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The synthetic aperture radar system includes a multi-beam antenna having many reception beams in different direction from one another, the multi-beam antenna being adapted to receive radar echoes from objects. synthetic aperture radar system can detect a low-speed moving object without degradation of the cross-range resolution, enable the low-speed moving object to display without positional error, and does all these without reduction of the transmission antenna gain.
This describes a synthetic aperture radar system utilizing the Doppler effect caused by the movement of a radar platform to improve the cross-range resolution and also the capacity to ddetect a moving object. The width the reception beams is selected in such a way that the band width of a Doppler shift in the radar echo of a moving target is broader than that of the Doppler shift in the radar echo of a stationary target. This radar echo is pulse compressed to increase the range resolution. the radar echo is filtered to separate the ones of the moving and that of the stationary objects from each other. These radar echoes subjected to Fourier transform with respect to the distance between the moving platform and the objects.As a final step, the spectrum of the radar echo from the moving object is further shifted such that the center frequency of the Doppler shift due to the velocity of the object becomes zero. This algorithm of reception, pulse compression, frequency shift and Fourier transform are done for every reception beam.
SUMMARY of the instrument
It is a system mounted on a moving platform and includes:
1) a multi-beam antenna having reception beams in different directions.
2)cross-range resolution improving system containing moving object echo separating means, moving object spectrum transforming means, moving object spectrum synthesizing means , eference spectrum generating means, moving object side multiplying means , moving object spectrum inverse transform means.
the multi-beam antenna recieves the signals and a filtering enables the separation between the stationary and moving objects. The separation between the stationary and moving objects and the transform to the spectrum are carried out for each reception beam.Thus the apparent reception beam width is enlarged into the total width of the actual reception beams.Thus this apparatus can detect a low-speed moving object without degradation of the cross-range resolution.
The whole system working can be described as:
First of all, the frequency of the radar echo acquired by the multi-beam antenna is shifted, for reception beam, depending on the center frequency of the Doppler shift contained in the echo of the stationary object which his removes the Doppler shift due to the velocity of the moving platform from the radar echo. beam is high-pass filtered after the frequency shifting and echo of moving object is extracted from each reception beam. If low pass filtering is done, you get the echo of the stationary object. This is resampled to reduce the amount of data and then transformed into a spectrum.. Doppler shift due to the velocity of object is compensated. Then the echoes are multiplied by the respective reference spectrums. Finally, The result of inverse transform from the moving object spectrum inverse transform means is transformed as into information suitable for use in display.
full seminar report pdf:
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Synthetic Aperture Radar System
Introduction
When a disaster occurs it is very important to grasp the situation as soon as possible. But it is very difficult to get the information from the ground because there are a lot of things which prevent us from getting such important data such as clouds and volcanic eruptions. While using an optical sensor, large amount of data is shut out by such barriers. In such cases, Synthetic Aperture Radar or SAR is a very useful means to collect data even if the observation area is covered with obstacles or an observation is made at night at night time because SAR uses microwaves and these are radiated by the sensor itself. The SAR sensor can be installed in some satellite and the surface of the earth can be observed.
To support the scientific applications utilizing space-borne imaging radar systems, a set of radar technologies have been developed which can dramatically lower the weight, volume, power and data rates of the radar systems. These smaller and lighter SAR systems can be readily accommodated in small spacecraft and launch vehicles enabling significantly reduced total mission cost.
Specific areas of radar technology development include the antenna, RF electronics, digital electronics and data processing. A radar technology development plan is recommended to develop and demonstrate these technologies and integrate them into the radar missions in a timely manner. It is envisioned that these technology advances can revolutionize the approach to SAR missions leading to higher performance systems at significantly reduced mission costs.
The SAR systems are placed on satellites for the imaging process. Microwave satellites register images in the microwave region of the electromagnetic spectrum. Two mode of microwave sensors exit- the active and the passive modes. SAR is an active sensor which carry on -board an instrument that sends a microwave pulse to the surface of the earth and register the reflections from the surface of the earth.
One way of collecting images from the space under darkness or closed cover is to install the SAR on a satellite . As the satellite moves along its orbit, the SAR looks out sideways from the direction of travel, acquiring and storing the radar echoes which return from a strip of earth's surface that was under observation.
The raw data collected by SAR are severely unfocussed and considerable processing is required to generate a focused image. The processing has traditionally been done on ground and a downlink with a high data rate is required. This is a time consuming process as well. The high data rate of the downlink can be reduced by using a SAR instrument with on-board processing.
