The abbreviation AFC stands for amplitude-frequency response. In English, this term sounds like “frequency response,” which literally means “frequency response.” The amplitude-frequency characteristic of the circuit shows the dependence of the output level of this device on the frequency of the transmitted signal at a constant amplitude of the sinusoidal signal at the input of this device. The frequency response can be determined analytically through formulas or experimentally. Any device is designed to transmit (or amplify) electrical signals. The frequency response of the device is determined by the dependence transmission coefficient(or gain) on frequency.
Transmission coefficient
What is transmission coefficient? Transmission coefficient is the ratio of the output of the circuit to the voltage at its input. Or the formula:
Where
U out– circuit output voltage
U in– voltage at the circuit input
In amplifying devices, the transmission coefficient is greater than unity. If the device introduces attenuation of the transmitted signal, then the transmission coefficient is less than unity.
The transmission coefficient can be expressed in terms of:
We build the frequency response of RC circuits in the Proteus program
In order to thoroughly understand what the frequency response is, let's look at the figure below.
So, we have a “black box”, to the input of which we will supply a sinusoidal signal, and at the output of the black box we will remove the signal. The condition must be met: you need to change the frequency of the input sinusoidal signal, but its amplitude must be constant.
What should we do next? We need to measure the amplitude of the output signal after the black box at the input signal frequency values of interest to us. That is, we must change the frequency of the input signal from 0 Hertz (direct current) to some final value that will satisfy our goals, and see what the amplitude of the signal will be at the output at the corresponding input values.
Let's look at this whole thing with an example. Let us have the simplest one in the black box with already known values of radioelements.
As I already said, the frequency response can be constructed experimentally, as well as using simulator programs. In my opinion, the simplest and most powerful simulator for beginners is Proteus. Let's start with it.
We assemble this circuit in the working field of the Proteus program
In order to apply a sinusoidal signal to the input of the circuit, we click on the “Generators” button, select SINE, and then connect it to the input of our circuit.
To measure the output signal, just click on the icon with the letter “V” and connect the pop-up icon to the output of our circuit:
For aesthetics, I have already changed the name of the input and output to sin and out. It should look something like this:
Well, half the work is already done.
Now all that remains is to add an important tool. It is called “frequency response”, as I already said, literally translated from English – “frequency response”. To do this, click the “Diagram” button and select “frequency” from the list.
Something like this will appear on the screen:
We click LMB twice and a window like this opens, where we select our sine generator (sin) as the input signal, which now sets the frequency at the input.
Here we select the frequency range that we will “drive” to the input of our circuit. In this case, this is the range from 1 Hz to 1 MHz. When setting the initial frequency to 0 Hertz, Proteus throws an error. Therefore, set the initial frequency close to zero.
and as a result a window with our output should appear
Press spacebar and enjoy the result
So, what interesting things can you find if you look at our frequency response? As you may have noticed, the amplitude at the output of the circuit decreases as the frequency increases. This means that our RC circuit is a kind of frequency filter. This filter allows low frequencies, in our case up to 100 Hertz, and then with increasing frequency it begins to “crush” them. And the higher the frequency, the more it attenuates the amplitude of the output signal. Therefore, in this case, our RC circuit is the simplest f iltrom n izkoy h frequency (low-pass filter).
Bandwidth
Among radio amateurs and not only there is also such a term as. Bandwidth– this is the frequency range within which the frequency response of a radio circuit or device is sufficiently uniform to ensure signal transmission without significant distortion of its shape.
How to determine bandwidth? This is quite easy to do. It is enough to find a level of -3 dB from the maximum frequency response graph on the frequency response graph and find the point of intersection of the straight line with the graph. In our case, this can be done lighter than steamed turnips. It is enough to expand our diagram to full screen and, using the built-in marker, look at the frequency at a level of -3 dB at the point of intersection with our frequency response graph. As we see, it is equal to 159 Hertz.
The frequency that is obtained at a level of -3 dB is called cutoff frequency. For an RC circuit it can be found using the formula:
For our case, the calculated frequency turned out to be 159.2 Hz, which is confirmed by Proteus.
Those who do not want to deal with decibels can draw a line at the level of 0.707 from the maximum amplitude of the output signal and look at the intersection with the graph. IN in this example, for clarity, I took the maximum amplitude as a level of 100%.
How to build frequency response in practice?
How to build the frequency response in practice, having in your arsenal and?
