[aprssig] Phase modulation question

[Chris Hansen]

Yes, they are the same.  Look at it this way:
 
The directly modulated carrier is y(t) = cos(2*pi*430e6*t + phi(t))  where phi(t) is the PSK modulation.  If a DSP is used to put the PSK on a low frequency carrier, say 1 KHz which is then up-converted to 430 MHz you will get:
 
y(t) = cos(2*pi*429.990e6*t + 2*pi*1e3*t + phi(t)), which is the same.
 
Chris Hansen, KQ6DW




________________________________
From: Andrew Rich <vk4tec at tech-software.net>
To: TAPR APRS Mailing List <aprssig at tapr.org>
Sent: Saturday, September 12, 2009 8:09:59 PM
Subject: [aprssig] Phase modulation question

 
I have a question 
 
You get a carrier on 430 MHz and modulate it with a 
an audio signal that changes phase eg PSK
 
You get a DSP to create a low level phase shifted 
carrier and then up convert to 430 MHz and send that to air
 
Are they different ?
 
 
 
 
----------------------------------------------------------
Andrew 
Rich 
Airways Technical Officer Grade 4
Surveillance - RADAR 
ADS-B
Amateur Radio Callsign VK4TEC
email: vk4tec at tech-software.net
web: www.tech-software.net


      
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.tapr.org/pipermail/aprssig_lists.tapr.org/attachments/20090912/02bbdbc1/attachment.html>