I decided to post this article after reading
this publication from
bigdhost , I doubted it, because Many parameters were taken "from the ceiling", but I decided that the numbers are still not the main thing.
Here the emphasis is on Starlink from SpaceX, but the laws of physics are the same for everyone.
Frequencies and capacities
First you need to decide which bands will be used on satellite Internet starlink. As far as is known, for satellites with a high orbit, this is the K-Ka range (in this range there is a frequency of 22 GHz, at which strong absorption of waves occurs by atmospheric moisture, which makes that part of the range unsuitable for long-distance communications), and for satellites with a low orbit this is V range from 60 GHz.
The K-Ka band is already used by various means of communication, so there may be difficulties with obtaining frequencies, the bandwidth more than 200 MHz is hardly to be expected, but V is almost free now and here it can be better.
Obtaining permits for the use of frequencies is carried out in each country separately. For example, the entire range of wi-fi 2400-2480 MHz for 14 channels is allowed to use in Japan, 13 in Russia, and only 9 in France. These channels occupy 20 MHz and hit adjacent channels, it is also possible to make a dual channel at 40 MHz, which can double the bandwidth, but not recommended for multiple devices or interference. The width of only 4g is also about 100 MHz, which is much more than 3g. This expansion is one of the main reasons for the increase in speed.
Also assigned is the maximum signal transmit power. For non-directional wi-fi allow 0.1 W, for phones is determined San. standards and is about 1 W, for satellite Internet, I think about 1 W too. Then the question arises on what band this power falls.
Now it is necessary to divide the frequencies between devices, if there are too many devices, you have to narrow the band and, as a consequence, the transmission speed. The same thing happens when interference occurs, it is necessary to increase the power to frequency ratio (W / Hz) until the level of interference is exceeded. So you won’t get a miracle with a lot of devices or interference, you will have to sacrifice speed;
How effectively will it be used? Take efficiency 5g times 2018 in the yard) wiki achieved a throughput of 4.5 Gbit / s with a bandwidth of 200 MHz, so 40 GHz would be required for the stated 1 Gbit / s, which is a bit too much for K band, but not very loaded for V areas really. In contrast to 5g, difficulties arise due to the Doppler effect, but solved on the side of the “pizza box”.
The ratio of 1 Gbit / s at 40 MHz shows that there is not enough range for high speed for many subscribers, so it is possible to install several directional antennas on the satellite instead of one wide-directional, as a result we get several base stations on one satellite.
Antennas
Now about the antennas. From the subscriber side, the requirements are clearer - to create the maximum gain towards the satellite, all signals coming from other directions are noise. In order not to move the antenna mechanically, the HEADLIGHT is used.
To create a sharper directivity angle, which provides a higher gain, you need to use more dipoles in the rows and columns of the antenna. Such high frequencies are good because the dipoles and the pitch between them are small and you can make a very directional antenna with small sizes. You can get a gain of over a thousand.
In addition to the directivity, the antenna also has an area, which, if necessary, can be increased by also adding dipoles. But this not only increases the level of the useful signal, but also the noise, the signal-to-noise ratio with a simple increase in the area remains. Why this may be needed? The receiver can work with a very weak input signal, but all but the ideal receiver cooled to 0 degrees Kelvin create internal noise, but if the input signal is stronger, this noise will not interfere with almost any conditions.
Also, besides strong amplification in the right direction of order 1000 times, there will be radiation and reception in other directions with an uneven coefficient of 0.01-0.5 unless of course you cover it with something from those sides :)
With the satellite situation is more complicated. From it it is necessary to cover a huge territory. On cell towers, as a rule, 4 antennas are installed with a directivity of 110 ° in azimuth and 4 ° in height (near the horizon line, in order not to direct energy uselessly to heaven and earth). Here in the case of a low orbit an angle of 102 ° is declared.
It is quite easy to make one such antenna, but ... then forgiven for high speeds with a large number of subscribers, do not get in there all, but if the jammer breaks in there ...
