'*** 밑에 분류 무시'에 해당되는 글 131건
- 2009.02.18 archive, archiving: GRE words in daily life
- 2009.02.18 circuit board: printed circuit board (PCB) 1
- 2009.02.17 integrated circuit
- 2009.02.17 first 5 minutes with Mathematica: Mathematica startup palette
- 2009.02.13 Laptop disassembly: HP Pavilion dv2000
- 2009.02.12 HP laptop disassembly: hard drive part
- 2009.02.10 HP laptop: hard drive data 살리기 여정
- 2009.02.05 [article] why is the army interested in spread spectrum? [IEEE Commun. magazine Jul 1983]
- 2009.02.04 spread spectrum - principles and possible application to spectrum utilization and allocation: pseudorandom sequence spread spectrum (DS system)
- 2009.02.04 Simulink tutorial from the Mathworks: Simulink on-ramp
- 2009.01.30 Lincoln's Gettysburg speech: Nov. 19. 1863
- 2009.01.30 Proposal: A proposal to review the Spread Spectrum technology
- 2009.01.28 iPod 시대: iTunes and audio files format converting 실험
- 2009.01.20 virus vaccine software
- 2009.01.17 11. spread spectrum communications: applications of spread spectrum - commercial
- 2009.01.17 11. spread spectrum communications: applications of spread spectrum - military: LPI system
- 2009.01.17 11. spread spectrum communications: applications of spread spectrum - military: AJ system
- 2009.01.17 11. spread spectrum communications: spread spectrum techniques - hybrid
- 2009.01.17 11. spread spectrum communications: spread spectrum techniques - TH
- 2009.01.16 11. spread spectrum communications: spread spectrum techniques - FH
- 2009.01.12 digital modulated signal: binary & multilevel modulating signal
- 2009.01.12 Communication systems: analog & digital communication system 1
- 2009.01.10 11. spread spectrum communications: spread spectrum techniques - DS
- 2009.01.10 introduction: signal and system
- 2009.01.09 SOTEC laptop disassembly: hard drive part
- archive, archiving: GRE words in daily life
- *** 밑에 분류 무시
- 2009. 2. 18. 03:37
지난 2008년 미국 대선시 학교에서 이루어진 vice president debate와 관련하여,
도서관에서 발행된 magazine에서...
archiving the debate
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- circuit board: printed circuit board (PCB)
- *** 밑에 분류 무시
- 2009. 2. 18. 02:27
printed circuit board (PCB)
- ddd
printed circuit assembly (PCA)
- a PCB populated with electronic components is a printed circuit assembly (PCA).
rigid laminate
conduction layers are typecally made of thin copper foil. insulation layers dielectric are typically laminated together with epoxy resin prepreg. the board is typically coated with a solder mask that is green in color. other colors that are normally available are blue, and red.
from K9APE.com
variety of board types
- single sided board (cross section view)
- double sided board (corss section view)
- multilayer board (corss section view)
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- integrated circuit
- *** 밑에 분류 무시
- 2009. 2. 17. 12:58
The first working integrated circuit on germanium was demonstrated by Jack Kilby at Texas Instruments in 1958. This prototype has a transistor (small left dot) attached to two gold wires and a capacitor (middle black dot). The germanium itself, secured on a glass slide, is divided into three resistors by the tabs at the bottom. By showing that all three types of components could work in the same slice of germanium, Kilby offered a way to improve the performance and lower the cost of electronic devices. [from Technology Review Vol.112/No.1]
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| Laptop disassembly: HP Pavilion dv2000 (0) | 2009.02.13 |
| HP laptop disassembly: hard drive part (0) | 2009.02.12 |
- first 5 minutes with Mathematica: Mathematica startup palette
- *** 밑에 분류 무시
- 2009. 2. 17. 12:09
Mathematica is a computational software program which is developed by Wolfram Research.
