How does Starlink Satellite Internet Work?📡☄🖥

Summary

This script delves into the revolutionary technology of Starlink, a satellite internet system. It explains how a pizza-sized dish transmits data to satellites orbiting 550 km above Earth, using phased array antennas and beamforming to maintain a focused beam for high-speed data transfer. The video explores the inner workings of the satellite dish, the communication process between the dish and the satellite using 64QAM, and the challenges of sending and receiving signals in a rapidly moving environment. It offers a detailed look at the engineering marvels that make satellite internet both feasible and efficient.

Takeaways

• 🛰️ Starlink uses a phased array satellite dish that both sends and receives internet data from low Earth orbit satellites, unlike traditional TV satellite dishes that only receive signals.
• 🚀 The Starlink satellites orbit at a much lower altitude of 550 kilometers compared to TV satellites at 35,000 kilometers, requiring precise and continuous beam steering to maintain connection.
• 🔄 The dish switches between different satellites every few minutes due to the fast movement of the satellites across the sky.
• 📡 Inside the Starlink dish, there's a sophisticated setup including motors, a PCB with microchips, and a massive array of 1280 antennas arranged in a hexagonal pattern for phased array communication.
• 📶 Each antenna in the array is controlled by microchips to generate and steer electromagnetic waves, creating a focused beam to communicate with the satellite.
• 🌐 The phased array uses beamforming to combine the signals from all antennas, resulting in a powerful beam capable of reaching the satellite in space.
• 🔧 Phased array beam steering is achieved by adjusting the phase of the signals sent to each antenna, allowing the beam to be directed towards the fast-moving satellite.
• 📈 The system uses GPS and software to calculate the precise angles and phase shifts needed for the antennas to maintain a lock on the satellite.
• 🔊 Data transmission between the dish and satellite utilizes 64QAM modulation, encoding 6-bit binary values with different amplitude and phase permutations, enabling high-speed data transfer.
• 🎥 The video codec h.264 is used to compress and transmit high-quality video data, allowing users to stream content smoothly.
• 👨‍🏫 The script highlights the multidisciplinary nature of the technology, touching on fields like electromagnetics, signal processing, and antenna design.

Q & A

What is the primary function of the Starlink satellite dish compared to a traditional TV satellite dish?

The Starlink satellite dish, also known as Dishy McFlatface, both sends and receives internet data from a Starlink satellite orbiting 550 kilometers away, unlike traditional TV satellite dishes which only receive TV signals from broadcast satellites orbiting at an altitude of 35,000 kilometers.

How fast do the Starlink satellites move and what is the significance of their speed?

Starlink satellites move at an incredible speed of around 27,000 kilometers per hour. This speed is significant as it allows for the rapid transmission of data at hundreds of megabits per second, despite the continuous need to angle or steer the data beam between the moving dish and satellite.

Why do Starlink satellites need to be in low Earth orbit?

Starlink satellites are in low Earth orbit to provide low latencies of around 20 milliseconds, which is critical for activities such as online gaming or web browsing without noticeable delays.

What is the purpose of the phased array in the Starlink ground dish?

The phased array in the Starlink ground dish is used to send and receive electromagnetic waves that are angled to and from a Starlink satellite. It consists of 1280 antennas arranged in a hexagonal honeycomb pattern, working together to focus the signal into a tight, powerful beam.

How does the phased array beam steering work in the Starlink dish?

Phased array beam steering works by continuously changing the phase of the signals sent to the antennas, which alters the timing of the peaks and troughs emitted from each antenna. This creates a sweeping zone of constructive interference that can be directed towards the satellite.

What is the role of the motors in the Starlink dish during its operation?

The motors in the Starlink dish are used only for initial setup to get the dish pointed in the proper general direction. They do not continuously move the dish to point directly at the Starlink satellite during operation.

How does the Starlink dish ensure it is communicating with the correct satellite?

The Starlink dish uses its GPS coordinates and the known orbital position of the Starlink satellite. The software in the dish computes the exact set of 3D angles and required phase shift for each of the antennas to perfectly aim the beam at the satellite.

What is the maximum data transfer rate achievable with the Starlink system?

