IVIE IE-10A, Руководство владельца и оператора

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ON
OCTAVE FILTER CHARACTERISTICS
The t e n octave f i l t e r s i n the Spectrum Analyzer meet the requirements
o f t h e A N S I S1.ll-1966 1975) Class I f i l t e r standards.
A p l o t comparing
t h e second order Chebychev f i l t e r s i n t h e w i t h t h e ANSI standard
curves can be seen i n Figure 2.
FREQUENCY RATIO
-
F i g u r e 2
I n t h e above p l o t o f an octave w i d t h
f i t e r , t h e frequency
s c a l e ( h o r i z o n t a l a x i s ) has been so t h a t t h e same p l o t
can be used t o represent any one o f t h e o c t a v e f i l t e r s . For
example, t h e number
1 on t h e h o r i z o n t a l a x i s r e p r e s e n t s t h e f i l t e r
c e n t e r frequency fm, 2 i s a frequency t h a t i s t w i c e f m ( t h e second
and 0.4 i s a frequency t h a t i s f o u r t e n t h s t h a t o f t h e f i l t e r
c e n t e r frequency.
.
A w e l l designed f i l t e r should low t o be
t t e d through i t w i t h o u t s i g n i f i c a n t energy l o s s whi l e frequencies
o u t s i d e t h e should be r e j e c t e d o r a t t e n u a t e d t o some degree.
Transmission l o s s ( v e r t i c a l a x i s o f Fig. 2 ) i s s i m p l y a measurement of
t h e " a t t e n u a t i o n " o f energy ( u s u a l l y expressed i n dB) as
i t
passes
through a device o r c i r c u i t .
If we i n j e c t a pure tone i n t o an octave f i l t e r having a center
frequency o f 1 KHz, t h e " transmission l o s s " would be minimal, o r c l o s e
t o dB. However, an out- of- band 2 KHz tone i n t o t h e
1
KHz octave
t e r o f t h e would have a " transmission l o s s " of approximately
15 dB as can be seen by studying
F i g . 2.
3