A computational simulation method for high-frequency fourth-order active bandpass filter

Abstract

The invention relates to the technical field of power electronics and large-scale integrated circuits, and in particular to a calculation simulation method for a high-frequency fourth-order active bandpass filter, comprising the following steps: S1: two second-order Bessel bandpass filters are used to form a fourth-order bandpass filter; S2: when performing calculation and simulation, since the transfer function of the fourth-order bandpass filter is H(s): since the fourth-order bandpass filter is composed of two second-order bandpass filters, it can be known from a high-order filter coefficient table that the frequency coefficients of the two-stage bandpass filters are 1 / K=1.046 and 1.039 respectively; two second-order Bessel bandpass filters are used to form a fourth-order bandpass filter, and the Bessel filter is a linear filter with a maximum flat group delay, which maintains a filtered signal waveform on a passband and can be used to reduce the inherent nonlinear phase distortion of all IIR filters.

Description

Technical Field

[0001] The invention relates to the technical field of power electronics and large-scale integrated circuits, and in particular to a calculation simulation method for a high-frequency fourth-order active bandpass filter. Background Art

[0002] Active filtering is widely used in power electronics, large-scale integrated circuits and other industries. In circuit systems, it has the functions of filtering out harmonics, improving signals, and protecting circuits.

[0003] With decades of development, the more mature implementation methods of active filters are mainly: active filters composed of operational amplifiers, state variable integrated active filters, and switched capacitor filters. This design mainly describes filters with operational amplifiers as the core. From the perspective of the effect of the filter implementation, the filter is divided into low-pass and high-pass filters, band-pass and frequency-selective filters, band-stop filters and notch filters, and all-pass filters. Among them, the band-pass filter is a filter that allows signals within a certain frequency range to pass through, and suppresses signals below or above this frequency band. High-pass and low-pass filters can be designed respectively. The cutoff frequencies of the two are very different and do not affect each other. The characteristic frequency of the band-pass filter refers to the frequency point with the largest gain, and its bandwidth is located on both sides of the center frequency. Summary of the invention

[0004] In view of the shortcomings of the prior art, the present invention provides a computational simulation method for a high-frequency fourth-order active bandpass filter. Two second-order Bessel bandpass filters are used to form a fourth-order bandpass filter. The Bessel filter is a linear filter with a maximum flat group delay. The filtered signal waveform is maintained in the passband, and can be used to reduce the nonlinear phase distortion inherent in all IIR filters.

[0005] The present invention is achieved through the following technical solutions:

[0006] A computational simulation method for a high-frequency fourth-order active bandpass filter comprises the following steps:

[0007] S1: Two second-order Bessel bandpass filters are used to form a fourth-order bandpass filter;

[0008] S2: When performing calculations and simulations,

[0009] Since the transfer function of the 4th order bandpass filter is:

[0010]

[0011] ,Since the 4th-order bandpass filter is composed of two 2nd-order bandpass filters, according to the high-order filter coefficient table, the frequency coefficients of the two-stage bandpass filters are 1 / K=1.046 and 1.039 respectively;

[0012] The center frequency of the first-stage bandpass filter is f 01 =f0 / K=470.8kHz, Q=4.158, constrain the capacitance and resistance, where C=C1=C2=100pF, R5=4.99kΩ,

[0013] According to the formula f 01 =1 / ω,

[0014] The calculation results show that R3 = 18.7 kΩ, R4 = 2.61 kΩ;

[0015] The center frequency of the second-stage bandpass filter is f 02 =f0 / K=467.9kHz, Q=7.668, constrain the capacitance and resistance, where C=C3=C4=100pF, R8=4.87kΩ,

[0016] According to the formula f 02 =1 / ω,

[0017] The calculated value is R7 = 34.8 kΩ, R 10 =2.55kΩ.

[0018] Preferably, when the computational simulation method is used, an LT6234CS8#PBF chip operational amplifier is used, which is a dual-channel low-noise, rail-to-rail output, unit-gain stable operational amplifier with a noise voltage of 1.9, and is suitable for ultrasonic amplifiers and active filters.

[0019] Preferably, two stages of bandpass filters are cascaded to form a fourth-order bandpass filter, and a dual power supply is used. When the input signal fluctuates based on 0V, both the input and output ends of the operational amplifier will have positive and negative fluctuations based on 0V, and their instantaneous voltages are within the power supply voltage range.