The Starlink system can achieve a data transfer rate of up to 540 million bits per second using 64QAM (Quadrature Amplitude Modulation), which allows for the transmission of 6-bit binary values through different combinations of amplitude and phase.

How does the Starlink dish handle the transition between different satellites as they move out of its field of view?

The Starlink dish switches between different satellites every 4 or so minutes as they move out of its field of view. This is managed by the dish's software, which constantly computes and updates the phase shifts required for communication with the next satellite in view.

What is the significance of the 100-degree field of view for the Starlink dish?

The 100-degree field of view allows the Starlink dish to steer the beam in any direction within that range, ensuring continuous communication with the rapidly moving satellites without the need for physical movement of the dish.

How does the Starlink system minimize latency in data transmission?

The Starlink system minimizes latency by distributing the time slots for data transmission throughout a single second, rather than grouping them all together. This ensures that the data is sent and received with minimal delay.

Outlines

00:00

🛰️ Starlink Satellite Internet Technology

This paragraph introduces the Starlink satellite internet system, highlighting its impressive technological feats. The system uses a large satellite dish, capable of transmitting data to satellites orbiting at 550 kilometers above Earth. The Starlink satellites move at an astonishing speed of 27,000 kilometers per hour, facilitating high-speed data transfer with minimal latency. The dish dynamically adjusts to maintain a direct connection with the rapidly moving satellites, switching between them every few minutes. The video promises an in-depth exploration of the technologies enabling this system, including the inner workings of the satellite dish, its ability to steer the data beam, and the data transmission capabilities that allow for simultaneous streaming of multiple HD movies.

05:08

🔍 Dissecting Dishy McFlatface and Its Antennas

The second paragraph delves into the technical differences between traditional TV satellite dishes and the Starlink ground dish, humorously named 'Dishy McFlatface.' Unlike TV dishes that only receive signals, Dishy sends and receives internet data. The Starlink satellite's lower orbit of 550 kilometers allows for faster data transmission but requires precise beam steering. The paragraph describes the internal components of Dishy, including its motors, ethernet cable, and the intricate printed circuit board (PCB) with microchips and GPS module. It also explains the phased array of 1280 antennas that work together to send and receive signals to the satellite, emphasizing the complexity and precision of the technology.

10:10

📡 Understanding Antenna Function and Beamforming

This paragraph explains the function of a single antenna within Dishy's phased array, focusing on the aperture-coupled patch antenna. It describes the process of generating an electromagnetic wave through the antenna's layers, including the microstrip transmission line feed and the antenna patch. The paragraph simplifies the complex process by illustrating how high-frequency signals create oscillating electric fields, leading to the formation of electromagnetic waves. It also touches on the antenna's ability to transmit and receive signals, the importance of phase shifting, and the concept of beamforming, which combines the power of multiple antennas to create a focused beam capable of reaching outer space.

15:15

🚀 Steering the Beam with Phased Array Technology

The fourth paragraph discusses the advanced technique of phased array beam steering, which is essential for maintaining a connection with the fast-moving Starlink satellite. It explains how phase shifting the signals sent to the antennas can angle the beam without physically moving the dish. The paragraph uses a simplified two-antenna example to demonstrate how constructive and destructive interference patterns can be manipulated to steer the beam. It also explains how Dishy uses GPS coordinates and software to calculate the necessary phase shifts for each antenna, allowing for precise beam direction and the ability to track satellites across a 100-degree field of view.

20:20

🌐 Data Transmission via 64QAM Modulation

The fifth paragraph explores how data is transmitted between Dishy and the Starlink satellite using 64QAM (Quadrature Amplitude Modulation). It describes the process of encoding binary data into variations of amplitude and phase, creating a constellation diagram with 64 different permutations. The paragraph explains how these symbols, each containing 6 bits of data, are transmitted in rapid succession, resulting in a high data transfer rate. It also discusses the division of transmission time between upload and download, and the distribution of these time slots to reduce latency.

25:22

📚 Conclusion and Further Exploration

The final paragraph wraps up the video script by acknowledging the complexity of the technology and the effort put into creating the video. It invites viewers to engage with the content through subscriptions, likes, and comments, and provides a link for further learning through Brilliant.org. The paragraph also clarifies some of the video's visual representations, emphasizing the actual scale of Dishy and the satellite, and the speed at which electromagnetic waves travel. It concludes by thanking sponsors and collaborators, and encourages viewers to explore more of Branch Education's content.

