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翻訳と辞書　辞書検索 [ 開発暫定版 ] スポンサード リンク Binary offset carrier modulation ： ウィキペディア英語版 Binary offset carrier modulation Binary Offset Carrier modulation〔ION-AM99〕〔MITRE00〕 (BOC modulation) was developed by John Betz, PhD, in order to allow interoperability of satellite navigation systems. It is currently used in the US GPS system and in Galileo〔SIS-ICD08〕 and is a square sub-carrier modulation, where a signal is multiplied by a rectangular sub-carrier of frequency $f\_$ equal or higher to the chip rate. Following this sub-carrier multiplication, the spectrum of the signal is divided into two parts, therefore BOC modulation is also known as a split-spectrum modulation. The main idea behind BOC modulation is to reduce the interference with BPSK-modulated signal, which has a sinc function shaped spectrum. Therefore, BPSK-modulated signals such as C/A GPS codes have most of their spectral energy concentrated around the carrier frequency, while BOC-modulated signals (used in Galileo system) have low energy around the carrier frequency and two main spectral lobes further away from the carrier (thus, the name of split-spectrum). BOC modulation has several variants: sine BOC (SinBOC),〔ENC-GNSS04〕〔ION-GPS02〕 cosine BOC (CosBOC)〔〔GJU〕〔Wiley06〕 Alternative BOC (AltBOC),〔Septentrio〕〔GPSJournal07〕〔Margaria08〕〔IEE06〕 multiplexed BOC (MBOC),〔InsideGNSS07〕〔ION-GNSS07〕〔ION-GNSS07bis〕〔EW07〕〔ESA06〕 Double BOC (DBOC)〔 etc. and some of them have been currently selected for Galileo GNSS signals. A BOC waveform is typically denoted via BOC(m,n) or BOC$(f\_\backslash ;,f\_c)$, where $f\_$ is the sub-carrier frequency, $f\_c$ is the chip frequency, $m=f\_/f\_$, $n=f\_/f\_$, and $f\_=1.023$ Mcps is the reference chip frequency of C/A GPS signal. A sine BOC(1,1) modulation is similar to Manchester code, that is, in digital domain, a '+1' is encoded as a '+1 −1' sequence, and a '0' is encoded as a '−1 +1' sequence. For an arbitrary $N\_=2m/n$ modulation order, in sine BOC(''m'',''n'') case, a '+1' is encoded as an alternating sequence of '+1 −1 +1 −1 +1 ...', having $N\_$ elements, and a '0' (or '−1') is encoded as an alternating '−1 +1 ...' sequence, also having $N\_$ elements. BOC modulation is typically applied on CDMA signals, where each chip of the pseudorandom code is split into BOC sub-intervals, as explained above (i.e., there are $N\_$ BOC intervals per chip). The power spectral density of a BOC-modulated signal depends on the BOC modulation order $N\_=2\backslash frac=2\backslash frac$ and its derivation can be found, for example, in 〔〔VTC04〕 ==References== 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「Binary offset carrier modulation」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.