[0020] Preferably, when the fourth-order active bandpass filter is used, -5V to +5V is used for power supply, and the fourth-order active bandpass filter is simulated and analyzed by multisim software.

[0021] Preferably, when the fourth-order active bandpass filter is simulated and analyzed by multisim software, its input signal amplitude A=1Vpp, frequency f=450kHz, output signal amplitude A=2.577Vpp, frequency f=459.6kHz, Gain=1.3.

[0022] Preferably, according to the amplitude-frequency characteristic curve and the phase-frequency characteristic curve, the gain of the fourth-order active bandpass filter at the center frequency is 2.186 dB, and there is a phase shift of 11.58 degrees.

[0023] The beneficial effects of the present invention are:

[0024] Two second-order Bessel bandpass filters are used to form a fourth-order bandpass filter. The Bessel filter is a linear filter with a maximum flat group delay. It maintains the waveform of the filtered signal in the passband and can be used to reduce the nonlinear phase distortion inherent in all IIR filters. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0026] Figure 1 It is a circuit schematic diagram of a fourth-order active bandpass filter in the present invention;

[0027] Figure 2 It is the Multisim simulation waveform diagram in the present invention;

[0028] Figure 3 It is the amplitude-frequency characteristic curve diagram of the present invention;

[0029] Figure 4 It is a phase-frequency characteristic curve diagram in the present invention. DETAILED DESCRIPTION

[0030] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0031] Embodiment 1:

[0032] See also Figures 1 to 4 As shown, this embodiment specifically discloses a technical solution of a calculation simulation method for a high-frequency fourth-order active bandpass filter, including the following steps:

[0033] S1: Two second-order Bessel bandpass filters are used to form a fourth-order bandpass filter;

[0034] S2: When performing calculations and simulations,

[0035] Since the transfer function of the 4th order bandpass filter is:

[0036]

[0037] Since the 4th-order bandpass filter is composed of two 2nd-order bandpass filters, according to the high-order filter coefficient table, the frequency coefficients of the two-stage bandpass filters are 1 / K=1.046 and 1.039 respectively;

[0038] The center frequency of the first-stage bandpass filter is f 01 =f0 / K=470.8kHz, Q=4.158, constrain the capacitance and resistance, where C=C1=C2=100pF, R5=4.99kΩ,

[0039] According to the formula f 01 =1 / ω,

[0040] The calculation results show that R3 = 18.7 kΩ, R4 = 2.61 kΩ;

[0041] The center frequency of the second-stage bandpass filter is f 02 =f0 / K=467.9kHz, Q=7.668, constrain the capacitance and resistance, where C=C3=C4=100pF, R8=4.87kΩ,

[0042] According to the formula f 02 =1 / ω,

[0043] The calculated value is R7 = 34.8 kΩ, R 10 =2.55kΩ.

[0044] Specifically, when the calculation simulation method is used, an LT6234CS8#PBF chip operational amplifier is used. The operational amplifier is a dual-channel low-noise, rail-to-rail output, unit-gain stable operational amplifier with a noise voltage of 1.9, and is suitable for ultrasonic amplifiers and active filters.

[0045] Specifically, two-stage bandpass filters are cascaded to form a fourth-order bandpass filter, which adopts a dual power supply mode. When the input signal fluctuates on the basis of 0V, both the input and output ends of the operational amplifier will have positive and negative fluctuations based on 0V, and their instantaneous voltages are within the power supply voltage range.

[0046] Specifically, when the fourth-order active bandpass filter is used, -5V to +5V is used for power supply, and the fourth-order active bandpass filter is simulated and analyzed by multisim software.

[0047] Specifically, when the fourth-order active bandpass filter is simulated and analyzed by multisim software, its input signal amplitude A=1Vpp, frequency f=450kHz, output signal amplitude A=2.577Vpp, frequency f=459.6kHz, Gain=1.3.

[0048] Preferably, according to the amplitude-frequency characteristic curve and the phase-frequency characteristic curve, the gain of the fourth-order active bandpass filter at the center frequency is 2.186 dB, and there is a phase shift of 11.58 degrees.

[0049] The technical solution adopts two second-order Bessel bandpass filters to form a fourth-order bandpass filter. The Bessel filter is a linear filter with a maximum flat group delay, which maintains the waveform of the filtered signal in the passband and can be used to reduce the nonlinear phase distortion inherent in all IIR filters.