So, let's go. Let's assemble our chain in real life:
Well, now we attach a frequency generator to the input of the circuit, and with the help of an oscilloscope we monitor the amplitude of the output signal, and we will also monitor the amplitude of the input signal so that we are absolutely sure that a sine wave with a constant amplitude is supplied to the input of the RC circuit.
To experimentally study the frequency response, we need to assemble a simple circuit:
Our task is to change the frequency of the generator and observe what the oscilloscope shows at the output of the circuit. We will run our circuit through frequencies, starting from the lowest. As I already said, the yellow channel is intended for visual control that we are conducting the experiment honestly.
D.C, passing through this circuit, the output will give the amplitude value of the input signal, so the first point will have coordinates (0; 4), since the amplitude of our input signal is 4 Volts.
We look at the following value on the oscillogram:
Frequency 15 Hertz, output amplitude 4 Volts. So, the second point (15:4)
Third point (72;3.6). Note the amplitude of the red output signal. She begins to sag.
Fourth point (109;3.2)
Fifth point (159;2.8)
Sixth point (201;2.4)
Seventh point (273;2)
Eighth point (361;1.6)
Ninth point (542;1.2)
Tenth point (900;0.8)
Well, the last eleventh point (1907;0.4)
As a result of the measurements, we got a plate:
We build a graph based on the obtained values and get our experimental frequency response;-)
It turned out differently than in the technical literature. This is understandable, since they use a logarithmic scale for X, and not a linear one, as in my graph. As you can see, the amplitude of the output signal will continue to decrease as the frequency increases. In order to build our frequency response even more accurately, we need to take as many points as possible.
Let's go back to this waveform:
Here, at the cutoff frequency, the amplitude of the output signal turned out to be exactly 2.8 Volts, which are exactly at the level of 0.707. In our case, 100% is 4 Volts. 4x0.707=2.82 Volts.
Bandpass filter frequency response
There are also circuits whose frequency response looks like a hill or a pit. Let's look at one example. We will consider the so-called bandpass filter, the frequency response of which has the shape of a hill.
Actually the scheme itself:
And here is its frequency response:
The peculiarity of such filters is that they have two cutoff frequencies. They are also determined at a level of -3 dB or at a level of 0.707 from the maximum value of the transmission coefficient, or more precisely K u max /√2.
Since it’s inconvenient to look at the graph in dB, I’ll switch it to linear mode along the Y axis, removing the marker
As a result of the restructuring, the following frequency response was obtained:
The maximum output value was 498 mV with an input signal amplitude of 10 Volts. Hmmm, not a bad “amplifier”) So, we find the frequency value at a level of 0.707x498=352mV. The result is two cutoff frequencies - a frequency of 786 Hz and 320 KHz. Therefore, the bandwidth of this filter is from 786Hz to 320KHz.
In practice, to obtain the frequency response, instruments called characteristic curve analyzers are used to study the frequency response. This is what one of the samples looks like Soviet Union
PFC stands for phase-frequency characteristic, phase response - phase response. The phase-frequency characteristic is the dependence of the phase shift between the sinusoidal signals at the input and output of the device on the frequency of the input oscillation.
Phase difference
I think you have heard the expression more than once: “he experienced a phase shift.” This expression came into our vocabulary not so long ago and it means that a person has slightly moved his mind. That is, everything was fine, and then again! And that's all :-). And this often happens in electronics too) The difference between the phases of signals in electronics is called phase difference. It seems that we are “driving” some signal to the input, and for no apparent reason the output signal has moved in time relative to the input signal.
In order to determine the phase difference, the following condition must be met: signal frequencies must be equal. Even if one signal has an amplitude of Kilovolts, and the other of millivolts. Doesn't matter! As long as equal frequencies are maintained. If the equality condition were not met, then the phase shift between the signals would change all the time.
To determine the phase shift, a two-channel oscilloscope is used. The phase difference is most often denoted by the letter φ and on the oscillogram it looks something like this:
Building the phase response of an RC circuit in Proteus
For our test circuit
In order to display it in Proteus we again open the “frequency response” function
We also choose our generator
Don’t forget to indicate the frequency range being tested:
Without thinking for a long time, we select our exit out in the first window
And now the main difference: in the “Axis” column, put the marker on “Right”
Press spacebar and voila!
You can expand it to full screen
If desired, these two characteristics can be combined on one graph
Note that at the cutoff frequency the phase shift between the input and output signal is 45 degrees or in radians p/4 (click to enlarge)
In this experiment, at a frequency of more than 100 KHz, the phase difference reaches a value of 90 degrees (in radians π/2) and does not change.
