ADC decentralized communication technology
The value of AIC is determined by the number of public network shareholders, and the currency price increases with the increase of the number of shareholders
in the cloud wallet, gold stock is the sum of 50% equity of all innovation projects in the public network. There is huge room for appreciation. Therefore, gold shares in the exchange center is the recognition of the value of gold shares between shareholders. Through the realization of gold shares (equity) transactions, RMB as a crutch in the early stage is also the initial link to build trust< br />
Analog signal: poor confidentiality, weak anti-interference ability
digital signal: strong anti-interference ability and good communication confidentiality
digital signal, as the name suggests, means that the independent variable is discrete, and the dependent variable is also a discrete signal. The independent variable of digital signal is represented by integer, and its dependent variable is represented by limited number. Digital signal uses two physical states to represent 0 and 1, so the quality of digital signal is very strong, and the anti-interference ability is also relatively strong
analog signal refers to the continuous signal of information parameters in a given range. The characteristic quantity of analog signal information can be transformed into any numerical signal instantaneously. In the process of analog signal transmission, information signal needs to be converted into radio wave signal, and then transmitted by wired or wireless methods
disadvantages of analog signal:
poor confidentiality of analog signal: analog communication, especially microwave communication and wired communication, is easy to be eavesdropped. As long as the analog signal is received, it is easy to get the communication content
the anti-interference ability of analog signal is weak: in the process of transmission along the line, the electrical signal will be interfered by various external and internal noises of the communication system, and it is difficult to separate the noise and the signal after mixing, which makes the communication quality decline. The longer the line is, the more noise is accumulated
strong anti-interference ability of digital signal:
digital signal will be mixed with noise in the process of transmission. The threshold voltage (called threshold voltage) composed of electronic circuit can be used to measure the input signal voltage. Only when a certain voltage amplitude is reached, the circuit will have output value and automatically generate a neat pulse (called shaping or regeneration). When the small noise voltage arrives, it will be filtered out because it is lower than the threshold, and will not cause circuit action. Therefore, the regenerated signal is exactly the same as the original signal, unless the interference signal is larger than the original signal, the bit error will be generated. In order to prevent the error code, the method of checking and correcting the error is set in the circuit, that is, when the error code occurs, the backward signal can be used to make the other party retransmit. Therefore, digital transmission is suitable for long-distance transmission, but also for poor performance lines
advantages of digital signal:
digital signal strengthens the confidentiality of communication: after a / D transformation, digital voice signal can be encrypted first and then transmitted. After decryption at the receiving end, it can be restored to analog signal by D / a transformation. Speech digitization provides a very favorable condition for encryption processing, and the more bits of the password, the more difficult it is to decipher the password
extended data:
signals are physical quantities that represent messages, such as electrical signals, which can represent different messages through the changes of amplitude, frequency and phase. This kind of electrical signal has two kinds: analog signal and digital signal. Signal is the vehicle and carrier of message. Broadly speaking, it includes optical signal, acoustic signal and electrical signal. According to the actual use, the signals include TV signal, broadcast signal, radar signal, communication signal, etc; According to the time characteristics, there are deterministic signals and random signals
signal is the vehicle and carrier of message. Broadly speaking, it includes optical signal, acoustic signal and electrical signal. For example, the ancient people used the billowing smoke generated by lighting beacon towers to transmit the news of enemy invasion to distant troops, which belongs to the light signal; When we speak, sound waves are transmitted to other people's ears to make them understand our intentions. This is an acoustic signal