2 + 2
500!
make a plot
- type 'Plot[Sin[x], {x,0,10}]'
- not plot, but Plot
- not sin[x], but Sin[x]
-
make it dynamic. type 'Manipulate[Plot[Sin[c*x], {x,0,10}], {c,1,5}]'
-
go to 3D. type ''
algebra
- type 'Integrate[1/(x^5 -1), x]'
- make it dynamic. type 'Manipulate[Integrate[1/(x^n-1),x], {n,2,10,1}]'
a random sample of the zillions of things Mathematica knows about...
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| integrated circuit (0) | 2009.02.17 |
| Laptop disassembly: HP Pavilion dv2000 (0) | 2009.02.13 |
| HP laptop disassembly: hard drive part (0) | 2009.02.12 |
| HP laptop: hard drive data 살리기 여정 (0) | 2009.02.10 |
- Laptop disassembly: HP Pavilion dv2000
- *** 밑에 분류 무시
- 2009. 2. 13. 07:27
2008년 2월.
내 두번째 laptop, HP Pavilion dv2000, 1년 6개월의 일기로 괴사.
하지만, 나는 너를 포기하지 않았다.
데이터 반드시 살려야 한다.
증상으로서 power on시, black screen 만 뜨고 부팅이 전혀 되지 않음.
specification
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| HP laptop disassembly: hard drive part (0) | 2009.02.12 |
| HP laptop: hard drive data 살리기 여정 (0) | 2009.02.10 |
| [article] why is the army interested in spread spectrum? [IEEE Commun. magazine Jul 1983] (0) | 2009.02.05 |
- HP laptop disassembly: hard drive part
- *** 밑에 분류 무시
- 2009. 2. 12. 13:48
HP Pavilion dv2000의 hard drive.
laptop 뒷면 하단부의 플라스틱 커버를 드라이버를 이용하여 제거하니,
사진과 같이 마운트에 장착되어 있는 hard drive set 일체를 볼 수 있었다.
hard drive set 일체 분리.
각 part 하나하나에 대해서 알아본다.
- hard drive
- hard drive - laptop 플라스틱연결 부품
- laptop 접촉부
hard drive
Seagate momentus 5400.3 120GB serial AT disc drive
laptop과의 접속 부분 macro 사진.
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- HP laptop: hard drive data 살리기 여정
- *** 밑에 분류 무시
- 2009. 2. 10. 15:18
고장난 laptop의 hard drive을 살리기 위해 필요한 부품을 알아보려고 amazon.com을 검색하던 중
왠지...이거면 문제를 풀 수 있을 것 같다는 item을 하나 발견했다.
HDD case enclosure. 가격은 $ 5.99.
밑져야 본전이라는 생각에 오더를 했고, 몇일이 지나서 제품을 받았다.
첫눈에 보아도 SATA HDD가 쏙 들어갈 것 같은 연결부.
HDD와 합체!
영롱한 붉은 빛!
아름다운 hard drive 돌아가는 소리~ 위위잉~
Tada!
HP hard drive는 마침내 인식이 되고, 자료는 살릴 수 있었다.
이번 troubleshooting으로 인해 크게,
- storage device interface (SATA)
- windows OS의 자료 저장법 (폴더 위치)
에 대해서 알게 있었다.
'*** 밑에 분류 무시' 카테고리의 다른 글
- 2009. 2. 5. 16:00
보호되어 있는 글입니다.
내용을 보시려면 비밀번호를 입력하세요.
내용을 보시려면 비밀번호를 입력하세요.
- 2009. 2. 4. 17:00
보호되어 있는 글입니다.
내용을 보시려면 비밀번호를 입력하세요.
내용을 보시려면 비밀번호를 입력하세요.
