R&S FSV-K70, Руководство пользователя

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Brief Description of Vector Signal Analysis
R&S
®
FSV-K70
62 Operating Manual 1176.7578.02 ─ 09
The GSM standard describes the transmission of binary data using MSK (i.e. 2FSK)
modulation with a modulation index of
h=1/2 at a symbol rate of 270.8333 KHz. The
reference deviation is therefore given by:
   
kHz 67.7083 kHz 270.8333 1 2
2
1
2
1
   






  
REF
The APCO Project 25 standard (phase 2) defines a H-CPM signal (i.e. 4FSK) with a
modulation index of
h=1/3 and a symbol rate of 6 KHz. The reference deviation is:
   
kHz 3 kHz 6 1 4
3
1
2
1
   






  
REF
2.5.2.1 Error Model
The FSK measurement model used assumes that signal distortions in both the magni-
tude and phase/frequency are present, as well as additive noise. The measured signal
model is expressed as:
   
 
 
t n e t A t MEAS
t j
DIST
DIST
  
 
with
n(t) is a disturbing additive noise process of unknown power,
A
DIST
(t) is the distorted magnitude model and
φ
DIST(t) is the distorted phase model.
The magnitude model is given by:
 
t
DIST
e K t A
 
 

with
K is a constant scaling factor which can be interpreted as the system gain and
⍺
is the amplitude droop in Nepers per second.
The phase model is given by:
   
   
       
2
2
1
t D t C t B t
REF DIST
with
B is a scaling factor which results in a reference deviation error,
C is a carrier frequency offset in radians per second,
D is a frequency drift in radians per second per second,
τ
is a timing offset in seconds and
ϕ
is a phase offset in radians.
Signal Model, Estimation and Modulation Errors