all kinds of radio waves traveling in space and electric current in the telephone network extending in all directions can be used to express all kinds of messages to distant places, which are electrical signals. Only by receiving light, sound and electric signals, can people know what the other party wants to express
1. ADC is the physical output
APC is the output of magic3. The upper unit generally undertakes the auxiliary output of the team
4. Medium single ad assassin AP mage is the main magic output
5
6
an instrument for measuring the shape of alternating current or pulse current wave, which is composed of electron tube amplifier, scanning oscillator, cathode ray tube, etc. In addition to observing the current waveform, the frequency and voltage intensity can also be measured. All the periodic physical processes that can be changed into electrical effects can be observed by oscillograph
waveform display
according to the principle of oscillograph, when a DC voltage is applied to a pair of deflection plates, a fixed displacement of light spot on the fluorescent screen will be proced, and the displacement is proportional to the applied DC voltage. If two DC voltages are applied to the vertical and horizontal deflectors at the same time, the position of the light spot on the screen is determined by the displacement in both directions
If a sinusoidal AC voltage is applied to a pair of deflectors, the light spot on the fluorescent screen will move with the change of voltage. When a sinusoidal AC voltage is applied to the vertical deflection plate, the voltage is VO (zero value) at the moment of time t = 0, and the position of the light spot on the fluorescent screen is at the coordinate origin 0. At the moment of time t = 1, the voltage is V1 (positive value). The light spot on the fluorescent screen is at 1 above the coordinate origin 0, and the displacement is proportional to the voltage V1; At the moment of time t = 2, the voltage is V2 (maximum positive value), the light spot on the screen is at 2 points above the zero point of the coordinate origin, and the displacement distance is proportional to the voltage V2; And so on, at each instant of time t = 3, t = 4,..., t = 8, the positions of light spots on the fluorescent screen are 3, 4,..., 8 respectively. The first cycle will be repeated in the second and third cycle of AC voltage. If the frequency of the sinusoidal AC voltage applied to the vertical deflection plate is very low, only lhz ~ 2Hz, then a light spot moving up and down will be seen on the fluorescent screen. The instantaneous deflection value of the light point from the coordinate origin is proportional to the instantaneous value of the voltage applied to the vertical deflection plate. If the frequency of the AC voltage applied to the vertical deflector is above 10Hz ~ 20Hz, what you can see on the screen is not a moving point up and down, but a vertical bright line, because of the afterglow of the screen and the persistence of human vision. The length of the bright line depends on the peak to peak value of the sinusoidal AC voltage when the vertical amplification gain of the oscilloscope is fixed. If a sinusoidal AC voltage is applied to the horizontal deflector, a similar situation will occur, except that the light spot moves on the horizontal axis
If a time-varying voltage (such as sawtooth voltage) is applied to a pair of deflectors, how will the light spot move on the screen? When there is sawtooth wave voltage on the horizontal deflection plate, the voltage is VO (maximum negative value) at the moment of time t = 0. The light spot on the fluorescent screen is at the starting position (zero point) on the left side of the coordinate origin, and the displacement distance is proportional to the voltage vo; At the moment of time t = 1, the voltage is V1 (negative value), the light spot on the fluorescent screen is at 1 point to the left of the coordinate origin, and the displacement distance is proportional to the voltage V1; By analogy, at each instant of time t = 2, t = 3,..., t = 8, the corresponding positions of light spots on the fluorescent screen are 2, 3,..., 8. At the moment of T = 8, the sawtooth voltage jumps from the maximum positive value V8 to the maximum negative value VO, and the light spot on the fluorescent screen moves from 8 to the zero point of the starting position very quickly. If the sawtooth voltage is periodic, the first cycle will be repeated in the second cycle, the third cycle,... Of the sawtooth voltage. If the frequency of sawtooth wave voltage applied to the horizontal deflector is very low at this time, which is only 1 Hz ~ 2 Hz, the light spot can be seen on the fluorescent screen moving uniformly from the zero point of the left starting position to the zero point of the right 8 points, and then the light spot moves extremely