- Simulink tutorial from the Mathworks: Simulink on-ramp
- *** 밑에 분류 무시
- 2009. 2. 4. 06:48
* reference: http://www.mathworks.com/ then click the Academia tab
introduction: what is simulink
- simulink Library browser
- file extension name: *.mdl
constructing and running a simple modle
simulationg a model
- modify the step size (parameter)
- simulink documentation (for help)
working with MATLAB
- using inputs from MATLAB
- sending outputs to MATLAB
creating subsystems
- masked subsystem
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- Lincoln's Gettysburg speech: Nov. 19. 1863
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- 2009. 1. 30. 13:01
* 연설 전문
Gettysburg, PA.
Washington D.C.에서 차로 약 1시간 30분 정도.
Four score and seven years ago our fathers brought forth on this continent a new nation, conceived in Liberty, and dedicated to the proposition that all men are created equal.
Now we are engaged in a great civil war, testing whether that nation, or any nation, so conceived and so dedicated, can long endure. We are met on a great battle-field of that war.
We have come to dedicate a portion of that field, as a final resting place for those who here gave their lives that that nation might live. It is altogether fitting and proper that we should do this.
But, in a larger sense, we can not dedicate—we can not consecrate—we can not hallow—this ground. The brave men, living and dead, who struggled here, have consecrated it, far above our poor power to add or detract. The world will little note, nor long remember what we say here, but it can never forget what they did here.
It is for us the living, rather, to be dedicated here to the unfinished work which they who fought here have thus far so nobly advanced. It is rather for us to be here dedicated to the great task remaining before us—that from these honored dead we take increased devotion to that cause for which they gave the last full measure of devotion—that we here highly resolve that these dead shall not have died in vain—that this nation, under God, shall have a new birth of freedom—and that government of the people, by the people, for the people, shall not perish from the earth.
Now we are engaged in a great civil war, testing whether that nation, or any nation, so conceived and so dedicated, can long endure. We are met on a great battle-field of that war.
We have come to dedicate a portion of that field, as a final resting place for those who here gave their lives that that nation might live. It is altogether fitting and proper that we should do this.
But, in a larger sense, we can not dedicate—we can not consecrate—we can not hallow—this ground. The brave men, living and dead, who struggled here, have consecrated it, far above our poor power to add or detract. The world will little note, nor long remember what we say here, but it can never forget what they did here.
It is for us the living, rather, to be dedicated here to the unfinished work which they who fought here have thus far so nobly advanced. It is rather for us to be here dedicated to the great task remaining before us—that from these honored dead we take increased devotion to that cause for which they gave the last full measure of devotion—that we here highly resolve that these dead shall not have died in vain—that this nation, under God, shall have a new birth of freedom—and that government of the people, by the people, for the people, shall not perish from the earth.
Gettysburg, PA.
Washington D.C.에서 차로 약 1시간 30분 정도.
'*** 밑에 분류 무시' 카테고리의 다른 글
- Proposal: A proposal to review the Spread Spectrum technology
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- 2009. 1. 30. 04:25
WashU에 있는 engineering writing center.
평상시 무심히 지나치던 곳도, 마지막 학기에 불등(?)이 떨어지니까 찾아가게 된다.
처음 office을 찾아갔을 때 맞아주었던 Seema, lecturer 와 미팅 약속을 잡고 내가 작성을 한 proposal을 revising 했다.
spreadsprectrumproposal.docformal writing, technical writing general guide line
- technical writing과 general writing의 차이점?: 둘 모두 writing이라는 카테고리 안에서 다른 점이 없다. 1) 하지만, technical writing의 경우 좀더 정확한 용어로, 간단 명료하게 말하고자 하는 것을 표현하여야 한다. 2) technical writing의 경우 audience의 수준을 고려하여 back ground knowledge을 제공여부도 고려하여야 한다.
- formal writing, technical writing article에 쓰인 용어는 가능하면 acronym을 사용하지 않는다.
lesson from revision
- the의 사용
- 단수/복수의 사용
- area, arena 의 사용: area가 general 하게 사용될 수 있다면, arena의 경우 specific한 case에 사용된다.
