LMH6714, LMH6720

LMH6722, LMH6722-Q1

SNOSA39G – NOVEMBER 2002 – REVISED APRIL 2013

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AMPLITUDE EQUALIZATION

Sending signals over coaxial cable greater than 50 meters in length will attenuate high frequency signal

components much more than lower frequency components. An equalizer can be made to pre emphasize the

higher frequency components so that the final signal has less distortion. This process can be done at either end

of the cable. The circuit in Figure 38 shows a receiver with some additional components in the feedback loop to

equalize the incoming signal. The RC networks peak the signal at higher frequencies. This peaking is a

piecewise linear approximation of the inverse of the frequency response of the coaxial cable. Figure 39 shows

the effect of this equalization on a digital signal that has passed through 150 meters of coaxial cable. Figure 40

shows a Bode plot of the frequency response of the circuit in Figure 38 along with equations needed to design

the pole and zero frequencies. Figure 41 shows a network analyzer plot of an LMH6714/LMH6720/LMH6722 with

the following component values:

R1 = 450

Ω

C1 = 470pF

R2 = 91

Ω

C2 = 68pF

Figure 38. Equalizer Circuit Schematic

Figure 39. Digital Signal without and with Equalization

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