deepak kumar panda
- Mar 21, 2012
- 8
- Joined
- Mar 21, 2012
- Messages
- 8
why is it called balanced?it is doing modulation,but is der ne specific reson to call it balanced?
Sorry,
this is as much information as I am able to supply. I'm not an expert in modulation technology and it's been quite some years I haven't done anything in this field.
But from what I understand the paradigm of aunbalanced or balanced modulator says nothing about how this type of modulation is achieved. A multiplier may as well be used as any other circuit that gives the same result. Balanced vs. unbalanced only refers to the spectrum of the modulated signal. If the spectrum is mirror symmetrical around the carrier frequency, this would be the result of a balanced modulation, whatever technology was employed to achieve this.
If the spectrum of the modulated signal is asymmetrical around the carrier frequency, this would be the result of a unbalanced modulation, whatever technology was employed to achieve this.
Harald
A sideband balanced modulator is made so that a carrier signal and its inverted signal are combined into a diode array and no carrier is coming out when no modulating signal is fed into the modulator. Now when the modulating signal becomes positive relative to a no signal condition the output of the modulator passes through one of the carrier signals. And when the modulating signal becomes negative the other carrier phase is fed through. The amplitude of the carrier phase coming out of the modulator is proportional to the plus or minus amplitude of the modulating signal. The term "balanced" comes from the fact that no net signal is coming out of the modulator when no modulating signal is applied to the modulator. The resultant output signal generates an upper and lower frequencies with no carrier signal. In single band operation one of the bands is filtered off in the transmitter, usually with a crystal filter, while the other band gets passed to the power stage. This is done to reduce bandwidth of the transmitted signal. And the receiver usually is designed to receive either the upper or lower band only so as to reduce the incoming signal. Modulation factor usually applies to amplitude modulation which is different from sideband modulation. The formula for this is (Vmax - Vmin)/(2Vavg).