- 명사와 동사의 사용: 글의 내용은 동명사 형태 (~ing)로 사용하는 것이 more easy하고 direct하게 다가온다.
- : (colon), ; (semi-colon)의 사용: ':'은 무엇인가를 나열할 경우에, ';'은 밀접한 sentence가 나열될 경우에 사용된다. 아주 좋은 예가 첨부문서 (proposal)의 Objective section 목적을 열거한 부분에서 찾을 수 있다.
- , (comma)의 사용: 용어를 정의해 주기 위해서 which, where etc. 이 사용되어 지는 경우 ','을 사용하지는 않지만, 용어를 수식, 추가설명하기 위해서 which, where etc. 이 사용되어 지는 경우 ','을 함께 사용한다.
- 미국애들은 날짜를 나타낼 때 주로 0/00로 표기한다나...어쩐다나...-_-;
'technical communication, 8th, by Mike Markel'을 추천해 주었다.
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| virus vaccine software (0) | 2009.01.20 |
| 11. spread spectrum communications: applications of spread spectrum - commercial (0) | 2009.01.17 |
- iPod 시대: iTunes and audio files format converting 실험
- *** 밑에 분류 무시
- 2009. 1. 28. 10:37
일개(?) 회사에서 나온 제품을 '연구'까지 해야된다는 사실이 탐탐치 않게 생각되지만,
그래도...참 대단한 회사요, 대단한 제품이요, 대단한 CEO다.
Time magazine 2009년 1월 19일(USA ed.) 일자에 쓰여진 기사의 일부를 인용하자면,
Can Apple survive without Jobs?, by Josh Quittner
... Beyond that, Jobs' Apple has helped right the music, TV, and film industries, whose business models had been upended by the promise of free everything on the Internet. His coveted devices gave people a reason - and a way - to pay for media again. ...
iTunes is a proprietary digital media player application, introduced by Apple Inc.
- proprietary software is software covered by copyright, patent, or trademark law or controlled by a single legal entity. The term is often contrasted with open source.
- iTunes 8 can currently read, write and convert between MP3, AIFF, WAV, MPEG-4, AAC and Apple Lossless. it can also play any audio files that QuickTime can play (as well as some video formats), including Protected AAC files from the iTunes Store and Audible.com audio books.
QuickTime is a multimedia framework (MMF) developed by Apple Inc.
apple site에 접속하여 iTunes을 다운받아 설치하게 되면 내 컴퓨터 계정 my music 폴더에 iTunes 폴더가 생성된다.
보통 사람들이 가지고 있는 audio file의 경우 format이 *.wma or *.mp3 인 경우가 대부분이다.
이러한 format을 가지고 있는 파일들을 iTunes library에 집어 넣는 과정에서 iTunes에서 자동으로 파일변환 과정이 일어난다.
알아두어야 할 것은 2 종류의 파일에 대해서 iTunes에서 실행되는 convert 과정이 조금 다르다는 것인데,
아래와 같이 실험을 해보았다.
각각 mp3, wma 형식을 가지는 음악파일을 library에 불러들이자,
wma 형식을 가지는 파일에 대해서는 위와 같은 message가 나타났다.
음... AAC format...-_-;
변환이 필요하다던 WMA file은 iTunes 폴더의 iTunes Music 폴더에 위와 같이 저장되었다.
파일 포맷은 *.M4A
파일 용량은 3.36 MB (변환 전 wma 용량은 1.38MB)
파일 용량은 3.36 MB (변환 전 wma 용량은 1.38MB)
반면, mp3 파일의 경우에는 format convert 과정이 없었을 뿐만 아니라, iTunes 폴더 내에 특별히 저장도 되지 않았다.
더 재미있는(?) 것은 만약 원본파일 (iTunes library에 등록하기 위한 파일들)을 지워버리거나, 경로를 변경할 경우
다음과 같은 변화가 iTunes에서 일어났다.
