As a physicist who has studied abroad for many years, Lao Guo is naturally no stranger to the Doppler effect.
This is a physical phenomenon discovered by Christian Doppler in 1842. To put it simply:
The wavelength of an object's radiation changes due to the relative motion of the wave source and observer.
For example, when standing still and an ambulance approaching, the sound heard is higher than before.
When the car leaves, the sound is lower than before. This is the Doppler effect.
The essence of this phenomenon is that when the ambulance drives towards a person, it continuously emits sound waves, and the emission position of the sound wave gets closer and closer to the person.
So the arrival time of each sound wave is shorter than the previous sound wave, and the distance between the wave crests...that is, the wavelength will be shortened.
Therefore, the frequency of sound waves perceived by the human body increases and the pitch rises.
Similarly.
as the ambulance leaves.
The source of the emitted sound wave becomes farther and farther away, causing the wavelength to increase, the frequency to decrease, and the pitch to decrease.
This is a physical phenomenon that was proposed and concluded very early, and it has no mystery or practical value in itself.
It can be said like this.
Up to now.
This effect has almost no supporting application technology.
So after Xu Yun said this word.
Instead of feeling relieved, the expression on Lao Guo's face became even more confused:
"Comrade Han Li, I know a little bit about the Doppler effect, but what does it have to do with increasing data sampling?"
"What we need is more sample data. It doesn't seem to have anything to do with acoustic Doppler, right?"
Xu Yun nodded when he heard this, not too anxious, but said patiently:
"Yes, the Doppler effect of existing physics mainly appears in the macroscopic field, such as ambulances and the like."
"But don't forget, the real core of the Doppler effect is not macroscopic, but... relative motion."
Lao Guo was stunned for a moment.
Xu Yun paid little attention to Lao Guo's expression and continued:
"In the macroscopic world, the relative movement of people and cars is reflected in the movement of cars and the movement of people - this is also everyone's subconscious understanding, because this example is so easy to understand."
"But the essence of the Doppler effect is to accept changes in frequency. That is, the macro situation can be that a car whistles but does not move, and a person slowly walks towards the car..."
This time.
Lao Guo nodded slightly.
Just like when people think of the author Novice Fisherman when talking about tentacle monsters, in life, people often use a classic example to explain a certain concept.
But in fact.
Examples and concepts are not completely equivalent. For example, in addition to novice fishermen, the starting point also includes tentacle monsters such as eagles, etc.
The same goes for the Doppler effect.
The ambulance example can clearly explain the Doppler effect, but it is not the actual cause of the effect itself.
Do not know why.
When he heard Xu Yun's words, the outline of a huge creature vaguely appeared in his heart...
Then Xu Yun tried his best to take his hand out from the quilt, drew a circle in the air with his index finger, and gestured:
"Gong Guo, you should know that according to the principle analysis of the Doppler effect, this phenomenon also holds true in the microscopic field."
"That is, these people moving towards the stationary ambulance can actually be replaced by various different particles, such as precipitation particles and rainfall particles."
"In addition, the dielectric constant of each particle is different, for example, water is 0.93, ice is 0.18, etc..."
Say it.
Xu Yun made a fist with his left hand and put it high, raised a finger with his right hand below and said:
"Then Guo Gong, hypothetical...I mean hypothetical."
"If there is such an instrument, when it is operating, it can biu from time to time and emit electromagnetic waves of some special bands into the sky."
"At the same time when it emits a waveband, particles with different dielectric constants are also moving on the cloud layer."
"These movements are irregular. Some may go up and down, some may move left and some may drift right, some may draw an S and some may draw a B, but in short, they will undergo relative displacement relative to the instrument."
"So, what do you think will happen to electromagnetic waves after they come into contact with them?"
boom--
Xu Yun's words were like thunder from the sky, exploding in Lao Guo's heart.
For Lao Guo, who majored in physics, this question was simply a scoring question. It couldn't be simpler.
But that's why.
Lao Guocai became increasingly afraid to make judgments.
"..."
after awhile.
Lao Guo just adjusted his glasses with his trembling left hand and slowly gave an answer:
"If the target particles are moving closer to the instrument, then... the frequency of the reflected wave will be higher than the frequency of the emitted wave."
"If the target particle is moving away from the instrument, the frequency of the reflected wave will be lower than the frequency of the emitted wave."
"At the same time, due to the difference in dielectric constant, different particles will scatter to different degrees, and what is fed back to the instrument is different degrees of... frequency shift."
"And through this frequency shift, real-time atmospheric turbulence conditions can be reversed..."
Say the last thing.
Lao Guo suddenly leaned back on his chair, exhaled a deep breath, and remained silent.
A long time passed.
Lao Guo then raised his head again, slowly looked at Xu Yun, and asked with a subtle expression:
"Comrade Han Li, does this instrument have a name?"
Xu Yun stopped trying to be pretentious this time and answered directly:
"Yes, it's called weather Doppler radar."
That's right.
