The following is what I've picked up along the way ..

Phase modulation, FM, and AM are analog modulations. There are rough equiv.
in digital (like PAM) but you might be mixing apples and oranges if you are
trying to make phase modulation apply to the SIRCS code.

When you modify the width of the pulse of a carrier signal to communicate
information, you have pulse modulation and pulse width modulation
specifically.  In the case of the Sony code, the signal is either on or off.
The time it is on and transmitting 40Khz IR is the pulse time. The pulse
time is important since it determines whether a start pulse, a logical 1 or
a logical 0 is received.  In the Sony case, the time between pulses is
constant (.6 ms - which also corresponds to most detector specs for state
transition time).  If you want a good treatment of the Sony code that is
easy to understand, look at:

http://www.fet.uni-hannover.de/purnhage/dat/sircs.html.

You asked for a detailed explanation of the types of modulation. If you
meant that, then you need a text:  Try Computer Networks, Third
Edition, Tanenbaum, Prentice Hall.  If you meant you wanted a couple of
pages of information, then try:

http://www.avista.com/AppNotes/PhaseNoise/page1.htm

or

http://rlacs.hanyang.ac.kr/combook/node55.html


Good luck

-----Original Message-----
From: Goovaerts <goofy1@GLO.BE>
To: PICLIST@MITVMA.MIT.EDU <PICLIST@MITVMA.MIT.EDU>
Date: Tuesday, July 27, 1999 5:44 AM
Subject: Modulation ?


>Can somebody give me a rather detailed explenation about modulation (fase,
>frequency and amplitude - modulation !) ?
>
>Also can somebody tell me what kind of modulation an IR-signal uses ??
>(IR-signal ---> I mean the IR-standard of Sony : SIRCS !) I know they use
>pulse-width coding :
>
>When using such an IR-signal is looks like this :
>
>1. GUIDEPULS (Signal high during 2,4 ms)
>2. DATA OFF TIME (Signal low during 0,6 ms)
>3. ZERO represented by 0,6 ms low signal
>4. ONE represented by 1,2 ms high signal
>
>(A ONE or ZERO is always followed by a DATA OFF TIME)
>                              __
>The carrier is a _|     |_ with a frequency of 40 kHz !
>
>So, you get a signal containing pulses with a different width !! I want to
>know what form of modulation this is ?? (Think is fase modulation, but
don't
>know why ?)
>
>Any ideas ?
>
>Greetings from Glenn Goovaerts from Belgium