quickly from the right 8 points to the zero point of the left starting position. This process is called scanning. When a periodic sawtooth voltage is applied to the horizontal axis, the scanning will be repeated. The instantaneous value of the distance between the light spot and the zero point of the starting position is proportional to the instantaneous value of the voltage applied to the deflector. If the frequency of sawtooth wave voltage applied on the deflector is above 10Hz ~ 20Hz, a horizontal bright line can be seen e to the afterglow phenomenon of the fluorescent screen and the visual persistence phenomenon of the human eye. The length of the horizontal bright line is determined by the sawtooth wave voltage value when the horizontal amplification gain of the oscilloscope is fixed, and the sawtooth wave voltage value is proportional to the time change, The displacement of light spot on the screen is proportional to the voltage value, so the horizontal bright line on the screen can represent the time axis. Any equal line segment on this bright line represents an equal period of time
if the measured signal voltage is added to the vertical deflection plate and the sawtooth wave scanning voltage is added to the horizontal deflection plate, and the frequency of the measured signal voltage is equal to that of the sawtooth wave scanning voltage, the waveform curve of the measured signal voltage with time in one cycle will be displayed on the fluorescent screen (as shown in Figure 5-6). As shown in Figure 5-6, at the moment of time t = 0, the signal voltage is VO (zero value), the sawtooth voltage is V0 '(negative value), the light spot on the fluorescent screen is on the left side of the coordinate origin, and the displacement distance is proportional to the voltage V0' At the moment of time t = 1, the AC voltage is V1 (positive value), the sawtooth voltage is V1 '(negative value), and the light spot on the screen is in the second quadrant of the coordinate. Similarly, at the moment of time t = 2, t = 3,..., t = 8, the light spots on the fluorescent screen are located at 2, 3,..., 8 respectively. At the moment of T = 8, the sawtooth voltage jumps from the maximum positive value V8 'to the maximum negative value V0', so the light spot on the screen moves from 8 to the starting position 0 very quickly. After that, when the first cycle is repeated in the second and third cycle of the measured periodic signal, the trace of the light spot on the fluorescent screen is also overlapped in the first trace. Therefore, the measured signal voltage displayed on the screen is a stable waveform curve varying with time
it can be seen from the above that in order to stabilize the graphics on the fluorescent screen, the frequency of the signal voltage to be measured should keep the integer ratio of the frequency of the sawtooth wave voltage
shs1000
system, that is, the synchronous relationship. In order to achieve this, the frequency of sawtooth voltage is required to be continuously adjustable, so as to adapt to observe a variety of periodic signals with different frequencies. Secondly, because of the relative instability between the frequency of the measured signal and the frequency of the sawtooth oscillation signal, even if the frequency of the sawtooth voltage is temporarily adjusted to an integral multiple of the frequency of the measured signal, the graph can not be kept stable all the time. Therefore, the oscilloscope is equipped with synchronization device. In other words, a synchronous signal is added to a certain part of the sawtooth wave circuit to promote the synchronization of scanning. For simple oscilloscopes (such as domestic sb-10 oscilloscopes) that can only proce continuous scanning (i.e. generate continuous sawtooth wave), a synchronous signal related to the frequency of the observed signal needs to be input into the scanning circuit, When the frequency of the added synchronization signal is close to the self oscillation frequency of the sawtooth wave frequency (or close to its integral multiple), the sawtooth wave frequency can be "pulled into synchronization" or "locked". For the oscilloscopes (such as domestic st-16 oscilloscopes, sbt-5 synchronous oscilloscopes, sr-8 al trace oscilloscopes, etc.) with the function of waiting for scanning (that is, not generating sawtooth wave at ordinary times, but generating a sawtooth wave to scan once when the measured signal arrives), it is necessary to input a trigger signal related to the measured signal on the scanning circuit, The scanning process is closely coordinated with the measured signal. In this way, as long as the appropriate synchronization signal or trigger signal is selected according to the needs, any process to be studied can be synchronized with the sawtooth scanning frequency.
