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AESA radar characteristics

Cool ice

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Are there any documents regarding the beam steering speed of modern AESA antennae?
Also , are there some reliable sources about the antenna gain of a modern air mounted AESA(X-Band , D=500-1000 mm).Of Any company of course , not necessaily raytheon or northrop G.

Thanks
 

Dragon029

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The steering speed is simply whatever the field of view of the AESA is (typically 120 degrees), multiplied by the pulse repetition frequency of the radar (eg: 10,000Hz). All you're doing is shifting the frequency offsets for each T/R module between pulses.

As for gain, you might want to look up the AESA radar performance Excel spreadsheet calculator from stealthflanker on this forum, but typically gain values would be in the mid or high 30dBi range.
 

stealthflanker

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Are there any documents regarding the beam steering speed of modern AESA antennae?

Unfortunately no. You can try however finding technical specs for various means to do beamsteering (e.g Phase shifters). Current Electronically scanned array radar use phase shifters of various designs. Commonly used however is ferrite with beamsteering time of some 0.5 microseconds to about miliseconds range, and Diode phase shifters with some nanoseconds beamsteering time.

The French use RADANT lens in their early RBE-2 Radar. But i have no information yet on their beam switching time.

Also , are there some reliable sources about the antenna gain of a modern air mounted AESA(X-Band , D=500-1000 mm).Of Any company of course , not necessaily raytheon or northrop G.

Thanks

To my knowledge there are none.

AESA and perhaps electronically scanned array in general can have specific weighting algorithm or means (e.g "dead"/passive elements) to their radiation
pattern and it may change it in real time according to detection requirements. Thus the gain may not be fixed as what one would find in conventional antenna.

However providing you know the size of the antenna you can find the beamwidth, then use K.Barton's simple approximation to determine gain.

To find the beamwidth you can simply use the equation : K*(lambda/D)

Where K is the beamwidth broadening factor (0.886 for unweighted array, while typical fighter radar antenna may use Taylor -40 dB with factor of 1.25) D is the width or height of the antenna from which you determine the beamwidth. Lambda is the wavelength of the radar.

If the antenna have equivalent dimension in both height and width. you only need to do the calculation once and go ahead with K.Barton's approximation with the beamwidth squared. If the antenna is not the same in height and width (e.g a rectangular or eliptical array) You have to do the calculation twice to find both the horizontal and vertical beamwidth.

The Barton's approximation for gain is as follows : 30000/(BeamV * BeamH) Where the beam are in Degrees.

Example is as follows :

We have a radar with following antenna dimension and information :

Width : 0.75 m
Height : 0.48 m
Operating wavelength : 3 cm or 0.03 m

This AESA antenna use Taylor -40 dB (Beamwidth factor 1.25).

Find the Gain of the antenna in those modes :

We find the Horizontal beamwidth first :

BeamH= 1.25*(0.03/0.48)
BeamH= 0.078 Radians or 4.46 Degrees

Then the vertical beamwitdh

BeamV= 1.25*(0.03/0.75)
BeamV= 0.05 Radians or 2.86 Degrees

Then we proceed to find the gain as follows :

G(power ratio)=30000/(4.46*2.86)
G(power ratio)=2351.9

Then we convert it to Decibel (10*LOG(2351.9)) Thus the gain is 33.71 dB in Decibel.

Above however is not the only way to calculate gain. People will commonly use the usual equations which based on the area. The advantage i see for above compared to usual method however is that :

1.One does not need to know the antenna efficiency which may not necessarily be known or may cause confusion as will be shown in number 2.
2.One can take account of possible use of different weighting scheme (e.g Taylor -40 dB for horizontal while for vertical beamwitdh one could use say... Cos^5) Yes, Phased arrays can be that flexible. Considering weighting scheme affects all the antenna pattern, beamwidth, gain and the antenna efficiency, use of typical equation may lead to confusion on which antenna efficiency figure to use as Taylor -40 dB would yield antenna efficiency of about 76% While the Cos^5 would give about 68%.
 

Cool ice

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Thank you dragon29 and stealthflanker for your answers , i highly enjoyed them !
 

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