WMA 파일이어서 변환이 필요했고, iTunes 폴더에 저장이 필요했던 audio file은 그대로 play가 가능한 반면에,
mp3 파일은 '느낌표' 마크가 뜨면서, play가 되지 않았다.
결국... WMA냐 mp3냐 하는 파일 format 결정의 문제에 맞닥드리게 되는구나...
choose the side!
mp3 선택.
보너스로 wma에서 mp3로 포맷을 바꿔주는 utility을 첨부했다. ㅎㅎㅎ
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| Lincoln's Gettysburg speech: Nov. 19. 1863 (0) | 2009.01.30 |
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| Proposal: A proposal to review the Spread Spectrum technology (0) | 2009.01.30 |
| virus vaccine software (0) | 2009.01.20 |
| 11. spread spectrum communications: applications of spread spectrum - commercial (0) | 2009.01.17 |
| 11. spread spectrum communications: applications of spread spectrum - military: LPI system (0) | 2009.01.17 |
- virus vaccine software
- *** 밑에 분류 무시
- 2009. 1. 20. 07:20
2009. 1. 19.
마틴 루터 킹 데이를 맞이하여 랩탑을 포맷했다. -_-;
새롭게 프로그램들을 설치하면서
예전부터 알아보려고 하였던 virus vaccine SW에 대해서 정리하여 보았다.
안철수 연구소, V3
- 안철수 연구소: http://home.ahnlab.com/
- V3 Lite: http://www.v3lite.com/main.do
Peter Norton Computing, Inc
Symantec Corporation, Norton AntiVirus
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- 11. spread spectrum communications: applications of spread spectrum - commercial
- *** 밑에 분류 무시
- 2009. 1. 17. 14:30
11.5.2 commercial
multiple access communications
from the perspective of commercial applications, probably the most important use of spread spectrum communications is as a multiple accessing technique.
- SS technique and multiple access, CDMA
commonly used multiple access techniques: TDMA, FDMA, CDMA
in the CDMA, each signal in the set is given its own spreading sequence. all signals occupy the same bandwidth and are transmitted simultaneously in time: the different waveforms in CDMA are distinguished from one another at the receiver by the specific spreading codes they employ.
- CDMA detector
- CDMA application area: wireless communications
CDMA has been of particular interest recently for applications in wireless communications; including cellular communications, personal communications services (PCS), and wireless local area networks.
the reason for this popularity is primarily due to the performance that spread spectrum waveforms display when transmitted over a multipath fading channel, and concept known as the reuse factor, and property of achievable additional gain in the capacity by the use of voice activity detection.
- CDMA (SS technique) performance over multipath channel
- reuse factor
in conventional cellular systems, in order to avoid excessive interference from one cell to its neighbor cells, the frequencies used by a given cell are not used by its immediate neighbors. for CDMA, however, such spatial isolation is typecally not needed, so-called universal reuse is possible.
- voice activity detection
interference rejection
spread spectrum techniques are of interest in the commercial sector for basically the same reasons they are in the military community, namely their AJ and LPI characteristics.
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- 2009. 1. 17. 13:35
보호되어 있는 글입니다.
내용을 보시려면 비밀번호를 입력하세요.
내용을 보시려면 비밀번호를 입력하세요.
- 2009. 1. 17. 13:30
보호되어 있는 글입니다.
내용을 보시려면 비밀번호를 입력하세요.
내용을 보시려면 비밀번호를 입력하세요.
- 2009. 1. 17. 09:03
보호되어 있는 글입니다.
내용을 보시려면 비밀번호를 입력하세요.
내용을 보시려면 비밀번호를 입력하세요.