We build FCHH in practice
In practice, the phase response can be measured in the same way as the frequency response, simply by observing the phase difference and recording the readings in a tablet. In this experiment, we will simply make sure that at the cutoff frequency we actually have a phase difference between the input and output signals of 45 degrees or π/4 in radians.
So, I got this waveform at a cutoff frequency of 159.2 Hz
We need to find out the phase difference between these two signals
The entire period is 2p, which means half the period is π. We have about 15.5 divisions per half-cycle. There is a difference of 4 divisions between the two signals. Let's make a proportion:
Hence x=0.258p or one could say almost 1/4p. Therefore, the phase difference between these two signals is equal to n/4, which almost exactly coincided with the calculated values in Proteus.
Summary
Amplitude-frequency response circuit shows the dependence of the level at the output of a given device on the frequency of the transmitted signal at a constant amplitude of the sinusoidal signal at the input of this device.
Phase-frequency response is the dependence of the phase shift between the sinusoidal signals at the input and output of the device on the frequency of the input oscillation.
Transmission coefficient is the ratio of the output of the circuit to the voltage at its input. If the transmission coefficient is greater than one, then the electrical circuit amplifies the input signal, but if it is less than one, it weakens it.
Bandwidth– this is the frequency range within which the frequency response of a radio circuit or device is sufficiently uniform to ensure signal transmission without significant distortion of its shape. Determined by the level of 0.707 from the maximum value of the frequency response.
It is known that dynamic processes can be represented by frequency characteristics (FC) by expanding the function into a Fourier series.
Suppose there is some object and you need to determine its frequency response. When experimentally measuring the frequency response, a sinusoidal signal with amplitude Ain = 1 and a certain frequency w is supplied to the input of the object, i.e.
x(t) = A input sin(wt) = sin(wt).
Then, after passing transient processes at the output, we will also have a sinusoidal signal of the same frequency w, but of a different amplitude A out and phase j:
y(t) = A output sin(wt + j)
At different meanings w the values of Aout and j, as a rule, will also be different. This dependence of amplitude and phase on frequency is called frequency response.
Types of frequency response:
· 
y” “ s 2 Y, etc.
Let us define the derivatives of the frequency response:
y’(t) = jw A out e j (w t + j) = jw y,
y”(t) = (jw) 2 A out e j (w t + j) = (jw) 2 y, etc.
This shows the correspondence s = jw.
Conclusion: frequency characteristics can be constructed from transfer functions by replacing s = jw.
To construct the frequency response and phase response, the following formulas are used:
, 
,
where Re(w) and Im(w) are the real and imaginary parts of the expression for the AFC, respectively.
Formulas for obtaining AFC from AFC and PFC:
Re(w) = A(w) . cos j(w), Im(w) = A(w) . sinj(w).
The frequency response graph is always located in one quarter, because frequency w > 0 and amplitude A > 0. The phase response graph can be located in two quarters, i.e. phase j can be either positive or negative. The AFC schedule can run through all quarters.
When plotting the frequency response graphically using a known frequency response, several key points corresponding to certain frequencies are identified on the frequency response curve. Next, the distances from the origin of coordinates to each point are measured and plotted on the frequency response graph: vertically - measured distances, horizontally - frequencies. The construction of the AFC is carried out in a similar way, but not distances are measured, but angles in degrees or radians.
To plot the AFC graphically, you need to know the type of AFC and PFC. In this case, several points corresponding to certain frequencies are identified on the frequency response and phase response. For each frequency, amplitude A is determined from the frequency response, and phase j is determined from the phase response. Each frequency corresponds to a point on the AFC, the distance to which from the origin is equal to A, and the angle relative to the positive semi-axis Re is equal to j. The marked points are connected by a curve.
Example: 
.
For s = jw we have
= = 
= =
Linear devices have an frequency response, nonlinear devices do not have an frequency response, since they have spectrum distortions leading to an infinite set of spectral components.
Phase and amplitude characteristics are in most cases related to each other.
Methods for obtaining frequency response:
1) Obtaining frequency response by points:
The frequency response is uniquely related to the transmission coefficient K(w).
By adjusting the frequency of the generator, with a constant signal amplitude, we supply this signal as an input stimulus for the circuit under study. We take the response from the output of the circuit under study; this requires a voltmeter or oscilloscope. To plot the frequency response, we mark the value of the output voltage in accordance with the generator frequencies on the frequency axis.
