Page 445 - Analog and Digital Filter Design

442 Analog and Digital Filter Design

resonant frequency is equal to the bandpass center frequency. Finally,
denormalize for load impedance.
6.2 Each series arm will have two parallel LC circuits connected in series.
One LC circuit has high impedance above the passband, and the other
has high impedance below the passband. Each series arm thus gives
two notches in the frequency response: one above and one below the
filter's passband.
6.3 R3 = lOl(n80.10j.220. lo-") = 180.86kQ
R1 = R3140 = 4.521 kn
R2 = R3/(400 - 40) = R3l360 = 502Q

6.4 R=R3= R4= 1/(2.~35.10~4.7.10-~)=967.5Q
R1' = QR = 50 x 967.5 = 48.375kQ
R1 = 2 x 48.275kl1.5 = 64.5kQ
R2 = 2 x 48.275 kIO.5 = 193.5 kQ

Chapter 7

7.1 Start with lowpass prototype, and convert to highpass prototype using
reciprocal values (i.e., a lowpass prototype inductor with a value of
2.0 becomes a highpass prototype capacitor with a value of 0.5).
Frequency scale the highpass prototype to have a cutoff frequency
equal to the bandstop filter's stopband. The highpass design must now
be translated into a bandstop design by resonating each component at
the stopband center frequency. Series capacitors require a parallel
connected resonant inductor. Shunt inductors should have a series-
connected resonant capacitor. Finally, scale the components for the
correct load impedance.

7.2 Lowpass prototype Cl = C3 = 1.0 and L2 = 2.0.
(FL, -FL).l
C(shunt) =
~RFL! FL R
Fu = 1.05MHz and FL = 0.95MHz
1 OOk
C(shunt) = = 319pF
2~9.975 lO"50
50
L(shunt) = ~ = 79.58pH
2n100k
1
C(series) = = 15.9nF
2n100k50 2
L(series) = = 1.595pH
2~9.97510"