
RF AMP & SERVO SIGNAL PROCESSOR
S1L9226X
5
PRELIMINARY
RF EQUALIZE & AGC
The modulator output, which had the Veqc's Tanh term multiplied at the input, passes through the approximately
3X gain terminal to the ARF pad. On the one hand, the output is - rectified as it passes through the HPF having
50kHz pole frequency and follows the peak envelope the RF level. At this time, the pole frequency of the HPF is
set to 50kHz so that the 3T - 11T component can pass through without attenuation. The RF level peak value is
integrated at the 's CAP node after wave rectification. If this peak value is less than the already set voltage
comparison, sinking current is output and, if not, sourcing current is output. The maximum peak value at this time is
10uA, which is I/V converted and applied as the modulator control voltage. Under the sinking condition, the Vcagc
increases to 1outx10K and multiplied by Tanh (1-X); the sourcing condition, Vcagc decreases to Iout x10K and
multiplied by Tanh (1+X), where X is (Veqc/2Vt).
Overall, after detecting the 3T and 11T levels by full-wave rectification, it is compared to Tanh using the modulator
and multiplied to the gain to realize the wave-form equalize. The above is related to the AGC concept, which
means that a specific RF level is always taken
Modulator
3x Gain AMP
HPF
(3dB: 50kHz)
I/V Converter
Control Range
I * 10K
Full Wave Rectifier
(RF Peak Envelope)
Iout = 2gm (Vid/2)
= gm * Vid
= (Iref) * (Vid/Vt)
= Iref * (Vp-Vn)/Vt
if Vn > Vp
Vcagc Increment (tanh (1-X))
if Vn < Vp
Vcagc Decrement (tanh (1+X))
tanh
±
0.1 =
±
0.1
tanh
±
0.5 =
±
0.462
tanh
±
0.1 =
±
0.7
tanh
±
2.0 =
±
0.964
Vref
Vp
Vn
V = I/C (115pF)
EQO-AGC Output
Vin (t)
Vcagc (t)
Vo (t)
+
-
Vin(t) = 0.73x (RFO)
Vo(t) =
R6 (5.5K)
(
2Vt
Vcagc(t)
)