bitcoin is not easy to understand, and it is not easy to be understood. It has nothing to do with understanding ability. It has a certain relationship with the knowledge system. The complexity of bitcoin is beyond any layman's imagination, but if the research is clear, it is relatively simple, at least understandable. Unfortunately, no one is willing to admit that they "don't understand", and even fewer admit that they don't understand and are willing to learn by themselves
bitcoin is a Ponzi scheme, and Ponzi scheme is a typical scheme to dismantle the east wall and supplement the west wall. It uses new people's funds to protect the interests of the elderly, so as to expand the fund fraud of investment fraud, until it can not last and the whole structure collapses. Obviously bitcoin is not. The operation of bitcoin is completely transparent. Its adoption and growth are beyond anyone's control. The price of bitcoin depends entirely on the price the market is willing to pay for it, rather than the needs of the elderly investors< br />
supplement.. By using the platform of China mobile application hosting center, group customers can realize the demand of enterprise informatization with the least investment in the way of renting, which can not only save costs, but also improve efficiency and increase revenue
it belongs to the group.. Is it difficult for the company to add it for you? You call 10086.. They are familiar with the local business.. Later, we need to know how and how it was opened. How about you? I don't know. And 20 yuan. Then he said, you don't need a password or certificate to open any business. I really don't know how to get it. You're angry
ADC
five design steps of front end circuit
reprinted: Electronic Engineering album
Author:
rob Reeder senior converter application engineer email: rob [email protected] American analog device companies often need to digitize analog signals as soon as possible in modern communication systems and test equipment,
in order to complete the signal
processing in the digital domain< However,
it is very challenging to design transformer front-end circuit for analog-to-digital converter (ADC)
especially in high and medium frequency (if)
system
this paper summarizes
5
design steps to help develop the best
ADC
front end
this
5
steps include:
1; 2. Determine the input impedance of
ADC; 3. Determine the basic performance of
ADC; 4. Select
transformer and passive components matching with load; 5. Benchmark the design. This design method is simple and fast,
can achieve ideal performance in any application
the first step sounds simple, but it's very important, because only knowing the requirements of a special application can rece the number of iterations,
and choose the right components from the beginning,
quickly achieve the desired performance. The list of
including each design requirement should be listed, and the desired performance index boundary value should be set, so that
ADC
and transformer can be selected quickly<
for example,
suppose that an application requires a sampling rate of
61.44msps,
to capture the input signal on a
20MHz
bandwidth (1
00 ~ 120mhz) with a center frequency of
110Mhz
< A signal to noise ratio (SNR) higher than
72db
means that
14b ADC
is needed to achieve the required
SNR
performance. The power consumption of each channel should be less than
500MW. ADI's
14b, 80
MSPs ad9246 ADC can meet these system level performance requirements,
its working voltage is
1.8 ~ 3.3V,
it has broadband
and low power consumption characteristics<
in this case,
ADC
input is
110Mhz if
signal (bandwidth is
20MHz), sampling rate is
61.44msps. Since the bandwidth of the input signal
is relatively narrow (1
Nyquist bandwidth), the resonant matching technique is adopted here. This matching technology provides
narrow bandwidth,
but very good matching performance in a given frequency range
this technique usually requires an additional inctor or ferrite bead on the analog input to remove the parasitic capacitance seen from the
ADC
input stage
if the
If
of interest is located on the baseband (the first Nyquist bandwidth), a simple
RC
network can be used to construct a low-pass filter< The second step is to determine the input impedance of the ADC (Fig.
1)< The ad9246 is a non buffered or switched capacitor ADC, so the input impedance is time-varying and varies with the frequency of the analog input. To determine the input impedance of the device, please refer to the proct data sheet of
a
d9246
with the help of proct data table, find the impedance measured in
110Mhz
tracking mode
in this case,
ADC
internal input load is equivalent to a
6.9k Ω The differential resistor is connected in parallel with a
4pf
capacitor. It is better to match the tracking pattern of
ADC
because
ADC
is sampling at this time< The internal input impedance of ADC can be regarded as a parallel structure of a resistor and a capacitor
the third step determines the basic performance of
ADC, so as to better understand how
ADC
works before trying to optimize all design parameters. To establish this benchmark, the evaluation board in the default state is used. The
a
DC
features in the proct data book are probably determined in this way<
in the third step, the performance parameters are collected first,
SNR
of
72db
and clutter free dynamic range (s
FDR) of
82.7dbc
are obtained. These values are very close to the parameters in the data book. Please note that high performance signal generator and filter should be used for characteristic measurement to remove the harmonic and clutter components of any signal generator ring the test
