averaged data into the memory locations of the memory at the rate at which the memory circulates. - View Dependent Claims (8, 9, 10, 11)
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12. Apparatus for receiving and processing Loran C navigation signals comprising:
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(a) means for receiving a radio signal containing the Loran C signal of interest and providing an electrical signal corresponding thereto; (b) means for sampling the electrical signal at periodic points in time to provide data corresponding thereto; (c) an acquisition memory having addressable locations for storing data; (d) group repetition interval counter means for causing data to be stored in the acquisition memory at memory locations which are cycled every selected group repetition interval; and (e) means for averaging the sampled data as received from the means for sampling with the data at the corresponding memory location within the group repetition interval and storing the averaged data at the memory location. - View Dependent Claims (13, 14, 15, 16, 17, 18, 19)
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Specification