Equalization is the technique used to improve the received signal quality.Equalization compensates for inter symbol interference (ISI) created by multipath within time dispersive channels. ISI –Inter symbol Interference: if the modulation bandwidth exceeds the coherence bandwidth of the radio channel,ISI occurs and modulation pulses are spread in time.
Fundamentals of Equalization:
- Equalization is a technique used to combat inters symbol interference.
- In radio channels, a variety of adaptive equalizers can be used to cancel interference while providing diversity .
- Since the mobile fading channel is random and time varying equalizers must track the time varying characteristics of the mobile channel, and thus are called adaptive equalizers.
- In radio channels, a variety of adaptive equalizers can be used to cancel interference while providing diversity
Figure 13.1 Block Diagram of equalizer
- If x (t) is the original information signal, and f(t) is the combined complex baseband impulse response of the transmitter, channel, and the RF/IF sections of the receiver, the signal received by the equalizer may be expressed as
- where f* (t) is the complex conjugate off(t) , nb(t) is the baseband noise at the input of the equalizer. If the impulse response of the equalizer is heq (t) , then the output of the equalizer is
- where cn is the complex filter coefficients of the equalizer