MIL-STD-469 Radar Engineering Interface Requirements, Electromagnetic Compatibility See Notice 1 For Replacement InformationThis standard establishes the engineering interface requirements to control the electromagnetic emission and susceptibility characteristics of all new military radar equipment and systems operating between 100 megahertz MHz, and 100 gigahertz GHz, to ensure EMC in all intended operational environments, and to conserve the frequency spectrum available to military radar systems.

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MIL-STD-469B APPENDIX A

50.2.4.7  The azimuthal beam-scanning measurement should be performed if the main beam can be easily steered at will. The main beam of the phased array should be steered as close as possible to the elevation of the test antenna and, with the elevation constant, should be sequentially stepped in azimuth through the complete scan sector. The azimuthal beam-scanning measurement should be taken with the test antenna at the azimuthal array normal test position, at the test position nearest the maximum angle of the scan sector, at an optional test position, and at the test position 180 degrees in azimuth from the array normal test position.

50.2.5  Sample calculations.  The results from the antenna characteristics measurements consist of antenna pattern recording (strip chart or polar format) and associated calibration data such as attenuation inserted, cable loss, system antenna rotation rate, relative amplitude level, and test receiver and recorder response times. A sample antenna pattern recording (strip chart format) is shown (see figure 24).

50.2.5.1  A sample calculation to determine the power density measured at the test site from measured data follows:

Transmitter tuned frequency (F o): 3000 MHz

Signal generator calibration level at peak of antenna pattern mainlobe (P       ):    13.0 dBm

Attenuation inserted at test receiver input (A  ): 50.0 dB Attenuation, coax to test antenna (A  ): 1.5 dB

Test antenna gain (G  ): 16 dBi

Wavelength = 300/3000 = 0.10 meters.

The received level at the test antenna is determined from:

PR       = PGEN  + A1  + A2

=    13.0 + 50.0 + 1.5

= 38.5 dBm.

Next, the power density at the test antenna is calculated (see 50.2.4.2) as follows:

PD      = PR

20 log (  )     GR  + 11.0

= 38.5     20 log(0.1)     16.0 + 11.0

= 53.5 dBm/m2.

The sample calculation for the expected power density assumes the following parameters:

Radar antenna power input (P T): 90.0 dBm

Radar antenna gain (G T): 25.0 dBi

Distance from radar antenna to test antenna (R): 316 meters.

Using the equation (see 50.2.4.2) the expected power density at the test site is calculated as follows:

PD      = PT  + GT

20 log(R)     11.0

= 90.0 + 25.0     20 log(316)     11.0

= 54.0 dBm/m2.

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