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radar:measurements

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radar:measurements [2018/06/05 15:09] – dipaoloradar:measurements [2026/04/28 16:58] (current) – mauro
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->it is ok for the moment. You can start  --- //[[webmaster@localhost|DokuWiki Administrator]] 2018/04/19 11:25// 
->  Where do the figures come from? Please cite the document as decribed in [[:start|Welcome!]] --- //[[webmaster@localhost|DokuWiki Administrator]] 2018/05/03 16:16// 
  
 ====== Radar Measurement ====== ====== Radar Measurement ======
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 ===== Range ===== ===== Range =====
 +
 +//An overall discussion about radar techniques to detect the range of a given target//
  
 To start our dissertation, let's assume that we have a radar system that is able to emit pulses of energy in any direction of the space in order to detect some desired objects. The shape of the transmitted pulse can be modelled as in fig.1. It has a rectangular envelope which duration is $\tau$ and its carrier is a sinusoidal waveform which has a wavelength equal to $\lambda$ and so frequency $f_0 = c/\lambda$. To start our dissertation, let's assume that we have a radar system that is able to emit pulses of energy in any direction of the space in order to detect some desired objects. The shape of the transmitted pulse can be modelled as in fig.1. It has a rectangular envelope which duration is $\tau$ and its carrier is a sinusoidal waveform which has a wavelength equal to $\lambda$ and so frequency $f_0 = c/\lambda$.
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 ===== Angle ===== ===== Angle =====
 +
 +//Angular detection of the target, starting from knowing how a given antenna is able to detect the presence of a taget in the space//
  
 To univocally identify the position of a target we must measure not only the distance but also the angle from which the scattered energy comes from. For this reason, very directive antennas are used, i.e. antennas that perform a radiation diagram with a maximum along a given direction.  To univocally identify the position of a target we must measure not only the distance but also the angle from which the scattered energy comes from. For this reason, very directive antennas are used, i.e. antennas that perform a radiation diagram with a maximum along a given direction. 
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 ===== Velocity ===== ===== Velocity =====
 +
 +//Analysis of the velocity parameter of the target, with a main focus on the Doppler frequency//
  
 Once we have defined the previous parameters that allow us to measure the distance from the radar, another information that can be derived from the echo signal is the radial velocity of the target. Of course, this quantity is revealed by the radar only if the target is moving. Once we have defined the previous parameters that allow us to measure the distance from the radar, another information that can be derived from the echo signal is the radial velocity of the target. Of course, this quantity is revealed by the radar only if the target is moving.
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 ===== Ambiguity cases ===== ===== Ambiguity cases =====
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 +//According to the characteristics of our radar system, we can incur some troubles about the accuracy of the measurements. Let's see it in detail//
  
 We can now understand that when we have to define the working characteristics of our radar system, we have to take into account the right choice of the $PRF$ value. According to its value, we have pointed out the following: We can now understand that when we have to define the working characteristics of our radar system, we have to take into account the right choice of the $PRF$ value. According to its value, we have pointed out the following:
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 ===== Dwell Time ===== ===== Dwell Time =====
 +
 +//Analysis of the Dwell time and the corresponding number of pulses available for the eleboration//
  
 Assume to work with a pulse radar whose beam is able to move to scan all the space. If there is an object that can be approximated by a point at a certain distance it will be lighted up by the -3dB beamwidth of the antenna for a certain period of time. This target will be hit by a certain number $N$ of pulses transmitted by the radar. Consequently, on the receiving side, we will detect $N$ different echoes, attenuated and delayed, associated to the target. By definition, this number $N$ is equal to: Assume to work with a pulse radar whose beam is able to move to scan all the space. If there is an object that can be approximated by a point at a certain distance it will be lighted up by the -3dB beamwidth of the antenna for a certain period of time. This target will be hit by a certain number $N$ of pulses transmitted by the radar. Consequently, on the receiving side, we will detect $N$ different echoes, attenuated and delayed, associated to the target. By definition, this number $N$ is equal to:
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 ===== Temporal scales for radar signal ===== ===== Temporal scales for radar signal =====
 +
 +//A brief recall of all the temporal concepts seen up to now//
  
 In this chapter all the measurements that a radar system is able to perform have been defined, taking into account the presence of a target approximable to a point, i.e. the object is very small with respect to the dimensions of the radar cell.\\ They are the following: In this chapter all the measurements that a radar system is able to perform have been defined, taking into account the presence of a target approximable to a point, i.e. the object is very small with respect to the dimensions of the radar cell.\\ They are the following:
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