- 11. spread spectrum communications: spread spectrum techniques - TH
- *** 밑에 분류 무시
- 2009. 1. 17. 05:11
11.4.3 time hopping (TH) modulation
mathematical expression of signal
- modulating signal, and its complex envelope,
- spreading signal, and its complex envelope,
- spread spectrum signal, TH
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(FYI) chap 5. AM, FM, and digital modulated systems: spread spectrum systems: FH system
참조 포스팅에서 다루고 있는 내용 및 접근방식은 기본적으로 본 포스팅의 내용과 맥락을 함께 한다.
the SS signal is
TEXT: spread spectrum systems with commercial applications / Robert C. Dixon 에서 FH processing에 접근하는 방식은 조금 차이가 있다. BFSK 방식의 modulation tech에서 응용이 된, multiple-frequency, code-selected, FSK 로 설명한다. it is nothing more than FSK that the set of frequency choices is greatly expanded.
11.4.2 frequency hopping (FH) modulation
mathematical expression of signal
- modulating signal, and its complex envelope,
FH modulation is traditionally used with multiple-frequency-shift-keyed (MFSK) information signal, which have the complex form
where
- 수식에 의해서, information signal 에 의해서 변화되는 것은 frequency 라는 것을 알 수 있다.
- spreading signal, and its complex envelope,
where pulse has a duration
- spread spectrum signal, FH/MFSK
FH/MFSK signal is formed by complex multiplying the MFSK signal by
, resulting in the real transmitted signal,
FH system block diagram
- transmission processing
FH/MFSK signal, 
(here, above figure 
) is obtained by applying the sequence of pseudorandom frequency shifts 
directly to the frequency synthesizer that generates the carrier frequency 
.
Q)
의 경우 spread signal
와 관련된 variable이며,
는 information signal
와 관련된 variable이다. 그런데,
와
모두 PRN generator에 의해 생성되는 것인가?
successive (not necessarily disjoint)
segments of a PN sequence drive a frequency synthesizer, which hops the carrier over 
frequencies.
Q)
successive (not necessarily disjoint)
- receiving processing
the sum of the transmitted FH/MFSK signal and the channel interference is multipled by the identical FH modulation (known as dehopping). it returns the FH/MFSK signal to its original MFSK form, and the real interference singal became the wideband (in the average sense) signal.
the exact relation between
- chap 5. AM, FM, and digital modulated systems: spread spectrum systems, http://worthatry.tistory.com/448 [본문으로]
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About modulated digital(binary) modulating signal
OOK(ASK)
BPSK
BFSK
About modulated digital(multilevel) modulating signal
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- Communication systems: analog & digital communication system
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Definiton of analog system and digital communication system
* source: Digital and Analog Communication Systems(7th) by Leon W. Couch
- an analog information source produces messages that are defined on a continuum.
- a digital information source produces a finite set of possible messages.
- an analog communication system transfers information from an analog source to the intended receiver.
- a digital communication system transfers information from a digitla source to the intended receiver.
Communication system block-diagram model
- regardless of the particular application, all communications systems involve 3 main sub-systems: the transmitter, the channel, and the receiver.
- source: the message information(m(t)) may be in analog or digital form, depending on the particular system, and it may represent audio, video, or some other type of information.
- Tx signal processor: the signal-processing block at the transmitter conditions the source for more efficient transmission. For example, in an analog system, the signal processor may be an analog LPF. In a hybrid system (analog system + digital system), the signal processor may be an analog-to-digital converter (ADC).
- Tx carrier circuit: it converts the processed baseband signal into a bandpass that is appropriate for the tranmission medium of the channel. If the channel propagates baseband signals, no carrier circuits are needed.
- Channel: Channels may be classified into 2 categories: wire and wireless.
- Rx (carrier circuit + signal processor): the receiver takes the corrupted signal at the channel output and converts it to a baseband signal that can be handled by the receiver baseband processor.
