AKG Acoustics WMS 4000 - Manual (Page 36)

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AKG WMS MULTICHANNEL TECHNOLOGY
H
OW TO DEAL WITH
I
NTERMODULATION AND KEEP YOUR
F
REQUENCIES STRAIGHT
SETTING UP MULTICHANNEL SYSTEMS
Calculation of intermodulation products
f
IM
= | m
1
f
1
+ m
2
f
2
+ m
3
f
3
+ m
4
f
4
+ … |
m
v
= 0, ±1, ±2, ±3, ±4, …
The order of IM products depends on the non-linearity of the transfer characteristic.
f
IM
= | 2 f
1
± f
2
| , f
IM
= | f
1
± f
2
± f
3
| 3 rd order
Derivation of 3 rd order intermodulation products
Dual-tone products are obtained from lines 1 through 4,
e.g., | f
IM
= 2f
1
- f
2
|
Three-tone products are obtained from line 5,
e.g., | f
IM
= f
1
+ f
2
- f
3
|
e j ω
1
t + e - j ω
1
t 3
2
(cos
ω
1
t + cos
ω
2
t + cos
ω
3
t) 3 =
+
+
3
( )
e j ω
1
t + e - j ω
1
t 2
2
( )
e j ω
2
t + e - j ω
2
t 3
2
( )
e j ω
2
t + e - j ω
2
t
2
e j ω
3
t + e - j ω
3
t
2
+
e j ω
3
t + e - j ω
3
t 3
2
( )
+ 3
e j ω
1
t + e - j ω
1
t 2
2
( )
3
e j ω
2
t + e - j ω
2
t 2
2
( )
e j ω
1
t + e - j ω
1
t
2
e j ω
3
t + e - j ω
3
t
2
+ 3
e j ω
2
t + e - j ω
2
t 2
2
( )
+
3
e j ω
3
t + e - j ω
3
t 2
2
( )
e j ω
1
t + e - j ω
1
t
2
e j ω
2
t + e - j ω
2
t
2
+ 3
e j ω
3
t + e - j ω
3
t 2
2
( )
+
e j ω
1
t + e - j ω
1
t
2
e j ω
2
t + e - j ω
2
t
2
e j ω
3
t + e - j ω
3
t
2
+ 6
Frequency Management: a good idea for any multichannel system
One way to run a multichannel system would be to hire an RF engineer with a university degree for doing nothing but the number
crunching required for finding clean frequencies and keeping an eye on all the batteries in the system. Unfortunately, it is not
easy to find someone with this kind of knowledge, and then these experts are extremely busy and expensive.
Don't worry, there is an easier way. WMS Series wireless systems from AKG provide both an integrated Frequency Management
System and clear battery status readouts to remove the hassle from setting up and operating a multichannel system and save
time and money.
6052_WMSKern_engl.qxd 01.03.2006 11:54 Uhr Seite 36