Dynamic range The device under study must be such that there are no distortions under a single influence of the generator (in other words, almost any device is linear only within a certain range of input influences, and beyond it, it ceases to be linear and obtaining its frequency response makes no sense). The frequency range of the voltmeter must satisfy the operating frequency band of the device under study.
Flaw: done manually, this is a rather long process, especially if it is necessary to obtain a large number of points.
2) Automatic analyzer frequency characteristics.
To speed up the determination of the frequency response, automatic frequency response analyzers are used. The structure of such an analyzer is shown below:
A harmonic signal (G1) and a rectangular pulse (G3) are supplied to the mixer; at some point in time, the frequency of G1 (sweeping frequency generator) and the frequency of the pulse signals will coincide and the difference components (fgch - fi) = 0, as a result of which the output of the mixer will appear constant components (“bursts” - moments of equality fgkch and fi). These bursts are fed through a low-pass filter to amplifiers.
Before using the analyzer, you must make sure that the measuring path is calibrated.
Posted on Allbest.ru
Another important parameter of a radio-electronic device is its amplitude-frequency characteristic. The amplitude-frequency characteristic is the dependence of the transmission coefficient of a radio-electronic device on frequency.
The amplitude-frequency response is one of the main qualitative parameters of radio-electronic equipment. An approximate view of the amplitude-frequency response is shown in Figure 1.
Figure 1. Frequency response
The amplitude-frequency response of a device is determined relative to its center frequency. For amplifiers audio frequency the frequency of 1 kHz is taken as the central frequency (in telephone networks 800 Hz). Figure 1 shows how, from the amplitude-frequency response graph, you can determine the upper and lower limits of the passband of a radio-electronic unit (amplifier or filter). Typically, the passband boundaries are determined at a level of 3 dB (0.707 from the center frequency). However, the flatness can be set to something else, for example, 0.1 dB.
For RF amplifiers, the center frequency is defined as the geometric mean of the upper and lower pass frequencies. The amplitude-frequency characteristic allows you to evaluate the unevenness of the gain depending on frequency.
When assessing the unevenness of the transmission coefficient within the bandwidth of the amplitude-frequency characteristic, this parameter may change slightly. At the same time, outside the passband and within the stopband, the transmission coefficient can change by hundreds and thousands of times. Visually, this change in the amplitude-frequency response is difficult to assess, since values less than one tenth of the maximum value will be indistinguishable on the amplitude-frequency response graph. In this case, the gain or gain is estimated on a logarithmic scale. To do this, the gain is expressed in decibels:
No less important is that for broadband amplifiers, which include audio frequency amplifiers in the low frequency region and the region high frequencies have to be analyzed separately. In order to display both the low-frequency region (tens of hertz) and the high-frequency region (tens of kilohertz) on one graph, the frequency axis is graduated on a logarithmic scale. An example of an amplitude-frequency response plotted on a logarithmic scale is shown in Figure 2.
Figure 2. Amplitude-frequency response with logarithmic graduation of the frequency axis
The amplitude-frequency response is most often constructed using values measured using a generator and an electronic voltmeter or oscilloscope; less often, a specialized device is used - a curve tracer or frequency response meter. Currently, such a device is increasingly being implemented on the basis personal computer or laptop. Structural scheme measurements of the amplitude-frequency response are shown in Figure 3.
Figure 3. Block diagram of amplitude-frequency response measurement
The curve tracer uses a sweep frequency generator (sweep generator), the limits of frequency change of which correspond to the width of the amplitude-frequency characteristic. An oscilloscope screen is used to display the amplitude-frequency response. Nowadays it is usually a liquid crystal display. The block diagram of connecting the curve tracer to the radio-electronic unit (amplifier) under study is shown in Figure 4.
Figure 4. Block diagram of measuring the amplitude-frequency response using a curve tracer
Time to measure the amplitude-frequency response at this method its measurements can be significant. This is due to the fact that when rapid change input frequency, the response at the output of the radio-electronic unit should take a steady value. Otherwise, the appearance of the amplitude-frequency response may be distorted.
