AKG Acoustics WMS 4000 manual Frequency Management a good idea for any multichannel system

AKG WMS MULTICHANNEL TECHNOLOGY

SETTING UP MULTICHANNEL SYSTEMS

HOW TO DEAL WITH INTERMODULATION AND KEEP YOUR FREQUENCIES STRAIGHT

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.

Calculation of intermodulation products

fIM = m1f1 + m2f2 + m3f3 + m4f4 + …

mv = 0, ±1, ±2, ±3, ±4, …

The order of IM products depends on the non-linearity of the transfer characteristic.

fIM = 2 f1 ± f2 , fIM = f1 ± f2 ± f3 3rd order

Derivation of 3rd order intermodulation products

(cosω 1t + cosω 2t + cosω 3t)3 = (		e jω 1t + e -jω1t			)3		+ (		e jω 2t + e -jω2t		)3		+ (	e jω 3t + e -jω3t			)3
	2						2						2
	+ 3(			e jω 1t + e -jω1t		)2		e jω 2t + e -jω2t		+ 3(		e jω 1t + e -jω1t			)2	e jω 3t + e -jω3t
	2						2						2					2
	+ 3(			e jω 2t + e -jω2t		)2		e jω 1t + e -jω1t		+ 3(		e jω 2t + e -jω2t			)2	e jω 3t + e -jω3t
	2						2						2					2
	+ 3(			e jω 3t + e -jω3t		)2		e jω 1t + e -jω1t		+ 3(		e jω 3t + e -jω3t			)2	e jω 2t + e -jω2t
	2						2						2					2
	+ 6		e jω 1t + e -jω1t				e jω 2t + e -jω2t			e jω 3t + e -jω3t
	2						2			2
Dual-tone products are obtained from lines 1 through 4,
e.g., fIM =	2f1 - f2
Three-tone products are obtained from line 5,
e.g., fIM =	f1 + f2 - f3

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