X-Band SAR Instrument Demonstrator
The X-band SAR instrument demonstrator forms the standardized part or basis for a future Synthetic Aperture Radar (SAR) instrument with active front- end. SAR is an active sensor. Active sensors carry on-board an instrument that sends a microwave pulse to the surface of the earth and register the reflections from the surface of the earth. Different sensor use different bands in the microwave regions of the electromagnetic spectrum for collecting data. In the X-band SAR instrument, the X-band is used for collecting data.
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Introduction
When a disaster occurs it is very important to grasp the situation as soon as possible. But it is very difficult to get the information from the ground because there are a lot of things which prevent us from getting such important data such as clouds and volcanic eruptions. While using an optical sensor, large amount of data is shut out by such barriers. In such cases, Synthetic Aperture Radar or SAR is a very useful means to collect data even if the observation area is covered with obstacles or an observation is made at night at night time because SAR uses microwaves and these are radiated by the sensor itself. The SAR sensor can be installed in some satellite and the surface of the earth can be observed.
To support the scientific applications utilizing space-borne imaging radar systems, a set of radar technologies have been developed which can dramatically lower the weight, volume, power and data rates of the radar systems. These smaller and lighter SAR systems can be readily accommodated in small spacecraft and launch vehicles enabling significantly reduced total mission cost.
Specific areas of radar technology development include the antenna, RF electronics, digital electronics and data processing. A radar technology development plan is recommended to develop and demonstrate these technologies and integrate them into the radar missions in a timely manner. It is envisioned that these technology advances can revolutionize the approach to SAR missions leading to higher performance systems at significantly reduced mission costs.
The SAR systems are placed on satellites for the imaging process. Microwave satellites register images in the microwave region of the electromagnetic spectrum. Two mode of microwave sensors exit- the active and the passive modes. SAR is an active sensor which carry on -board an instrument that sends a microwave pulse to the surface of the earth and register the reflections from the surface of the earth.
One way of collecting images from the space under darkness or closed cover is to install the SAR on a satellite . As the satellite moves along its orbit, the SAR looks out sideways from the direction of travel, acquiring and storing the radar echoes which return from a strip of earth's surface that was under observation.
The raw data collected by SAR are severely unfocussed and considerable processing is required to generate a focused image. The processing has traditionally been done on ground and a downlink with a high data rate is required. This is a time consuming process as well. The high data rate of the downlink can be reduced by using a SAR instrument with on-board processing.
X-Band SAR Instrument Demonstrator
The X-band SAR instrument demonstrator forms the standardized part or basis for a future Synthetic Aperture Radar (SAR) instrument with active front- end. SAR is an active sensor. Active sensors carry on-board an instrument that sends a microwave pulse to the surface of the earth and register the reflections from the surface of the earth. Different sensor use different bands in the microwave regions of the electromagnetic spectrum for collecting data. In the X-band SAR instrument, the X-band is used for collecting data.
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[attachment=5157]
Introduction
When a disaster occurs it is very important to grasp the situation as soon as possible. But it is very difficult to get the information from the ground because there are a lot of things which prevent us from getting such important data such as clouds and volcanic eruptions. While using an optical sensor, large amount of data is shut out by such barriers. In such cases, Synthetic Aperture Radar or SAR is a very useful means to collect data even if the observation area is covered with obstacles or an observation is made at night at night time because SAR uses microwaves and these are radiated by the sensor itself. The SAR sensor can be installed in some satellite and the surface of the earth can be observed.
To support the scientific applications utilizing space-borne imaging radar systems, a set of radar technologies have been developed which can dramatically lower the weight, volume, power and data rates of the radar systems. These smaller and lighter SAR systems can be readily accommodated in small spacecraft and launch vehicles enabling significantly reduced total mission cost.
Specific areas of radar technology development include the antenna, RF electronics, digital electronics and data processing. A radar technology development plan is recommended to develop and demonstrate these technologies and integrate them into the radar missions in a timely manner. It is envisioned that these technology advances can revolutionize the approach to SAR missions leading to higher performance systems at significantly reduced mission costs.
The SAR systems are placed on satellites for the imaging process. Microwave satellites register images in the microwave region of the electromagnetic spectrum. Two mode of microwave sensors exit- the active and the passive modes. SAR is an active sensor which carry on board an instrument that sends a microwave pulse to the surface of the earth and register the reflections from the surface of the earth.
One way of collecting images from the space under darkness or closed cover is to install the SAR on a satellite . As the satellite moves along its orbit, the SAR looks out sideways from the direction of travel, acquiring and storing the radar echoes which return from a strip of earth's surface that was under observation.
The raw data collected by SAR are severely unfocussed and considerable processing is required to generate a focused image. The processing has traditionally been done on ground and a downlink with a high data rate is required. This is a time consuming process as well. The high data rate of the downlink can be reduced by using a SAR instrument with on-board processing.
