Panoramic passive radar
In this article I want to talk about the next experiment with a passive panoramic radar. The previous experiments are described in the articles "Radio telescope" and "Microwave passive radio telescopter in the 10 GHz range" .
The first panoramic radio images were obtained using a fixed-parabolic antenna with a diameter of 1.8 m installed permanently.
The next radar was not panoramic, i.e. he could only work in the azimuth plane. But he allowed to experiment, both in terms of mechanics and electronics, and in terms of the use of small diameter antennas. At first it was not clear - would there be effective mirrors with a diameter of about 50 cm when receiving the object's own noise?
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After the first experiments, it immediately became clear that it was quite possible, and the thought came to me to make a small mobile panoramic radar with an antenna of 50 cm in diameter.
For support, I used a tripod from an optical telescope, which I borrowed from a friend. The rotary mechanism is assembled from two worm gearboxes, to which the gearmotors with built-in sensors are connected.
A direct-focus antenna with a diameter of 50 cm is fixed on the output flange of the turning mechanism. The converter from satellite television is installed in focus.
The signal from the converter goes to the high frequency amplifier, then to the amplitude detector and then to the DC amplifier. After the amplifier, the signal is digitized by a single-byte ADC. The controller of the rotary mechanism control console, at the request of the computer, reads the position of the antenna, polls the ADC and sends this data back to the computer.
The control program in the computer first prepares the task in accordance with the specified coordinates of the panorama, and then, as necessary, sends the necessary coordinates to the control panel.
At the same time, the computer constantly (every 20 ms) sends requests for antenna position and signal level. Based on this data, a picture is drawn in the program window.
This is actually the floor of the room. The middle of the picture is the corner of the room. Accordingly, there are two windows on the left wall and two windows on the front wall. The left windows do not go out onto the street, but onto the glassed-in balcony (this is east). The front wall faces south and the windows face the street.
What can be seen on these pictures:
A. In the leftmost window, the vertical bar on the right is part of the frame of this window, and the vertical bar on the left is part of the frame of the balcony window. In the next window, all the same. The two windows on the left appear smaller in height compared to the windows on the right side of the image. In fact, they are the same in size. In the windows on the left, the ceiling of the balcony shines strongly from above.
B. Windows on the right side of the radio image. In the window that is closer to the center, the vertical bar is part of the window frame. At the bottom of the window you can see the roof of the neighboring house. In the far right of the window is also viewed part of the frame and still visible light bar coming from the upper left corner, almost diagonally down. I’m not exactly sure, but I suspect that the spread signal from satellites in geostationary orbit is so visible.
I took this radio shot by installing the antenna directly in front of the window.
At the bottom of the picture you can see the roof of the neighboring house. The vertical bar on the right is part of the window frame. The light arc in the middle of the image going from left to right is blurred satellite signals, and the sources of these signals can be seen on the left (bright spot) and on the right (bright blurred spot).
Experimenting with a portable radiometer, I found that the human body also emits radio noise.
However, with the help of such a radiometer you cannot take a radio picture. Now I have the opportunity and this experiment was for me the most interesting. I made some radio pictures of myself. It turned out that the human body glows strongly in the radio.
In the left picture I am standing with my arms down, on the middle arms are spread to the sides and on the right hands are raised up. For the purity of the experiment, I took off my clothes to be sure that it is the body that radiates, not the clothes.
I did not take pictures of the light bulbs. The experiment was conducted on an energy-saving light bulb, LED and conventional (incandescent). Energy-saving lamp shines brightly in the range of 10 GHz, which can not be said about the other light bulbs. In the video you can see how I took radio photographs and light bulbs as well.
Now I have outlined the following experiments on passive radar, but somewhat on different equipment. This will be another article.
The first panoramic radio images were obtained using a fixed-parabolic antenna with a diameter of 1.8 m installed permanently.
The next radar was not panoramic, i.e. he could only work in the azimuth plane. But he allowed to experiment, both in terms of mechanics and electronics, and in terms of the use of small diameter antennas. At first it was not clear - would there be effective mirrors with a diameter of about 50 cm when receiving the object's own noise?
')
After the first experiments, it immediately became clear that it was quite possible, and the thought came to me to make a small mobile panoramic radar with an antenna of 50 cm in diameter.
Device
For support, I used a tripod from an optical telescope, which I borrowed from a friend. The rotary mechanism is assembled from two worm gearboxes, to which the gearmotors with built-in sensors are connected.
A direct-focus antenna with a diameter of 50 cm is fixed on the output flange of the turning mechanism. The converter from satellite television is installed in focus.
The signal from the converter goes to the high frequency amplifier, then to the amplitude detector and then to the DC amplifier. After the amplifier, the signal is digitized by a single-byte ADC. The controller of the rotary mechanism control console, at the request of the computer, reads the position of the antenna, polls the ADC and sends this data back to the computer.
The control program in the computer first prepares the task in accordance with the specified coordinates of the panorama, and then, as necessary, sends the necessary coordinates to the control panel.
At the same time, the computer constantly (every 20 ms) sends requests for antenna position and signal level. Based on this data, a picture is drawn in the program window.
Experiment №1 - panoramic radio image of the room
This is actually the floor of the room. The middle of the picture is the corner of the room. Accordingly, there are two windows on the left wall and two windows on the front wall. The left windows do not go out onto the street, but onto the glassed-in balcony (this is east). The front wall faces south and the windows face the street.
What can be seen on these pictures:
A. In the leftmost window, the vertical bar on the right is part of the frame of this window, and the vertical bar on the left is part of the frame of the balcony window. In the next window, all the same. The two windows on the left appear smaller in height compared to the windows on the right side of the image. In fact, they are the same in size. In the windows on the left, the ceiling of the balcony shines strongly from above.
B. Windows on the right side of the radio image. In the window that is closer to the center, the vertical bar is part of the window frame. At the bottom of the window you can see the roof of the neighboring house. In the far right of the window is also viewed part of the frame and still visible light bar coming from the upper left corner, almost diagonally down. I’m not exactly sure, but I suspect that the spread signal from satellites in geostationary orbit is so visible.
Experiment number 2 - a radio image from the window
I took this radio shot by installing the antenna directly in front of the window.
At the bottom of the picture you can see the roof of the neighboring house. The vertical bar on the right is part of the window frame. The light arc in the middle of the image going from left to right is blurred satellite signals, and the sources of these signals can be seen on the left (bright spot) and on the right (bright blurred spot).
Experiment number 3 - a radio image of a person
Experimenting with a portable radiometer, I found that the human body also emits radio noise.
However, with the help of such a radiometer you cannot take a radio picture. Now I have the opportunity and this experiment was for me the most interesting. I made some radio pictures of myself. It turned out that the human body glows strongly in the radio.
In the left picture I am standing with my arms down, on the middle arms are spread to the sides and on the right hands are raised up. For the purity of the experiment, I took off my clothes to be sure that it is the body that radiates, not the clothes.
Experiment number 4 - radio images of light bulbs
I did not take pictures of the light bulbs. The experiment was conducted on an energy-saving light bulb, LED and conventional (incandescent). Energy-saving lamp shines brightly in the range of 10 GHz, which can not be said about the other light bulbs. In the video you can see how I took radio photographs and light bulbs as well.
Now I have outlined the following experiments on passive radar, but somewhat on different equipment. This will be another article.
Source: https://habr.com/ru/post/248969/
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