then remove the filter,
re connect the
ADC
evaluation board to the test signal generator
the output level of the signal generator (in this case, + 14dbm) should be readjusted and recorded to collect the number of drives. The sweep frequency of the input frequency should have enough bandwidth to observe the change of bandwidth smoothness and get - 3dB
points
in this example,
the front end is equipped with a simple
RC
filter by default, so that the pass band smoothness reaches
1.2dB and the bandwidth is about
100MHz
after the data is collected, the decision can be made. For
72db SNR
and
83dbc SFDR
requirements, the use of anti aliasing filter (AAF) is very important to improve the anti-counterfeiting performance and keep the signal harmonic at a low level. However, the problems of input drive and pass band smoothness have not been solved<
AAF on the default evaluation board attenuates the band of interest very fast< Because the attenuation of the parallel inctor to the frequency of interest is less and the roll off outside the passband is better, it is helpful to use a simple parallel inctor<
for input driver,
consider using
1:4
transformer to make
ADC
reach full range,
this will increase the signal by + 6dB,
further rece the input driver requirements. Finally, vector network analyzer (VNA) should be used to measure input impedance and
vs
WR. Adjust to the frequency of interest and see how the input matches. In this case,
35 was measured at
110Mhz
Ω， From
to
VSWR
was
1.44:1
the fourth step is to select the transformer and passive components to match the load impedance. The component values of transformer and
R and l
must match the load,
and build a new
AAF that can make the overall performance between
ADC
and secondary transformer reach the expected value (Figure
2)<
figure
2: in this
ADC
front-end principle block diagram, the values of resistance and inctance must match the load
experience and experiment can play a role at this time
as the performance of different transformers varies greatly, it is easy to choose a transformer without
after measuring the transformer and knowing its performance,
the transformer shown in this example is selected
generally speaking, it is very important to select a transformer with good phase balance characteristics. The application of this example has narrow bandwidth and requires low dynamic voltage of input driver, so the common
1:4
impedance ratio transformer is adopted
some simple principles for selecting
ADC
transformers include careful examination of technical parameters< For example,
technical parameters such as reflection loss,
insertion loss, and phase and amplitude imbalance should be carefully compared. If these parameters are not given in the data sheet, they can be obtained from the manufacturer,
or measured with a vector analyzer
the choice of standard magnetic coupling transformer or unbalanced transformer depends on whether the bandwidth requirement can be met
the bandwidth of standard transformer is generally not higher than
1GHz,
while that of unbalanced transformer is much larger
Please note that termination may be required at both primary and secondary levels, but in order to minimize the number of components in this example, only secondary termination is performed. Depending on the application, it may be more reasonable to terminate both primary and secondary
the analog input should be connected in series with a resistance value of
15 ~ 50 Ω The resistance of the sensor
in this case, two
33 Ω The purpose of
is to limit the amount of reverse charge injected into the analog input by
unbuffered
ADC, which also helps to define the source impedance according to the previous stage. In the case of
9
0%, you can use
33 Ω， But in some cases, changing this value can slightly improve performance
then calculate the differential termination of transformer secondary. The results show that the secondary differential termination is less than
251 Ω Start to compare
well. Ideal
1:4
impedance ratio transformer is generally
200 Ω The termination resistance of. At the beginning of calculation, the reflection loss at a given center frequency
is used to calculate the actual characteristic impedance (Z0)<
when selecting transformers,
please remember that there are great differences among different transformers,
and the best way to compare different components is to fully understand the performance parameters of transformers. If there are no performance parameters, they can be obtained from the manufacturer. Remember that high
If
Design
can have a sensitive effect on transformer phase balance
If
very high design may require two transformers or unbalanced
balanced transformers to suppress even harmonic distortion
select
ADC
to determine whether to select buffered
ADC
or unbuffered
ADC. Unbuffered
ADC
or switched capacitor
ADC
has
time-varying input impedance, which is more difficult to design in the case of high
If
If a unbuffered
ADC is used,
in any case, input matching should be performed in the tracking
mode,
and the input impedance meter on the manufacturer's website should be used. Although buffered
ADC
consumes more power than unbuffered
ADC
, buffered
ADC
is often easier to design, even in the case of high
If
. When calculating
R
and
L
values,
remember that this is a good start
but not all applications have the same layout and parasitic parameter values, so some design iterations may be needed to finally determine the performance requirements of a specific application.