* FYI: digital communication system
- digital communication system의 경우, transmitter 내부의 연산과정 중 ADC(in general, signal processor)을 통과한 digital modulating signal은 carrier circuit을 통과한 뒤 channel로 들어간다. 여기서 carrier circuit을 통과한 modulated signal은 신호가 가진 내용은 digital 이며, 신호의 waveform은 analog 형태이다. 결국 외향적으로 전송되는 signal의 형태는 analog signal이든 digital signal 이든 모두 analog waveform 이다. [refer. digital modulated signal: binary & multilevel modulating signal]
* digital signal의 경우, ADC에서 이루어지는 좀더 상세한 signal processing 과정은 'Sampler-Quantizer-Encoder' 이며, 최종 단계 encoder 이후의 신호의 형태는 내용적으로 0 or 1의 형태이며, 다양한 modulation scheme에 따라 다양한 waveform으로 전송이 된다.
* digital signal의 경우, AD conversion 에 대한 개략적인 개념적 접근은 "digital and analog communication systmes (specific chap. 3)"에서 알아본다. "digital signal processing" 에서는 이런 조작과정 결과물(digital signal) 과 이를 처리할 system(digital system) 사이에서 일어나는 다양한 부분을 조금더 detail하게 알아본다.
* source: Digital and Analog Communication Systems(7th) by Leon W. Couch
- an analog information source produces messages that are defined on a continuum.
- a digital information source produces a finite set of possible messages.
- an analog communication system transfers information from an analog source to the intended receiver.
- a digital communication system transfers information from a digitla source to the intended receiver.
Communication system block-diagram model
- regardless of the particular application, all communications systems involve 3 main sub-systems: the transmitter, the channel, and the receiver.
- source: the message information(m(t)) may be in analog or digital form, depending on the particular system, and it may represent audio, video, or some other type of information.
- Tx signal processor: the signal-processing block at the transmitter conditions the source for more efficient transmission. For example, in an analog system, the signal processor may be an analog LPF. In a hybrid system (analog system + digital system), the signal processor may be an analog-to-digital converter (ADC).
- Tx carrier circuit: it converts the processed baseband signal into a bandpass that is appropriate for the tranmission medium of the channel. If the channel propagates baseband signals, no carrier circuits are needed.
- Channel: Channels may be classified into 2 categories: wire and wireless.
- Rx (carrier circuit + signal processor): the receiver takes the corrupted signal at the channel output and converts it to a baseband signal that can be handled by the receiver baseband processor.
* FYI: digital communication system
- digital communication system의 경우, transmitter 내부의 연산과정 중 ADC(in general, signal processor)을 통과한 digital modulating signal은 carrier circuit을 통과한 뒤 channel로 들어간다. 여기서 carrier circuit을 통과한 modulated signal은 신호가 가진 내용은 digital 이며, 신호의 waveform은 analog 형태이다. 결국 외향적으로 전송되는 signal의 형태는 analog signal이든 digital signal 이든 모두 analog waveform 이다. [refer. digital modulated signal: binary & multilevel modulating signal]
* digital signal의 경우, ADC에서 이루어지는 좀더 상세한 signal processing 과정은 'Sampler-Quantizer-Encoder' 이며, 최종 단계 encoder 이후의 신호의 형태는 내용적으로 0 or 1의 형태이며, 다양한 modulation scheme에 따라 다양한 waveform으로 전송이 된다.
* digital signal의 경우, AD conversion 에 대한 개략적인 개념적 접근은 "digital and analog communication systmes (specific chap. 3)"에서 알아본다. "digital signal processing" 에서는 이런 조작과정 결과물(digital signal) 과 이를 처리할 system(digital system) 사이에서 일어나는 다양한 부분을 조금더 detail하게 알아본다.
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11.4.1 direct sequence (DS) modulation
mathematical expression of signal
- modulating signal, its complex envelope
where 
is a binary-valued data waveform of
- spreading signal, its complex envelope,
- spread spectrum signal, DS/BPSK
DS/BPSK signal is formed by multiplying the BPSK signal by 
, resulting in the real transmitted signal
DS system block diagram
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1.2 types of signals
1.3 systems
1.4 a familiar signal and system example
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