Kenwood DP-1100 B Service Manual page 7

D P - 1 1 0 0 B II
On t h e o t h e r h a n d , s u p p o s i n g t h a t an i n p u t signal is a
sinusoidal w a v e w h o s e a m p l i t u d e at the p e a k - t o - p e a k value is
V , the signal p o w e r S is:
1-5 E F M ( E I G H T T O F O U R T E E N M O D U L A T I O N )
T o c o n v e r t a level of an a n a l o g signal at every interval of a fix­
ed p e r i o d ( 1 / 4 4 . 1 kHz = 2 2 . 7 /is), as d e s c r i b e d in 1-4, t o a
binary c o d e (1 a n d 0 ) after q u a n t i z a t i o n is called a " P C M "
(Pulse Code M o d u l a t i o n ) .
PCM has v a r i o u s kinds of m o d u l a t i o n s y s t e m s , b u t here a
S o n y a n d Philips j o i n t l y d e v e l o p e d n e w s y s t e m , called E F M ,
used f o r D A D is d e s c r i b e d .
(1) EFM is t h e m o d u l a t i o n t o first divide a 1 6 - b i t d a t u m (data
bit) into t w o 8 - b i t data a n d t h e n c o n v e r t e a c h of these
8 - b i t d a t a t o a 1 4 - b i t d a t u m ( c h a n n e l bit) as s h o w n in
Fig. 1.8. T h e c o n v e r s i o n is t o select patterns of 2
a m o n g p a t t e r n s of 2
d i t i o n . C h a n n e l bits of 2
b e e n p r e d e t e r m i n e d by a c o m p u t e r as indicated in Tables
1-1 a n d 1-2:
II. FUNDAMENTALS
Sample A
M S B
Symbol 1 ( = 8 bits)
Symbol 1 ( = 17 channel bits)
8
1 4 k i n d s , m e e t i n g the f o l l o w i n g c o n ­
8 m e e t i n g this c o n d i t i o n have
T h e r e f o r e , the p o w e r ratio is:
T h e p u r p o s e of t h e m a r g i n bits is t o r e d u c e a DC c o m p o n e n t
a n d l o w f r e q u e n c y c o m p o n e n t s by a d d i n g three additional
bits t o t h e signals c o n v e r t e d into EFM.
One of 1 4 bits c o n v e r t e d f r o m 8 bits is called a c h a n n e l bit.
One word
Symbol 2 ( = 8 bits)
EFM
Margin bits
added
Symbol 2 { = 17 channel bits)
Fig. 1.8
T w o or m o r e b u t 10 or less Os (zeros) s h o u l d be a l w a y s i n ­
serted b e t w e e n c h a n n e l bits 1 a n d 1 4 .
kinds
(2) T h r e e c h a n n e l bits are a l w a y s inserted b e t w e e n 1 4 - b i t
b l o c k s . T h e role of these 3 bits is t o m a k e a d j u s t m e n t so
t h a t the a b o v e c o n d i t i o n (enclosed in t h e box) is m e t
e v e n at t h e c o n n e c t i o n of b l o c k s .
Role of Margin Bits
C h a n n e l Bits
L S B