Meteorological Doppler radar.
This is the big killer that Xu Yun had in mind when he took out the damper!
Doppler effect.
This is a classic physical phenomenon that has been proposed for nearly a hundred years in this era.
When Xu Yun was finishing the 1850 copy, he had met its proposer, Christian Doppler, at Cambridge University.
This effect has also been widely used in later generations, involving a large number of military and civilian fields.
For example, weather Doppler radar, color ultrasound, Doppler imager, etc.
For students who are often ticketed for speeding, the speed radar that detects your speeding record also relies on the Doppler effect.
But on the other hand.
These Doppler technologies, which have become so popular in later generations that they can no longer be popularized, were almost not developed until the 1970s.
That is to say, in the 130 years or so from 1842 to 1970, there was almost no corresponding physical technology for the Doppler effect.
The main reason why "almost" is used here is that sonar detection is related to the Doppler effect.
But it does not appear due to the Doppler effect, it can only be regarded as a barely related relationship.
The earliest Doppler effect instrument in human history was...
Meteorological Doppler radar.
The principle of weather Doppler radar has been introduced once before and will not be repeated here.
Its concept was proposed in the early 1960s, and its actual application would take place somewhere close to the 1970s. The specific time is too sensitive and will not be detailed.
In short, at this time, the weather Doppler radar does not even have a physical object across the sea, and the design process has only reached about 40%.
As for the first domestic meteorological Doppler radar, it came even later.
In China, it was not until the late 1980s that the National Meteorological Administration and the 784 Factory in Chengdu cooperated to successfully develop the first S-band 714SD and the first C-band 714CD Doppler weather radar prototypes.
Yes, this is just a prototype.
As for the first meteorological Doppler radar that was actually put into use, it would not be until 1992.
Before the advent of meteorological Doppler radar.
Weather radar in the meteorological field can only conduct qualitative analysis through echoes, otherwise it would not have been until 1954 before the first numerical weather prediction in human history appeared.
His eyes returned to reality.
At this moment.
Lao Guo leaned back on the wooden chair provided by the hospital and murmured the name:
"Weather Doppler Radar..."
While speaking, he was filled with emotions in his heart.
As a professional physics practitioner.
Although Lao Guo has not seen the actual object Xu Yun mentioned.
However, based on the principles described by Xu Yun alone, it can be determined that the instrument he mentioned is highly likely to be operational and achieve results.
And the data that this kind of radar can collect is more than 100,000 times as simple as that?
After all, there are too many particles in the Taiqi layer...
As long as the conditions are right, millions or even tens of millions of times the data can be collected - then calculation will become a big problem.
more importantly.....
This is a weather radar!
To know.
in the current field of scientific research.
Whether at home or abroad, even if there are woolly bears across the sea, their level of development of weather radar is only the same.
The first human weather radar appeared in 1943, less than twenty years ago.
At that time, MIT designed a storm radar, which was mainly used for the location of storms. The principle is extremely primitive, and it is still running today.
Another example is the current domestic weather radar.
The first conventional weather radar in China was launched three years ago. It was modified from the military 843 height measurement radar by Lao Guo’s friend Bao Zheng. Its full name is Type 703 radar.
It has only one main purpose:
Used to predict typhoons.
It can be said like this.
Today, weather radars around the world are basically used to observe large-scale meteorological disasters, such as typhoons, hurricanes, etc.
Other than that.
They can't predict ordinary rainfall, snowfall, sandstorms, etc. In a sense, they are equivalent to a large telescope.
But now the weather Doppler radar mentioned by Xu Yun seems to have opened a new road to the sky in front of Lao Guo...
Many, many years later.
The day when Lao Guo and Xu Yun met was endowed with many special colors, and the exchange between the two was also given an inexplicable aura.
For example, the steady one is [A conversation that changed human history].
The whole thing is [Comrade, this is the password of your accelerator] and so on.
Some people jokingly call it "chicken and rabbit in the same cage", so they call it "pair in the cage"...
.........
After a while.
Lao Guo completely 'digested' the shock in his heart, and then turned his attention to Xu Yun again:
"Comrade Han Li, what processes and parts are needed to assemble this weather... weather Doppler radar?"
Lao Guo did not ask Xu Yun if he could give an assembly plan. After all, Xu Yun had said one thing before:
The investment for the entire equipment is about tens of thousands of yuan, and the time can be three to four days at a time, or seven or eight days at a time.
In other words, Xu Yun must know the specific steps and even some more detailed inside information.
"Parts..."
as expected.
Xu Yun quickly touched his chin and said slowly:
"Structurally speaking, a weather Doppler radar can basically be divided into eight links."
"That is, antennas, radomes, signal processors, servos, transmitters, receivers, waveguides and displays..."
"Comrade Han Li, please wait."
Before Xu Yun could finish speaking, Lao Guo interrupted him.
I saw Lao Guo take out paper and pen from his briefcase, put them on the table, and then signaled:
"Please continue, Comrade Han Li."
