Results 171 to 180 of about 441 (195)

Two experimental pearls in Costas arrays

2008 42nd Annual Conference on Information Sciences and Systems, 2008
The results of 2 experiments in Costas arrays are presented, for which theoretical explanation is still not available: the number of dots on the main diagonal of exponential Welch arrays, and the parity populations of Golomb arrays generated in fields of characteristic 2.
Konstantinos Drakakis, Rod Gow
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The Enumeration of Costas Arrays of Size 26

2006 40th Annual Conference on Information Sciences and Systems, 2006
We present results of a grid computer search which enumerated the number of 26-by-26 Costas arrays. Of the 26! possible permutation matrices, only 56 of them satisfy the Costas condition that the N choose 2 line segments connecting pairs of ones are all distinct.
Scott Rickard, Edward Connell, Frank Duignan, Bruce Ladendorf, Aidan Wade   +4 more
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On Costas arrays with various types of symmetry

2009 16th International Conference on Digital Signal Processing, 2009
Using the database of Costas arrays of orders 27 and below, a table is generated showing the number of arrays which exhibit some kind of symmetry. The number of diagonal, anti-reflective and consecutive arrays are given, correcting previously published results in a small number of cases.
Ken Taylor, Scott Rickard, Konstantinos Drakakis   +2 more
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A remark on the definition of Costas arrays

Proceedings of the IEEE, 1987
A weaker definition of Costas arrays is shown to be equivalent to the standard one. A Costas array is a diagram whose corresponding frequency-hopping pattern has good range-doppler ambiguity properties. Our result implies that even when we demand ostensibly less restrictive ambiguities in the doppler direction, the resulting waveform becomes a Costas ...
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The enumeration of Costas arrays of order 28

2010 IEEE Information Theory Workshop, 2010
We present the results of the enumeration of Costas arrays of order 28: all arrays found are accounted for by the Golomb and Welch construction methods, making 28 the first order (larger than 5) for which no sporadic Costas arrays exist. The enumeration was performed on several computer clusters and required the equivalent of 70 years of single CPU ...
Konstantinos Drakakis, Francesco Iorio, Scott Rickard   +2 more
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Generating Costas Arrays to Order 200

2006 40th Annual Conference on Information Sciences and Systems, 2006
Number-theoretic generators of Costas arrays and generalizations in the literature and some presented here produce 526,908 of the known 663,703 known Costas arrays for orders up to 200. For orders higher than seven, there are more Costas arrays than the generators produce.
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A Structural Constraint for Golomb Costas Arrays

IEEE Transactions on Information Theory, 2010
A structural constraint (symmetry property) of Golomb Costas arrays constructed in finite fields of odd size is presented, analogous to the anti-reflective symmetry of Welch Costas arrays.
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Optimum Costas-like decompositions of Costas arrays for channel characterization and communications

Proceedings of ICASSP '94. IEEE International Conference on Acoustics, Speech and Signal Processing, 2002
In the paper we show that any subset or decomposition of Costas arrays are themselves non-full Costas arrays with ideal auto-, and cross-ambiguity and multiple access properties. The decomposed waveform's "thumbtrack" like auto-ambiguity functions, and their low cross-ambiguity or mutual interference would make them applicable in various multiple ...
Sanjay K. Mehta, Edward L. Titlebaum
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A Regularity Property of Golomb-Costas Arrays

2006 40th Annual Conference on Information Sciences and Systems, 2006
A Golomb-Costas array is an arrangement of dots and blanks, defined for each positive integer power of a prime and satisfying certain unusual conditions. A dot occurring in such an array is an even/even position if it occurs in the i-th row and j-th column, where i and j are both even integers, and there are similar definitions of odd/odd, even/odd and
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On the parity populations of Welch-constructed Costas arrays

2006 40th Annual Conference on Information Sciences and Systems, 2006
We prove that, in the case of Welch-constructed Costas arrays, the number of dots whose coordinates are both even (ee), both odd (oo), even and odd (eo), and odd and even (oe) are all equal if the prime p used has the property that p mod 4 = 1; and that, if p mod 4 = 3, the relation between these 4 quantities can again be determined, and that it ...
Konstantinos Drakakis, Rod Gow, Scott Rickard   +2 more
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