Groups > sci.electronics.design > #447145

Re: Diode laser FM/AM modulation

From	Tauno Voipio <tauno.voipio@notused.fi.invalid>
Newsgroups	sci.electronics.design
Subject	Re: Diode laser FM/AM modulation
Date	2017-02-10 15:04 +0200
Organization	A noiseless patient Spider
Message-ID	<o7kdmf$7vp$1@dont-email.me> (permalink)
References	<36233cba-41c1-4f7f-adbd-3738a6bb5202@googlegroups.com> <78225b1e-f09c-48b2-852d-6e53b07954c1@googlegroups.com> <UZqdnXUwG6eKAgHFnZ2dnUU7-KWdnZ2d@giganews.com> <c062c28d-3d44-4c2b-9daa-b027703a0577@googlegroups.com>

Show all headers | View raw

On 9.2.17 19:39, George Herold wrote:
>
> Hmm can I ask a silly radio question.  If I've got
> (say) 50% AM, modulation index = 0.5, how big are the side bands compared
> to the central carrier?  (I guess I should be able to go look that up somewhere.)
> (Or measure it myself)
>
> I could then go measure the AM MI for the laser and get some number.
>
> George H.


There's no such thing as modulation index in AM. MI belongs to
angle modulation (PM, FM).

An AM signal modulated with a single sine wave is

  AM(t) = A(1 + M cos(omega_m t)) cos(omega_c t),

where

  A = carrier amplitude
  M = modulation depth (0 .. 1)
  omega_m = modulation signal angle frequency
  omega_c = carrier signal angle frequency
  t = time.

The expansion of the expression and cranking out the sideband
signals from the cos(omega_m t) cos(omega_c t) is left as homework.

-- 

-TV

Thread

Diode laser FM/AM modulation George Herold <gherold@teachspin.com> - 2017-02-09 06:26 -0800
  Re: Diode laser FM/AM modulation George Herold <gherold@teachspin.com> - 2017-02-09 07:22 -0800
    Re: Diode laser FM/AM modulation Tim Wescott <tim@seemywebsite.com> - 2017-02-09 10:55 -0600
      Re: Diode laser FM/AM modulation pcdhobbs@gmail.com - 2017-02-09 09:23 -0800
        Re: Diode laser FM/AM modulation Tim Wescott <seemywebsite@myfooter.really> - 2017-02-09 12:06 -0600
          Re: Diode laser FM/AM modulation Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> - 2017-02-09 14:11 -0500
            Re: Diode laser FM/AM modulation George Herold <gherold@teachspin.com> - 2017-02-09 12:33 -0800
      Re: Diode laser FM/AM modulation George Herold <gherold@teachspin.com> - 2017-02-09 09:39 -0800
        Re: Diode laser FM/AM modulation Tauno Voipio <tauno.voipio@notused.fi.invalid> - 2017-02-10 15:04 +0200
          Re: Diode laser FM/AM modulation George Herold <gherold@teachspin.com> - 2017-02-10 06:24 -0800
            Re: Diode laser FM/AM modulation Tauno Voipio <tauno.voipio@notused.fi.invalid> - 2017-02-10 17:36 +0200

csiph-web