In some cases, another method is used to determine the amplitude-frequency response. A short pulse with characteristics close to a delta pulse is applied to the input of the device being measured. At the output, a pulse is generated corresponding to the impulse response of the block under study. It is converted into digital form and the fast Fourier transform is calculated. As a result, the output produces a curve corresponding to the amplitude-frequency response. It is displayed on the computer monitor screen. This approach can significantly reduce analysis time and reduce the cost of measuring equipment.
date last update file 10/12/2013
Literature:
Together with the article "Amplitude-frequency response" read:
Interference differs from noise in that it enters a radio-electronic device from the outside. Noises are generated inside the radio-electronic device...
http://site/Sxemoteh/Shum/
http://site/Sxemoteh/LinPar/
http://site/Sxemoteh/NelinPar/
One of the most important parameters of a radio-electronic device is its amplitude characteristic.
http://site/Sxemoteh/LinPar/AmplHar/
Introduction
primary goal course work- systematization, consolidation and deepening of theoretical knowledge, as well as the acquisition of practical skills in analytical calculations and experimental measurement of the main characteristics of electrical circuits.
The work in the course “Electrical Engineering and Electronics” is devoted to the calculation of frequency (input and transfer) and transient characteristics of an electrical circuit.
The analysis of frequency characteristics is carried out by the frequency method, in which the electrical circuit is specified by its frequency characteristics (AFC and PFC), which in most practical cases can be simply measured or calculated. The frequency analysis method includes the task of frequency or spectral representation of the impact in the form of a sum of harmonic components with certain amplitudes, initial phases and frequencies, as well as the task of determining the reactions of the circuit to each harmonic component of the impact and their summation.
To analyze the transient characteristics of electrical circuits, there are a number of analytical methods: classical, operator, Duhamel’s method. In this work, we used the operator method based on the use of direct and inverse conversion Laplace, and is associated with the solution of algebraic equations with respect to the image.
Information from theory
Depending on the number of outputs (poles), all circuits are divided into two-terminal, four-terminal and multi-terminal.
The part of the electrical circuit, considered in relation to any two pairs of its terminals, is called a four-terminal network.
Quadripoles can be classified according to various criteria. Based on the linearity of the elements included in them, quadripoles are divided into linear and nonlinear. Also, quadripoles are active and passive. A four-terminal network is called active if it contains sources of electrical energy inside. Moreover, if these sources are independent, then in the case of a linear two-port network, a mandatory additional condition for the activity of the two-port network is the presence on one or both pairs of its open terminals of voltage caused by the sources of electrical energy located inside it, i.e. it is necessary that the actions of these sources are not mutually compensated within the quadripole network. Such an active quadripole is called autonomous.
In the case when the sources inside the four-terminal network are dependent, as is the case, for example, in equivalent circuits of electronic tubes and transistors, then after disconnecting the four-terminal network from the rest of the circuit, the voltage at its open terminals is not detected. Such an active quadripole is called non-autonomous.
A four-terminal network is called passive if it does not contain sources of electrical energy.
There are four-terminal networks, symmetrical and asymmetrical. A four-terminal network is symmetrical in the case when reversing its input and output terminals does not change the currents and voltages in the circuit to which it is connected. Otherwise, the quadripole is asymmetrical.
A four-port network is called invertible if the reversibility theorem is satisfied, i.e. the ratio of the input voltage to the output current, or what is the same, the transfer resistance of the input circuits does not depend on which of the two pairs of terminals is the input and which is the output. Otherwise, the four-port network is called irreversible.
Passive linear quadripoles are reversible, while asymmetrical active (autonomous and non-autonomous) quadripoles are irreversible. Symmetrical ones are always reversible.
According to the scheme of internal connections of quadripoles, there are L-shaped, T-shaped, U-shaped, bridge, T-shaped-bridge and others.
The main meaning of the quadripole theory is that, using some generalized parameters of the quadripole, you can find the currents and voltages at the input and output of the quadripole.
Frequency response analysis
We will call an input a pair of terminals (poles) to which each of the independent sources that define external influence on the chain. Terminals used to connect the load, i.e. We will call the branches whose current or voltage needs to be determined output.
The electrical oscillations created at the input of a circuit are called input signal or influence.
The signal at the output of a circuit that affects a load is called the circuit's reaction, response, or output signal.
For a quadripole network, all parameters can be divided into four groups:
1) input parameters. In relation to the signal source, the four-port network is a two-port network, and therefore has parameters similar to it:
a) complex input impedance;
b) complex input conductance.
2) transfer parameters. They characterize the transmission of signals through a four-port network from input to output, i.e. in forward direction:
a) complex voltage transfer coefficient;
b) complex current transfer coefficient;
c) complex resistance of direct transmission;
d) complex transmission conductivity or transmission coefficient J to U.
3) output parameters:
a) complex output impedance;
b) complex output conductance.