Keywords

💡Starlink

Starlink is a satellite internet constellation operated by SpaceX, providing internet coverage from low Earth orbit (LEO) satellites. In the video, Starlink is central to the discussion of how internet is beamed from space to a ground station using advanced technology. The script mentions Starlink's ability to send and receive data at high speeds, highlighting its role in providing high-speed internet access to remote areas.

💡Satellite Dish

A satellite dish, also known as an antenna, is a device that captures and focuses satellite signals. The video script describes a specific type of satellite dish used for Starlink, humorously named 'Dishy McFlatface,' which both sends and receives internet data from satellites orbiting 550 kilometers above Earth. The dish's ability to focus powerful beams and continuously steer them towards moving satellites is a key aspect of the technology explained in the video.

💡Phased Array

A phased array is an array of antennas that work together to focus the radio signals in a specific direction without moving the antennas physically. The script explains that the Starlink dish uses a phased array of 1280 antennas to send and receive signals to and from the satellites. This technology is crucial for the dish's ability to steer the beam and maintain a connection with fast-moving satellites.

💡Beamforming

Beamforming is a signal processing technique used in antenna arrays to form a directional beam towards a specific location. In the context of the video, beamforming is how the Starlink dish combines the signals from its 1280 antennas to create a powerful, focused beam that can reach the satellites in space. The script describes how this technique amplifies the signal strength and directs it towards the satellite.

💡Parabolic Reflector

A parabolic reflector is a curved surface that reflects radio waves to a single focal point, or reflects from a single point to wide areas. The script contrasts the parabolic reflector used in traditional TV satellite dishes, which only receive signals, with the more complex technology in the Starlink dish that both sends and receives signals.

💡Orbital Position

Orbital position refers to the specific location of a satellite in its orbit around Earth. The video script mentions that the Starlink dish uses the known orbital position of the satellites, along with its own GPS coordinates, to calculate the exact angles for directing the beam towards the satellites. This is essential for maintaining a stable internet connection.

💡Microchips

Microchips, or integrated circuits, are tiny devices that process and control electronic signals. The script describes the Starlink dish's internal components, including 640 small microchips and 20 larger microchips on a printed circuit board (PCB), which control the operation of the 1280 antennas and facilitate the phased array's functionality.

💡Quadrature Amplitude Modulation (64QAM)

64QAM is a modulation technique that conveys digital data as variations in the amplitude and phase of an analog signal. The video script explains that Starlink uses 64QAM to send 6-bit values, allowing for the transmission of hundreds of megabits of data per second. This technique is vital for the high data rates required for streaming and internet usage.

💡Electromagnetic Waves

Electromagnetic waves are waves of oscillating electric and magnetic fields that can propagate through space. The script discusses how the Starlink dish generates and manipulates electromagnetic waves to communicate with the satellites. These waves are the medium through which the internet data is transmitted and received.

💡Constellation Diagram

A constellation diagram is a graphical representation used in digital communications to show the different signal states that can be transmitted over a communication channel. In the script, the constellation diagram is used to illustrate how 64QAM encodes 6-bit binary values into different combinations of amplitude and phase for transmission.

Highlights

Beaming internet from the woods using a large satellite dish to a satellite 550 km away is a technological marvel.

Starlink satellites move at 27,000 km/h, with data speeds of hundreds of megabits per second.

The dish and satellite continuously angle to maintain a direct data beam connection.

The dish switches between different satellites every 4 minutes to maintain connectivity as they move out of view.

The video explores key technologies enabling satellite internet, including the satellite dish's inner workings.

Dishy McFlatface, the Starlink ground dish, both sends and receives internet data from orbiting satellites.

Starlink satellites are in low earth orbit for lower latency, requiring thousands for global coverage.

Dishy McFlatface contains 1280 antennas arranged in a hexagonal honeycomb pattern for phased array communication.

Each antenna in Dishy is controlled by microchips to generate and steer electromagnetic waves to the satellite.

Phased array beam steering uses phase shifting to angle the beam without physically moving the dish.

64QAM is used to encode 6-bit binary values into variations of amplitude and phase for data transmission.

