Help me design an IIR low pass filter?

IIR filters.

It has the following characteristics:

The system function of an IIR digital filter can be written in the form of a closed function.

IIR digital filters have a recursive structure, i.e., they have a feedback loop on the structure. The IIR filter operation structure is usually composed of basic operations such as delay, multiplication coefficient and addition, which can be combined into four structural forms: direct type, alignment type, cascade type, and parallel type standby type, all of which have feedback loops. Due to rounding in the operation, errors accumulate and sometimes weak parasitic oscillations occur.

3] IIR digital filter can be used with the help of mature analog filter results, such as Butterworth, Chebyshev and elliptical filter Bu Yinrui, etc., there are ready-made design data or charts can be checked, the design workload is relatively small, the requirements for the calculation of the work are not high. When designing an IIR digital filter, we first write the formula of the analog filter according to the indicator, and then convert the formula of the analog filter into the formula of the digital filter through a certain transformation.

4] The phase characteristics of the IIR digital filter are not easy to control, and when the phase requirements are high, the phase calibration network needs to be added.

It's really hard to explain all at once, so it's best to go to the hard city and check it out.

The full name of IIR filter is:"infinite impulse response filter", the Chinese name is"Infinite impulse response filter"。

The IIR filter is a digital filter characterized by an infinitely long impulse response. The opposite of the mountain is the FIR filter, which has a finite impulse response.

IIR filters have the advantage of having high filtering efficiency and small delay, but are prone to stability problems due to the infinite length of their impulse response. Therefore, when designing an IIR filter, special consideration needs to be given to its stability.

IIR filter bench inwave converters are widely used in the field of digital signal processing, such as audio processing, communication systems, image processing, etc. Common IIR filter coarse grip types include Butterworth filters, Chebyshev filters, Elliptic filters, etc. These filter types differ in terms of filter performance, group delay, stopband attenuation, etc., and can be selected according to specific application scenarios.

The bauder shows the radial frequency and phase frequency characteristics, and the sine of your input frequency is fixed, and there should be only one point displayed on the baud meter.

To make the input waveform a little more complicated, you change it to a periodic impulse signal, so that the spectrum is periodically continuous.

Here's the calculated Bode plot:

The DC gain is 2, you see that 1hz is basically 2 times, you have to amplify the frequency a little bit.

In addition, your filter, the output phase is ahead of the curve, you have to change it, at least it must become laggy, otherwise it is easy to be unstable, so calculate the transfer function of this filter, the two roots of the poles: 32+56i and 32-56i, sure enough, it's all positive, and the divergence is not good. >

The input is the output signal impulse response of the impulse signal:

32te (56t-pi/2)*i -(56t+pi/2)*i

vo= --e + e )

56 will be a few hundred milliseconds to kv.

I believe that it is normal for such circuits to be connected to the kv level after connecting other circuits.

You need to modify the rc parameter again.

Some of these concepts are juxtaposed, and some are contained.

Distinguished from functions: high-pass, low-pass, band-pass, and band-resistance, its meaning is as the name suggests.

From the processing signal is distinguished: analog (used to process analog signals, circuit implementation, typical is the frequency modulation in the radio), digital (this is achieved with limited precision, like the data in the computer can not be infinite, the typical example is the digital image).

For digital filters, which are distinguished from the structure, there are:

1. IIR, which is characterized by an infinitely long impact response (due to the existence of an infinite number of feedbacks), and which contains several structures (direct, parallel, cascade, frequency sampling, and its characteristics are as the name suggests). One of the more confusing aspects is that the textbook gives two models (Butterworth, Chebyshev, this has nothing to do with the structure, he just said that after years of development, such a design can better meet the specified requirements). Again, let's talk about the design methodology.

2. FIR, its shock response length is limited (the physical structure also has direct type, parallel connection, frequency sampling type). It corresponds to the IIR, but the design approach is very different.

According to the duration of the shock response, the filter can be divided into two implementation methods: IIR (infinite shock response) and FIR (limited impact response). From the perspective of filtering function, it can be divided into low-pass filter, high-pass filter, bandwidth filter, and band-stop filter (notch is a special band-stop filter), which can be realized in two ways: IIR and FIR. Analog filters and digital filters are distinguished from the continuity of the signal, the signal of the analog filter is continuous, and the signal of the digital filter is discrete.

Here's the main difference.