4) postback parameters. They characterize the transmission of signals through a four-port network, from output to input, i.e. in the opposite direction.
If there are reactive elements in the circuit (in this case capacitance), then due to the dependence of their reactance on the frequency of influence, the circuit parameters also become frequency dependent. In the general case, complex functions and resistances are complex functions of the frequency of influence and represent a set of frequency characteristics of the circuit.
The complex function of the input resistance is the frequency dependence of the ratio of the complex input voltage to the complex current 
Since the complex input resistance is a complex number, it can be represented in the form of an algebraic form:
where is the frequency response of the active input impedance;
Frequency response of input reactance.
The complex input impedance function, often called simply the input function, depends on two real frequency characteristics:
The modulus of a complex function (the length of a vector representing a complex number) is called the frequency response of the input impedance. The module of complex resistance is equal to the ratio of the amplitudes or effective values of voltage and current at the terminals of the considered section of the circuit
The module of the complex function shows how the total input impedance depends on the frequency of the harmonic influence.
The argument of the frequency response of the input impedance is called the phase-frequency response of the input impedance. It shows how the phase difference between the input voltage and current depends on frequency:
The complex voltage transfer function is the frequency dependence of the ratio of the complex harmonic voltage at the output to the complex voltage at the input of the quadripole:
The modulus of this function is called the amplitude-frequency characteristic.
This characteristic shows the frequency dependence of the ratio of the amplitudes of the output and input harmonic oscillations.
Complex transfer function argument:
Called the phase-frequency characteristic, it shows how the phase difference between the output and input voltages of a four-terminal network depends on frequency.
Frequency characteristics do not depend on the amplitudes and initial phases of influences and are determined only by the circuit data: number, properties, values, order of connection of its elements to each other. Thus, the frequency characteristics describe the circuit itself.
At graphic representation Frequency characteristics usually construct separate graphs of impedance, amplitude-frequency and phase-frequency characteristics. When the frequency range under study is wide, a logarithmic scale is used along the frequency axis. In addition to separate graphs of amplitude and phase frequency characteristics, one graph of the complex plane is sometimes used. In this case, each value of the function corresponds to a point on the complex plane or, what is the same, a vector connecting the origin of coordinates with the specified point. With a change in ω, the end of the specified vector describes a certain curve on the complex plane - the hodograph of the complex transfer function. Thus, the hodograph is the trajectory of movement of the end of the vector of the desired parameter in the complex plane. The hodograph can be constructed in Cartesian as well as polar coordinates.
The hodograph reflects the information contained in the amplitude and phase frequency characteristics of the circuit, since each point of the hodograph corresponds to a certain complex number - the complex transmission coefficient at a certain frequency.
Resonant or oscillatory circuits are electrical circuits in which voltage or current resonance phenomena can occur. Resonance is a mode of a passive electrical circuit containing inductance and capacitance in which the reactance and reactance of the circuit are zero; Accordingly, the reactive power at the terminals of the circuit is also zero. The frequencies at which the phenomenon of resonance is observed are called resonant frequencies. The frequency band near resonance, at the boundaries of which the current decreases to 0.707 of the maximum (resonant) value I 0, is usually called the bandwidth of the resonant circuit. The higher the quality factor of the circuit, the narrower its passband and, accordingly, the sharper the resonant curve. The sharpness of the resonance curve characterizes the frequency selectivity of the oscillatory circuit, i.e. its ability to transmit or delay electrical vibrations only of a certain frequency - resonant or close to it.
In practice, there is a need to allocate not only one particular frequency, but an entire frequency band. This frequency separation is carried out using electrical filters.
An electric filter is a passive four-port network that passes a certain frequency band with low attenuation; outside this frequency band the attenuation is large. The frequency band at which attenuation is small is called the filter passband. The rest of the frequency range is the stopband (or attenuation) of the filter.
Electrical filters can be classified in various ways.
Classification by transmitted frequencies. Depending on the transmitted frequency spectrum, filters are divided into filters: a) low-pass (low-frequency); b) high frequencies (high frequencies); c) strip; d) blocking (rejector).
Classification according to link diagrams. Filters can consist of L-, T-, U-shaped, bridge, etc. links. Depending on the number of links, the filter can be single-link or multi-link.
Classification of filters by characteristics. In contrast to the simplest filters of type k, there are filters of a higher class - derived filters of type m, etc.
Classification of filters by element types. There are filters: a) reactive; b) piezoelectric; c) non-inductive, etc.
Loading...
