§ 7-1 Characteristics of sinusoids
f r e q u e n cyf
p er i o dT
??
??
)( 振幅a m p l i t u d eV m ??
)(u m e n ta r gt 幅角???
f r e q u e n c ya n g u l a r???
t?
?
?2?
tV m ?s in
mV
0
)2,2,/1( fTfT ???? ???
t?
?
?2?
?
tV m ?s in
)s i n ( ?? ?tV m
0
A more general form of the sinusoid
a n g l ep h a s e
u m en ta r g)t(
??
???
?
??
)s i n ( ??? ?? tV m
.)s i n (s i n
,s i n)s i n (
r adbytVl agstVor
r adbytVl e adstV
mm
mm
????
????
?
?
（滞后）
（超前）
tV m ?? s i n?
In either case,leading or lagging,we say that sinusoids are
out of phase（ 异相）,if phase angles equal they are said to be
in phase（ 同相）,
VtVt )30314s i n (220)6/314s i n (220 ???? ?????
Two sinusoidal waves that are to be compared in phase must
written as sine-waves,or both as cosine-waves,both waves
must be written with positive amplitudes,and each must be of
the same frequency.
)305s i n (11 ?? ?? tV m
)105co s (22 ?? ?? tV m
)1005s i n (2 ??? tV m
?
?
??
??
130
130
21
21
?
?
byl a g sor
byl e a d s
Normally,the difference in phase between two sinusoids is
expressed by that angle which is less than or equal to 180o in
magnitude.