Xu Yun didn't care about this at all, nodded and continued:
"The simplest ones are the radome and the display. I won't talk about the radome. The display only needs to be able to show the echo and vertical profile."
"As for the transmitter and receiver, they can be temporarily improved using the hospital's X-ray machine - provided the leaders can convince Dr. Lin Yu."
"As for the antenna, just use a parabolic antenna for the front feeder, with a diameter of about 1 meter, and the feeder only needs to be horizontally polarized..."
This chapter is not finished yet, please click on the next page to continue reading the exciting content! Same as the engine.
Small Doppler detection radar is also a very common piece of equipment in later DIY circles.
When Xu Yun was at Chengdu Aircraft Corporation of China, he tinkered with this thing many times - although it was a small, low-power wind Doppler radar with a receiving sensitivity of only -60dbm, the principles were still the same.
Considering that the industrial level of rabbits in this era is relatively low, and time is tight at this time.
Therefore, Xu Yun also used an old idea as always:
We don’t build official equipment, we only build the most cost-effective beggars... Ahem, youth version of weather Doppler radar.
After all, Lao Guo and the others only need 50 million sets of data.
The data collected by an ordinary weather Doppler radar in later generations is very exaggerated, often reaching tens of billions or even hundreds of billions of data.
For example, the very unique "dolphin-style" radar tower in Jiuquan can even collect 300 billion sets of data in a single time.
no way.
There are simply too many particles in the atmosphere.
Therefore, regardless of demand or actual situation, Xu Yun does not need to come up with a formal version of the weather Doppler radar.
In Xu Yun's design.
The display can only consider the echo and vertical profile. For the experts from the 221 factory, they only need to use the TV screen to improve it.
Transmitters, receivers, and waveguides can all be obtained from the hospital:
The X-ray machine in the hospital has its own X-wave frequency, which can provide the X-band dual polarization effect required by the transmitter and receiver.
The waveguide came from the electrocardiogram monitor next to him - the string galvanometer and waveguide of this thing have almost the same principle.
As for the servo system, it's not difficult either.
Later generations of servo systems mainly used servo amplifiers and pulse width modulators, such as SMPR-v1 and so on.
But students who have been doing Doppler radar in this life should all know it.
The essence of the servo amplifier in weather radar is actually to drive the pitch switch of the extension unit.
As for the pulse width modulator, it is even simpler. Just apply forces in two directions to achieve dynamic lubrication.
Therefore, the latter only needs to ask the boss of the third factory to design an IGBT module, while the former requires a ready-made RC absorption circuit.
Yes, RC absorption circuit.
See here.
Presumably some smart students have already realized this.
That’s right!
The thermocouple hygrometer currently placed on the watchtower can provide a complete RC absorption circuit.
"...."
A few minutes later.
Looking at the words written all over the paper, Lao Guo couldn't help blinking and asked Xu Yun:
"Comrade Han Li, I have a question that I would like to confirm."
"According to what you said before, the cost of building a weather Doppler radar starts at about 20,000 to 30,000 yuan, right?"
"But from the looks of these parts, the cost shouldn't even cost 5,000 yuan. Where did the difference go?"
As an expert who has been engaged in aviation engineering research for a long time, Lao Guo is very sensitive to information on equipment costs.
He just did a simple mental calculation and found out that the cost of all the parts Xu Yun mentioned together would be at most four to five thousand yuan.
Not to mention components like RC absorption circuits, they can be put back into the original device after use.
So the actual cost is even a little smaller than the value he calculated.
Four or five thousand versus twenty or thirty thousand.
This is obviously not consistent with what Xu Yun said before, and it is difficult to explain the past with the reason of not understanding the market.
Looking at Lao Guo with a confused look on his face.
Xu Yun couldn't help but smile on the bed, pointed at Lao Guo's notebook, and said:
"Gong Guo, I'm afraid you haven't noticed that among the eight links I just mentioned, there is still one that I haven't finished yet."
"There is still one?"
Lao Guo was stunned for a moment.
He had just taken notes before, and only jotted down a rough outline of the project. Hearing this, he couldn't help but glance at his notes again:
"Antenna...radome...transmitter...waveguide..."
After a while.
Lao Guo slowly raised his head and confirmed:
"There are seven parts in total, and one is indeed missing...the signal processor."
After speaking, Lao Guo realized something and asked:
"Comrade Han Li, is it possible that the cost of this component is very high?"
Xu Yun glanced at him, with a trace of amusement in his eyes:
"Guo Gong, let me tell you the truth."
"This part is not a matter of high cost, but..."
"The question is whether you dare to use it or not."
...
Note:
I’m going to worship my ancestors in my hometown tomorrow. I’m going to take a day off. I haven’t worshiped my ancestors in three years. I have to go there, and there’s a high chance that there will be a fight.
We sold part of the ancestral temple and everyone shared the money. The other families among us disagreed. My dad said that there will probably be another quarrel this year.)