But maybe not in vain starlink positioned high-speed? Maybe it is not for nothing that these satellites weigh 380 kg, and not 120 as OneWeb?
In principle, you can make a dozen. By design, you can make options here, since there is no need to quickly redirect them, unless you redistribute the load with neighboring satellites, and you can work with stationary ones.
The variant with PHAR allows for more active redistribution of zones, but it is necessary to work out the system so that there is less mutual influence between them (about how to put 10 people in one room and at the same time they have to talk on the phone).
The variant with a parabolic mirror or a split with horns separates it from its neighbors, but it is necessary to redirect mechanically, and this is weight, energy, and a decrease in reliability. So for mutual redistribution of the zone is not suitable.
Well, a little fiction) antenna counter the director of interference. You can determine where the jammer is, cleanly remove his signal from a very narrow-focus antenna and select the level to subtract it from the received signal during processing. Well, what is needed for this is a special antenna, complication of signal processing, opposition to only one producer (well, if you add another antenna, you can two) You can do such things, but it is not suitable for such a system.
Most mysterious
The EW troops are probably one of the most secret, so there will only be assumptions about their capabilities.
(The paint is designed to "dazzle" the aircraft, there is no more data)
The first jamming option is a directional interference to the satellite. In this case, the interference should occupy the entire allocated spectrum and have a spectral power higher than the subscriber transmitters.
But the communication protocol will have a minimum transmission rate and the narrowest band allocated for it, the reduction of which is not supported.
For evaluation, let the transmitter be 1 W, speed 2 Mbit / s, which requires a 100 kHz band (by analogy 5g) which gives 10 W / MHz.
Multiply by the range, we get the interference power of 2 kW (for V it is possible more). This is all roughly taken if the antenna gains of the subscribers and the jammer are the same, but I don’t think that they will be very different due to the difficulty of creating a narrow beam and positioning it on a moving satellite.
Can EW products give 2 kW? Yes, and perhaps 10 can be in the stationary. Theoretically, they do not need to send this noise all the time, they need short enough pulses to spoil the transmitted packets until it is impossible to recover data. But in full it will only come to the satellite from one direction. If there are several antennas on it and everything is well untied, it will not affect other channels.
V-range retreat. At the very beginning (60 GHz), there is a frequency of absorption by atmospheric oxygen, which gives large attenuation in the air. So it is known that the US military used it specifically for communication over short distances, so that from a distance it was more difficult to listen and / or drown out, also in space where there is no such attenuation. And I did not hear it higher in frequency. So there is more of a jam in this range, but perhaps it is almost the same.
Well, now about a simpler way if you jam those who are on the ground. Only one thing is saved here - the directivity of the antennas. The satellite can not transmit to all antennas more than 200-300 W in total, it will receive an average of a kilowatt with a battery. Here the main characteristic is the level of side lobes.
If there was an opportunity to get the data of this parameter, it was possible to get quite real estimates, but for now the principle itself.
Suppose UBL -20 dB which means on the sides of the reception is 100 times weaker than in the main beam. If the director had the same power, then he needs to be located no farther than the root of 100 = 10 times closer than the satellite, with UBL -40, respectively, 100 times closer. In the array of vibrators, the distribution of the signal amplitude is uneven, the amplitude decreases towards the edges, and the side lobes decrease. At the same time, the gain is slightly reduced, and if it is necessary to preserve, the dimensions and price increase, so this is usually a secondary parameter that can be sacrificed.
You can divide 340 and 1100 kilometers (you can add the influence of the location angle) to these values yourself, but at the same time the jamming should be in the line of sight, the reflected noise will be much weaker, and Kulibiny can also stick their antenna into the funnel. There is also an opportunity to use several low-cost low-power jammers over the required territory, which may be suitable for restricting access at closed enterprises.
Well, the conclusion is that of course it is possible to drown, the question is how far and what means are needed, and with directional antennas a very large area is blocked only by impact on satellites.