- R7 10k R8 10k C4 0 010 Do Hh R2 3 3m U1 1 Tl082cdr U3 2 Tl082cdr Vcc Vcc C3 Ro 10k Co R1 1 8m 0 010 2 R5 9 1k 00 R3 3 7 1 (64.03 KiB) Viewed 32 times
a) Assume that C3 has a as a deviation of +5%, i.e.,
C3=0.0105uF, while the parameters of other elements are consistent
with the nominal values. Can the trap achieve zero output at 50Hz
frequency point through R4 and R6? If possible, determine the
resistance values of R4 and R6.
(2) Can you adjust R6 first and then R4 to achieve zero output
of the notch at 50Hz frequency point?
(3)The transfer function HNotch(s) is a frequency function, and
its output is a complex number, whose mode and amplitude angle
correspond to the amplitude-frequency response and phase-frequency
response of the system respectively. Please draw the
amplitude-frequency response and phase-frequency response of the
notch filter in the frequency range of 40Hz~60Hz, and briefly
analyze the image.
R7 10k R8 10k C4 0.010 DO HH R2 3.3M U1.1 TL082CDR U3.2 TL082CDR VCC VCC C3 RO 10K CO R1 1.8M 0.010 2 R5 9.1k 00 R3 3 7 R6 2k NOTCH 50 27k 5 -CH1 +CH2- BPF R4 10k VEE VEE Figure 1.1 The circuit diagram of the 50Hz notch trap is given in Figure 1.1, and the nominal values of the components have been marked on the diagram. R4 and R6 are variable resistors with maximum resistances of 10K and 2K respectively. The transfer function of its circuit response is: 1 RC H2PF(s) = 1 1 1 1 1 (1) R.CZ RC RCC R R +R, s $? +5 + + BERARE + H Notch(s) R RE + R, Rs+R H BPF(S) Å TROR #aroo where s = jor j* 27 f. o The adjustment process of the 50Hz notch filter is briefly described as follows: The 50Hz sinusoidal signal is used to stimulate the notch filter, which can be adjusted to fine-tune the notch frequency R4, so that at 50Hz, the BPF output and input of the bandpass filter are 180 degrees out of phase. At this point, substitute s=j*21*50 into equation (1), confirm HBPA(S) is a real number. After that, R6 is adjusted to fine-tune the proportional coefficient of the addition circuit, so that NOTCH output end has no signal at 50Hz, such that H(S)=0.