The video provides a detailed explanation of how Dishy and the Starlink satellite communicate using electromagnetic waves.

The video explains advanced concepts in an accessible way, including the use of Brilliant for further learning.

The video clarifies misconceptions about the scale of Dishy and the satellite, and the speed of electromagnetic wave transmission.

The video script underwent extensive revisions to ensure accuracy and depth of information.

The video concludes with an invitation to support the creators and explore more technology through their animations.

Transcripts

Beaming internet from the middle of the  woods using an extra-large pizza-sized

satellite dish placed on top of your house up  to a satellite orbiting 550 kilometers outside

Earth’s atmosphere, well let’s be honest, is  technologically mind-blowing. What’s even crazier

is that the Starlink satellites move incredibly  fast, around 27,000 kilometers per hour,

and data is being sent back and forth between them  at hundreds of megabits per second, all while the

dish and satellite are continuously angling  or steering the beam of data pointed directly

between them. On top of that, the dish switches  between different satellites every 4 or so minutes

because they move out of the dishes’ field of  view rather quickly. If you have no clue as to

how this is possible, stick around because we’re  going to dive into the multiple key technologies

which enable satellite internet to magically work. First, we’ll explore inside the satellite dish and

see how it generates a beam of data that is able  to reach space. Second, we’ll see how this dish

continuously steers the beam so that it points  directly at a satellite moving across the sky. And

third, we’ll dive into what exactly the dish and  satellite are sending inside the beam that results

in your ability to stream five HD movies or shows  simultaneously. This video is quite long as it’s

full of in-depth details. We recommend watching  it first at one point two five times speed,

and then a second time at one and a half speed  to understand it as a complete technology. So,

stick around, and let’s jump right in. First, let’s start by clarifying the

difference between a television satellite dish  such as this one, and the Starlink ground dish,

which Elon Musk dubbed Dishy McFlatface or Dishy  for short. TV dishes use a parabolic reflector

to focus the electromagnetic waves which are  the TV signals sent from broadcast satellites

orbiting the Earth at an altitude of 35 thousand  kilometers. TV satellite dishes only receive

TV signals from space, they can’t send data. Dishy, however, both sends and receives internet

data from a Starlink satellite orbiting 550  kilometers away. While the Starlink satellite is

60 times closer than TV satellites, it’s still an  incredible distance to wirelessly send a signal,

and thus the beams between Dishy and the Starlink  satellite need to be focused into tight powerful

beams that are continuously angled or steered to  point at one another. Compare this to TV broadcast

signals which come from a satellite the size of  a van, and whose signals propagate in a wide fan

that covers land masses larger than North  America. Table size Starlink satellites,

however, need to be in a low earth orbit  to provide for 20-millisecond latencies,

which is critical for smoothly playing internet  games or surfing the web, and as a result, their

coverage is much smaller. Thus 10,000 or more  Starlink satellites, all orbiting at incredibly

fast speeds in a low earth orbit, are required to  provide satellite internet to the entire earth.

Let’s now open up Dishy McFlatface. At the back,  we have a pair of motors and an ethernet cable

that connects to the router. Note that these  motors don’t continuously move Dishy to point

directly at the Starlink satellite; they’re used  only for initial setup to get the dish pointed in

the proper general direction. Opening up Dishy,  we find an aluminum structural back-plate and on

the other side, we find a massive printed circuit  board or PCB. One side has 640 small microchips

and 20 larger microchips organized in  a pattern with very intricate traces

fanning out from the larger to smaller microchips,  along with additional chips including the main CPU

and GPS module on the edge of the PCB. On the  other side are 1,400ish copper circles with a grid

of squares between the circles. On the next layer,  there’s a rubber honeycomb pattern with small,

notched cop-per circles, and behind that, we find  another honeycomb pattern and then the front side

of Dishy. So, what are we looking at? Well, in  essence, we have 1280 antennas arranged in a

hexagonal honeycomb pattern, with each stack of  copper circles being a single antenna controlled

by the microchips on the PCB. This massive array  works together in what’s called a phased array

in order to send and receive electromagnetic  waves that are angled to and from a Starlink

satellite orbiting 550 kilometers above. Let’s  zoom in and see how a single antenna operates.

