翻訳と辞書 Words near each other ・ Barking Abbey ・ Barker (coachbuilder) ・ Barker (Essex cricketer) ・ Barker (occupation) ・ Barker (surname) ・ Barker and Stonehouse ・ Barker Bank ・ Barker baronets ・ Barker Bill's Cartoon Show ・ Barker Bill's Trick Shooting ・ Barker Black ・ Barker Building ・ Barker Burnell ・ Barker by-election, 1956 ・ Barker channel ・ Barker code ・ Barker College ・ Barker Crossing ・ Barker Crossroads, Virginia ・ Barker Dam ・ Barker Dam (California) ・ Barker Fairley ・ Barker Field ・ Barker General Store ・ Barker Heights, North Carolina ・ Barker House ・ Barker House (Edenton, North Carolina) ・ Barker House (Houston, Texas) ・ Barker House (Manitou Springs, Colorado) ・ Barker House (Vance County, North Carolina) Dictionary Lists mini英和辞書 mini和英辞書 Webster 1913 Latin-English FOLDOC Wikipedia English ウィキペディア

翻訳と辞書　辞書検索 [ 開発暫定版 ] スポンサード リンク Barker code ： ウィキペディア英語版 Barker code A Barker code or Barker sequence is a finite sequence of ''N'' values of +1 and −1, :$a\_j\; \backslash text\; j\; =\; 1,\; 2,\; \backslash dots,\; N$ with the ideal autocorrelation property, such that the off-peak (non-cyclic) autocorrelation coefficients :$c\_v\; =\; \backslash sum\_^\; a\_j\; a\_$ are as small as possible: :$|c\_v|\; \backslash le\; 1\backslash ,$ for all . Only nine〔https://oeis.org/A091704〕 Barker sequences are known, all of length ''N'' at most 13. Barker's 1953 paper asked for sequences with the stronger condition :$c\_v\; \backslash in\; \backslash$ only four such sequences are known, shown in bold in the table below.〔 == Known Barker codes == Here is a table of all known Barker codes, where negations and reversals of the codes have been omitted. A Barker code has a maximum autocorrelation sequence which has sidelobes no larger than 1. It is generally accepted that no other perfect binary phase codes exist.〔http://www.math.wpi.edu/MPI2008/TSC/TSC-MPI.pdf〕 (It has been proven that there are no further odd-length codes,〔Turyn and Storer, "On binary sequences", Proceedings of the AMS, volume 12 (1961), pages 394–399〕 nor even-length codes of ''N'' < 1022.〔Leung, K., and Schmidt, B., "The Field descent method", Design, Codes and Cryptography, volume 36, pages 171–188〕) Barker codes of length ''N'' equal to 11 and 13 ( ) are used in direct-sequence spread spectrum and pulse compression radar systems because of their low autocorrelation properties (The sidelobe level of amplitude of the Barker codes is 1/N that of the peak signal).〔Introduction to Radar Systems, 3rd Edition, Merrill I. Skolnik, McGraw–Hill, 2001〕 A Barker code resembles a discrete version of a continuous chirp, another low-autocorrelation signal used in other pulse compression radars. The positive and negative amplitudes of the pulses forming the Barker codes imply the use of biphase modulation or binary phase-shift keying; that is, the change of phase in the carrier wave is 180 degrees. Similar to the Barker codes are the complementary sequences, which cancel sidelobes exactly when summed; the even-length Barker code pairs are also complementary pairs. There is a simple constructive method to create arbitrarily long complementary sequences. For the case of cyclic autocorrelation, other sequences have the same property of having perfect (and uniform) sidelobes, such as prime-length Legendre sequences and $2^n-1$ maximum length sequences (MLS). Arbitrarily long cyclic sequences can be constructed. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Barker code」の詳細全文を読む スポンサード リンク 翻訳と辞書 : 翻訳のためのインターネットリソース Copyright(C) kotoba.ne.jp 1997-2016. All Rights Reserved.