Copyright © S.Witthayapradit Frequency Power Spectrum Magnitude (dB) Frequency Power Spectrum Magnitude (dB)
Analog Filter Digital Filter Passive Filter Active Filter • Resistor • Inductor • Capacito r • Active devices • Resistor • Capacitor IIRFIR • Direct form I • Direct form II • Rectangula r • Hanning • Hamming • Blackman • Kaiser Copyright © S.Witthayapradit 2012
รู้จักชนิดของวงจรกรองความถี่ทาง อิเล็กทรอนิกส์ ใช้สัมประสิทธิ์ในการออกแบบ วงจรได้ สามารถออกแบบวงจรกรองความถี่ ทางการแพทย์ได้
Copyright © S.Witthayapradit 2012
INPUT OUTPUT 1 st Order 2 nd Order 3 rd Order 4 th Order 1 st Order 2 nd Order 1 st Order 2 nd Order
Copyright © S.Witthayapradit Magnitude(dB) Frequency(Hz) 0.1f 1f 10f 1 st Order 2 nd Order 3 rd Order 4 th Order
Copyright © S.Witthayapradit 2012 มีช่วงแถบเปลี่ยนกว้าง (Transition band) แต่มีมุม เฟสเชิงเส้นแถบเปลี่ยน ให้ค่า ขนาด คงที่ในช่วงแถบ ผ่าน (pass Band)แถบ ผ่าน มีช่วงเปลี่ยนแคบมาก แต่ ช่วงแถบผ่านมีแรงดัน กระเพื่อม (Pass band Ripple) Bessel Butterwort h Tschebysch eff
Copyright © S.Witthayapradit 2012 Bessel Butterwort h Tschebysch eff Frequency 100Hz1.0kHz 10kHz Bessel Butterworth Tschebyscheff Copyright © S.Witthayapradit
Copyright © S.Witthayapradit 2012 a 1 : Coefficient Order BesselButterworthTschebyscheff(3db) AiAi bibi aiai bibi aiai bibi
Copyright © S.Witthayapradit 2012 a 1 : Coefficient Order BesselButterworthTschebyscheff(3db) AiAi bibi aiai bibi aiai bibi
Copyright © S.Witthayapradit 2012 a 1 : Coefficient Order BesselButterworthTschebyscheff(3db) AiAi bibi aiai bibi aiai bibi
Copyright © S.Witthayapradit 2012
2 nd OrderBesselButterworthTschebyscheff(3dB) a i b i Q a i, b i = สัมประสิทธิ์ (Coefficient) f C = ความถี่ตัด
Copyright © S.Witthayapradit 2012 “Butterworth” ให้ C 1 = 33nF 2 nd OrderBesselButterworthTschebyscheff(3dB) a i b i Q C 2 = 68nF f C = 2kHz
Copyright © S.Witthayapradit R 4 /R Q bibi aiai Tschebyscheff(3db)ButterworthBessel2 nd Order Coefficient R 1 = R 2 = R and C 1 = C 2 = C กำหนดค่าของ C แล้ว คำนวณหาค่า ของ R และอัตราขยายได้ เท่ากับ ; f C = ความถี่ตัด = 1/Q
Copyright © S.Witthayapradit bibi aiai Tschebyscheff(3db)ButterworthBessel2 nd Order Coefficient
Copyright © S.Witthayapradit 2012 Frequency 100Hz 1.0KHz10KHz MFB-LPF General LPF Unity Gain LPF
Copyright © S.Witthayapradit 2012 Frequency 100Hz1.0KHz10KHz -100d 0d 100d -180d 180d MFB-LPF Unity Gain-LPF General-LPF
Copyright © S.Witthayapradit 2012 [b,a]=butter(5,10/1000,'low '); filter_y=filtfilt(b,a,rec_y ); plot(filter_y) xlabel('Sample number') ylabel('Low Pass Filtered EMG signal') Sample number Rectified EMG signal Sample number Low Pass Filtered EMG signal
Copyright © S.Witthayapradit th Order Unity-gain Butterworth Low Pass Filter with f C = 10Hz C 1 = 82nF R 1 = 200K C 2 = 22nF C 3 = 10nF R 2 = 560K R 3 = 2M C 4 = 390nF C 5 = 33nF R 4 = 100K R 5 = 200K
Copyright © S.Witthayapradit 2012 Input Signal Output Signal
Copyright © S.Witthayapradit 2012
a 1 : Coefficient Order BesselButterworthTschebyscheff(3db) AiAi bibi aiai bibi aiai bibi
Copyright © S.Witthayapradit 2012 a 1 : Coefficient Order BesselButterworthTschebyscheff(3db) AiAi bibi aiai bibi aiai bibi
Copyright © S.Witthayapradit 2012
C 1 = C 2 = C a 1, b 1 = Coefficient
Copyright © S.Witthayapradit 2012 C 1 = C 2 = C = 56nF f C =10kHz ; Butterworth bibi aiai Tschebyscheff(3db)ButterworthBessel2 nd Order Coefficient
Copyright © S.Witthayapradit 2012 C 1 = C 2 = C a 1, b 1 = Coefficient
Copyright © S.Witthayapradit 2012 C 1 = C 3 = C
Copyright © S.Witthayapradit 2012 Frequency 100Hz1.0KHz10KHz100KHz MFB HPF General HPF Unity Gain HPF
Copyright © S.Witthayapradit 2012 Frequency 100Hz 1.0KHz 10KHz100KHz -100d 0d 100d -180d 180d MFB HPF General HPF Unity-Gain HPF
Copyright © S.Witthayapradit 2012 y=load('emg.txt'); subplot(211) plot(y) xlabel('Sample number') ylabel('EMG signal') Remove any DC offset of the signal subplot(212) y2=detrend(y) xlabel('Sample number') ylabel('EMG signal') Sample number Sample number
Copyright © S.Witthayapradit 2012 Frequency 100mHz1.0Hz10Hz Vdb(OUT)
Copyright © S.Witthayapradit 2012 Time 0s5s10s v in v out -2.0V 0V 2.0V
Copyright © S.Witthayapradit 2012 Order BesselButterworthTschebyscheff(3db ) aiai bibi aiai bibi aiai bibi
Copyright © S.Witthayapradit 2012 [1] Sergio Franco, “Design with Operational Amplifiers and Analog Integrated Circuits”, Third edition, McGraw-Hill, [2] Ron Mancini, “ Op Amps for Everyone”, Texas Instruments,2002. [3] James W.Nilsson, Susan A.Riedel, “Electric Circuits”, 8 th Edition, Prentice Hall, [4] Thomas L.Floyd, “Electronic Devices”, 7 th Edition, Prentice Hall Inc., 2005.