Here we have an aperture coupled patch antenna  composed of 6 layers, most of which are inside

the PCB. It looks very different from the  antenna of an old-school radio, and is honestly,

incredibly complicated, so let’s simplify  it. We’ll remove a few of the layers for now,

and step through the basic principles of  how we generate an electromagnetic wave

that propagates out from this antenna. To start, at the bottom we have a microstrip

transmission line feed coming from one of the  small microchips. This transmission line feed is

just a copper PCB trace or wire that abruptly ends  under the antenna stack. We send a 12 Gigahertz

high-frequency voltage or signal to the feed  wire which is a voltage that goes up and down

in a sinusoidal fashion, going from positive  to negative and back to positive once every 83

pico-seconds, 12 billion times a second, or 12  Gigahertz. Note that high-frequency electricity

works differently from direct current or low  frequency 50 or 60-hertz household electricity.

For example, above the copper feed wire, we  have a copper circle with notches cut into it

called an antenna patch. With DC or  low-frequency alternating current,

there wouldn’t be much happening because the patch  is isolated, but with a high-frequency signal,

the power sent to the feed wire is coupled or sent  to the patch. How exactly does this happen? Well,

as mentioned earlier, a 12 Gigahertz signal is  applied to the copper feed wire. When the voltage

is at the bottom of its sinusoidal, or trough,  we have a concentration of electrons pushed to

the end of the feed wire thus creating a zone of  negative charge which corresponds to the maximum

negative voltage. This concentration of electrons  on the tip of the wire repels all electrons away,

including the electrons on the top of the patch,  and as a result, these electrons are pushed to

the other side of the circular patch. Thus, one  side of the patch becomes positively charged,

while the other becomes negatively  charged, thereby creating electric

fields between the patch and feed wire like so. However, when we reverse the voltage to the

copper feed wire 42 picoseconds later, we have a  concentration of positive charges, or a lack of

electrons at the end of the wire, and thus the  electrons in the patch flow to the other side,

the voltage in the patch is flipped, and the  direction of the electric fields are also flipped.

Because the feed wire voltage oscillates back and  forth, 42 picoseconds between one peak and trough,

the electric fields in the patch will also  oscillate as the electrons, or current,

flows back and forth. If we pause the oscillation

we can see some of these electric field vectors,  or arrows, from the patch, are vertical, and

because they are equal and opposite, they cancel  out. However, other electric fields are horizontal

in the same plane of the patch and are called  fringing fields. These fringing fields are in the

same direction and thus they add to each other,  resulting in a combined electric field pointing

in this direction. At the same time, electrons  flowing from one side of the disk to the other,

which is an electric current, generate a  magnetic field with a strength and direction,

or vector, perpendicular to the fringing  electric field vector. As a result,

we have an electric field pointing one way, and  a magnetic field pointing perpendicular to that.

Let’s move forward in time to where the  voltage on the feedline becomes positive,

and now, we’re at the peak of the sinusoid, 42  picoseconds later. The charge concentrations,

or voltage, as well as the current, is all  flipped, and thus the electric and magnetic

fields point in the opposite directions. Electric  and magnetic fields propagate in all directions,

and by creating these oscillating fields,  we’ve generated an electromagnetic wave

which travels in the direction perpendicular to  both the electric and magnetic field vectors.

Because the two sets of field vectors are not  all in the same plane, but rather are curved, the

propagating electromagnetic wave travels outwards  in an expanding shell or balloon-like fashion,

kind of like a light bulb on the ceiling. Let’s  simplify the visual so we only see the peak and

trough or top and bottom of each wave and note  that the trough is just a vector pointed in the

opposite direction. Additionally, the strengths  of these field vectors directly relate back to

the voltage and signal that we originally sent  to the copper microstrip feed wire at the bottom

of the stack. Which means, if we want to make  these electric and magnetic fields stronger,

we just have to increase the voltage sent to the  feedline. It’s like a dimmer on a light switch:

more power equals a brighter light. Thus far we’ve been talking about this

aperture-coupled patch-antenna as transmitting;  however, it can also be used for receiving a

signal. In this microchip, called a front-end  module, we switch the antenna from transmit to

receive and turn off the 12 Gigahertz signal.  When an electromagnetic wave from the satellite