[0050] The technical indicators expected to be obtained by this technical solution are as follows:

[0051] The desired 4th-order bandpass filter has a center frequency of f0=450kHz, a bandwidth BW of 50kHz, and a gain Gain of 2.

[0052] In order to effectively reduce the impact of noise on the signal, the LT6234CS8#PBF chip produced by ADI is selected. This operational amplifier is a dual-channel low-noise, rail-to-rail output, unity-gain stable operational amplifier with a noise voltage of 1.9, which is suitable for the design of ultrasonic amplifiers and active filters.

[0053] The two-stage bandpass filter is cascaded to form a fourth-order bandpass filter, which adopts dual power supply mode. When the input signal fluctuates on the basis of 0V, the input and output ends of the operational amplifier will have positive and negative fluctuations based on 0V, and their instantaneous voltages are within the power supply voltage range. Figure 1 The figure shows the schematic diagram of the fourth-order active bandpass filter, which uses -5V to +5V power supply and uses multisim software to simulate and analyze the circuit. Figure 2 As shown, the input signal amplitude A = 1Vpp, the frequency is f = 450kHz, the output signal amplitude A = 2.577Vpp, the frequency is f = 459.6kHz, and Gain = 1.3. Figure 3 , 4 shows the amplitude-frequency characteristic and phase-frequency characteristic curves. At the center frequency, the circuit gain is 2.186dB, and there is a phase shift of 11.58deg. Since the theoretical calculation is carried out under ideal operational amplifier conditions, the simulation uses the actual operational amplifier, and there is a certain error between the theory and the simulation. Within the error range, it is basically consistent with the design requirements.

[0054] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A computational simulation method for a high-frequency fourth-order active bandpass filter, characterized in that: The steps include: S1: Two second-order Bessel bandpass filters are used to form a fourth-order bandpass filter; S2: When performing calculations and simulations, Since the transfer function of the 4th order bandpass filter is: Since the 4th-order bandpass filter is composed of two 2nd-order bandpass filters, according to the high-order filter coefficient table, the frequency coefficients of the two-stage bandpass filters are 1 / K=1.046 and 1.039 respectively; The center frequency of the first-stage bandpass filter is f 01 =f0 / K=470.8kHz, Q=4.158, constrain the capacitance and resistance, where C=C1=C2=100pF, R5=4.99kΩ, According to the formula f 01 =1 / ω, The calculation results show that R3 = 18.7 kΩ, R4 = 2.61 kΩ; The center frequency of the second-stage bandpass filter is f 02 =f0 / K=467.9kHz, Q=7.668, constrain the capacitance and resistance, where C=C3=C4=100pF, R8=4.87kΩ, According to the formula f 02 =1 / ω, The calculated value is R7 = 34.8 kΩ, R 10 =2.55kΩ.

2. The computational simulation method for a high-frequency fourth-order active bandpass filter according to claim 1, characterized in that: When the calculation simulation method is used, the LT6234CS8#PBF chip operational amplifier is used. The operational amplifier is a dual-channel low-noise, rail-to-rail output, unit-gain stable operational amplifier with a noise voltage of 1.9, and is suitable for ultrasonic amplifiers and active filters.

3. The computational simulation method of a high-frequency fourth-order active bandpass filter according to claim 2, characterized in that: The two-stage bandpass filter is cascaded to form a fourth-order bandpass filter, which adopts dual power supply. When the input signal fluctuates based on 0V, both the input and output ends of the op amp will have positive and negative fluctuations based on 0V, and their instantaneous voltages are within the power supply voltage range.

4. The computational simulation method for a high-frequency fourth-order active bandpass filter according to claim 3, characterized in that: When the fourth-order active bandpass filter is used, -5V to +5V is used for power supply, and multisim software is used to perform simulation analysis on the fourth-order active bandpass filter.

5. The computational simulation method for a high-frequency fourth-order active bandpass filter according to claim 4, characterized in that: When the fourth-order active bandpass filter is simulated and analyzed by multisim software, its input signal amplitude A=1Vpp, frequency f=450kHz, output signal amplitude A=2.577Vpp, frequency f=459.6kHz, Gain=1.

3.

6. The computational simulation method for a high-frequency fourth-order active bandpass filter according to claim 5, characterized in that: According to the amplitude-frequency characteristic curve and the phase-frequency characteristic curve, the gain of the fourth-order active bandpass filter at the center frequency is 2.186 dB, and there is a phase shift of 11.58 degrees.

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