is directed towards Dishy, the electric fields  from this incoming signal will influence the

electrons in the copper patch, thus generating  an oscillating flow of electrons. This received

high-frequency signal is then coupled to the  feedline where it’s sent to the front-end module

chip which amplifies the signal. Thus, these  antennas can be used to both transmit and receive

electromagnetic waves, but, not at the same time. Two quick things to note. First, as seen earlier,

this antenna has many more layers and is more  complicated than we’ve discussed. For example,

here are two circular patches. The bottom is  used to transmit at 13 Gigahertz while the top

to receive at 11.7 Gigahertz. Additionally,  there are two H slots and two feed wires to

support circular polarization, a reflective plane  in the back, and also, there are multiple features

for isolating the operation of one antenna from  the adjacent antennas. We’ve included these and

many more details in the creator’s comments which  you can find in the English Canadian subtitles.

The second note is that there are electromagnetic  waves of all different frequencies from

thousands of different sources passing through  every point on Earth, whether it be visible

light from the sun, radio waves from radio or  cell towers, or TV signals from satellites or

towers. Therefore in order to block out all  other frequencies of electromagnetic waves,

these antenna patches are designed with  very exact dimensions so that they receive

and transmit only a very narrow range of  frequencies, and all the other frequencies

outside this range are essentially ignored  by the antenna. Let’s move on and see how

a single antenna can be combined with others in  order to amplify the beam to reach outer space.

This single antenna is only a centimeter or  so in diameter and using only it would be

like turning on and off one light bulb and trying  to see it from the international space station.

What we need is a way to make the light a few  thousand times brighter, and then focus all the

electromagnetic waves into a single powerful  beam. Enter the massive Mr. McFlatface PCB,

55 centimeters wide with a total of 1280  identical antennas in a hexagonal array. The

technique of combining all the antennas’  power together is called beamforming.

So how does it work? Well, let’s first see what  happens when we have two simplified antennas

spaced a short distance away. As mentioned before,  one antenna generates an electromagnetic wave that

propagates outwards in a balloon shape. At every  single point in space, there’s only one electric

field vector with a strength and direction and  thus the two antennas’ oscillating electric

field vectors combine together at all points in  space. In some areas, the electric fields from

the antennas are pointing in the same direction  with overlapping peaks, and thus add together via

constructive interference, and in other locations,  they’re oppo-site with one peak and one trough,

and thus they cancel each other via destructive  interference. We can now see that the zone where

they add together constructively is far tighter,  or more focused, than a single antenna alone.

When we add even more antennas, the zone of  constructive interference becomes even more

focused in what is called a beam front.  Thus, by adding 1280 antennas together

we can form a beam with so much intensity and  directionality that it can reach outer space.

Now you might be thinking that the strength of 1  antenna duplicated 1280 times over would result in

a combined power of, well, 1280 times a single  antenna, but you’d be mistaken. The effective

power and range of the main beam from all these  antennas combined is actually closer to 3500 times

that of a single antenna. The quick explanation  is that by having these patterns of constructive

and destructive interference, it’s as if we  took a single antenna, multiplied it by 1280,

and then placed a whole bunch of mirrors around  it and left only a single hole for the main beam

to exit through. The long explanation requires  a ton of math and physics, so let’s move on.

Dishy McFlatface and the Starlink Satellites  undoubtedly have some rather complicated science

and engineering inside and to fully comprehend it  all you have to be a multidisciplinary student.

To help you do that, check out Brilliant, which  is sponsoring this video. Brilliant is an amazing

tool for learning. They teach a wide range  of STEM topics in hands-on, interactive ways,

many of which directly relate to Starlink  and other cutting-edge technologies such as

electric cars, quantum computers,  rocketry, or neural networks. For example,

they have an entire course dedicated  to Waves and Light, and another one on

gravitational physics which will greatly help  in understanding Starlink and SpaceX rockets.

Brilliant is nothing like a boring textbook,  but rather all the courses use interactive

modules to make the lessons entertaining  and to help the concepts stick in your head.

To really understand today’s frontier technologies  and to help you become a revolutionary engineer

and entrepreneur like Elon Musk, you have  to be versed in a wide range of fields in

science and engineering. We recommend you sign  up, try out some of the lessons for free and,

if you like them, which we’re sure you will, sign  up for an annual subscription. To the viewers of

this channel, Brilliant is offering 20% off an  annual subscription to the first 200 people who

sign up. Just go to brilliant.org/brancheducation.  You can find that link in the description below.

Now let’s continue exploring how a powerful  beam can be continuously swept across the sky,

and then how we fill it with hundreds  of megabits of data every second.

As a quick refresher from before, here’s  an array of 1280 antennas and we fed them

all with the same 12 Gigahertz signal in order to  create a laser-like beam propagating perpendicular

to Dishy. However, as mentioned earlier, we need  to be able to angle this beam so that it points

directly at the Starlink satellite zooming  across the sky at 27,000 kilometers per hour.

Using the motors isn’t feasible because they would  break within a month and aren’t accurate enough.

So, the solution is to use what’s  called phased array beam steering.

Let’s go back to our two-antenna  example. Before we were feeding

the same signal to the two antennas, and thus  the antennas were in phase with one another.

Understanding phase is critical, so quickly:  changing the height or amplitude of the signal

is done by changing the power sent to the  antenna, thus making the signal stronger

or weaker. The frequency is how many peaks and  troughs, or wavelengths there are in one second,

and changing the phase is shifting the signal left  or right. Phase shifting is measured in degrees

between 0 and 359, because, if we shift the signal  360 degrees, or one full wavelength, then we’re

back at the beginning, exactly as if we were to  loop around a circle. For example, here’s a signal

with a 45-degree phase shift, here’s another  with a 180-degree shift, and then another with a

315-degree shift. Your eyes can’t see differences  in phase shifted visible light, however, high-tech

circuitry such as what’s inside Dishy is really  good at detecting and working with phase shifts.

So then, how do we use phase shifting to angle the  beam and have it point directly at the satellite?

The solution is to phase shift the signal sent to  one antenna with respect to the other antenna and,

as a result, the timing of the peaks and troughs  emitted from one antenna is different from

the other. These peaks and troughs propagate  outwards, and the location of the constructive

interference is now angled to the left with  destructive interference everywhere else.

If we change the phase of the antennas again, the  zone of constructive interference is angled to

the right. Therefore, by continuously changing  the phase of the signals sent to the antennas,

we can create a sweeping zone of  the constructive interference.

Let's bring in six more antennas and simplify  the visual so that we only see a section of the

peaks from each wave. Far away from the  antennas, the waves join to form a wave

front that is a planar wave. Kind of like ocean  waves crashing on a shoreline. Just as before,

by continuously changing the timing of when  each wave peak is emitted by each antenna,

we can change the angle at which the wave front  is formed, essentially steering the beam in one

direction or another. And, if we bring in  more antennas in a two-dimensional array,

we can now steer the beam in any direction  within a one-hundred-degree field of view.

Let’s move back to view all 1280 antennas in  Dishy. In order to know the exact angle the beam

needs to be pointed or steered, we use the GPS  coordinates of Dishy from this chip over here,

along with the orbital position of the Starlink  satellite which is known in Dishy’s software. The

software computes the exact set of 3D angles and  the required phase shift for each of the antennas.

These phase shift results are then sent  to the 20 larger chips called beamformers,

and each beamformer coordinates between 32 smaller  chips called front end modules, each of which

controls 2 antennas. Every few microseconds, these  computations are recalculated and disseminated to

all the microchips in order to perfectly aim the  beam at the satellite. As a result, the beam can

be steered anywhere in a 100-degree field of view. There are a few quick notes. First, the main beam,

also called the main lobe looks like this.  However, constructive and destructive

interference isn’t perfect, and as a result  there are additional side lobes of lesser power.

Third, Mr. McFlatface holds is a single phased  array, however, on the Starlink satellite,

there are in fact 4 phased array antennas. Two  are used to communicate with multiple Dishys,

and 2 are used to communicate with the ground  stations to relay the internet traffic.

And fourth, phased arrays are used in many  applications, and interestingly they’re used

on commercial airlines to allow for mid-flight  internet. So this video also tangentially

explains how mid-flight internet works. Before we explore how actual data is sent,

we want to mention that this video took a month  to research, two dozen script revisions, and two

months to model and animate. If your mind is blown  by the complexity of this technology and the depth

of this video click the subscribe button, like  this video, write a comment below, and we’ll

be sure to create more videos like this one. The third topic we’re going to dive into is how

information gets sent between Dishy and  the Starlink satellite. For example,

we’ve talked about high-frequency  sinusoid-shaped electromagnetic waves,

but that doesn’t look anything like binary  and even less like your favorite TV show.

So, what’s happening? Well, Dishy and the  satellite indeed send a signal that looks like

this; however, they vary the amplitude and the  phase of the transmitted signal and then assign

or encode 6-bit binary values to each different  combination or permutation of amplitude and phase.

With 6 bits, there are 64 different  values, and thus we need 64 different

permutations of amplitude and phase. However,  instead of listing all the permutations,

it’s more easily visualized by arranging the 64  different values in a graph called a constellation

diagram as shown. Let’s look at the point 011 101  and draw a line from the origin to this point.

The distance from the origin is the amplitude  of the signal, and the angle from the positive-X

axis is the phase. It’s a bit like using polar  coordinates. Thus, for Dishy to send these 6-bits,

it transmits a signal with an amplitude  of 59% and a phase shift of 121 degrees.

Then, if the next value being sent is 101 000, the  signal switches to an 87% amplitude or brightness,

and a 305-degree phase shift. After that it sends  the next value with a different amplitude and

phase shift. Each of these 6-bit groupings are  called symbols and they last for only 10 or so

nanoseconds before the next symbol is sent. Lots of times you see the signal scrunched

up like this however, because the frequency of  the signal is just once every 83 picoseconds,

or 12 Gigahertz, and since a symbol lasts 10  nanoseconds, it’s more accurate to have around

120 wavelengths per symbol before the next symbol  is sent. Because we’re dealing on the order of

pico and nanoseconds, that means that we  can fit 90 million 6-bit groups or symbols,

resulting in 540 million bits per second. However,  note that this data transfer is shared between

download and upload. Since this particular antenna  can’t transmit and receive data at the same time,

about 74 milliseconds of every second is  used to send data from Dishy to the Starlink

satellite and 926 milliseconds is used to send  data from the satellite down to Dishy. And,

for the sake of reducing latency, these time  slots get distributed throughout a single second

instead of grouping them all together. This technique of sending 6-bit values

using different variations of amplitude and  phase is called 64QAM or Quadrature Amplitude

Modulation and is more complicated than we  discussed but let’s not get sidetracked.

Now that we have a stream of millions of 6-bit  symbols yielding hundreds of megabits of data per

second, in order to turn it into your favorite  TV show we use the advanced video codec, or

h.264 format. You can learn more about that in our  video that explores image compression shown here.

I’m sure you have many questions, and by  all means put them in the comments below,

but before we finish let’s clarify two things. First, the scale of practically everything in this

video is off. Here’s the correct scale of Dishy  and the Starlink Satellite, however Dishy is 550

kilometers away which we can’t correctly show. In  stark contrast, the emitted electromagnetic waves

are only around 2.5 centimeters apart, and thus  between Dishy and the satellite there are around

22 million wavelengths which is many more than the  few waves that you see here. Additionally, in this

animation we’re showing the wavelengths slowly  making their way up and down, when in reality

it only takes around 2 milliseconds for an  electromagnetic wave emitted from Dishy or

the Starlink satellite to reach the other. The second clarification is that we

disproportionately show Dishy emitting  electromagnetic waves and sending them

to the satellite. In reality the satellite dish  is more frequently in receive mode and the steps

and physics of receiving an electromagnetic wave  are similar to emitting one, just in reverse.

That’s pretty much it for how Starlink and Dishy  send data to each other. The original script for

this video was over 45 minutes long, so all the  details that were cut got thrown in the creator’s

comments found in the English Canada subtitles. Thank you to all of our Patreon and YouTube

Membership Sponsors for helping to make  this video. Also, thank you to Colin

O’Flynn at NewAE Technology for lending us a  Starlink Dishy PCB for imaging and research.

This is Branch Education, and we  create 3D animations that dive

deep into the technology that drives our  modern world. Watch another Branch video

by clicking one of these cards or click here  to subscribe. Thanks for watching to the end!